CM
Out of service LED behaviour for P742xxxxxxxxx5J or for P743xxxxxxxxx5K:
− The Commission Test menu structure in the PU also allows for an 'Overhaul' mode
where secondary injection of the PU is permitted. In this mode the isolators must be
open for testing, but all information is passed back to the CU for inclusion in the zone
calculations. While in this mode the Peripheral Unit can be tested locally, secondary
injections tests, for example, can be carried out (the system is stable because during
the current injection there is a differential current in the CZ but not in the Zone). In this
case, since the system must have primary action (i.e open isolators), the ‘Out of
Service’ LED is ON.
− The Commission Test menu structure in a Peripheral Unit allows for a '50BF Disabled'
mode where the PU does not initiate the breaker fail protection, but can respond to
commands to trip from the CU (in the event of a busbar protection trip or CB failure
backtrip). In this case, since the busbar protection is not out of service, the ‘Out of
Service’ LED remains OFF in the CU.
4.2.3.2
Testing the Trip LED
The trip LED can be tested by initiating a manual circuit breaker trip from the relay. However,
the trip LED will operate during the setting checks performed later. Therefore, no further
testing of the trip LED is required at this stage. Please note that the CB control function does
not exist in the Central Unit (P741) as only the Peripheral Unit (P742/P743) may trip/close
the local circuit breakers.
4.2.3.3
Testing the user-programmable LEDs
To test the user-programmable LED’s set cell [COMMISSION TESTS, Test LED’s] to ‘Apply
Test’. Check that all the LED’s of the relay illuminate.
In the P741 and P743:
− The ‘Red LED Status’ cell is an eighteen bit binary string that indicates which of the
user-programmable LEDs on the relay are illuminated when accessing the relay from
a remote location, a ‘1’ indicating a particular Red LED is lit.
− The ‘Green LED Status’ cell is an eighteen bit binary string that indicates which of the
user-programmable LEDs on the relay are illuminated when accessing the relay from
a remote location, a ‘1’ indicating a particular Green LED is lit.
− If a ‘Red LED Status’ cell AND the same ‘Green LED Status’ cell are at ‘1’ the
particular LED is lit Orange
− If a ‘Red LED Status’ cell AND the same ‘Green LED Status’ cell are at ‘0’ the
particular LED is not lit.
In the P742:
− The ‘LED Status’ cell is an eight bit binary string that indicates which of the
user-programmable LEDs on the relay are illuminated when accessing the relay from
a remote location, a ‘1’ indicating a particular LED is lit and a ‘0’ not lit.
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