FORM 2
THE PATENTS ACT, 1970
(39 of 1970) &
THE PATENTS RULES, 2003 COMPLETE SPECIFICATION
[See section 10, Rule 13]
AN INNOVATIVE SYSTEM FOR PROTECTION OF SWITCHGEAR FROM SINGLE PHASING & WELDING IN ELECTRICAL LIFE TESTING;
LARSEN & TOUBRO LIMITED, A COMPANY INCORPORATED UNDER THE COMPANIES ACT, 1956, WHOSE ADDRESS IS L&T HOUSE, BALLARD ESTATE, MUMBAI - 400 001, MAHARASHTRA, INDIA
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.

Field of the Invention
The present invention relates generally to circuit arrangement for finding out fault. More particularly, circuit arrangement for finding out fault such as single phase & welding in test unit and provide more safety to electrical load, electrical circuit and its elements.
Background of the invention
Conventional test methods commonly detect failures such as knob damage, no continuity across poles & mechanism failure etc by physical observation. But failures like contact bouncing, contact damage, contact momentarily closing, contact welding, instant tripping, delatching are not detectable. Further when switchgear test unit is put on endurance test then, if any failures like single phasing & contact welding occurs, then also the test unit keeps on running continuously.
In case of welding, electrical load & electrical test circuit may get damage due to the continuous flow of current & in case of single phasing, we cannot detect the fault until & unless we check it manually, for that we have to observe each & every circuit manually after some

interval. With this the end user will never be able to track the actual number of operations & the type of failure that may occur. Figure 1 shows the conventional test circuit.
Thus, there is a need to overcome the problems of the prior art.
Summary of the Invention
An aspect of the present invention is to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below.
Accordingly, an aspect of the present invention is an improved system for tracking failure in test unit that would provide accurate data of performance & test failure. A system for tracking failure like single phase and welding in a test unit, the system comprising a MCCB connected to the R, Y, B phases, a Backup contactor having the R, Y, B, phases connected through the MCCB contacts respectively, a test unit 1 and a test unit 2, each of these receiving R, Y , B phases at three phase inputs lines through the backup contactor, a three phase electrical load receiving R, Y, B phases at its one end and forming star point at the other end of the three phase. Contactors K1, K2, K3 connected across the R, Y, B phases respectively and the secondary of

the coil of the contactors is star pointed and connected to the star point of the load, contactor K4, having its coil connected serially through the contact of contactor K1, contactor K2, contactor K3 to the power supply, contactor K5, having its coil connected parallelly through the contact of contactor K1, contactor K2, contactor K3 to the power supply,
Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.
Brief description of the drawings
The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:
Figure 1 shows conventional setup (Prior Art)
Figure 2. shows an improved system for detecting failures in circuit breakers providing accurate performance of a system under test.
Figure 3. illustrates a series circuit for detecting single phasing

Figure 4 illustrates a PLC ladder diagram for single phasing
Figure5 illustrates a parallel circuit for detecting welding
Figure 6 illustrate a PLC ladder diagram for welding
Figure 7 illustrate the flow chart of the testing method
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.
Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.
Detail description of the Invention
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that

understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
Accordingly in the present invention there is provided an improved system for tracking failure like Single Phasing & Welding circuit. For avoiding the limitations of the conventional setup as shown in fig. 1, an additional circuit is added across the load as shown in fig. 2.
K1(9), K2(10), K3(11) contactors are added across the R(1), Y(2), B(3) phases respectively and the secondary of the coil of

contactor K1(9),K2(10),K3(11) are star pointed & connected to the star point of load.
As per an embodiment of the present invention depicted in the figure 2 the system for tracking failure like single phase and welding in a test unit, the system comprising a MCCB(4) connected to the R(1), Y(2), B(3) phases, a Backup contactor(5) having R(1),Y(2),B(3) phases connected through the MCCB(4) contacts respectively, a test unit 1(6) and a test unit 2(7), each of these receiving R(1), Y(2) , B(3) phases at three phase inputs lines through the backup contactor(5), a three phase electrical load(8) receiving R(1), Y(2), B(3) phases at its one end of test contactor and forming star point at the other end, three phase contactor K1(9), K2(10), K3(11) connected across the R(1), Y(2), B(3) phases respectively and the secondary of the coil of the contactors star pointed and connected to the star point of the load.
The figure 3 illustrates yet another aspect of the present invention wherein a series circuit for detecting single phasing is depicted. The figure shows circuit placement of the contactor K4(15). Contactor K4(15) having its coil connected serially through the contact of contactor K1(12), contact of contactor K2(13), contact of contactor K3(14) to the power supply(16).

The figure 5 illustrates yet another aspect of the present invention. The figure shows circuit placement of the contactor K5(17). Contactor K5(17), having its coil connected parallelly through the contact of contactor K1(12), contact of contactor K2(13), contact of contactor K3(14)to the power supply(16).
The figure 4 illustrate a PLC ladder diagram for single phasing detection. As per the one aspect of the embodiment of the present invention a counter(20) is used as a detecting element. The counter receives PLC input(19) at its input. The counter structured to adopt necessary trigger sensitivity wherein the reset of the counter gets asserted on operation of contactor K4(15) and contacts of the counter(18) gets operated to stop the test(test off(21)) on saturation of the counter to a set value.
The figure 6 illustrate a PLC ladder diagram for welding which depicts contactor K5(17), Test unit contact (22) and PLC o/p 001(23). As per the one aspect of the embodiment of the present invention a delay timer(25) is used as a detecting element. The delay timer, wherein the contacts of the delay timer(25) get signal when contact of PLC o/p001 (24) gets operated.

The PLC control the test cycle wherein determination of faults is through the operating status of the contactor K4(15) and contactor K5(17).
As per one of the embodiment of the present invention the method for tracking failure like single phase and welding in a test unit, the method comprising steps of initializing and verifying mains voltage; initializing the test by applying sequence to close MCCB(4) and Backup contactor(5) and test units((6) & (7)); determination of faults through the operating status of the contactor K4(15) and contactor K5(17); generation of stop test command to PLC; termination of test through PLC; finalization of test result for the units under test;
The figure 7 illustrate the detailed flow chart of the method for tracking failure like single phase and welding in a test unit. The method is initiated by switching on the power supply to provide the three phase input. As per another step the three phase input mains voltage are verified and if no accurate required voltage found the fault at mains source shall be rectified. Further to the availability of the accurate source voltage the test sequence is started. The test sequence is applied to the contactors for their closure. The fault detection may be performed based on the observed conditions such as if continuous supply in main contacts is observed the fault may be identified as welding wherein the contactor K5(17) operates or if main contacts gets

opened the fault may be termed as single phasing wherein the contactor K4(15) operates. The test is terminated on detection of the fault and the final result is concluded.
As per one of the embodiment of the present invention the circuit functionality is explain herewith:
After starting the test, MCCB(4) gets closed then Backup contactor(5) will get closed, after that the test unit will get closed & circuit gets completed because of supply flowing through the circuit, the fault detecting contactors K1(9),K2(10),K3(11) will get operate with test unit, if SINGLE PHASING occurs in test unit then one, two or all the phases of test unit may get opened. Because of single phasing the main circuit will not get completed and the fault detecting contactors K1(9),K2(10),K3(11)will miss their regular operation. As shown in fig. 3, if any of the contactors K1(9),K2(10),K3(11) will not operate the circuit will not get completed & contactor K4(15) will not operate, hence as shown in fig 4,as the contactor K4(15) is not operating the value of the counter keeps on increasing and when the counter value becomes equal to set value (i.e. SV=2) of the counter, then the contacts of the counter gets operated and before any major damage occurs in main circuit the PLC will stop the test. If WELDING occurs in test unit then one, two or all the phases of test unit may get welded. Because of welding, the supply continuously flows through the main circuit and also

through the fault detecting contactors. As continuous supply is flowing through the contactors K1(9),K2(10),K3(11) operates continuously. As shown in fig. 5 if any of the contacts ((12), (13), (14)of contactors K1(9),K2(10),K3(11) remain closed the contactor K5(17) also operates continuously, hence as shown in fig 6,as the contactor K5(17) is operating continuously because of that the contacts of PLC O/P 001(23) gets operated. After 100 ms the contacts of delay timer(25) gets signal and give command to PLC to stop the test before any major damage occurs.

We Claim:
1. A system for tracking failure like single phase and welding in a test unit, the system comprising: a MCCB(4) connected to the R(1), Y(2), B(3) phases; a Backup contactor(5) having the R(1), Y(2), B(3) phases connected through the MCCB(4) contacts respectively; a test unit 1(6) and a test unit 2(7), each of these receiving R(1), Y(2), B(3) phases at three phase inputs lines through the backup contactor(5);
a three phase electrical load(8) receiving R(1), Y(2), B(7) phases at its one end three phase contactor and forming star point at the other end three phase contactor;
contactors K1(9), K2(10), K3(11) connected across the R(1), Y(2), B(3) phases respectively and the secondary of the coil of the contactors star pointed and connected to the star point of the load;
contactor K4(15), having its primary of the coil connected serially through the contact((12), (13), (14)) of contactor K1(9), contactor K2(10), contactor K3(11) to the power supply(16); contactor K5(17), having its primary connected parallel through thecontact((12), (13), (14)) of contactor K1 (9), contactor K2(10), contactor K3(11) to the power supply(16);

a counter(20), wherein the reset of the counter gets asserted on
operation of contactor K4(15) and contacts of the counter(18)
gets operated to stop the test on saturation of the counter to a
set value;
a delay timer(25), wherein the contacts of the delay timer(26) get
signal when contact of PLC o/p001(24) gets operated;
a PLC to control the test pattern execution.
2. The PLC as claimed in the claim 1 , wherein PLC stops the test when the counter(20) value becomes equal to set value of the counter(20) thereby operating the contacts of the counter(18).
3. The PLC as claimed in the claim 1, wherein the contacts of the PLC O/P 001(24) gets operated when contactor K5(17) is operating continuously.
4. The PLC as claimed in claiml, wherein the PLC receives command to stop the test when the contacts of delay timer(26) receive signal due to operations of contacts of PLC O/P 001(24).
5. A method for tracking failure like single phase and welding in a test unit, the method comprising steps of:
initializing and verifying mains voltage;

initializing the test by applying sequence to close MCCB(4) and
Backup contactor(5) and test units((6) & (7));
determination of faults through the operating status of the
contactor K4(15) and contactor K5(17).
generation of stop test command to PLC;
termination of test through PLC;
finalization of test result for the units under test