The DEIF loss of mains relay type LMR-122D forms part of a complete DEIF series of relays for protection and control of generators. A mains failure will be detected, provided a disconnection at an arbitrary point of the network results in a swift change of the generator frequency (vector shift). An opening signal is then transmitted to the mains circuit breaker, and the generator will thus be protected against damages caused by an automatic reconnection to the high-voltage network.
After five periods have passed (after connection to the mains) the relay will thus have performed the first measurement. After this the LMR-122D will within 30 ms for vector shift and 100 ms for ROCOF (df/dt) detect a possible mains failure. The ROCOF (Rate of change of frequency - df/dt) supervises the change in frequency for every period. If the change in frequency for four periods in a row exceeds the set point, the output is activated. Within 100 ms (inclusive of contact delay), an opening signal is transmitted to mains circuit breaker, and the LED marked “MAINS FAIL” is lit
Relay outputs :
The LMR-122D is provided with two output contacts (with common set points), either normally energised or normally de-energised. The contacts may be set to open or to close on activation.
Normally energised contact :
Recommended for warning and alarm purposes. In case of an auxiliary supply drop-out, the contact is immediately activated.
Normally de-energised contact :
Recommended for regulating and control purposes. An auxiliary supply failure will not result in an unwanted activation of the contact.
Power-up circuit :
The relays are provided with a 200 ms power-up circuit, ensuring the correct function of the relay on connection of the auxiliary voltage.
- Detection of vector shift and ROCOF (df/dt)
- Mains disconnection on mains failure
- Ensures no asynchronous reconnection
- LED indication of fault condition
- LED indication for activated relay
- 35 mm DIN rail or base mounting
Borna Niroo Karan (Bornika) is the exclusive agent of DEIF in the fields of consultation , sales and distribution of power industry products including DEIF Loss of mains relay products .