FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A system and a method for monitoring surges in a power transmission line
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Word", (Vfumbai - 400 030, Maharashtra, India, an Indian Company
INVENTORS
Satadal Dash, of Crompton Greaves Limited, S4 Division, Switchgear Complex, A-3 Ambad, Nasik, Maharashtra, India, an Indian National
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
This invention relates to a system and a method for monitoring surges in a power transmission line.
BACKGROUND OF THE INVENTION
It is known in the art to shield systems and equipment from high voltage surges by placing, specialized devices tike "surge arrestor units" as close as practical to the system being protected, to shunt the current produced during surges. Surge arresters units are installed over the transmission towers to shunt the large amounts of current generated during surges at the point of surge entering into the system.
Surge arresters units are generally made of semiconductor materials which have non¬linear resistance characteristics. They exhibit a high resistance below a certain voltage and conduct rapidly above it. Such a feature allows thenfl to heavily conduct when a surge occurs (high voltage that appears across a surge arrestor unit) and remain non-conductive otherwise. Over a period of time, the characteristic non-linear resistance deteriorates by some factor. The operation of the surge arrester units becomes unpredictable due to such degradation and as a result the surge current is not effectively shunted. Failure of surge arrestor units in shunting the surge current may result in power transmission breakdown. Therefore it is desirable to monitor the "health" of surge arrestor units, so that they are replaced in time to avert a transmission breakdown. The present invention discloses a system and a method in which surge arrestor units are remotely monitored for surge currents shunted during surges. Surge information corresponding to surge current shunted by surge arrestor units are recorded and monitored continuously. Such a record can be used for timely

replacement of degraded surge arrester, thereby preventing a power transmission
breakdown.
Some techniques known in the art and their drawbacks are presented in the sited patent literature as below.
Chinese Patent Application 1467897 discloses electrified wire wireless data monitoring control equipment for monitoring power consumption in a three phase supply system to a monitoring control center. However such equipment may not be useful for monitoring transient electrical bursts (surges) of signals in a power transmission line as current/voltage involved in surges is significantly high.
US Patent No. 6452373 describes a voltage transient recorder system to detect lightning induced transient voltage. The system records the voltage magnitude and time of arrival when it crosses a predetermined level. The said prior an is similar to the present invention in detecting the surge and recording it. However, in using such a voltage transient recorder system an operator would have to monitor every surge arrestor unit by traveling to each transmission tower located over distance inspecting each of them physically.
OBJECTS OF THE INVENTION
An object of this invention is to provide a system to monitor for surges in power transmission lines.

Another object of this invention is to provide a method to monitor surges in power transmission lines
DETAILED DESCRIPTION OF THE INVENTION
According to the invention there is provided a method to monitor surges in power transmission line comprising of a plurality of transmission towers and a surge arrestor unit associated with each of the transmission towers, the method comprising
following steps:
(i) attenuating the surge current in respective surge arrester units and generating a
signal proportional to the surge current at the occurrence of a surge; (ji} digitizing said attenuated signal; (iii) mixing said digitized attenuated signal with surge arrester unit identification
to form a composite signal ; (iv) modulating said composite signal on a carrier signal to form a surge
information signal and transmitting the surge information signal ; (v) demodulating said surge information signal to recover said composite signal ; (vi) processing said composite signal to recover said digitized attenuated signal
and said surge arrester unit identification;
(vii) comparing said digitized attenuated signal with a reference value to
measure the intensity of the surge; and (viii) . maintaining a record of the intensity of surge along with associated
surge arrester unit identification in respect of each of the surge arrestor units.
According to invention there is also provided a system for monitoring surges in power

transmission line is provided said system a plurality of remote signal transmitter units, each one of the remote signal transmitter units being connected across a surge arrestor unit associated with a transmission tower to generate a surge information signal for ever occurrence of a surge and transmit it; and a base unit for receiving said
surge information signals from all of said plurality of remote signal transmitter units and processing them to recover surge information relating to respective surge arrestor unit; and a recording unit for maintaining a record of surge information as received from said base unit for all said surge information signals.
In a preferred embodiment the remote signal transmitter unit comprises of a signal attenuator unit to generate an attenuated signal proportional to surge current generated at the respective surge arrester unit; and a analog to digital converter to receive said attenuated signal and to generate a digitized attenuated signal; and a summing circuit to mix the said digitized attenuated signal with surge arrester unit identification to generate a composite signal; and a modulating unit to modulate said composite signal on a carrier signal to form said surge information signal.
In the same preferred embodiment as described above, the base unit comprises of a demodulating unit to isolate said composite signal from said surge information signal and process the isolated composite signal to derive said digitized attenuated signal and said surge arrester unit identification; and a comparator unit to compare said digitized attenuated signal with a reference value and provide intensity of the surge.
The following is a detailed description of the invention with reference to the accompanying drawings, in which:

Figure 1 is a diagram of showing a portion of a power transmission system according to an aspect of the present invention.
Figure 2 is a block diagram for a system for monitoring surges according to an aspect of the present invention.
In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements.
Figure 1 depicts a portion of a power transmission system comprising of power transmission towers 1, 2 and 3, remote signal transmitting units 110,120 and 130, a substation housing base unit 140 and recording unit 150. Each of power transmission towers 1, 2 and 3 is shown connected to surge arrestor units 10, 20, 30. Signal transmitter units ] 10,120,130 are connected across surge arrestor units 10, 20 and 30. The manner in which health of a surge arrestor can be monitored is explained in detail with reference to Figure 2.
Figure 2 illustrates the manner in which information regarding surge arrestor unit 10 is.transmitted by signal transmitting unit 110, received at base unit 140 and is recorded by recording unit 150. Signal transmitting unit 110 is shown to comprising of signal attenuator unit 21, A/D converter 22, summing circuit 23, non-volatile memory unit 25, modulating unit 24. Base unit 140 is shown comprising of demodulating unit 26, comparator unit 27.

A very high surge current (in the order of kilo-amperes) is known to pass through a surge arrestor whenever surges occur. Signal attenuator unit 25, is a specialized circuitry that receives the high surge current and generates a proportional amount of current (in the order of mA). A/D converter 22 digitizes the current generated by the signal aUciwator unit 25. Non-volatile memory unit 25 provides a digital data representing the surge arrestor unit. Each surge arrestor in the power transmission system has a digital code associated with it. Non-volatile memory unit 25 can additionally provide the date and time for every occurring surge. Summing circuit 23 mixes the information as received from A/D converter 22 and the non-volatile memory 25 to generate a composite signal. Modulating unit 24, modulates the composite signal on a high frequency carrier signal and transmits it to the substation.
Base unit 140, located at the substation receives the modulated composite signal. Demodulating unit 26 demodulates modulated composite signal and processes the composite signal to obtain the digitized attenuated signal and digital code corresponding to the surge arrestor unit and the date and time of the surge.
Comparator unit 27 compares the digitized attenuated signal to a reference value to obtain measure the intensity of the surge. The recording unit 150 receives the data as processed by the base unit 140 and stores the data related for every signal transmitted from the remote transmitting units. Such data as recorded by the recording unit 150 can be displayed on a display unit like a monitor or a CRT. An operator at the substation can monitor such a data and take a pre-emptive measure of replacing a surge arrestor which is de-graded due to multiple number of high intensity surges,

thus averting a power transmission breakdown. Signal transmitting units 120,130 function similar to the signal transmitting unit 1 10.

We Claim
1. A system for monitoring surges in a power transmission line, the system
comprising:
a plurality of remote signal transmitter units, each one of the remote signal
transmitter units being connected across a surge arrestor unit associated with a
transmission tower to generate and transmit a surge information signal for every
occurrence of a surge ; and
a base unit for receiving all surge information signals from all of said plurality of
remote signal transmitter units and processing the said surge information signals to
recover surge information related to respective surge arrestor units; and
a recording unit for maintaining a record of surge information as received from said
base unit related to all said surge information signals.
2. A system of claim 1, wherein each of said remote signal transmitter units comprises
of
a signal attenuator unit to generate an attenuated signal proportional to surge
current generated at the respective surge arrester unit; and
an analog to digital converter to receive said attenuated signal and to generate
a digitized attenuated signal; and
a summing circuit to mix the said digitized attenuated signal with the
respective surge arrester unit identification to generate a composite signal; ^ i
&J1U
a modulating unit to modulate said composite signal on a carrier signal to form said surge information signal; and wherein said base unit comprises of

a demodulating unit to isolate said composite signal from said surge
information signal and process the isolated composite signal to derive said
digitized attenuated signal and said surge arrester unit identification ; and
a comparator unit to compare said digitized attenuated signal with a reference
value and provide intensity of the surge; and
wherein said recording unit comprises of
a display unit to display said surge arrestor unit identification and intensity of
the surge; and
a printer unit to print the data as displayed on said display unit.
3, A system of claim 2, wherein said surge arrester unit identification comprises of
digital data representing
the surge arrester unit; and
a date and the time of the occurrence of surge.
4. A method to monitor surges in power transmission line comprising of a plurality of
transmission towers and a surge arrestor unit associated with each of the transmission
towers, the method comprising:
(]) attenuating the surge current in respective surge arrester units and generating a signal proportional to the surge current at the occurrence of a surge;
(ii) digitizing said attenuated signal;
(iii) mixing said digitized attenuated signal with surge arrester unit identification to form a composite signal ;
(iv) modulating said composite signal on a carrier signal to form a surge information signal and transmitting the surge information signal :

(v) demodulating said surge information signal to recover said composite signal; (vi) processing said composite signal to recover said digitized attenuated signal
and said surge arrester unit identification;
(vii) comparing said digitized attenuated signal with a reference value to
measure the intensity of the surge; and
(viii) maintaining a record of the intensity of surge along with associated
surge arrester unit identification in respect of each of the surge arrester units.