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Tuesday, June 28, 2011

Power Circuit Breaker Closing Circuit Diagram (substation equipment operation)

The basic closing circuit for a power circuit breaker is illustrated below. Closing circuit consists of miniature circuit breaker (CB2) that protects the closing coil from overcurrent. Tracing the first node is the push button PB1 52C. This is the push button for local closing of the power circuit breaker.
The L and R contacts are from the selector switch which ensures that closing operation is done one location at a time only. Going down, there is an optional customer lockout where the customer connected can control whether the power circuit breaker is to be closed after tripping operation. But at our substation, we just bypass that portion of the circuit thus explaining the shorting from TB2 7 to TB2 8. On the closing circuit, there are three important coils that have respective functions. First is the anti-pumping coil ES52Y, the closing coil MC52CC and the gas pressure coil EA63GX1. Anti-pumping coil ES52Y prevents the power circuit breaker from closing immediately if tripping is initiated upon closing operation. For example, the substation engineer push the button for breaker closing, but did not release it. Then, if the tripping circuit is complete or there is a sustained fault along the line, the tripping coil attempts to trip the breaker. Since the push button is still depressed, then the power circuit breaker attempts to close and trip itself at the same time. This can cause damage to the moving contact of the breaker as well as to the tripping and closing coils. Therefore, anti-pumping coil will prevent the closing coil from operation continuously when the closing circuit is complete. It ensures that during closing, no matter how long you press the push button or turn the knob switch, it will only give a single closing operation. Looking back the circuit, before the closing coil MC52CC is energized, it will pass through a series of normally closed contacts (ES52Y-anti-pumping contact, EA63GX1-gas pressure contact, MA1 52-1 -breaker contact, and MB188LS-spring limit switch). The SF6 gas pressure must be normal so that EA63GX1 will remain at closed position, the spring charge status must also be normal (either charged or uncharged, depending on the specification of power circuit breaker involved) so that MB188LS will be at closed position. Upon closing of the power circuit breaker, contact ES52Y will become open since the anti-pumping coil ES52Y has been energized upon closing of breaker. The SF6 gas pressure coil EA63GX1 is located on the closing circuit which will give lockout to either closing and tripping operation of the power cirucit breaker once the SF6 pressure is below limit.

Diagram: from Siemens Circuit Breaker


  1. paano basahin yan sir?

  2. sir, what part of the circuit is not clear?

  3. sir, bale i tried to explain the diagram and posted it above. mas maganda sana kung tagalog pero english po kasi blog ko. pls just message me on what part of my explanation is not clear.

  4. Sir paexplain naman po ng remote closing operation...saka ano po ung TB1, TB2, AT2???....ska yung pressure switch na EGA, saan po po bang parte ng breaker xa nakakabit??? kung my illustration o photo..i would really appreciate....tnx in advance...and nga pla ung blog nyo maganda...one of a kind....


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