A METHOD FOR SUPERVISING A TRIP CIRCUIT AND A TRIP SUPERVISION
RELAY THEROF
FIELD OF THE INVENTION
The present invention relates generally to a trip circuits and more particularly to a method of supervising a trip circuit using a trip supervision relay.
BACKGROUND OF THE INVENTION
A conventional trip circuit in an apparatus, such as a medium voltage circuit breaker, controls the opening and closing driver that drives the opening and closing operations operated through a switch. In a traditional mechanical circuit breaker, the driver is a shunt release consisting an electromagnet that releases a spring. As a result, the spring performs the required opening or closing operation.
As known to the person skilled in art, circuit breakers are provided in electrical circuits to disconnect part of high voltage electrical circuit in response to the closing of a contact (the trip contact) attached to a low voltage electrical circuit. The trip contact and a supply voltage form a part of a trip circuit. Closing the trip contact causes current to flow in the trip coil of the circuit breaker, which results in the opening of the circuit breaker and the disconnection of the high voltage circuit. When a fault occurs in the high voltage circuit, it is important that the circuit breaker can operate to disconnect the circuit, to minimize the damage caused. It is important to detect the condition (health) of the trip circuit to ensure functionality and reliability and continuous checking (detecting condition) is carried out with a Trip Circuit Supervision (TCS) relay. Common Trip Circuit Supervision relays are designed to check the low impedance of the trip circuit and to detect when the trip circuit turns into an open circuit. This occurs when the connection is broken or the wire of the electromagnet winding is burned by an overcurrent.
It is common to use a supervision relay to supervise during post-close condition of the circuit breaker trip coil. Certain utilities have the practice of supervising the trip coil even during pre-close condition to ensure proper healthiness of the trip circuit. In this supervision for pre-close condition, additional relays and a separate auxiliary voltage are generally used to derive this functionality.

It is advantageous to achieve monitoring of trip coil and cable circuit connecting to the trip contact of breaker in both pre-close and post-close condition with minimal devices and simplified circuitries, and also breaker contact failure such that the logic circuit should be rugged enough to sustain intermediate disturbances caused during the operation of the trip coil (mainly inductance).
SUMMARY
The above-mentioned shortcomings, disadvantages and problems are addressed herein which will be understood by reading and understanding the following specification.
In one aspect, the present invention provides a method for monitoring a health condition of a trip circuitry associated with trip operation of a circuit breaker and a status of circuit breaker contacts with a trip circuit supervision relay, the circuit breaker is connected in an electrical line and operates to interrupt a current flowing in the electrical line by opening main contacts and has auxiliary contacts to indicate the status of the circuit breaker contacts, and wherein the circuit breaker is electrically connected with a protection relay at the trip contacts and is tripped with a signal from the protection relay, and wherein the trip circuitry includes the electrical connection between the protection relay and the circuit breaker, and the trip coils to activate tripping of the circuit breaker, the method comprises: utilizing auxiliary contacts for monitoring the status of circuit breaker with the trip circuit supervision relay by electrically connecting the auxiliary contacts with a first coil in the trip circuit supervision relay; utilizing the trip contacts for monitoring the health condition of the trip circuitry associated with trip operation of the circuit breaker with a second coil in the trip circuit supervision relay; wherein the first coil and the second coil are comprised within a single trip circuit supervision relay and the trip circuit supervision relay is magnetically operated by any of the first coil and the second coil to indicate the status of the circuit breaker and the health condition of the trip circuitry associated with the circuit breaker.
In an embodiment the auxiliary contact is a normally closed contact during main contact open condition of the circuit breaker.

In an embodiment, monitoring a health condition of a trip circuitry associated with trip operation of a circuit breaker further comprises monitoring the health of a cable connecting trip contact to the circuit breaker through auxiliary contacts.
In an embodiment, the first coil is wound on top of second coil and the first coil is electrically insulated from the second coil.
In another aspect, the present invention provides a trip circuit supervision (TCS) relay for monitoring a health condition of a trip circuitry associated with trip operation of a circuit breaker and a status of circuit breaker contacts, the circuit breaker is connected in an electrical line and operates to interrupt a current flowing in the electrical line by opening main contacts and has auxiliary contacts to indicate the status of the circuit breaker contacts, and wherein the circuit breaker is electrically connected with a protection relay at the trip contacts and is tripped with a signal from the protection relay, and wherein the trip circuitry includes the electrical connection between the protection relay and the circuit breaker, and the trip coils to activate tripping of the circuit breaker, the trip circuit supervision relay comprising: a first coil and a second coil and wherein the trip circuit supervision relay is magnetically operated by any of the first coil and the second coil to indicate the status of the circuit breaker and the health condition of the trip circuitry associated with the circuit breaker,
In an embodiment the TCS relay comprises an RC circuit for achieving a drop-out delay during change-over of position of the circuit breaker auxiliary contact.
BRIEF DESCRIPTION OF DRAWINGS
The appended drawings illustrate exemplary embodiments as disclosed herein, and are not to be considered limiting in scope. In the drawings:
Figure la shows a block diagram of the elements for monitoring health condition of trip circuitry;
Figure lb shows a truth table illustrating the status of the trip circuit supervision relay;
Figure 2 shows a construction of the trip circuit supervision relay;

Figure 3 shows a flow diagram of the method for monitoring health condition of trip circuitry;
Figure 4a shows a condition when the circuit breaker is in pre-close condition with protection trip contact in open condition;
Figure 4b shows the circuit breaker closing position with protection trip open;
Figure 4c shows the circuit breaker in post-close condition with protection trip in open state;
Figure 4d shows the circuit breaker in opening condition with protection trip in close state; and
Figure 4e shows the circuit breaker in pre-close condition with protection trip in closed condition
DETAILED DESCRIPTION
The present invention is related to monitoring a health condition of a trip circuitry associated with trip operation of a circuit breaker and a status of circuit breaker contacts with a trip circuit supervision relay.
In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments, which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized. The following detailed description is, therefore, not to be taken in a limiting sense.
Figure 1 shows a block diagram of the elements for monitoring health condition of trip circuitry associated with trip operation of a circuit breaker 110 and a status of circuit breaker contacts (not shown) with a trip circuit supervision relay 120. The trip circuit supervision (TCS) 120 relay comprises two coils, coil A (120a) and coil B (120b). The circuit breaker 110 is connected in an electrical power line and operates to interrupt a current flowing in the electrical power line by opening contacts (main contacts) to interrupt the electrical current flowing in the electrical power line. The mechanism operating the circuit breaker main contacts also operates to open auxiliary contacts 130, which are used to determine the status of the circuit breaker main contacts. The circuit breaker 110 is operated with a trip signal from a protection relay 140 and the signal is connected at the trip contacts 150 that connects to a coil which is energized for tripping with the signal from the protection relay 140. The trip circuitry includes the electrical connection between the protection relay and the circuit breaker, and the trip coils to activate tripping of the circuit

breaker 110. Figure 1 also shows the other elements associated with the TCS relay 120 like the alarm and annunciation block 160. The alarm and annunciation block 160 may comprise means for alerting a status of the TCS relay for example alarms, Light Emitting Diodes (LEDs) to indicate health condition of the trip circuitry. DC Excitation and Signal Conditioning block 170 is provided for DC supply and requisite electronics for conditioning signals for achieving desired time delays for example an RC (resistor-capacitor) circuit to ensure that alarms from the TCS relay is reliable.
In an embodiment of the invention in order to achieve monitoring of trip coil and cable circuit connecting to the trip contact of the circuit breaker in both pre-close and post-close condition along with breaker contact failure an OR gate logic is being utilized with two input & one output. The circuit is rugged enough to sustain intermediate disturbances and changes caused during the operation of the trip coil (mainly inductance). To achieve the ruggedness a double layer winding on single magnetic circuit is used, means coils are electrically isolated but magnetically linked and each coil is connected to separate RC circuits for drop-off delay. The relay armature holds a dual coil winding so that one coil will be connected across protection trip contact 150 and the cable will be in series to the second coil that gets energized in breaker pre-close condition. The cable which is connecting the protection trip contact to the circuit breaker auxiliary contact is being monitored by the second coil (coil B). Thus an effective implementation with two coils and use of the same power supply to detect conditions with the TCS relay. As will be appreciated by persons skilled in the art that the coil winding be calculated for accommodating both the coils (coil A 120a and coil B 120b) on same bobbin space of core.
There are three possible healthy conditions for the coil A and B coil B to trigger functioning of the trip circuit relay 120 i.e. for the TCS relay to be in picked up state:
a) A coil get energized,
b) B coil get energized,
c) A and B both get energized.
Both the coils are designed with a maximum AT (ampere-turn) ratio needed for the TCS relay to pick up at rated voltage. The advantage of double layer winding when both coils are in series is that the total resistance gets doubled and the current reduces to half the value, but the overall

ampere turns get doubled thereby compensating the required AT to the same value of pick up voltage.
Figure lb shows a truth table illustrating the status of the trip circuit supervision relay. The condition of circuit breaker trip coil and its associated contacts can be considered as an OR gate logic. Based on the logic table the armature has to hold the coil during conditions where any of the coils A or coil B is energized.
In an embodiment of the present invention the, an electronics circuit (DC excitation and signal conditioning) can be designed to have two RC network for drop-off delay and diodes for directional blocking. A set of LEDs to indicate the position and healthiness of the circuit and to hold the coil armature when there is an intermittent state of the circuit breaker position. An RC circuit for achieving the drop off time required to prevent the relay from issuing false alarm during change-over of breaker auxiliary contact positon. Also, the LED to indicate the status that the breaker coil has been getting monitored in pre-close and post- close condition of the breaker.
Monitoring of circuit breaker closing and opening is done by two different coils of the same TCS relay which is achieved by having dual coil windings on a single core which are wound one above the other which are electrically isolated using insulations. The coil A, the first layer over bobbin will monitor when protection trip contact is in open position and coil B will monitor through the auxiliary breaker contact (referred as the 52b normally closed contact or auxiliary contact) that will be in normally closed position during circuit breaker open condition.
Figure 2 shows a construction of the trip circuit supervision relay 120. In this TCS relay 120 there are two coils are used as mentioned in the text herein above. The coils are electrically insulated and magnetically connected. One insulation layer is just above the core and the second layer is above one of the coils to isolate electrically. The TCS relay 120 shown in Figure 2 shows a relay angle to support the armature that actuates the contacts wherein the armature is the moving part of the TCS relay that is magnetically operated by the set of coils: coil A and coil B. The TCS relay 120 is designed to monitor DC supply of trip coil in breaker and its associated circuits to provide alarm. In case of trip coil supervision, the cable which is connecting from protection relay trip contact to the beaker coil through auxiliary contacts of it will be monitored as an additional feature.

Figure 3 shows a flow diagram 300 of the method for monitoring health condition of trip circuitry. As shown in Figure 3, as a first step of the method for monitoring health condition of trip circuitry, step 310 shows the auxiliary contacts of the circuit breaker are used for monitoring the status of circuit breaker with the trip circuit supervision relay by electrically connecting the auxiliary contacts with the first coil in the trip circuit supervision relay. The auxiliary contacts or 52b contacts as known to the persons skilled in the art are normally closed contacts for circuit breaker in open position. As a second step 320, the trip contacts are used for monitoring the health condition of the trip circuitry associated with trip operation of the circuit breaker with the second coil in the trip circuit supervision relay. As observed in Figure la and Figure 2, the first coil and the second coil (coil A and coil B) are comprised within a single trip circuit supervision relay. As shown in step 330 the trip circuit supervision relay is magnetically operated by any of the first coil and the second coil to indicate the status of the circuit breaker and the health condition of the trip circuitry associated with the circuit breaker.
In an embodiment two LEDs can be provided for alerting purposes to indicate the various monitoring conditions. For example in a configuration both LEDs can glow in case of circuit breaker open/pre-close condition and protection trip contact in open position. And only one LED glows when breaker is in post close condition. In such a manner all the conditions for monitoring can be alerted using LEDs.
In an embodiment a self-resettable flag which drops out when there is loss of DC supply due to faults on trip coil and its associated circuits irrespective of breaker position can be achieved. In an embodiment failure of TCS relay itself can be indicated for example while monitoring operation of auxiliary contacts if a dropout delay of more than 300ms is observed an abnormal operation can be detected.
The TCS relay comprises an electromechanical auxiliary contact and parallel RC circuit for drop-out delay. The TCS relay has dual coil circuit on a single magnetic core that supervise the trip coil circuit irrespective of breaker position. The LEDs can be connected in series with the auxiliary contacts of the relay coil to show healthiness of the trip coil circuit and circuit breaker position.
Figure 4a, Figure 4b, Figure 4c, Figure 4d and Figure 4e show the various conditions for the circuit breaker position and protection trip contacts.

Figure 4a shows a condition when the circuit breaker 410 is in pre-close condition with protection trip contact 420 in open condition. When the circuit breaker is in open condition and protection trip contact is in open position than the minimum current required to flow through the coil along with circuit breaker trip coil resistance should be of 2.5mA to supervise. In this condition LED to indicate pre-close condition (referred as pre-close LED) and LED to indicate post-close condition (post-close LED) will be showing healthy status. For example, LED A is in series with coil A and LED B is in series with coil B. Both LED A and LED B will glow in case of protection trip contact is open and breaker is in open position, LED A alone will glow when breaker is in close position and LED B alone will glow when protection trip contact is in close position and breaker is in open position. If the cable connecting the protection trip relay contact to the circuit breaker coil is opened or if DC supply is lost, the relay will dropout in greater than 300ms and gives an alarm.
Figure 4b shows the circuit breaker closing position 410 with protection trip 420 in open condition. When the circuit breaker gets closing command the auxiliary contacts of breaker will be in intermediate state which in turn will cause the dual coil to get de-energized. During this action, both coil will lose the supply and RC circuit will supply the coil to be in hold until the breaker changes its state. If contact changeover has some mal-operation/failure happens at greater than 300ms when it will provide an alarm.
Figure 4c shows the circuit breaker 410 in post-close condition with protection trip contact 420 in open state. When the circuit breaker in close condition and protection trip contact in open position than the minimum current required to flow through the coil along with circuit breaker trip coil resistance should be of 5mA to supervise. In this condition, Post-close LED (LED A) will be showing healthy status. In this position if DC supply is lost, the relay will dropout in greater than 300ms and sets of an alarm.
Figure 4d shows the circuit breaker 410 in opening condition with protection trip contact 420 in close state. When the circuit breaker gets trip command through protection trip contact the breaker trip coil energized to open breaker and the auxiliary contacts of breaker will be in intermediate state which in turn will cause one of the dual coil in relay across trip contacts

which was in supervision position gets de-energized. During this action, RC circuit will hold the supply to coil until the circuit breaker changes its state. If trip contact is latched and changeover has some mal-operation / failure happens leading to continuous supply to trip coil then it will provide an alarm.
Figure 4e shows the circuit breaker 410 in pre-close condition with protection trip 420 in closed or latch position condition. When protection trip contact is in latch position, the circuit breaker gets changed over to open condition and then the current required to flow through the coil along with circuit breaker trip coil resistance should be of 5mA in order to supervise the trip circuitry. This will be the current through pre-close LED (LED B) and one of the dual coil of the TCS relay via the auxiliary contact of the circuit breaker to the trip coil. In this condition, pre-close LED (LED B) will be showing healthy status. Also there is monitoring for a condition for a loss of DC supply or open circuit of the cable that is connecting the protection trip contact to the coils of the circuit breaker.
This written description uses examples to describe the subject matter herein, including the best mode, and also to enable any person skilled in the art to make and use the subject matter. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

We claim,
1. A method for monitoring a health condition of a trip circuitry associated with trip operation of a
circuit breaker and a status of circuit breaker contacts with a trip circuit supervision relay, the
circuit breaker is connected in an electrical line and operates to interrupt a current flowing in the
electrical line by opening main contacts and has auxiliary contacts to indicate the status of the
circuit breaker contacts, and wherein the circuit breaker is electrically connected with a
protection relay at the trip contacts and is tripped with a signal from the protection relay, and
wherein the trip circuitry includes the electrical connection between the protection relay and the
circuit breaker, and the trip coils to activate tripping of the circuit breaker, the method
comprises:
utilizing auxiliary contacts for monitoring the status of circuit breaker with the trip circuit supervision relay by electrically connecting the auxiliary contacts with a first coil in the trip circuit supervision relay;
utilizing the trip contacts for monitoring the health condition of the trip circuitry associated with trip operation of the circuit breaker with a second coil in the trip circuit supervision relay;
wherein the first coil and the second coil are comprised within a single trip circuit supervision relay and the trip circuit supervision relay is magnetically operated by any of the first coil and the second coil to indicate the status of the circuit breaker and the health condition of the trip circuitry associated with the circuit breaker.
2. The method for monitoring a health condition of a trip circuitry as claimed in claim 1 wherein the auxiliary contact is a normally closed contact during main contact open condition of the circuit breaker.
3. The method as claimed in claim 1, wherein monitoring a health condition of a trip circuitry associated with trip operation of a circuit breaker further comprises monitoring the health of a cable connecting trip contact to the circuit breaker through auxiliary contacts.

4. The method as claimed in claim 1, wherein the first coil is wound on top of second coil and the first coil is electrically insulated from the second coil.
5. A trip circuit supervision (TCS) relay for monitoring a health condition of a trip circuitry associated with trip operation of a circuit breaker and a status of circuit breaker contacts, the circuit breaker is connected in an electrical line and operates to interrupt a current flowing in the electrical line by opening main contacts and has auxiliary contacts to indicate the status of the circuit breaker contacts, and wherein the circuit breaker is electrically connected with a protection relay at the trip contacts and is tripped with a signal from the protection relay, and wherein the trip circuitry includes the electrical connection between the protection relay and the circuit breaker, and the trip coils to activate tripping of the circuit breaker, the trip circuit supervision relay comprising:
a first coil and a second coil and wherein the trip circuit supervision relay is magnetically operated by any of the first coil and the second coil to indicate the status of the circuit breaker and the health condition of the trip circuitry associated with the circuit breaker,
6. The TCS relay as claimed in claim 5 comprises an RC circuit for achieving a drop-out delay
during change-over of position of the circuit breaker auxiliary contact.