DEIF的短路保護(hù)繼電器用于僅需要短路電流保護(hù)的情況。

1. General information 1.1 Application and features 1.1.1 Application The protective current relay type RMC-121D forms part of a complete DEIF series of relays for protection and control of generators and is primarily designed for marine applications. Also available are short circuit relays (RMC-111D), combined short circuit and over-current relays (RMC-122D) and double over-current relays (RMC-132D). 1.1.2 Measuring principle The relay measures the highest of the 3-phase currents, 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 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. 1.1.3 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. 1.1.4 Relay outputs The RMC-121D 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 contacts are activated immediately. 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. Latch circuit The contacts can be locked in their warning position, even if the input currents return 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 relay.