Channel control unit 3BSE002616R1

Channel control unit 3BSE002616R1

Channel control unit 3BSE002616R1

The 1Ph High impedance differential protection HZPDIF function has a separate alarm level, which can be used to give alarm for problems with an involved current transformer circuit. The setting level is normally selected to be around 10% of the operating voltage U>Trip. As seen in the setting examples above the sensitivity of HZPDIF function is normally high, which means that the function will in many cases operate also for short circuits or open current transformer secondary circuits.

However the stabilizing resistor can be selected to achieve sensitivity higher than normal load current and/or separate criteria can be added to the operation, like a check zone.

This can be either another IED, with the same HZPDIF function, or be a check about the fault condition, which is performed by an earth overcurrent function or neutral point voltage function. For such cases where operation is not expected during normal service the alarm output should be used to activate an external shorting of the differential circuit avoiding continuous high voltage in the circuit. A time delay of a few seconds is used before the shorting and alarm are activated.

Auxiliary relays with contacts that can withstand high voltage shall be used, like RXMVB types. The metrosil operating characteristic is given in the following figure.