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Earth-fault relay and protection assemblies for EHV and HV systems

The RXIDG 21H/RAIDG relay is used as a selective and sensitive earth-fault protection in solidly earthed transmission networks. It is a single-phase time-overcurrent relay with a combined definite and logarithmic inverse time relay function.

The logarithmic inverse time characteristic has been choosen to produce selective tripping when used as earth-fault protection in solidly earthed transmission networks. The selectivity is ensured when the largest infeed is less than 80 % of current to the fault. All relay locations are set with the same primary sensitivity in order to provide selectivity, which is then achieved without having to use a directional measurement criteria.

RXIDG 21H has replaced the obsolete RXIDG 2H relay.

Main Features:

  • Earth-fault relay with logarithmic current-dependent and a minimum delayed operating time
  • Wide setting range of 15 mA to 2,60 A
  • Binary input for enabling or blocking, often in combination with a 2nd harmonic restraint additional relay or a directional earth-fault relay
  • Minimum definite time setting to achieve selectivity with instantaneous functions in distance protection at very high zero sequence fault currents 

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