Technical Guide P92x/EN GS/E11
Getting Started
MiCOM P921-P922-P923 Page 5/18
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6. INTRODUCTION TO THE MiCOM P921-P922-P923 RELAYS
The range of MiCOM protection relays follows on from the success of the MIDOS, K
and MODN ranges by incorporating the last changes in digital technology. The relays
MiCOM P921-P92 and P923 are fully compatible and use the same modular box
concept. The MiCOM P921-P92 and P923 of relays provides more protection for
the most demanding applications.
Each relay has a large number of functions for controlling and collecting data. This
can form part of a fully integrated system covering protection, control,
instrumentation, data acquisition and the recording of faults, events and
disturbances. The relays are equipped on the front panel with a liquid crystal display
(LCD) with 2 x 16 back-lit alphanumerical characters, a tactile 7 button keypad (to
gain access to all the parameters, alarms and measurements) and 8 LEDs simply
displaying the state of the MiCOM P921-P922 and P923 relays. In addition, the use
of the RS485 communication port makes it possible to read, reinitialise and change
the settings of the relays, if required, from a local or remote PC computer equipped
with appropriate software.
Its flexibility of use, reduced maintenance requirements and ease of integration allow
the MiCOM P921-P922 and P923 to provide an evolving solution for the problems of
the protection of electric networks.
The MiCOM P921-P922 and P923 relays provide comprehensive voltage and
frequency protection for phase and ground faults together with measurements,
control and recording facilities.
Functions MiCOM P921 MiCOM P922 MiCOM P923
Protection functions
Under voltage (27) XXX
Over voltage (59) XXX
Residual over voltage (59N) XXX
Negative sequence overvoltage (47) XX
Positive sequence undervoltage (27D) XX
Under frequency (81U) XX
Over frequency (81O) XX
Rate of change of frequency (81R) X
Undervoltage blocking (settable for P923) XX
Ancillary functions
Settings groups 122
Measurements XXX
Circuit Breaker Control XXX
Circuit Breaker Supervision XX
Output relay latching XXX
Blocking logic XXX
Programmable logic equations XXX
Peak demand XX
Rolling demand XX
Fault record XX
Events records XX
Disturbance recording XX
Rear communication port XXX
Front communication port XXX
Frequency disturbance recording X
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