Technical Field
The present invention relates to an earth leakage
detection device. More specifically, the present invention
pertains to an earth leakage detection device for
determining occurrence of an earth leakage in an alternative
current (AC) cable run based on the detection outputs of a
zero-phase current transformer.
Background Art
An earth leakage detection device is provided with a
zero-phase current transformer (ZCT) including a ring-shaped
iron core through which a plurality of primary conductors
forming a part of an AC cable run passes, the core made of a
magnetic body such as a soft magnetic material or the like,
and a toroidally-shaped coil wound around the core. The
earth leakage detection device determines whether an earth
leakage occurs or not in primary conductors, based on a
detection output, i.e., output voltage, detected between
ends of the coil of the zero-phase current transformer.
If an earth leakage occurs in one of the primary
conductors, a difference is generated between an electric
current flowing in an outgoing direction of the AC cable run

and an electric current flowing in an incoming direction of
the AC cable run. A leakage current corresponding to the
difference is generated. Since the electric currents
flowing through the primary conductors get unbalanced as a
whole, the state of magnetic flux of the core of the zero-
phase current transformer is changed by the magnetic flux
generated due to the leakage current. Accordingly, a
voltage induced by the leakage current is detected at the
ends of the coil of the zero-phase current transformer.
If no earth leakage occurs in any one of the primary
conductors, there is established a so-called equilibrium
state in which the sum of vectors of the electric currents
flowing through the primary conductors is equal to zero. In
the equilibrium state, magnetic fluxes exist in the core of
the zero-phase current transformer but the magnetic fluxes
are canceled each other. Thus, the induced voltage stated
above is not detected by the zero-phase current transformer.
Therefore, no output voltage is detected at the ends of the
coil of the zero-phase current transformer. That is, it is
possible to determine generation of a leakage current in the
AC cable run by outputting, as a detection output, an output
voltage across the coil of the zero-phase current
transformer.
An ordinary earth leakage state and a lightning surge
state are conceivable as earth leakage cases where leakage
currents are detected. The ordinary earth leakage refers to

an earth leakage in which a current value of a leakage
current emerges periodically. The lightning surge denotes
an earth leakage in which a current value of a leakage
current becomes relatively large and emerges temporarily.
In case of the ordinary earth leakage of the two kinds
of earth leakages, it is expected that an earth leakage
occurs for a long period of time. It is therefore
preferable to quickly stop the supply of electric power
through the AC cable run. On the other hand, in case of the
lightning surge, an earth leakage occurs only temporarily.
For that reason, it is not desirable to stop the supply of
electric power through the AC cable run every occurrence of
the lightning surge.
As a conventional earth leakage breaker, there is
known an earth leakage breaker capable of preventing
unnecessary cutoff caused by a lightning surge (JP H10-
094161A). This earth leakage breaker distinguishes a
lightning surge or a ground fault current caused by a heavy
ground fault (one of ordinary earth leakages relatively
large in a current value of a leakage current) from a
leakage current through the use of a second comparator with
a larger threshold value than that of a first comparator for
detecting a leakage current. Moreover, the earth leakage
breaker distinguishes a lightning surge from a heavy ground
fault by detecting, with a three-wave counter, whether a
pulse of three waves or more is outputted from the first

comparator during the period of time prepared by a
monostable multivibrator starting up with the output of the
second comparator. Accordingly, a cutoff signal output
circuit outputs a cutoff signal only when an ordinary earth
leakage including a heavy ground fault occurs.
However, in the earth leakage breaker disclosed in JP
H10-094161A, it is necessary, in some cases, to count three
times the leakage current having a relatively large current
value in order to distinguish a lightning surge from an
ordinary earth leakage. In an AC cable run, a leakage
current is generated pursuant to the waveform of an AC power
supply. A pulse is generated when a positive or negative
leakage current is equal to or larger than a specified
value. Occurrence of an earth leakage is determined by
consecutively counting the pulse three times. In the method
of determining occurrence of an earth leakage by counting a
leakage current three times, the earth leakage detection
time becomes increased. In case of the heavy ground fault
among the ordinary earth leakages, there is a possibility
that a relatively large leakage current flows continuously.
From the viewpoint of safety of the public, it is desirable
to quickly distinguish an ordinary earth leakage from a
lightning surge.
The earth leakage breaker disclosed in JP H10-094161A
is capable of breaking an earth leakage but is not designed
to indicate an earth leakage in an effective value depending

on the output voltage of a zero-phase current transformer.
For that reason, an operator or other person is unable to
recognize the level of an earth leakage. In case of
simultaneously performing an earth leakage breaking
operation and an earth leakage indicating operation, it is
desirable to simplify a configuration as far as possible,
thereby saving costs.
In view of the above, the present invention provides
an earth leakage detection device capable of quickly
distinguishing an ordinary earth leakage from a lightning
surge.
In view of the above, the present invention provides
an earth leakage detection device capable of simultaneously
performing an earth leakage breaking operation and an earth
leakage indicating operation with a simple and cost-
effective configuration.
Summary of the Invention
In accordance with a first aspect of the present
invention, there is provided an earth leakage detection
device, including: a zero-phase current transformer through
which an AC cable run passes; an integration calculation
unit configured to integrate output voltage of the zero-
phase current transformer; an integrated value comparison
unit configured to, when a calculation result obtained by

the integration calculation unit is larger than a
predetermined range, output a first signal; a waveform
identification unit configured to detect and count
inflection points of an output voltage waveform of the zero-
phase current transformer and to, when the number of the
inflection points reaches a predetermined number, output a
second signal; and an earth leakage detection unit
configured to, when the first signal is outputted by the
integrated value comparison unit and when the second signal
is outputted by the waveform identification unit, output an
earth leakage detection signal indicating that an earth
leakage is occurring in the AC cable run.
Preferably, the waveform identification unit starts
detection of the inflection points from the time when the
output voltage of the zero-phase current transformer is a
positive voltage or a negative voltage.
Further, the integration calculation unit may obtain
an, effective value of the output voltage of the zero-phase
current transformer using integration calculation.
Furthermore, the integration calculation unit may
obtain an average value of the output voltage of the zero-
phase current transformer using integration calculation.
The waveform identification unit may include a pulse
generation unit configured to generate pulses based on the
output voltage waveform of the zero-phase current
transformer and a pulse< count unit configured to count the

number of the pulses generated by the pulse generation unit
and to, when the number of the pulses reaches a
predetermined number, output the second signal.
Preferably, the pulse generation unit generates the
pulses when the output voltage of the zero-phase current
transformer falls in a regime beyond a predetermined range.
Further, the pulse generation unit may generate the
pulses when the output voltage of the zero-phase current
transformer continues to fall in a regime beyond the
predetermined range for a predetermined time or longer.
The pulse generation unit may stop generation of the
pulses when the output voltage of the zero-phase current
transformer becomes lower than a predetermined voltage after
the start of generation of the pulses.
Preferably, the pulse generation unit stops generation
of the pulses when a predetermined time is lapsed from the
start of generation of the pulses.
Further, the pulse, generation unit may generate a
second pulse after a lapse of a predetermined time from the
generation time of a first pulse.
The pulse count unit may count the number of rising
edges of the pulses generated by the pulse generation unit
and output the second signal when the number of rising edges
of the pulses reaches a predetermined number.
Preferably, the pulse count unit counts the number of
the pulses generated by the pulse generation unit which have

a width equal to or larger than a predetermined width, and
outputs the second signal when the number of the pulses
reaches a predetermined number.
Further, the pulse count unit may count the number of
falling edges of the pulses generated by the pulse
generation unit and output the second signal when the number
of falling edges of the pulses reaches a predetermined
number.
Further, the pulse count unit may count a second pulse
after a lapse of a predetermined time from the time when a
first pulse generated by the pulse generation unit is
counted.
The waveform identification unit MAY include a count
value changing unit configured to, when a pulse output width
of a pulse generated by the pulse generation unit is equal
to or larger than a predetermined width, change a count
value to be counted by the pulse count unit.
Preferably, the pulse output width is a time width
from the output start time of the pulses generated by the
pulse generation unit to the output end time of the pulses.
Further, the pulse output width may be a time width
from the output start time of a first pulse generated by the
pulse generation unit to the output start time of a second
pulse ensuing the first pulse.
Further, the pulse output width may be a time width
from the output end time of a first pulse generated by the

pulse generation unit to the output end time of a second
pulse ensuing the first pulse.
Further, the pulse output width may be a time width
from the output start time of a first pulse generated by the
pulse generation unit to the output end time of a second
pulse.
The earth leakage detection device may further include:
a pulse generation condition changing unit configured to,
based on the count value counted by the pulse count unit,
change generation conditions of the pulses to be generated
by the pulse generation unit.
Preferably, the pulse generation condition changing
unit changes at least one of a voltage threshold value used
in determining whether the pulse generation unit generates
the pulses and a pulse width threshold value used in
determining whether the pulse count unit counts the pulses.
Further, the pulse generation unit may generate
positive pulses which are based on a positive output voltage
of the zero-phase current transformer and negative pulses
which are based on a negative output voltage of the zero-
phase current transformer, and the pulse count unit may
count the positive pulses and the negative pulses and output
the second signal when at least one of the number of the
positive pulses and the number of the negative pulses is
equal to or larger than a predetermined number.
Further, the earth leakage detection device may

include: a signal input unit configured to input a signal-
output instruction signal for causing the integrated value
comparison unit to output the first signal or for causing
the waveform identification unit to output the second
signal.
Preferably, the signal input unit is configured to
input the signal-output instruction signal from an external
resistor.
The earth leakage detection device may further include:
an integration unit for integrating the output voltage of
the zero-phase current transformer; and a calculation result
output unit configured to perform an output operation
pursuant to the calculation result obtained by the
integration unit, and the calculation result output unit and
the earth leakage detection unit may be provided as a single
module.
Preferably, the earth leakage detection unit uses the
integration unit as the integration calculation unit.
The integration unit may calculate an average value of
the output voltage of the zero-phase current transformer for
a time period longer than an averaging time period of the
integration calculation unit and integrates the average
value.
Preferably, the calculation result output unit outputs
a warning signal when the calculation result obtained by the
integration unit falls in a regime beyond a predetermined

range which is narrower than a range of a voltage threshold
value used in determining whether the first signal is to be
outputted by the integrated value comparison unit.
Further, the calculation result output unit may change
an output form of the warning signal depending on the
calculation result obtained by the integration unit.
The earth leakage detection device may further
include: a calculation result storage unit configured to
store the information on the calculation result obtained by
the integration unit for a predetermined time.
Further, the earth leakage detection device may
further include: an external terminal unit configured to
output the information on the calculation result stored in
the calculation result storage unit.
The earth leakage detection device may further
include: an information output unit configured to output the
information on the calculation result stored in the
calculation result storage unit to a storage medium.
The earth leakage detection device may further
include: an information sending unit configured to send the
information on the calculation result stored in the
calculation result storage unit to an external server.
In accordance with a second aspect of the present
invention, there is provided an earth leakage detection
device, including: a zero-phase current transformer through
which an AC cable run passes; a first integration

calculation unit configured to integrate output voltage of
the zero-phase current transformer; an earth leakage
detection unit configured to, based on a calculation result
obtained by the first integration calculation unit, output
an earth leakage detection signal indicating that an earth
leakage is occurring in the AC cable run; a second
integration calculation unit configured to integrate the
output voltage of the zero-phase current transformer; and a
calculation result output unit configured to perform an
output operation pursuant to a calculation result obtained
by the second integration calculation unit, wherein the
calculation result output unit and the earth leakage
detection unit are provided as a single module.
The earth leakage detection unit may use the second
integration calculation unit as the first integration
calculation unit.
Preferably, the second integration calculation unit
calculates an average value of the output voltage of the
zero-phase current transformer for a time period longer than
an averaging time period of the first integration
calculation unit and integrates the average value.
The earth leakage detection device may further
include: a calculation result storage unit configured to
store the information on the calculation result obtained by
the second integration calculation unit for a predetermined
time.

Further, the earth leakage detection device may
include: an external terminal unit configured to output the
information on the calculation result stored in the
calculation result storage unit.
Furthermore, the earth leakage detection device may
include: an information output unit configured to output the
information on the calculation result stored in the
calculation result storage unit to a storage medium.
The earth leakage detection device may include: an
information sending unit configured to send the information
on the calculation result stored in the calculation result
storage unit to an external server.
The earth leakage detection device may include: an
integrated value comparison unit configured to, when a
calculation result obtained by the first integration
calculation unit falls in a regime beyond a predetermined
range, output a first signal, wherein the calculation result
output unit may output a warning signal when the calculation
result obtained by the second integration calculation unit
falls in a regime beyond a predetermined range which is
narrower than a range of a voltage threshold value used in
determining whether the first signal is to be outputted by
the integrated value comparison unit.
Preferably, the calculation result output unit changes
an output form of the warning signal depending on the
calculation result obtained by the second integration

calculation unit.
The earth leakage detection device may further
include: an integrated value comparison unit configured to,
when a calculation result obtained by the first integration
calculation unit falls in a regime beyond a predetermined
range, output a first signal; and a waveform identification
unit configured to detect and count inflection points of an
output voltage waveform of the zero-phase current
transformer and to, when the number of the inflection points
reaches a predetermined number, output a second signal,
wherein the earth leakage detection unit may output the
earth leakage detection signal when the first signal is
outputted by the integrated value comparison unit and when
the second signal is outputted by the waveform
identification unit.
Preferably, the waveform identification unit starts
detection of the inflection points from the time when the
output voltage of the zero-phase current transformer is a
positive voltage or a negative voltage.
Further, the first integration calculation unit may
obtain an effective value of the output voltage of the zero-
phase current transformer using integration calculation.
Further, the first integration calculation unit may
obtain an average value of the output voltage of the zero-
phase current transformer using integration calculation.
The waveform identification unit may include a pulse

generation unit configured to generate pulses based on the
output voltage waveform of the zero-phase current
transformer and a pulse count unit configured to count the
number of the pulses generated by the pulse generation unit
and to, when the number of the pulses reaches a
predetermined number, output the second signal.
Preferably, the pulse generation unit generates the
pulses when the output voltage of the zero-phase current
transformer falls in a regime beyond a predetermined range.
Further, the pulse generation unit may generate the
pulses when the output voltage of the zero-phase current
transformer continues to fall in a regime beyond the
predetermined range for a predetermined time or longer.
Furthermore, the pulse generation unit may stop
generation of the pulses when the output voltage of the
zero-phase current transformer becomes lower than a
predetermined voltage after the start of generation of the
pulses.
Preferably, the pulse generation unit stops generation
of the pulses when a predetermined time is lapsed from the
start of generation of the pulses.
Further, the pulse generation unit may generate a
second pulse after a lapse of a predetermined time from the
generation time of a first pulse.
The pulse count unit may count the number of rising
edges of the pulses generated by the pulse generation unit

and outputs the second signal when the number of rising
edges of the pulses reaches a predetermined number.
Preferably, the pulse count unit counts the number of
the pulses, generated by the pulse generation unit, which
have a width equal to or larger than a predetermined width,
and outputs the second signal when the number of the pulses
reaches a predetermined number.
Further, the pulse count unit may count the number of
falling edges of the pulses generated by the pulse
generation unit and output the second signal when the number
of falling edges of the pulses reaches a predetermined
number.
The pulse count unit may count a second pulse after a
lapse of a predetermined time from the counting time of a
first pulse generated by the pulse generation unit.
Further, the waveform identification unit may include
a count value changing unit configured to, when a pulse
output width based on the pulses generated by the pulse
generation unit is equal to or larger than a predetermined
width, change a count value to be counted by the pulse count
unit.
: Preferably, the pulse output width is a time width
from the output start time of a pulse generated by the pulse
generation unit to the output end time of the pulse.
The pulse output width may be a time width from the
output start time of a first pulse generated by the pulse

generation unit to the output start time of a second pulse
subsequent to the first pulse.
Further, the pulse output width may be a time width
from the output end time of a first pulse generated by the
pulse generation unit to the output end time of a second
pulse subsequent to the first pulse.
Further, the pulse output width may be a time width
from the output start time of a first pulse generated by the
pulse generation unit to the output end time of a second
pulse.
The earth leakage detection device may further
include: a pulse generation condition changing unit
configured to, based on the count value counted by the pulse
count unit, change generation conditions of the pulses to be
generated by the pulse generation unit.
Preferably, the pulse generation condition changing
unit changes at least one of a voltage threshold value used
in determining whether the pulse generation unit generates
the pulses and a pulse width threshold value used in
determining whether the pulse count unit counts the pulses.
Further, the pulse generation unit may generate
positive pulses which are based on a positive output voltage
of the zero-phase current transformer and negative pulses
which are based on a negative output voltage of the zero-
phase current transformer, and the pulse count unit may
count the positive pulses and the negative pulses and output

the second signal when at least one of the number of the
positive pulses and the number of the negative pulses is
equal to or larger than a predetermined number.
The earth leakage detection device may further
include: a signal input unit configured to input a signal-
output instruction signal for causing the integrated value
comparison unit to output the first signal or for causing
the waveform identification unit to output the second
signal.
Further, the signal input unit may be configured to
input the signal-output instruction signal from an external
resistor.
Effect of the Invention
In the present invention, it is possible to quickly
distinguish an ordinary earth leakage and a lightning surge.
Brief Description of the Drawings
Objects and features of the present invention will
become more apparent "from the following description of
preferred embodiments given in conjunction with the
accompanying drawings.
Fig. 1 is a circuit block diagram showing a
configuration example of; an earth leakage detection device

in accordance with a first embodiment of the present
invention.
Fig. 2 is a circuit block diagram showing a detailed
configuration example of a waveform identification unit in
accordance with the first embodiment of the present
invention.
Fig. 3 is a time chart for explaining a first
operation example of the earth leakage detection device in
accordance with the first embodiment of the present
invention.
Fig. 4 is a time chart for explaining a second
operation example of the earth leakage detection device in
accordance with the first embodiment of the present
invention.
Fig. 5 is a time chart for explaining a third
operation example of the earth leakage detection device in
accordance with the first embodiment of the present
invention.
Fig. 6 is a time chart for explaining a fourth
operation example of the earth leakage detection device in
accordance with the first embodiment of the present
invention.
Fig. 7 is a time chart for explaining a fifth
operation example of the earth leakage detection device in
accordance with the first embodiment of the present
invention.

Fig. 8 is a circuit block diagram showing a detailed
configuration example of a waveform identification unit in
accordance with a second embodiment of the present
invention.
Fig. 9 is a time chart for explaining an operation
example of an earth leakage detection device in accordance
with the second embodiment of the present invention.
Fig. 10 is a circuit block diagram showing a detailed
configuration example of a waveform identification unit in
accordance with a third embodiment of the present invention.
Fig. 11 is a time chart for explaining an operation
example of an earth leakage detection device in accordance
with the third embodiment of the present invention.
Fig. 12 is a circuit block diagram showing a detailed
configuration example of a waveform identification unit in
accordance with a fourth embodiment of the present
invention.
Fig. 13 is a time chart for explaining an operation
example of an earth leakage detection device in accordance
with the fourth embodiment of the present invention.
Fig. 14 is a circuit block diagram showing a
configuration example of an earth leakage detection device
in accordance with a fifth embodiment of the present
invention.
Fig. 15 is a block diagram showing a first
configuration example of an earth leakage detection device

in accordance with a sixth embodiment of the present
invention.
Fig. 16 is a block diagram showing a second
configuration example of the earth leakage detection device
in accordance with the sixth embodiment of the present
invention.
Fig. 17 is a block diagram showing a third
configuration example of the earth leakage detection device
in accordance with the sixth embodiment of the present
invention.
Fig. 18 is a block diagram showing a fourth
configuration example of the earth leakage detection device
in accordance with the sixth embodiment of the present
invention.
Fig. 19 is a block diagram showing a fifth
configuration example of the earth leakage detection device
in accordance with the sixth embodiment of the present
invention.
Fig. 20 is a block diagram showing a sixth
configuration example of the earth leakage detection device
in accordance with the sixth embodiment of the present
invention.
Mode for Carrying out the Invention
Embodiments of the present invention will now be

described in detail with reference to the accompanying
drawings which form a part of the subject specification.
Throughout the drawings, identical or similar parts will be
designated by like reference symbols with no duplicate
description made thereon.
(First Embodiment)
Fig. 1 is a block diagram showing a configuration
example of an earth leakage detection device in accordance
with a first embodiment of the present invention. The earth
leakage detection device 100 shown in Fig. 1 includes a
zero-phase current transformer 10, an integration
calculation unit 20, an integrated value comparison unit 30,
a waveform identification unit 40 and an earth leakage
detection unit 50.
The zero-phase current transformer 10 includes a ring-
shaped iron core thro.ugh which a plurality of primary
conductors forming a part of a three-phase-current-flowing
AC cable run passes, the core made of a magnetic body such
as a soft magnetic material or the like, and a toroidally-
shaped coil wound around the core. In the zero-phase
current transformer 10, if a difference is generated between
an electric current flowing in an outgoing direction of the
AC cable run and an electric current flowing in an incoming
direction of the AC cable run, a leakage current
corresponding to the difference is generated.

An induced voltage corresponding to the leakage
current is generated across the coil. The zero-phase
current transformer 10 outputs the induced voltage to the
integration calculation unit 2 0 and the waveform
identification unit 40 as an output voltage of the zero-
phase current transformer 10, i.e., a ZCT output voltage.
While not shown in the drawings, a resistor element is
provided in parallel with the zero-phase current transformer
10 in order to obtain a voltage output from the zero-phase
current transformer 10.
The integration calculation unit 20 includes an
integration circuit or the like. The integration
calculation unit 20 integrates the ZCT output voltage and
outputs the integrated voltage to the integrated value
comparison unit 30 as an output voltage.
The integration calculation unit 20 may find an
effective value of the ZCT output voltage using integration
calculation. For example, the integration calculation unit
20 integrates square values of the ZCT output voltages for
one cycle, divides the integrated value by the time of one
cycle and finds a square root of the divided value. In this
case, it is possible to accurately detect the leakage
current, thereby improving the earth leakage detection
performance against a distorted wave.
The integration calculation unit 2 0 may find an
averaged ZCT output voltage using integration calculation.

For example, the integration calculation unit 20 integrates
absolute values of the ZCT output voltages for one cycle and
divides the integrated absolute values by the time of one
cycle, thus calculating an averaged absolute value. The
averaged absolute value is used for comparison in the
integrated value comparison unit 30. In this case, as
compared with the case where the effective value is found,
it is possible to reduce the calculation load and to form
the earth leakage detection device 100 in a cost-effective
manner.
The integrated value comparison unit 30 includes a
comparison circuit or the like. If the absolute value of
the integrated value resulting from the calculation in the
integration calculation unit 20 is equal to or larger than
an integrated value determining threshold value thl as a
predetermined value, the integrated value comparison unit 30
outputs a high (H) voltage to the earth leakage detection
unit 50 (see Fig. 3). In this regard, the integrated value
determining threshold value thl is an integer.
On the other hand, if the absolute value of the
integrated value is smaller than the integrated value
determining threshold value thl, the integrated value
comparison unit 30 outputs a voltage L to the earth leakage
detection unit 50. The fact that the output voltage of the
integrated value comparison unit 30 is a voltage H means
that the integrated value comparison unit 30 outputs a

specified signal (a first signal). The voltage H is higher
than the voltage L.
The waveform identification unit 4 0 detects and counts
the inflection points of a voltage waveform of the ZCT
output voltage. If the number of inflection points reaches
a predetermined number, the waveform identification unit 4 0
outputs a voltage H to the earth leakage detection unit 50.
On the other hand, if the number of inflection points does
not reach the predetermined number, the waveform
identification unit 40. outputs a voltage L to the earth
leakage detection unit 50. The fact that the output voltage
of the waveform identification unit 40 is a voltage H means
that the waveform identification unit 40 outputs a specified
signal (a second signal). The term "predetermined number"
used herein is, e.g., "2", "3", and so forth. The detailed
configuration of the waveform identification unit 40 will be
described later.
Regardless of whether the ZCT output voltage is a
positive voltage or a negative voltage, the waveform
identification unit 40 may start detecting the inflection
points. This makes it possible to perform the detection of
the inflection points at a high speed and to cut off the AC
cable run at a higher speed in the event of an ordinary
earth leakage.
The earth leakage detection unit 50 includes an AND
circuit or the like. If the output voltage of the

integrated value comparison unit 30 is a voltage H and if
the output voltage of the waveform identification unit 4 0 is
a voltage H, the earth leakage detection unit 50 outputs a
voltage H. The fact that the output voltage of the earth
leakage detection unit 50 is a voltage H means that the
earth leakage detection unit 50 outputs a leakage detection
signal indicating that an earth leakage is occurring in the
AC cable run. The leakage detection signal is a cutoff
signal for opening the contact points of the AC cable run
(for cutting off the AC cable run) and is transmitted to a
trip coil (not shown) that serves to open the contact points
of the AC cable run. As a result, the contact points of the
AC cable run are opened.
Next, description will be made on the detailed
configuration of the waveform identification unit 40. Fig.
2 is a block diagram showing a detailed configuration
example of the waveform identification unit 40. The
waveform identification unit 40 shown in Fig. 2 includes a
pulse generation unit 41 and a pulse count unit 42.
The pulse generation unit 41 includes a pulse
generation circuit or the like. The pulse generation unit
41 generates a pulse on the basis of the ZCT output voltage.
In the example shown in Fig. 3, a voltage maintained at a
predetermined voltage value (voltage H) for a short period
of time is outputted as a pulse.
The pulse count unit 42 includes a pulse counter or

the like. The pulse count unit 42 counts the number of
pulses generated by the pulse generation unit 41. If the
number of pulses reaches a predetermined number, the pulse
count unit 42 sets the output voltage as a voltage H and
outputs the aforementioned second signal. On the other
hand, if the number of pulses does not reach the
predetermined number, the pulse count unit 42 sets the
output voltage as a voltage L and does not output the
aforementioned second signal.
Next, description will be made on the operation of the
earth leakage detection device 100 in accordance with the
present embodiment. Fig. 3 is a time chart for explaining a
first operation example of the earth leakage detection
device 100 in accordance with the present embodiment.
In the example shown in Fig. 3, it is assumed that,
when the absolute value of the ZCT output voltage becomes
equal to or larger than a leakage current detecting
threshold value th2, the pulse generation unit 41 generates
a pulse having a narrow width. In this regard, the leakage
current detecting threshold value th2 is an integer. The
pulse generation operation of the pulse generation unit 41
corresponds to the detection of the inflection points of an
output voltage waveform. Accordingly, the earth leakage
detection device can operate at a desired leakage current
value without erroneously operating by a lightning surge.
This makes it possible to detect an earth leakage at a

higher speed.
On the other hand, while the absolute value of the ZCT
output voltage is smaller than the leakage current detecting
threshold value th2, the pulse generation unit 41 does not
generate a pulse. In this example, the pulses are counted
by the pulse count unit 42 at the rising edge of the pulses.
The "leakage current" in Fig. 3 presents the leakage
currents generated in the zero-phase current transformer 10
in the respective cases (in case of an ordinary earth
leakage and a lightning surge). As shown in Fig. 3, in case
of an ordinary earth leakage, there is generated a
periodical leakage current. . In case of a lightning surge,
there is generated a temporary leakage current having a
relatively large current value.
The "ZCT output vo'ltage" in Fig. 3 presents the output
voltages (ZCT output voltages) of the zero-phase current
transformer 10 corresponding to the leakage currents in the
respective cases.
The "pulse generation unit output" in Fig. 3 presents
the output voltages of the pulse generation unit 41 in the
respective cases. In the example shown in Fig. 3, during
the same period of time, three pulses are generated in case
of an ordinary earth leakage but two pulses are generated in
case of a lightning surge. Thus, a larger number of pulses
are generated in the ordinary earth leakage than in the
lightning surge.

The "counter" in Fig. 3 presents the count values held
by the pulse count unit 42 in the respective cases.
The "counter output" in Fig. 3 presents the output
voltages of the pulse count unit 42 in the respective cases.
In the example shown "in Fig. 3, when a third pulse is
generated, the output voltage of the pulse count unit 42
becomes a voltage H.
The "integration calculation output" in Fig. 3
presents the output voltages of the integration calculation
unit 20 in the respective cases.
The "integrated value comparison output" in Fig. 3
presents the output voltages of the integrated value
comparison unit 30 in the respective cases.
The "leakage detection signal output" in Fig. 3
presents the output voltages, of the earth leakage detection
unit 50 in the respective cases.
With the first operation example, it is possible to
quickly distinguish an ordinary earth leakage from a
lightning surge.
Fig. 4 is a time chart for explaining a second
operation example of the earth leakage detection device 100
in accordance with the present embodiment.
In the example shown in Fig. 4, it is assumed that, if
the absolute value of the ZCT output voltage continues to be
equal to or larger than the leakage current detecting
threshold value th2 for a predetermined time or longer, the

pulse generation unit 41 generates a pulse having a narrow
width. On the other hand, if the absolute value of the ZCT
output voltage is smaller than the leakage current detecting
threshold value th2 or if the absolute value of the ZCT
output voltage does not continue to be equal to or larger
than the leakage current detecting threshold value th2 for
the predetermined time tl or longer, the pulse generation
unit 41 does not generate pulses.
Since the absolute value of the ZCT output voltage
exceeding the threshold value th2 and the predetermined time
continuation thereof are taken into account as shown in Fig.
4, the "pulse generation unit output" is outputted at the
timing delayed for a predetermined time as compared with
Fig. 3. In the present embodiment, the pulse count unit 42
counts the pulses at the rising edges thereof. For that
reason, the timings of the "count", the "counter output" and
the "leakage detection signal output" are also delayed.
Accordingly, the earth leakage detection device can operate
at a desired leakage current value without erroneously
operating by a lightning surge. This makes it possible to
detect an earth leakage at a higher speed. Moreover, the
earth leakage detection device is strong against noises,
which improves the robustness of the earth leakage detection
device.
In Fig. 4, the "integration calculation output", the
"integrated value comparison output" and the "leakage

detection signal output" are omitted.
Fig. 5 is a time chart for explaining a third
operation example of the earth leakage detection device 100.
In the example shown in Fig. 5, it is assumed that the
pulse generation unit 41 stops generation of a pulse when
the absolute value of the ZCT output voltage becomes smaller
than a pulse stop determining threshold value th3 after
starting the generation of the pulse. Further, while the
absolute value of the ZCT output voltage is equal to or
larger than the pulse stop determining threshold value th3,
the pulse generation unit 41 continues to keep generating
the pulse. Herein, th2 is larger than th3 which in turn is
larger than 0.
As can be seen from the "pulse generation unit output"
shown in Fig. 5, one pulse is generated after the absolute
value of the ZCT output voltage becomes equal to or larger
than the leakage current detecting threshold value th2 and
before the absolute value of the ZCT output voltage becomes
smaller than the pulse stop determining threshold value th3.
In the present embodiment, the pulses are counted by the
pulse count unit 42 at the falling edge thereof. Therefore,
as compared with a case where the pulses are counted at the
rising edge thereof, the timings of the "count", "the
counter output" and the "leakage detection signal output"
are delayed.
In Fig. 5, the "integration calculation output", the

"integrated value comparison output" and the "leakage
detection signal output" are omitted.
In the present embodiment, a voltage is taken into
account in order to decide the pulse stop time. However, a
time may be taken into account in place of the voltage. For
example, as shown in Fig. 6 to be described later, the pulse
generation unit 41 may stop generation of a pulse after a
lapse of a predetermined time (width) t2 from the start of
generation of the pulse. In this method, noises do not
affect the earth leakage detection for a predetermined time
after the start of generation of the pulse.
Fig. 6 is a time chart for explaining a fourth
operation example of the earth leakage detection device 100
in accordance with the present embodiment.
In the example shown in Fig. 6, it is assumed that the
pulse generation unit 41 does not generate the next pulse
for a specified time after a pulse having a predetermined
width t2 is generated. In other words, it is assumed that
the pulse generation unit 41 does not generate a second
pulse until a specified time is lapsed from the time of
generation of a first pulse. In the example shown in Fig.
6, the pulse output mask period is applied to only the
ordinary earth leakage.
In the example shown in Fig. 6, a one-pulse generating
time period is included in the pulse output mask period as
the specified time. In this case, the second pulse to be

generated by the pulse generation unit 41 overlaps with the
pulse output mask period. Therefore, the second pulse is
generated after the end of the pulse output mask period.
Accordingly, the count value of the pulse count is counted
at a timing delayed by one pulse.
In the example of lightning surge shown in Fig. 6, it
is assumed that the pulse generation unit 41 generates a
first pulse and a second pulse with no output mask period
and further that the pulse count unit 42 counts pulses at
the falling edges thereof and holds counting the second
pulse until a specified time is lapsed from the counting
timing of the first pulse. In the example shown in Fig. 6,
the count mask period > is applied to only the lightning
surge.
In the example of lightning surge shown in Fig. 6, a
one-pulse counting timing is included in the count mask
period as the specified time. In this case, the second
pulse to be counted by the pulse count unit 42 overlaps with
the count mask period. Therefore, the second pulse is
counted after the end of the count mask period. Accordingly,
the count value of the:pulse count is counted at a timing
delayed by one pulse. ... Since the timing of the "count" is
delayed,. the timings of the "counter output" and the
"leakage detection signal output" are also delayed.
In Fig. 6, the integration calculation output", the
"integrated value comparison output" and the "leakage

detection signal output" are omitted.
By providing the pulse output mask period and/or the
count mask period of specified time, it is possible to
accurately generate or count pulses. In particular, it is
possible to prevent erroneous detection of a lightning surge
and to prevent an erroneous operation of the earth leakage
detection device 100. In the present embodiment, a one-
pulse generating time is included in the pulse output mask
period and a one-pulse counting timing is included in the
count mask period. Therefore, when the second pulse is
counted, the output voltage of the pulse count unit 42
becomes a voltage H.
Fig. 7 is a time chart for explaining a fifth
operation example of the earth leakage detection device 100
in accordance with the present embodiment.
In the example shown in Fig. 7, the pulse generation
unit 41 generates one pulse starting from the time when the
absolute value of the ZCT output voltage becomes equal to or
larger than the leakage current detecting threshold value
th2 till the time when the absolute value of the ZCT output
voltage becomes smaller than the leakage current detecting
threshold value th2. It is assumed that the pulse count
unit 42 counts pulses, generated by the pulse generation
unit 41, each of which has a pulse width (time width) equal
to or larger than a predetermined width A. That is, the
pulse count unit 42 does not count pulses having a pulse

width smaller than the predetermined width A.
In the present embodiment, the pulses are counted by
the pulse count unit 42 at the falling edge thereof.
Therefore, as compared with a case where the pulses are
counted at the rising edge thereof, the timings of the
"count", "the counter output" and the "leakage detection
signal output" are delayed.
In Fig. 7, the "integration calculation output", the
"integrated value comparison output" and the "leakage
detection signal output" are omitted. With this operation
example, it is possible to easily distinguish a lightning
surge from an ordinary earth leakage.
(Second Example)
The earth leakage detection device 100 in accordance
with the second embodiment is provided with a waveform
identification unit 40B shown in Fig. 8, in place of the
waveform identification unit 40 described in respect of the
first embodiment. In describing the earth leakage detection
device 100 of the present embodiment, the same
configurations as those of the earth leakage detection
device 100 described with regard to the first embodiment
will be designated by like reference symbols with no
description made thereon.
Fig. 8 is a block diagram showing a configuration
example of the waveform identification unit 40B • in

accordance with the second embodiment. The waveform
identification unit 40B shown in Fig. 8 includes a pulse
generation unit 41, a pulse count unit 42 and a count value
changing unit 43.
The count value changing unit 43 includes a control
circuit or the like. The count value changing unit 43
detects a pulse output width of a pulse generated by the
pulse generation unit 41. Depending on whether the pulse
output width is equal to or larger than a predetermined
width or the pulse output width is smaller than the
predetermined width, the count value changing unit 43
changes the count value of the pulse count unit 42. For
example, if the pulse output width is equal to or larger
than the predetermined width, the count value changing unit
43 may increase the count value by 1. If the pulse output
width is equal to or smaller than the predetermined width,
the count value changing unit 43 may reduce the count value
by 1.
In the present embodiment, the pulse generation unit
41 generates a pulse every an interval for which the
absolute value of the ZCT output voltage is equal to or
larger than the leakage current detecting threshold value
th2. The pulses are counted at the falling edges thereof.
The "pulse output width" may be one of those as follows (see
Fig. 9 to be described later).
(A) A time width Al from the output start time point

to the output end time point of a pulse PI as a first pulse
(In this case, a threshold value Tl is used).
(B) A time pulse A2 from the output start time point
of a pulse PI as a first pulse to the output start time
point of a pulse P2 as a second pulse ensuing the first
pulse (In this case, a threshold value T2 is used).
(C) A time width A3 from the output end time point of
the pulse PI to the output end time point of the pulse P2
(In this case, a threshold value T3 is used).
(D) A time width A 4 from the output start time point
of the pulse PI to the output end time point of the pulse P2
(In this case, a threshold value T4 is used).
Fig. 9 is a time chart for explaining an operation
example of the earth leakage detection device 100 in
accordance with the present embodiment.
In the example shown in Fig. 9, the "count" is
increased by 1 when the pulse output width A3 is equal to or
larger than the threshold value T3. Thus, it is possible to
flexibly set the timing at which the count value is changed.
Accordingly, by using one of the time widths Al to A4 as the
pulse output width, it is possible to prevent an erroneous
operation of the earth.leakage detection device 100 with no
delay in the operation time thereof.
In the example shown in Fig. 9, the pulse output width
A3 is larger than thet threshold value T3 in case of an
ordinary earth leakage. Therefore, at the falling edge of

the pulse P2, the count value is increased from 1 to 3. At
this time point, a voltage H is generated from the pulse
count unit 42.
In Fig. 9, the "integration calculation output", the
"integrated value comparison output" and the "leakage
detection signal output" are omitted.
(Third Embodiment)
The earth leakage detection device 100 in accordance
with the third embodiment is provided with a waveform
identification unit 40C shown in Fig. 10, in place of the
waveform identification unit 40 described in respect of the
first embodiment. In describing the earth leakage detection
device 100 of the present embodiment, the same
configurations as those of the earth leakage detection
device 100 described with regard to the first embodiment
will be designated by like reference symbols with no
description made thereon.
Fig. 10 is a block diagram showing a configuration
example of the waveform identification unit 40C in
accordance with the third embodiment. The waveform
identification unit 40C shown in Fig. 10 includes a pulse
generation unit 41, a pulse count unit 42 and a pulse
generation condition changing unit 44.
The pulse generation condition changing unit 44
includes a control circuit or the like. Depending on the

count value counted by the pulse count unit 42, the pulse
generation condition changing unit 44 changes the pulse
generation conditions of the pulse generation unit 41 and/or
the pulse count conditions of the pulse count unit 42. An
example of the pulse generation conditions includes a
voltage threshold value used in determining whether the
pulse generation unit 41 generates pulses or not. An
example of the pulse count conditions includes a pulse width
(time width) threshold value. The pulse generation
condition changing unit 44 changes at least one of the
voltage threshold value .(e.g., the "leakage current
detecting threshold value th2" described in respect of the
first embodiment) and the pulse width threshold value (e.g.,
the "predetermined width A" described in respect of the
first embodiment).
Fig. 11 is a time chart for explaining an operation
example of the earth leakage detection device 100 in
accordance with the present embodiment.
In the example shown in Fig. 11, the first and second
pulses are counted at the falling edges thereof if the pulse
width is larger than the predetermined width A. At the time
point at which the count value becomes "2", the pulse
generation condition changing unit 44 changes a time
threshold value used in determining generation of pulses by
the pulse count unit 42. In other words, as the pulse
generation condition changing unit 44 changes the time width

threshold value, the pulse generation unit 41 is changed to
instantaneous detection at the time point when the count
value is "2". Thus, the pulses are counted at the rising
edges thereof. Accordingly, it is possible to prevent an
erroneous operation of the earth leakage detection device
100 otherwise caused by a lightning surge. It is also
possible to cut off the AC cable run at a higher speed in
case of occurrence of an ordinary earth leakage.
In Fig. 11, the "integration calculation output", the
"integrated value comparison output" and the "leakage
detection signal output" are omitted.
(Fourth Embodiment)
The earth leakage detection device 100 in accordance
with the fourth embodiment is provided with a waveform
identification unit 40D shown in Fig. 12, in place of the
waveform identification unit 40 described in respect of the
first embodiment. In describing the earth leakage detection
device 100 of the present embodiment, the same
configurations as those of the earth leakage detection
device 100 described with regard to the first embodiment
will be designated by like reference symbols with no
description made thereon.
Fig. 12 is a block diagram showing a configuration
example of the waveform identification unit 40D in
accordance with the fourth embodiment. The waveform

identification unit 40D shown in Fig. 12 includes a positive
pulse generation unit 41A, a negative pulse generation unit
41B, a positive pulse count unit 42A and a negative pulse
count unit 42B.
The positive pulse generation unit 41A generates
positive pulses which are based on a positive ZCT output
voltage. The negative pulse generation unit 41B generates
negative pulses which are based on a negative ZCT output
voltage. The conditions for generating the positive pulses
or the negative pulses based on the ZCT output voltage are
the same as described above.
The positive pulse count unit 42A counts the positive
pulses. If the count number is equal to or larger than a
predetermined number, the positive pulse count unit 42A
outputs a second signal by allowing the output voltage to
become a voltage H. The negative pulse count unit 42B
counts the negative pulses. If the count number is equal to
or larger than a predetermined number, the negative pulse
count unit 42B outputs a second signal by allowing the
output voltage to become a voltage H. Accordingly, the
second signal is outputted if at least one of the positive
pulse number and the negative pulse number is equal to or
larger than the predetermined number. The conditions for
counting- the positive pulses or the negative pulses are the
same as set forth above.
Fig. 13 is a time chart for explaining an operation

example of the earth leakage detection device 100 in
accordance with the present embodiment.
The "positive pulse generation unit output" in Fig. 13
indicates the output voltages of the positive pulse
generation unit 41A in the respective cases. In the example
shown in Fig. 13, during the same period of time, two
positive pulses are generated in case of an ordinary earth
leakage but one positive pulse is generated in case of a
lightning surge. Thus, a larger number of positive pulses
are generated in the ordinary earth leakage than in the
lightning surge.
The "positive count" in Fig. 13 indicates the count
values held by the positive pulse count unit 42A in the
respective cases.
The "negative pulse generation unit output" in Fig. 13
indicates the output voltages of the negative pulse
generation unit 41B in the respective cases. In the example
shown in Fig. 13, during the same period of time, one
negative pulse is generated in case of an ordinary earth
leakage and one negative pulse is generated even in case of
a lightning surge.
The "negative count" in Fig. 13 indicates the count
values held by the negative pulse count unit 42B in the
respective cases.
The "counter output" in Fig. 13 indicates the outputs
reflecting the positive counters and the negative counters.

In the example shown in Fig. 13, if at least one of the
positive pulse count unit 42A and the negative pulse count
unit 42B counts two or more pulses, the output voltage of
the counter output becomes a voltage H. Therefore, in the
example shown in Fig. 13, the counter output becomes a
voltage H only in case of the ordinary earth leakage. While
not shown in the drawings, the outputs of the positive pulse
count unit 42A and the negative pulse count unit 42B are
outputted to the earth leakage output unit 50 through an OR
gate.
In Fig. 13, the "integration calculation output", the
"integrated value comparison output" and the "leakage
detection signal output" are omitted.
If the pulse generation operation and the pulse
counting operation are performed by distinguishing the
positive side and the negative side of the ZCT output
voltage as stated above, it is possible to easily detect a
half-wave earth leakage.
(Fifth Embodiment)
Fig. 14 is a block diagram showing one configuration
example of an earth leakage detection device E in accordance
with a fifth embodiment of the present invention. The earth
leakage detection device lOOE includes a zero-phase current
transformer 10, an integration calculation unit 20, an
integrated value comparison unit 30, a waveform

identification unit 40, an earth leakage detection unit 50E
and a plurality of logic operation units as an integrated
circuit. While a first logic operation unit 60 and a second
logic operation unit 70 are provided as the plurality of
logic operation units . in the illustrated example, the
present invention is not limited thereto. Instead of the
waveform identification unit 40, it may be possible to use
the waveform identification units 40B to 40D described
earlier. In describing the earth leakage detection device
100E of the present embodiment, the same configurations as
those of the earth leakage detection devices 100 described
with regard to the first to fourth embodiments will be
designated by like reference symbols with no description
made thereon.
The first logic operation unit 60 and the second logic
operation unit 7 0 serve as signal input units that input
signal-output instruction signals. The signal-output
instruction signals cause the output voltage of the
integrated value comparison unit 30 to become a voltage H
(namely, for causing the integrated value comparison unit 30
to output a first signal) and cause the output voltage of
the waveform identification unit 40 to become a voltage H
(namely, for causing the waveform identification unit 40 to
output a second signal). Accordingly, the algorithms
described in respect of the first to fourth embodiments can
be changed by the logic operation units. In other words,

pursuant to the signal supplied from the outside, the first
logic operation unit 60 and the second logic operation unit
7 0 output the first and the second signal to the earth
leakage detection unit 50E regardless of the outputs of the
integrated value comparison unit 30 and the waveform
identification unit 40, respectively.
The first logic operation unit 60 includes an OR
circuit : or the like. The first logic operation unit 60
outputs a voltage H if at least one of the output voltage of
the integrated value comparison unit 30 and the output
voltage of the external circuit unit is a voltage H.
The second logic operation unit 7 0 includes an OR
circuit or the like. The second logic operation unit 70
outputs a voltage H if at least one of the output voltage of
the waveform identification unit 40 and the output voltage
of the external circuit unit is a voltage H.
As the external circuit units of the first logic
operation unit 60 and the second logic operation unit 70, it
is conceivable to use a low-capacity chip resistor. The
chip resistors are connected to the input pins of the first
logic operation unit 60 and the second logic operation unit
70. Accordingly, it is possible to form a circuit including
the external circuit unit in a cost-effective manner. Thus,
the signal-output instruction signal may be inputted from
the external resistor.
The earth, leakage detection unit 50E includes an AND

circuit or the like. If the output voltage of the first
logic operation unit 60 is a voltage H and if the output
voltage of the second logic operation unit 70 is a voltage
H, the earth leakage detection unit 50E outputs a voltage H.
The fact that the output voltage of the earth leakage
detection unit 50E is a voltage H means that there is
outputted a leakage detection signal indicating that an
earth leakage is occurring in the AC cable run. The leakage
detection signal is a cutoff signal for opening the contact
points of the AC cable run (for cutting off the AC cable
run) and is transmitted to; a trip coil (not shown) that
serves to open the contact points of the AC cable run. As a
result, the contact points of the AC cable run are opened.
With the earth leakage detection device 100E of the
present embodiment described above, the output voltage of
the external circuit unit connected to the first logic
operation unit 60 being a voltage H is equivalent to the
output voltage of the integrated value comparison unit 30 of
the first to fourth embodiments being a voltage H at all
times. It is therefore possible to nullify the function of
the integrated value comparison unit 30.
Similarly, the output voltage of the external circuit
unit connected to the second logic operation unit 7 0 being a
voltage H is equivalent to the output voltage of the
waveform identification unit 40 (one of the waveform
identification units 40, 40B, 40C and 40D) of the first to

fourth embodiments being a voltage H at all times. It is
therefore possible to nullify the function of the waveform
identification unit 40. In other words, the function of one
of the integrated value comparison unit 30 and the waveform
identification unit 40 can be nullified using the external
circuit unit.
While some of the functions of the earth leakage
detection device 100E are nullified using the first logic
operation unit 60 and the second logic operation unit 7 0 in
the present embodiment, it may be possible not to use the
logic operation units. For example, it may be possible to
employ a configuration in which an external device not shown
inputs a change signal for changing each of the threshold
values such as the voltage threshold value and the time
threshold value of at least one of the integration
calculation unit 20, the integrated value comparison unit 30
and the waveform identification unit 40 or a change signal
for changing the count value. In case of changing, e.g.,
each of the threshold values, it may be possible to make the
change such that the measured voltage or the measured time
exceeds each of the threshold values at all times. It may
also be possible to change the count value to, e.g., a value
exceeding the count threshold value at all times. With this
configuration, it is equally possible to nullify some of the
functions of the earth leakage detection device 100E.

(Sixth Embodiment)
Fig. 15 is a block diagram showing a configuration
example of an earth leakage detection device 100F in
accordance with a sixth embodiment of the present invention.
The earth leakage detection device 100F of the present
embodiment includes a zero-phase current transformer 10, a
first system (a leakage level detection unit 80) having the
function of the earth leakage detection device 100 or 100E
of the first to fifth embodiments excluding the zero-phase
current transformer 10. Further, the earth leakage
detection device 100F of the present embodiment includes a
second system for integrating the output voltage of the
zero-phase current transformer 10 (the ZCT output voltage)
and for performing an output operation in accordance with
the result of integration. The first system realizes a
function associated with the earth leakage cutoff. The
second system realizes a function of notifying a user of the
leakage amount (the leakage current value).
The leakage level detection unit 80 as the first
system includes the integration calculation unit 20, the
integrated value comparison unit 30, the waveform
identification unit 40 and the earth leakage detection unit
50, all of which are described above. Among them, the
leakage level detection unit 80 includes at least the
integration calculation unit 20 and the earth leakage
detection unit 50. In case where the leakage level

detection unit 80 includes only the integration calculation
unit 20 and the earth leakage detection unit 50, the earth
leakage detection unit 50 outputs a leakage detection signal
on the basis of the calculation result in the integration
calculation unit 20.
The second system includes an integration unit 91 and
a calculation result output unit 92. The integration unit
91 serves to integrate . the ZCT output voltage and has the
same configuration as the integration calculation unit 20
described earlier. The calculation result output unit 92
performs an output operation pursuant to the calculation
result (the integrated value) of the integration unit 91.
The calculation result output unit 92 outputs different
kinds of information through a display, a speaker or the
like not shown in the drawings. In the present embodiment,
for example, an effective value of the ZCT output voltage
calculated by the integration calculation described earlier
(an effective value calculation result) or an averaged ZCT
output voltage calculated by the integration calculation (an
average value calculation result) is outputted as the
calculation result.
In the present embodiment, the respective component
parts of the first system and the second system are formed
within a single integrated circuit (a single module). By
forming the earth leakage detection device 100F as one and
the same package in this manner, it is possible to reduce

the costs. In other words, it is possible to simultaneously
perform the leakage cutoff operation and the leakage
indication operation with a simple and cost-effective
configuration.
As shown in Fig. 16, an integration unit 91 may be
used as the integration calculation unit 20 described in
respect of the first embodiment. In other words, the
leakage level detection unit 80 may not be provided with the
integration calculation unit 20, and the output of the
integration unit 91 may. be inputted to the integrated value
comparison unit 30. If the configurations for integration
are used in common as described above, it is possible to
reduce the costs. Since the hardware such as the
integration circuit and so forth is used in common, the
integration does not depend on the difference in hardware
and the calculation method for integration. For that
reason, no error is generated in the level detection value
for leakage detection and in the indication value for
indication of the degree of earth leakage. It is therefore
possible to make adjustment so that contradiction should not
occur between the level detection value and the indication
value.
The calculation result output unit 92 may be
configured to output a value (average value) obtained by
averaging the integrated value calculated by the integration
unit 91. The integrated value comparison unit 30 may be

configured to compare a value (average value) obtained by
averaging the integrated value calculated in the integration
calculation unit 20 with a predetermined value (the
integrated value determining threshold value thl) . The
average value is, e.g., a time average value.
At this time, it is preferred that the averaging
duration in the calculation result output unit 92 is set
longer than the averaging duration in the integrated value
comparison unit 30. The integration unit 91 may calculate
an averaged ZCT output voltage by averaging the ZCT output
voltages for a time period longer than the averaging time
period of the integration calculation unit 2 0 and may obtain
an integrated value by integrating the average value. This
makes it possible to accurately output the integrated value
(corresponding to the leakage current value) without being
affected by the variation of the ZCT output voltages caused
due to the noises such as a surge voltage and the like.
While the average value is used in the present
embodiment, it may be possible to use the effective value in
place of the average value.
The calculation result output unit 92 may output a
warning signal (an alarm) if the absolute value of the
calculation result (integrated value) of the integration
unit 91 is larger than .a threshold value th4 which in turn
is smaller than the leakage current detecting threshold
value th2 for detection of earth leakage in the leakage

level detection unit 80 (where th2>th4>0). The warning
signal referred to here.in may be a warning in the form of
voice information or a warning in the form of display
information. In other words, the calculation result output
unit 92 may output the warning signal if the calculation
result in the integration unit 91 is larger than the
threshold value th2 used in determining whether the first
signal is to be outputted by the integrated value comparison
unit 30. This enables a user to recognize the state of an
earth leakage prior to detecting the earth leakage large
enough to cut off the AC cable run.
Depending on the calculation result from the
integration unit 91, the calculation result output unit 92
may change the output, form when outputting the warning
signal. In this case, for example, an LED may be turned on
if the absolute value of the calculation result from the
integration unit 91 exceeds 50% of the absolute value of the
leakage current detecting threshold value th2 and a warning
sound may be outputted if the absolute value of the
calculation result of the integration unit 91 exceeds 80% of
the absolute value of the leakage current detecting
threshold value th2. This makes it possible to accurately
notify the degree (level) of urgency of earth leakage
cutoff. Thus, it is possible to avoid a situation that the
earth leakage cutoff is unexpectedly performed.
As shown in Fig.. 17, the earth leakage detection

device 100F may be provided with a calculation result
storage unit 93 for storing the calculation results of the
integration unit 91. The calculation result storage unit 93
stores, e.g., the information on the calculation results
obtained for a predetermined time (such as one week) . In
this case, after the specified time is lapsed, new
information may be overwritten to update the existing
information. The information on the calculation results is
the integrated value (or the effective value or the average
value) of the ZCT output voltage, and so forth. By storing
the calculation results obtained for a predetermined time
until earth leakage cutoff, it becomes easy to specify the
cause of earth leakage cutoff.
As shown in Fig. 18, the earth leakage detection
device 100F may be provided with an external terminal unit
94 through which the information on the calculation results
of the integration unit 91 or the information on the
calculation results of the calculation result storage unit
93 can be outputted. The external terminal unit 94 is,
e.g., a Universal Serial Bus (USB) or the like. By
providing the external terminal unit 94, it becomes possible
to easily output the information on the calculation results
and it becomes easy to specify the cause of earth leakage
cutoff.
As shown in Fig. 19, the earth leakage detection
device 100F may be provided with an information output unit

95 through which the information on the calculation results
of the integration unit 91 or the information on the
calculation results of the calculation result storage unit
93 can be outputted to a storage medium. The storage medium
is, e.g., a USB memory, a secure digital (SD) card or the
like. By outputting, e:g., the calculation results obtained
for a predetermined time until earth leakage cutoff to the
storage medium, it becomes easy to carry data and to specify
the cause of earth leakage cutoff.
As. shown in Fig. 20, the earth leakage detection
device 100F may be provided with an information sending unit
96 for sending the information on the calculation results of
the integration unit 91 or the information on the
calculation results of the calculation result storage unit
93 to an external server. By sending, e.g., the calculation
results obtained for a predetermined time until earth
leakage cutoff to the external server, it is possible to
easily grasp the earth * leakage situation even in a remote
center and it becomes easy to specify the cause of earth
leakage cutoff.
All the embodiments, explanation examples and modified
examples described above may-be used in combination. While
certain preferred embodiments of the present invention have
been described above, the present invention is not limited
to these specific embodiments but can be changed or modified
in many different forms without departing from the scope of

the claims. Such changes or modifications fall within the
scope of the present invention.

WE CLAIM:
1. An earth leakage detection device, comprising:
a zero-phase current transformer through which an AC
cable run passes;
an integration calculation unit configured to integrate
output voltage of the zero-phase current transformer;
an integrated value comparison unit configured to, when
a calculation result obtained by the integration calculation
unit is larger than a predetermined range, output a first
signal;
a waveform identification unit configured to detect and
count inflection points of an output voltage waveform of the
zero-phase current transformer and to, when the number of
the inflection points reaches a predetermined number, output
a second signal; and
an earth leakage detection unit configured to, when the
first signal is outputted by the integrated value comparison
unit and when the second signal is outputted by the waveform
identification unit, output an earth leakage detection
signal indicating that an earth leakage is occurring in the
AC cable run.
2. The earth leakage detection device of claim 1, wherein
the waveform identification unit starts detection of the
inflection points from the time when the output voltage of

the zero-phase current transformer is a positive voltage or
a negative voltage.
3. The earth leakage detection device of claim 1 or 2,
wherein the integration calculation unit obtains an
effective value of the output voltage of the zero-phase
current transformer using integration calculation.
4. The earth leakage detection device of claim 1 or 2,
wherein the integration calculation unit obtains an average
value of the output voltage of the zero-phase current
transformer using integration calculation.
5. The earth leakage detection device of any one of claims
1 to 4, wherein the waveform identification unit includes a
pulse generation unit configured to generate pulses based on
the output voltage waveform of the zero-phase current
transformer and a pulse count unit configured to count the
number of the pulses generated by the pulse generation unit
and to, when the number of the pulses reaches a
predetermined number, output the second signal.
6. The earth leakage detection device of claim 5, wherein
the pulse generation unit generates the pulses when the
output voltage of the zero-phase current transformer falls
in a regime beyond a predetermined range.

7. The earth leakage detection device of claim 6, wherein
the pulse generation unit generates the pulses when the
output voltage of the zero-phase current transformer
continues to fall in a regime beyond the predetermined range
for a predetermined time or longer.
8. The earth leakage detection device of any one of claims
5 to 7, wherein the pulse generation unit stops generation
of the pulses when the output voltage of the zero-phase
current transformer becomes lower than a predetermined
voltage after the start of generation of the pulses.
9. The earth leakage detection device of any one of claims
5 to 7, wherein the pulse generation unit stops generation
of the pulses when a predetermined time is lapsed from the
start of generation of the pulses.
10. The earth leakage detection device of any one of claims
5 to 9, wherein the pulse generation unit generates a second
pulse after a lapse of a predetermined time from the
generation time of a first pulse.
11. The earth leakage detection device of any one of claims
5 to 10, wherein the pulse count unit counts the number of
rising edges of the pulses generated by the pulse generation

unit and outputs the second signal when the number of rising
edges of the pulses reaches a predetermined number.
12. The earth leakage detection device of any one of claims
5 to 10, wherein the pulse count unit counts the number of
the pulses generated by the pulse generation unit which have
a width equal to or larger than a predetermined width, and
outputs the second signal when the number of the pulses
reaches a predetermined number.
13. The earth leakage detection device of any one of claims
5 to 10, wherein the pulse count unit counts the number of
falling edges of the pulses generated by the pulse
generation unit and outputs the second signal when the
number of falling edges of the pulses reaches a
predetermined number.
14. The earth leakage detection device of any one of claims
5 to 13, wherein the pulse count unit counts a second pulse
after a lapse of a predetermined time from the time when a
first pulse generated by the pulse generation unit is
counted.
15. The earth leakage detection device of any one of claims
5 to 14, wherein the waveform identification unit includes a
count value changing unit configured to, when a pulse output

width of a pulse generated by the pulse generation unit is
equal to or larger than a predetermined width, change a
count value to be counted by the pulse count unit.
16. The earth leakage detection device of claim 15, wherein
the pulse output width is a time width from the output start
time of the pulses generated by the pulse generation unit to
the output end time of the pulses.
17. The earth leakage detection device of claim 15, wherein
the pulse output width is a time width from the output start
time of a first pulse generated by the pulse generation unit
to the output start time of a second pulse ensuing the first
pulse.
18. The earth leakage detection device of claim 15, wherein
the pulse output width is a time width from the output end
time of a first pulse generated by the pulse generation unit
to the output end time of a second pulse ensuing the first
pulse.
19. The earth leakage detection device of claim 15, wherein
the pulse output width is a time width from the output start
time of a first pulse generated by the pulse generation unit
to the output end time of a second pulse.

20. The earth leakage detection device of any one of claims
5 to 19, further comprising:
a pulse generation condition changing unit configured
to, based on the count value counted by the pulse count
unit, change generation conditions of the pulses to be
generated by the pulse generation unit.
21. The earth leakage detection device of claim 20, wherein
the pulse generation condition changing unit changes at
least one of a voltage threshold value used in determining
whether the pulse generation unit generates the pulses and a
pulse width threshold value used in determining whether the
pulse count unit counts the pulses.
22. The earth leakage detection device of any one of claims
5 to 21, wherein the pulse generation unit generates
positive pulses which are based on a positive output voltage
of the zero-phase current transformer and negative pulses
which are based on a negative output voltage of the zero-
phase current transformer, and wherein the pulse count unit
counts the positive pulses and the negative pulses and
outputs the second signal when at least one of the number of
the positive pulses and the number of the negative pulses is
equal to or larger than a predetermined number.
23. The earth leakage detection device of any one of claims

5 to 22, further comprising:
a signal input unit configured to input a signal-output
instruction signal for causing the integrated value
comparison unit to output the first signal or for causing
the waveform identification unit to output the second
signal.
24. The earth leakage detection device of claim 23, wherein
the signal input unit is configured to input the signal-
output instruction signal from an external resistor.
25. The earth leakage detection device of any one of claims
1 to 24, further comprising:
an integration unit for integrating the output voltage
of the zero-phase current transformer; and
a calculation result output unit configured to perform
an output operation pursuant to the calculation result
obtained by the integration unit,
wherein the calculation result output unit and the
earth leakage detection unit are provided as a single
module.
26. The earth leakage detection device of claim 25, wherein
the earth leakage detection unit uses the integration unit
as the integration calculation unit.

27. The earth leakage detection device of claim 25 or 26,
wherein the integration unit calculates an average value of
the output voltage of the zero-phase current transformer for
a time period longer than an averaging time period of the
integration calculation unit and integrates the average
value.
28. The earth leakage detection device of any one of claims
25 to 27, wherein the calculation result output unit outputs
a warning signal when the calculation result obtained by the
integration unit falls in a regime beyond a predetermined
range which is narrower' than a range of a voltage threshold
value used in determining whether the first signal is to be
outputted by the integrated value comparison unit.
29. The earth leakage detection device of claim 28, wherein
the calculation result output unit changes an output form of
the warning signal depending on the calculation result
obtained by the integration unit.
30. The earth leakage detection device of any one of claims
25 to 29, further comprising:
a calculation result storage unit configured to store
the information on the calculation result obtained by the
integration unit for a predetermined time.

31. The earth leakage detection device of claim 30, further
comprising:
an external terminal unit configured to output the
information on the calculation result stored in the
calculation result storage unit.
32. The earth leakage detection device of claim 30, further
comprising:
an information output unit configured to output the
information on the calculation result stored in the
calculation result storage unit to a storage medium.
33. The earth leakage detection device of claim 30, further
comprising:
an information sending unit configured to send the
information on the calculation result stored in the
calculation result storage unit to an external server.
34. An earth leakage detection device, comprising:
a zero-phase current transformer through which an AC
cable run passes;
a first integration calculation unit configured to
integrate output voltage of the zero-phase current
transformer;
an earth leakage detection unit configured to, based on
a calculation result obtained by the first integration

calculation unit, output an earth leakage detection signal
indicating that an earth leakage is occurring in the AC
cable run;
a second integration calculation unit configured to
integrate the output voltage of the zero-phase current
transformer; and
a calculation result output unit configured to perform
an output operation pursuant to a calculation result
obtained by the second integration calculation unit,
wherein the calculation result output unit and the
earth leakage detection unit are provided as a single
module.
35. The earth leakage detection device of claim 34, wherein
the earth leakage detection unit uses the second integration
calculation unit as the first integration calculation unit.
36. The earth leakage detection device of claim 34 or 35,
wherein the second integration calculation unit calculates
an average value of the output voltage of the zero-phase
current transformer for a time period longer than an
averaging time period of the first integration calculation
unit and integrates the average value.
37. The- earth leakage detection device of any one of claims
34 to 36, further comprising:

a calculation result storage unit configured to store
the information on the calculation result obtained by the
second integration calculation unit for a predetermined
time.
38. The earth leakage detection device of claim 37, further
comprising:
an external terminal unit configured to output the
information on the calculation result stored in the
calculation result storage unit.
39. The earth leakage detection device of claim 37, further
comprising:
an information output unit configured to output the
information on the calculation result stored in the
calculation result storage unit to a storage medium.
40. The earth leakage detection device of claim 37, further
comprising:
an information sending unit configured to send the
information on the calculation result stored in the
calculation result storage unit to an external server.
41. The earth leakage detection device of any one of claims
34 to 36, further comprising:
an integrated value comparison unit configured to, when

a calculation result obtained by the first integration
calculation unit falls in a regime beyond a predetermined
range, output a first signal,
wherein the calculation result output unit outputs a
warning signal when the calculation result obtained by the
second integration calculation unit falls in a regime beyond
a predetermined range which is narrower than a range of a
voltage threshold value used in determining whether the
first signal is to be outputted by the integrated value
comparison unit.
42. The earth leakage detection device of claim 41, wherein
the calculation result output unit changes an output form of
the warning signal depending on the calculation result
obtained by the second integration calculation unit.
43. The earth leakage detection device of any one of claims
34 to 42, further comprising:
an integrated value comparison unit configured to, when
a calculation result obtained by the first integration
calculation unit falls in a regime beyond a predetermined
range, output a first signal; and
a waveform identification unit configured to detect and
count inflection points of an output voltage waveform of the
zero-phase current transformer and to, when the number of
the inflection points reaches a predetermined number, output

a second signal,
wherein the earth leakage detection unit outputs the
earth leakage detection signal when the first signal is
outputted by the integrated value comparison unit and when
the second signal is outputted by the waveform
identification unit.
44. The earth leakage detection device of claim 43, wherein
the waveform identification unit starts detection of the
inflection points from the time when the output voltage of
the zero-phase current transformer is a positive voltage or
a negative voltage.
45. The earth leakage detection device of claim 43 or 44,
wherein the first integration calculation unit obtains an
effective value of the output voltage of the zero-phase
current transformer using integration calculation.
46. The earth leakage detection device of claim 43 or 44,
wherein the first integration calculation unit obtains an
average value of the output voltage of the zero-phase
current transformer using integration calculation.
47. The earth leakage detection device of any one of claims
43 to 46, wherein the waveform identification unit includes
a pulse generation unit configured to generate pulses based

on the output voltage waveform of the zero-phase current
transformer and a pulse count unit configured to count the
number of the pulses generated by the pulse generation unit
and to, when the number of the pulses reaches a
predetermined number, output the second signal.
48. The earth leakage detection device of claim 47, wherein
the pulse generation unit generates the pulses when the
output voltage of the zero-phase current transformer falls
in a regime beyond a predetermined range.
49. The earth leakage detection device of claim 48, wherein
the pulse generation unit generates the pulses when the
output voltage of the zero-phase current transformer
continues to fall in a regime beyond the predetermined range
for a predetermined time or longer.
50. The earth leakage detection device of any one of claims
47 to 49, wherein the pulse generation unit stops generation
of the pulses when the output voltage of the zero-phase
current transformer becomes lower than a predetermined
voltage after the start of generation of the pulses.
51. The earth leakage detection device of any one of claims
47 to 49, wherein the pulse generation unit stops generation
of the pulses when a predetermined time is lapsed from the

start of generation of the pulses.
52. The earth leakage detection device of any one of claims
47 to 51, wherein the pulse generation unit generates a
second pulse after a lapse of a predetermined time from the
generation time of a first pulse.
53. The earth leakage detection device of any one of claims
47 to 52, wherein the pulse count unit counts the number of
rising edges of the pulses generated by the pulse generation
unit and outputs the second signal when the number of rising
edges of the pulses reaches a predetermined number.
54. The earth leakage detection device of any one of claims
47 to 52, wherein the pulse count unit counts the number of
the pulses, generated by the pulse generation unit, which
have a width equal to or larger than a predetermined width,
and outputs the second signal when the number of the pulses
reaches a predetermined number.
55. The earth leakage detection device of any one of claims
47 to 52, wherein the pulse count unit counts the number of
falling edges of the pulses generated by the pulse
generation unit and outputs the second signal when the
number of falling edges of the pulses reaches a
predetermined number.

56. The earth leakage detection device of any one of claims
47 to 55, wherein the pulse count unit counts a second pulse
after a lapse of a predetermined time from the counting time
of a first pulse generated by the pulse generation unit.
57. The earth leakage detection device of any one of claims
47 to 56, wherein the waveform identification unit includes
a count value changing unit configured to, when a pulse
output width based on the pulses generated by the pulse
generation unit is equal to or larger than a predetermined
width, change a count value to be counted by the pulse count
unit.
58. The earth leakage detection device of claim 57, wherein
the pulse output width is a time width from the output start
time of a pulse generated by the pulse generation unit to
the output end time of the pulse.
59. The earth leakage detection device of claim 57, wherein
the pulse output width is a time width from the output start
time of a first pulse generated by the pulse generation unit
to the output start time of a second pulse subsequent to the
first pulse.
60. The earth leakage detection device of claim 57, wherein

the pulse output width is a time width from the output end
time of a first pulse generated by the pulse generation unit
to the output end time of a second pulse subsequent to the
first pulse.
61. The earth leakage detection device of claim 57, wherein
the pulse output width is a time width from the output start
time of a first pulse generated by the pulse generation unit
to the output end time of a second pulse.
62 . The earth leakage detection device of any one of claims
47 to 61, further comprising:
a pulse generation condition changing unit configured
to, based on the count value counted by the pulse count
unit, change generation conditions of the pulses to be
generated by the pulse generation unit.
63. The earth leakage detection device of claim 62, wherein
the pulse generation condition changing unit changes at
least one of a voltage threshold value used in determining
whether the pulse generation unit generates the pulses and a
pulse width threshold value used in determining whether the
pulse count unit counts the pulses.
64. The earth leakage detection device of any one of claims
47 to 63, wherein the pulse generation unit generates

positive pulses which are based on a positive output voltage
of the zero-phase current transformer and negative pulses
which are based on a negative output voltage of the zero-
phase current transformer, and wherein the pulse count unit
counts the positive pulses and the negative pulses and
outputs the second signal when at least one of the number of
the positive pulses and the number of the negative pulses is
equal to or larger than a predetermined number.
65. The earth leakage detection device of any one of claims
47 to 64, further comprising:
a signal input unit configured to input a signal-output
instruction signal for causing the integrated value
comparison unit to output the first signal or for causing
the waveform identification unit to output the second
signal.
66. The earth leakage detection device of claim 65, wherein
the signal input unit is configured to input the signal-
output instruction signal from an external resistor.