1.principle of operation:
  • Principle: A Continous Negative Voltage is given to one end of the Tripping Coil . If the Trip Circuit is Continous  (Healthy) 
    this Negative Voltage gets extended futher down the Trip Circuit, which can be used by the TCS Relay to check the continuity in the Tripping Circuit.
    Importance: 
    • A Breaker has a Closing Coil & A Tripping Coil. Now if a Closing Coil is Faulty, we can Close it Mechanically also. But Tripping is Automatic in the case of Fault and so when the Trip Circuit is Faulty, the Breaker won’t Trip  which  can have very bad consequences.
    • If its a 22kv or 33 kv bkr, Tfr LV bkr will operate, which will result in unnecessary power interruption for other Feeders.
    • If its 100 kv or 220 kv level, and if the breaker does not trip, LBB wil operate, tripping all the feeder in that section which will result in Huge Power Loss.
    We will be using Areva make VAX31 Type Trip Circuit Supervision Relay.
2. construction:
  1. Post Close Element (95A)- It is Energised when the Breaker is in ON Condition (Post Close Condition) & hence monitors the Healthiness of the TC in the Bkr is in ON cond. Permanant Positive is given to  one end of Coil of  95A and the other end of Coil of 95A is connected to the Tripping Coil through  NC Auxillary contact of the breaker. 
  2. Pre Close Element (95B)- It is Energised when the Breaker is in OFF Condition (PreClose Condition). Permanant Positive is given to  one end of Coil of  95B and the other end of Coil of 95B is connected to the Tripping Coil through  NO Auxillary contact of the breaker. 

  3. Main Element (95C)- Positive is given to the 95C through the parallely connected contacts of 95A & 95B. Permanant Negative is given to the other end of 95C. It is Energised when either 95A or 95B is Energised &  used for Annunciation purpose. It is a  reverse Flag Relays (Normally when the Relay is operated, we get an indication, but in the case of 95C Relay, when the Relay is not operated, we get the Indiction).
  4.  Resistances- Current flowing in the TCH ckt is restricted with the help resistances placed in series with the TCH relays, so that the Tripping coil does not operate. Also, in case the TCS Element gets shorted, the current through TC is limited and breaker does not Trips.
3. WORKINNG OF TCS RELAY WHEN THE BREAKER IS IN OFF POSITION:
  1. Permanant Positive is given to  one end of Coil of  95A and now, the other end of Coil of 95A gets the Negative Voltage  coming through the Tripping Coil &  NC Auxillary contact of the breaker. Hence, 95A Relay gets operated and so its Contact is Closed and so Positive  is extended to the 95C Relay. As the 95C Relay is already given Negative and now it is gettig Positive and so it gets OPerated & so there are Faulty Indications & Breaker Closing Interlock is also Inactive. 
  2. Permanant positive is given to the 95 B Relay but it is not getting the Negative Voltage coming through the Coil, and it remains in Reset Condition.
  3. Positive is given to the 95C through the parallely connected contacts of 95A & 95B. Permanant Negative is given to the other end of 95C.