Unit module card PM511V08 3BSE011180R1

Unit module card PM511V08 3BSE011180R1

Unit module card PM511V08 3BSE011180R1

There is a risk that a circuit breaker will get discordance between the poles at circuit breaker operation: closing or opening. One pole can be open and the other two closed, or two poles can be open and one closed. Pole discordance of a circuit breaker will cause unsymmetrical currents in the power system.

The consequence of this can be:

• Negative sequence currents that will give stress on rotating machines

• Zero sequence currents that might give unwanted operation of sensitive earthfault protections in the power system. It is therefore important to detect situations with pole discordance of circuit breakers. When this is detected the breaker should be tripped directly. Pole discordance protection CCPDSC will detect situation with deviating positions of the poles of the protected circuit breaker. The protection has two different options to make this detection:

• By connecting the auxiliary contacts in the circuit breaker so that logic is created, a signal can be sent to the protection, indicating pole discordance. This logic can also be realized within the protection itself, by using opened and close signals for each circuit breaker pole, connected to the protection.

• Each phase current through the circuit breaker is measured. If the difference between the phase currents is larger than a CurrUnsymLevel this is an indication of pole discordance, and the protection will operate.