DEIF The RMC-142D is CE-marked and is applied for protection of voltage sources

Application and features

Application

The protective stator earth fault relay type RMC-142D forms part of a complete

DEIF series of relays for protection and control of generators. The RMC-142D

is primarily designed for land-based installations. Also available are short circuit

relays (RMC-111D), combined short circuit and over-current relays (RMC-122D)

and double over-current relays (RMC-132D).

The RMC-142D is CE-marked and is applied for protection of voltage sources and

load networks against earth fault in a solid earthing or a low-resistance earthing system.

Measuring principle

The relay measures the leakage or a short circuit from one or more of the phases to earth.

In order to obtain a short response time on a fault condition, the measurement is based

on peak values.

The earth fault current protection is for example obtained by connecting an external current

transformer in the star point of the protected voltage source.

In order to prevent malfunction due to 3rd harmonic, the RMC-142D is equipped with

a special filter cutting off frequencies higher than 50/60 Hz.

The set point values are set on the front of the relay by means of potentiometers.

If exceeded, a fault signal is generated, and the associated yellow LED is lit.

Timer functions

When the set point is exceeded, its timer starts and will run as long as the fault condition prevails.

If the fault disappears, the timer is reset. When the timer expires, the contact is activated

and the associated red LED is lit.

Relay outputs

The RMC-142D is provided with two outputs with maximum contacts either normally

energised or normally de-energised.

The contact may be set to open or close on activation.

Normally energised contact

Recommended for warning and alarm purposes.

In case of an auxiliary supply dropout, the contact is immediately activated.

Normally de-energised contact

Recommended for installations for regulating and control purposes.

An auxiliary supply failure will not result in an unwanted activation of the contact.

Latch circuit

The contact can be locked in its warning position, even if the earth faulty current

(leakage current) returns to normal (add "L" to contact type in order specifications,

if this is required). The latch circuit is reset by disconnecting the auxiliary supply.

Hysteresis

In order to avoid "chatter" on the relay contacts the contact functions are provided

with a hysteresis, that is a difference of 2 % of full scale between energising and

de-energising of the delay.

Power-up/power-down circuits

The RMC-142D is provided with a 200 ms power-up circuit, ensuring the correct function

of the relay on connection of the auxiliary voltage.