Frequency relay SPAF 340 C

Not active product since 2011

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.


  • Overfrequency and underfrequency relay with four frequency stages

Product benefits

  •  Motor asset protection

Product features

  • Overfrequency and underfrequency relay with four frequency stages
  • Each frequency stage can be set for definite time overfrequency or underfrequency function
  • Each frequency stage can also be set for positive or negative frequency-rate-of-change (df/dt) function
  • The definite time operating principle and the rate of change operating principle can be combined
  • Each frequency stage can be given two separate operate times
  • Adjustable undervoltage blocking level
  • Field-adjustable relay rated frequency
  • The protection stages can be separately blocked via external blocking inputs
  • High system reliability due to continuous self-supervision
  • Member of the SPACOM product family and ABB’s Distribution Automation system

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