FIELD OF INVENTION
The present disclosure relates generally to the field of power control systems. In particular,
the present disclosure pertains to a simplified four wire Low Tension Auto Changeover
system and especially relates to the circuit arrangement of changing automatically from
standby each other power supply.
BACKGROUND ART
The low-voltage distribution system, adopt the operational mode of double loop
power supply inlet wire sectionalized single busbar connection to be in the great
majority, by two lead-in circuit breaker, give two sections bus I, II power
supplies respectively with two sections buses connect by bus-tie circuit breaker.
For improving the power supply reliability of this distribution system, require
under the situation of one road power supply dead electricity or fault, the bar
coupler that closes is given the dead electricity bussed supply by normal power
source.
At present duplicate supply is automatically switch to control two kinds of
schemes are arranged, a kind of is voltage relay and the other is time relay.
There is a discrete element such as auxiliary relay forms a control circuit. The
shortcoming of this scheme is that the circuit components are many, there is
wiring complexity which brings the reliability of control circuit to reduce.
Another kind of controlling schemes is to use the supporting duplicate supply
automatic switchover controller of part switch producer to. control, the
shortcoming of this scheme is the cost involved, volume is big, difficulty in
installation, versatility is also poor, and the product of a brand can only be
supporting with the switch of same producer.

For the VIP premises of CESC, which are being fed by an underground supply
system, use to had a single source of electricity in the form of a Distribution
transformer. Whenever there used to be any power outage either due to LT
fusing/fault or even a HT Feeder outage, the power supply used to get affected.
It used to take nearly an hour time to restore supply due to LT fusing and in
case of a HT fault the only respite was to send an operating engineer to operate
the feeder controlling Ring Main Unit for HT source changeover. This again
was a time-consuming affair and restoration time was not less than 2 hours.
In order to take care of the aforesaid problem and in line with our endeavor for
offering better customer service especially to the VVIPs, a lot of brainstorming
was done to finally arrive at a feasible and cost-effective solution. An auto LT
changeover system was conceived of, where in a standby UG service cable was
laid in the same premise and a second source was made available for auto
changeover through a device in case of any power outage.
There is, therefore a need in the art to provide a simple, efficient and a cost
effective device to automatically control switching of a plurality of pumps.
Further, there exists a need to automate the process of switching of pumps in
case of power failure of one of the power sources of the pumps to ensure
continuous operation of a required number of pumps.
SUMMARY OF INVENTION
The present invention provides a kind of quick automatic change-over switching
for solving the technical problem that exists in the known technology.
The technical scheme that the present invention takes for the technical problem
that exists in the solution known technology is: it includes two three pole power
contactor, coil voltage-230V AC, with 2 NO + 2 NC contact that link together
by mechanical interlock mechanism quick automatic change-over switch, an

A.C. contactor connects power supply commonly used and is used for
connection and disjunction power supply commonly used, another A.C.
contactor connects stand-by power supply and is used for connecting and the
disjunction stand-by power supply, it also includes a delay timer with 2 C/O,
aux. voltage-230V AC and two locking press buttons, the actuation coil of
described timer with after the actuation coil of the described A.C. contactor that
connects power supply commonly used is in parallel by connecting power
supply commonly used behind the described locking press button. The
described actuation coil that connects the A.C. contactor of stand-by power
supply is connected the back by connecting stand-by power supply behind
described another locking press button with the normally-closed contact of
described timer.
Therefore such as herein described there is provided a low-tension network
three-phase four-wire power supply switch device; comprises of. a control
cabinet, a earth leakage circuit-breaker, a plurality of LHD's indicating the
connected supply line, at least two 3 pole power contactor, coil voltage-230V
AC, with 2 NO+2 NC contact, a delay timer with 2 C/O, aux. voltage-230V AC,
a plurality of push button with NC / NO contact blocks, characterized in that
the sais three pole power contactor, are link together by mechanical interlock
mechanism quick automatic change-over switch wherein one A.C. contactor
connects power supply commonly used and is used for connection and
disjunction power supply commonly used, another A.C. contactor connects
stand-by power supply and is used for connecting and the disjunction stand-by
power supply and the actuation coil of said timer activates any of said A.C.
contactor which in turn connects the power supply commonly used is in parallel
by connecting power supply behind the said locking press button.
Described mechanical interlock mechanism is the mechanical interlock
mechanism that has two normally-closed contacts. The series circuit of the

actuation coil of the described A.C. contactor that connects power supply
commonly used and a normally-closed contact series connection of described
mechanical interlock mechanism with after the actuation coil of described
auxiliary relay is in parallel again by connecting power supply commonly used
behind the locking press button. The actuation coil of the described A.C.
contactor that connects stand-by power supply with connect stand-by power
supply after another normally-closed contact of the normally-closed contact of
described auxiliary relay, described mechanical interlock mechanism and
described another locking press button are connected.
Advantage and good effect that the present invention has are: because the
present invention has adopted electrical interlock and mechanical interlocking
duplicate protection, can dually avoid the two-way power supply to power
simultaneously, produce phase fault. Conversion speed is fast, and only be
controlled by timer setting the change-over time of two A.C. contactors. No
electromagnetism electronic jamming produces, and cost performance is high,
cost be on the market automatic change-over 1/3 ~ 1/2.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig 1 (a) illustrates the panel box with the LED display in accordance with the
present invention;
Fig 1 (b) illustrates the panel box with the LED display (open view) in
accordance with the present invention;
Fig 2 illustrates the circuit diagram for the control of the automatic changeover
in accordance with the present invention;
DETAILED DESCRIPTION
In pursuit with the constant endeavor to achieve excellence, it had been a
fruitful journey so far, for the "Mains department" of CESC Ltd. for being able

to innovate various processes and products as detailed below and create a
Centre of Excellence known as "LT Fault Management Centre" which acts as
a driving force behind this Excellence Journey.
There is a lot of Process Innovation which happened during last three years and
each of it, when stringed to form a bead, creates a Framework of Innovative
Process, which calls for protecting the Intellectual Proper Rights for CESC Ltd.
A) LT Auto Changeover System
Challenges:
» Providing Uninterrupted Power Supply.
» Economize the solution.
Changed Practice:
» Installation of an additional service cable being fed from a separate •
Distribution Transformer which in turn is fed by a different High-Tension
feeder
» Installation of the changeover module at the commencement of service
cable.
» In case of fault/fusing/HT feeder outage supply is automatically changed
over to the spare feed.
Advantage:
» Un-interrupted Power Supply
» Customer satisfaction
» Decrease in SAIDI

Auto Changeover Specification:
General Features: The panels are to be fabricated out of 2.0 mm sheet steel,
standing / wall mounted type suitable for being front operated. The panels
should be totally covered for being dust, damp and vermin proof.
Solution to be made into sections such that as far as feasible, there is no mixing
of control, power, the AC functions in the same section and they are sufficiently
segregated except where their bunching are required.
Arrangement preferably double leaf for access for routine inspection from the
rear and single leaf hinged door to be provided in the front. All indication
lamps, instruments etc. are to be flushed in the front door. The degree of
protection is required IP-42 conforming to IS: 2147.
i) Labeling: All internal components are to provide with suitable
identification labels suitably engraved. Labels are to be fixed on buttons,
indication lamps etc.
ii) Painting: The entire panels to is to be applied with powder coated paints
with minimum 7 tanks process before assembly of various items.
ii) Equipment requirements: The control cubical is to be incorporated into
assembling general equipment and systems as under:
a) Control system equipment and components such as relays, contactors,
timers, etc. both for automatic operation on main supply failure and as well as
for manual operation.
b) Necessary LED type indication lamps, fuses, terminal blocks, push
buttons, control switches etc., as required.
iii) System Operation: The above-mentioned facilities are to be provided to
afford the following operational requirements.

The disclosed schema includes two three pole power contactor, coil voltage-
230V ACv ac, with 2 NO + 2 NC contact that link together by mechanical
interlock mechanism quick automatic change-over switch, an A.C. contactor
connects power supply commonly used and is used for connection and
disjunction power supply commonly used, another A.C. contactor connects
stand-by power supply and is used for connecting and the disjunction stand-by
power supply, it also includes a delay timer with 2 C/O, aux. voltage-230V AC
and two locking press buttons, the actuation coil of described timer with after
the actuation coil of the described A.C. contactor that connects power supply
commonly used is in parallel by connecting power supply commonly used
behind the described locking press button. The described actuation coil that
connects the A.C. contactor of stand-by power supply is connected by
connecting stand-by power supply behind described another locking press
button with the normally-closed contact of described timer.
The present invention can also adopt following technical measures:
Described mechanical interlock mechanism is the mechanical interlock
mechanism that has two normally-closed contacts. The series circuit of the
actuation coil of the described A.C. contactor that connects power supply
commonly used and a normally-closed contact series connection of described
mechanical interlock mechanism with after the actuation coil of described
auxiliary relay is in parallel again by connecting power supply commonly used
behind the locking press button. The actuation coil of the described A.C.
contactor that connects stand-by power supply with connect stand-by power
supply after another normally-closed contact of the normally-closed contact of
described auxiliary relay, described mechanical interlock mechanism and
described another locking press button are connected.

Auto Mode:
a) A line voltage monitor shall monitor supply voltage on each phase. When
the mains supply voltage fails completely or falls below set value (variable
between 60 to 80% of the normal value) on any phase then main supply
contactor to open & standby supply contactor shall close and connect the load
automatically. The load is now on standby supply.
b) When the main supply is restored and is healthy as sensed by the line
voltage monitor setting, both for under voltage and unbalance, the system shall
be monitored by a suitable timer which can be set between 1 minute to 10
minutes for the load to be transferred automatically to main supply.
Manual Mode:
a) In a manual mode, it shall be feasible to start the contactor by the
operator on pressing the start push button.
b) The main & standby contactor closing and trip operations shall also be
through operator only by pressing the appropriate button on the panel.
SCOPE
This Section covers the detailed requirements of medium voltage switch Panel
for 430V, 3 phase 50 Hz 4 wire system. These shall be branded and/or
assembled/fabricated from a factory of repute. All switchgears are to be fully
rated at an ambient of 500 C.
TYPE OF PANEL
The medium voltage switch board panel shall comprise of the following types
of switchgears or combination thereof as specified.
• MCCBs of suitable ICs ratings as per BOQ.

• MCCBs shall invariably be Current Limiting type. Features like Thermal
magnetic as specified in BOQ, Double Break, and Positive Isolation functions
shall be preferred.
Cabling
a) Over heating due to loose thimbling/undersize cables causes most of
electrical failures and hence correct size of cable and thimbles should always be
used, if cable is specified.
b) While terminating cables, avoid any tension on the bolts/bus bars, (if
cable is specified) While terminating R,Y, & B phase notations should be
maintained in the power system and control panel for easy maintenance.
c) For control application, multi-core 1.5 sq.mm. flexible stranded copper
cables for control cabling are to be used.
After the installation, if there is any power outage due to any LT/MT fault in the
main source, the supply gets automatically changed over to the standby source
through the newly installed device and once the repair work is done in the main
feeder/source, the supply would again go back to the original source
automatically.
Thus, the consumer would effectively experience no power outage except in
case of 33kV or other EHT faults. Based on the performance of this system, we
have replicated this in the houses of many VVIP's and in LT vital installations
like Hospital etc


Although the foregoing description of the present invention has been shown and
described with reference to particular, embodiments and applications thereof, it
has been presented for purposes of illustration and description and is not
intended to be exhaustive or to limit the invention to the particular embodiments
and applications disclosed. It will be apparent to those having ordinary skill in
the art that a number of changes, modifications, variations, or alterations to the
invention as described herein may be made, none of which depart from the spirit
or scope of the present invention. The particular embodiments and applications
were chosen and described to provide the best illustration of the principles of
the invention and its practical application to thereby enable one of ordinary skill
in the art to utilize the invention in various embodiments and with various
modifications as are suited to the particular use contemplated. All such changes,
modifications, variations, and alteration should therefore be seen as being
within the scope of the present invention as determined by the appended claims
when interpreted in accordance with the breadth to which they are fairly,
legally, and equitably entitled.

CLAIMS
1. A low-tension network three-phase four-wire power supply switch
device; comprises of
a control cabinet including connection panel;
a earth leakage circuit-breaker;
a plurality of LED's indicating the connected supply line;
at least two 3 pole power contactor, coil voltage-230V AC, with 2 NO+2
NC contact;
a delay timer with 2 C/O, aux. voltage-230V AC,
a plurality of push button with NC / NO contact blocks;
a plurality of fuse base with 2 A HRC link;
characterized in that the sais three pole power contactor, are link together
by copper cables by mechanical interlock mechanism quick automatic
change-over switch wherein one A.C. contactor connects power supply
commonly used and is used for connection and disjunction power supply
commonly used, another A.C. contactor connects stand-by power supply
and is used for connecting and the disjunction stand-by power supply;
and
the actuation coil of said timer activates any of said A.C. contactor which
in turn connects the power supply commonly used is in parallel by
connecting power supply behind the said locking press button.
2. The low-tension network three-phase four-wire power supply
switch device as claimed in claim 1, wherein the said actuation coil that

connects the A.C. contactor of stand-by power supply is connected back
by connecting stand-by power supply behind said another locking press
button with the normally-closed contact of said timer.
The low-tension network three-phase four-wire power supply
switch device as claimed in claim 1, wherein multi-core 1.5 sq.mm.
flexible stranded copper cables for control cabling.
The low-tension network three-phase four-wire power supply
switch device as claimed in claim 1, wherein the panel includes MCCBs
of current limiting with double break and positive isolation functions are
employed.
The low-tension network three-phase four-wire power supply
switch device as claimed in claim 1,.includes manual closing and trip
operations through operator only by pressing the push button on the
panel.
The low-tension network three-phase four-wire power supply
switch device as claimed in claim 1, wherein the said timer is configured
to set between 1 minute to 10 minutes for the load to be transferred
automatically to main supply.