The protective differential current relay type RMC-131D forms part of a complete DEIF series of relays for protection and control of generators, and is primarily designed for marine applications. The RMC-131D is type-approved by major classification societies and is applied for protection of for example generators in 3-phase networks against leakage currents.
The relay compares the differential current of each of the three phases, providing an RMS measurement at sinusoidal currents. In order to obtain a short response time on a fault condition, the measurement is based on peak values. The differential currents are obtained by connecting the external current transformers for each winding in parallel with inverse polarity.
The three differential currents are measured by the relay and the highest of these is selected. If this exceeds the set point, the output is activated. The set point value is set on the front of the relay by means of a potentiometer. If exceeded, a fault signal is generated, and the associated yellow LED is lit.
Relay output :
The RMC-131D is provided with one relay coil with two maximum contacts. The relay can be configured either to normally energised or normally de-energised. The contacts may be set to open or to close on activation (same function on both contacts).
Normally energised contact :
Recommended for marine installations for warning and alarm purposes. In case of an auxiliary supply dropout, the contact is immediately activated.
Normally de-energised contact :
Recommended for marine installations for regulating and control purposes. An auxiliary supply failure will not result in an unwanted activation of the contact.
Borna Niroo Karan (Bornika) is the exclusive agent of DEIF in the fields of consultation , sales and distribution of power industry products including Differential current relay products .