Overvoltage and undervoltage relay SPAU 121 C

Not active product since 2009

The voltage relay SPAU 121 C is used for over- and undervoltage protection and supervision in distribution substations. Generally the relay measures the phase-to-phase voltage of the system.

The over- as well as the undervoltage stage can be given definite time characteristic or inverse time characteristic.

An external control signal can be used to block the operation of the undervoltage stage. The relay forms a whole including over- and undervoltage stage as well as flexible trip and alarm functions.


  • Combined overvoltage and undervoltage protection

Product benefits

  • Protecting power distribution networks

Product features

  • Combined overvoltage and undervoltage protection relay
  • Single-phase definite time or inverse time overvoltage stage
  • Single-phase definite time or inverse time undervoltage stage
  • Control input for blocking the function of the undervoltage stage by means of an external control signal
  • Automatic blocking of the undervoltage stage on loss of energizing voltage
  • Serial interface for bus connection module and fibre-optic substation bus
  • Continuous self-supervision of relay hardware and software for enhanced system reliability and availability


Are you looking for support or purchase information?

Loading documents

Related offering

Select region / language