Micom P721, Technical Manual

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Application Guide P72x/EN AP/C21
MiCOM P721/P723 Page 47/52
6. MAINTENANCE MODE
This menu allows the user to verify the operation of the protection functions without actually
sending any external command (Tripping or signaling).
The maintenance mode can be selected using a logic input, control command (rear or front
port), or by front panel interface. The end of maintenance mode is done by logic input, by
control command or on the front panel interface time out (5 minutes) and by turning off the
power supply.
Maintenance Mode
YES
When this menu is activated (set to YES), the Alarm LED flashes and the alarm message
MAINTENANCE MODE appears on the display. In this case, all the output contacts are
blocked and no command can be issued to these contacts, even if a protection threshold
associated to one of these output contacts has been crossed.
(If a protection threshold is crossed, all associated LEDs will be ON, even the TRIP LED, if
the threshold is associated to RL1).
RELAYS 8765W4321
CMD 000000000
This window allows the user to verify the external wiring to the relay output contacts. To do
this, the user must assign a 1 to any of the output contacts, which will close the contact, and
the continuity of the wiring can be verified.
7. LOGIC EQUATIONS (P721 & P723)
The logic equations can be used to construct complex Boolean logic using the following
operators: AND NOT, OR NOT, AND, OR.
An example logic implementation using Equation A is shown below:
8. REAL TIME CLOCK SYNCHRONIZATION VIA OPTO-INPUTS
In modern protective schemes it is often desirable to synchronize the relay’s real time clock
so that events from different relays can be placed in chronological order. This can be done
using the communication interface connected to the substation control system or through an
opto-input. Any of the available opto-inputs on the P72x relay can be selected for
synchronization. Pulsing this input results in the real time clock snapping to the nearest
minute. The recommended pulse duration is 20 ms, to be repeated no more than once per
minute.
The following table shows an example of the time synchronization function and assumes a
time format of hh:mm:ss.
Time of “Sync. Pulse” Corrected Time
19:47:00.000 to 19:47:29.999 19:47:00.000
19:47:30.000 to 19:47:59.999 19:48:00.000