Frequency RelaySPAF 140 C
The frequency relay SPAF 140 C is used for the protection of power generators and other AC equipment against overfrequency and underfrequency. The operation of the relay can be based on the definite time principle, on the rate of frequency change principle, or on a combination of these two principles. In generator protection applications the relay protects the generator and the prime mover against hazardous overspeeding and/or underspeeding. The relay can also be used for the protection of large synchronous motors in networks where automatic network restoration is used. The relay isolates the motor from the network in the event of an outage, averting dangerous unsynchronized connection.
Frequency RelaySPAF 340 C
The frequency relay SPAF 340 C is used for load shedding in situations where power consumption exceeds the available power of the network. In such a situation of unbalance, the network frequency tends to fall. The frequency relay can control four circuit breakers, allowing four feeders to be disconnected from the network, one by one. Should the power deficiency still persist, the relay disconnects the plant for island operation.
The operation of the relay can be based on set frequency values (f<), on the rate of decrease of frequency (negative df/dt), or on both criteria (f< and df/dt). In addition, output of each stage can be obtained via two separate time circuits and so eight different frequency/time combinations are available. Should the network frequency drop rapidly, this feature allows fast disconnection of various loads.