Alstom MiCOM P54 Series, Technical Manual, Page: 737 / 1024

Firmware Design P54x/EN FD/La4
MiCOM P543, P544, P545 & P546
(FD) 9-11
FD
3) Breaker fail
The technique to use 52a contacts in trip circuits was described above. However, in the
event of failure of the local circuit breaker (stuck breaker), or defective auxiliary contacts
(stuck contacts), the 52a contact action is incorrect. The interrupting duty at the local
breaker then falls on the relay output contacts which may not be rated to perform this
duty. MiCOM high break contacts will avoid the risk of burnt relay contacts.
4) Initiation of teleprotection
The MiCOM high break contacts also offer fast making. This can provide faster tripping:
additionally, fast keying of teleprotection is a benefit. Fast keying bypasses the usual
contact operation time, such that permissive, blocking and intertrip commands can be
routed faster.
2.6 IRIG-B board (optional)
The IRIG-B board is an order option which can be fitted to provide an accurate timing
reference for the relay. The IRIG-B signal is connected to the board via a BNC connector on
the back of the relay. The timing information is used to synchronize the relay’s internal real-
time clock to an accuracy of 1 ms. The internal clock is then used for the time tagging of the
event, fault maintenance and disturbance records.
The IRIG-B board can also be specified with a fiber optic transmitter/receiver which can be
used for the rear communication port instead of the EIA(RS)485 electrical connection
(IEC 60870 protocol only).
2.7 Second rear communications board
For relays with Courier, Modbus, IEC60870-5-103 or DNP3 protocol on the first rear
communications port there is the hardware option of a second rear communications port,
which will run the Courier language. This can be used over one of three physical links:
twisted pair K-Bus (non polarity sensitive), twisted pair EIA(RS)485 (connection polarity
sensitive) or EIA(RS)232.
The second rear comms board and IRIG-B board are mutually exclusive since they use the
same hardware slot. For this reason two versions of second rear comms board are
available; one with an IRIG-B input and one without. The physical layout of the second rear
comms board is shown in Figure 4.