Woodward
Manual MRIK3-C EN
10
DOK-TD-MRIK3-C Rev. A
2. Introduction and Application
The digital net protection relay MRIK3-C an universal time - over -current and earth fault relay with
integrated control- and supervision function as well as optional an integrated auto reclosing func-
tion The earth fault protection is applicable for insulated and compensated grids. The controlling of
the circuit breaker take place by the means of the front plate via push button in the case of a local
operation, the remote operation can be done via digital inputs or via the serial communication inter-
face.
The earth-fault supervision is either realised in Holmgreen connection or by means of a core-type
current transformer. The MRIK3-C is available with rated currents of 1 A or 5 A.
3. Characteristics and Features
Microprocessor technology with self-supvervision,
Measuring of phase currents as RMS value,
Digital filtering of the earth current with discrete Fourier analysis, by which the influence of
interference signals, such as harmonics and transient DC components during an earth-fault are
suppressed.
Two sets of parameters,
Operation cycle counter,
Suppression of an LED indication after activation (LED flash),
Selectable protective functions : Definite time overcurrent protection (DMT) and inverse
time overcurrent protection (IMT),
Selectable IMT trip characteristics of IEC 255-4:
Normal inverse (Type A)
Very inverse (Type B)
Extremely
inverse
(Type
C)
Special-purpose
characteristics
eg. RINV, LINV and RXIDG in earth path
Reset mode for DMT/IMT trip characteristics is selectable,
Definite element for short-circuit high-speed trip
Defined time overcurrent protection without directional feature (DEFT)
Inverse time overcurrent protection without directional feature (INV)
Two element defined- or inverse time earth fault protection,
Optionally with integrated directional feature for the earth fault element.
Control of the CB via potential free auxiliary relays,
Supervision of the CB via digital wide range inputs,
Remote indication of the CB position via serial interface.,
CB failure protection,
Display of the measuring values as primary quantities,
Measuring of the phase currents during short-circuit free operation,
Blocking of the individual protective elements or the trip elements can be set freely,
The protective functions can be freely allocated to the output relays. (Relay Matrix),
automatic auto reclosing (optional),
free assignment of protective function for every reclosing separately adjustable,
Free assignment of the input function to the digtial input,
Saving of trip values and the switch-off times (t
CBFP
) of 25 fault events (voltage fail-safe),
Recording of up to 8 fault events with time stamp,
Display of date and time,
Trip via digital inputs,
Rack mounting, with self-acting short-circuit mechanism for CT circuits,
Possibility of serial data exchange via the RS485 or RS232 interface, with Modbus Proto-
col.
The minimum operating time including boot time (power-on-time) is <100ms