Current Protection

2C81 DC Current Sensing Relay


This product is obsolete. 

Consider the alternative CU-I/J or DI series relays for your application. Note that these relay series are not directly equivalent to the 2C81.


  • High sensitivity
  • 40-300V DC auxiliary supply Power supply fail relay drops out if the auxiliary supply fails.
  • Optional 20-70V DC supply
  • Optional mV input ranges
  • Custom front dial calibration scale
  • Two C/O output contacts
  • One C/O fail alarm contact
  • Optional delay timer
  • Current pick up LED indication
  • Power supply healthy LED indication
  • Size 2M28-S draw out case
  • Made in Australia


The 2C81 is a DC current measuring relay. The measured input current is derived from a mV drop across a current shunt. A switchmode power supply provides a very wide auxiliary operatingrange. A relay fail alarm is provided in the form of a C/O contact which is picked up when the auxiliary supply is healthy.

The 2C81 relay may be applied to provide a trip signal to a circuit breaker in a DC system in the event of a short circuit on the downstream side of the CB. An integrated timer may be specified to provide an adjustable delay to allow coordination with other protective devices.

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Railway rolling stock
Railway signalling