Areva MiCOM P921, Technical Manual

Page: 265 / 376

Technical Guide P92x/EN CT/E11
Courier Database
MiCOM P921-P922-P923 Page 75/118
Similarly, if the computerized system used takes in charge the auto addressing, the
relay address can be settled on 0 by activating the auto-addressing characteristics of
the computer software. The relay receives then the next valid address on the bus.
If the address is 255 or not known, it can be modified by sending a new address,
with a global message, to a periphery possessing a particular serial number. This
method is used for those peripheries which do not have any user interface for reading
or changing the address in process.
2.4.2 Measured Values
Each measured value can be periodically extracted by a selective call of MiCOM
P921, P922 and P923 relays.
2.4.3 Status word
Each response of a slave periphery contains an octet of status. This octet is resent by
the relay at the beginning of each message for signaling important data. The
principal workstation can be designed to respond automatically to these important
data.
The contained indications are the following:
Bit 0 : 1=Recording of disturbance available for retrieval
Bit 1 : 1=Change of the unit status word
Bit 2 : 1=Change of the control status word
Bit 3 : 1=Relay busy, no response possible in time
Bit 4 : 1=Relay out of service
Bit 5 : 1=Recording of events available for retrieval
Bit 6 : 1=Switched Alarm indicator
Bit 7 : 1=Switched tripping indicator
2.4.4 Unit Status word
The unit status word is located in the menu 000C
Each bits pair of the unit status word serves to indicate the status (position ) of the unit
elements checked through the relay.
This functionality is not supported on MiCOM P921,P922 and P923 relays.
2.4.5 Control status word
The control status word is located in the cell of the menu 000D
It is used for transmitting the control information of the slave periphery to the central
unit. Nevertheless, the relays described in this manual are protection relays , which
do not use this control characteristic.