Woodward
Manual MRR1 GB
4
DOK-TD-MRR1 Rev.A
1. Introduction and application
The generator rotor protection relay MRR1 com-bines rotor earth fault protection, excitation over-
and undercurrent protection as well as rotating diode failure protection.
Thus providing a powerful protection regarding the rotor of synchronous generators, covering the
following ANSI codes:
37
DC undercurrent relay
40
Field
relay
58
Rectification
failure
relay
64
Ground detector relay
76
DC over current relay
The MRR1 is recommended for synchronous generators and motors above 1 MVA rating.
The rotor earth fault element detects high- and low resistance earth faults of the rotor winding. It is
equipped with two stages, one for alarm, one for trip.
The excitation current protection element super-vises the DC excitation current of brushless excitor
machines. The protective functions are: Undercurrent, over current and ripple detection for diode
failure protection.
2. Features and characteristics
Besides features described in the general MR-description, MRR1 provides:
Detection of high impedance earth faults with a test frequency of 0.5 Hz
Short circuit and overvoltage proof measuring input for the earth fault protection
Excitor current measurement galvanically isolated via Hall-transducer, measuring range
0 to 20 A
Display of insulation resistance
Display of the excitation current
Excitation current over- and undercurrent protection with independent settings for current
and delay time
Detection of diode failures by supervision of the ripple component of the excitation current
Two stage supervision of the rotor insulation resistance with independent settings for
resistance and time delay
Two trip relays, one for excitation under- and over current, one for diode failure detection
Digital inputs for blocking and for remote reset
Programmable function of the blocking input
Programmable assignment of protective functions to output relays
Remote interfacing via RS485
