FEATURES & FUNCTIONALITY

The MRG3 is a universal mains decoupling device that covers all the protection functions which are required by VDEW and by most other utilities for the mains parallel operation of power stations such as:  over/and under voltage protection,  over/and under frequency protection,  extremely fast generator mains decoupling in case of vector surges or rate of change of frequency df/dt The MRG3 can furthermore be equipped with a multi-purpose over current time and earth fault protection re-lay and it has been designed as to be also used for grids with isolated and compensated star points respectively. It is applicable for the mains parallel operation of power generating gen.- sets and includes the following protection functions.  Independent (Definite) time over current relay,  dependent time over current relay with selectable characteristics, independent short circuit protection  two-element (low and high set) earth fault protection with definite or inverse time characteristics,  integrated determination of earth fault direction for application to power system networks with isolated star point or earth fault compensation (ER/XR-relay type),  two-step protection for the residual voltage For applications where only individual protection functions are required Woodward can, of course, also offer the following MR-relays as individual devices:  MRU3-1 four step independent over-/ and under-voltage protection (also used for generator earth fault protection).  MRU3-2 two step independent over-/ and under-voltage protection with evaluation of the symmetrical voltage components.  MRF3 four step independent over/ and under- frequency protection and two step frequency gradient supervision df/dt.  MRI3-I Independent (Definite) time over current relay, inverse time over current relay with selectable tripping characteristics, independent short circuit protection  MRI3-E two-element (low and high set) earth fault protection with definite or inverse time characteristics,