Table of Contents
Advertisement
APPENDIX E
IEC 60870-5-2 offers a selection of link transmission procedures using a control field and an optional address field. Links
between stations may be operated in either an unbalanced transmission mode. Appropriate function codes for the control
field are specified for both modes of operation.
If the links from a control system to several protection equipments share a common physical channel, then these links
shall be operated in an unbalanced mode to avoid the possibility that more than one protection equipment attempts to
transmit on the channel at the same time. The sequence in which the various protection equipments are granted access
to transmit on the channel is then determined by an application layer procedure in the control system.
The companion standard specifies whether an unbalanced or a balanced transmission mode is used, together with which
link procedures (and corresponding link function codes) are to be used.
The companion standard specifies an unambiguous address (number) for each link. Each address may be unique within
a specific system, or it may be unique within a group of links sharing a common channel. The latter needs a smaller
address field but requires the control system to map addresses by channel number.
A companion standard shall specify one frame format chosen from those offered in IEC 60870-5-1. The format chosen
shall provide the required data integrity together with the maximum efficiency available for an acceptable level of
convenience of implementation.
E.3.2.1 UNBALANCED TRANSMISSION
The control system constitutes the master, the protection equipment the slave; i.e. the control system is always primary
station, the protection equipment always secondary station. The RES bit is not used.
The following function codes are used:
PRM = 1
0, 3, 4, 9, 10, 11
PRM = 0
0, 1, 8, 9, 11
Address field A always consists of one octet only, for broadcast (send/no reply) the address is defined as 255.
E.3.2.2 ADDITIONAL SPECIFICATIONS TO IEC 60870-5-2
The following additional function code is defined in the reserved range:
PRM = 1
F-Code 7:= reset FCB
This SEND function code is used to set the internal FCB bit to the value 0, i.e. the next successive primary message with
FCV = 1 expected with the setting FCB = 1 by the protection equipment. No other reset function such as those associated
with function code 0 (reset communication unit) are triggered.
The following codes are already specified in the standard. They are used here as follows:
PRM = 0
F-Code 14:= link service not functioning
Primary messages that cannot be passed on due to a malfunction are answered with an F-Code 14. The FCB bit is
processed alternately.
PRM = 0
F-Code 15:= link service not functioning
GEK-106237P
FCB and FCV = 0
MIFII Digital Feeder Relay
E.3 IEC 60870-5-103
E.3.2 LINK LAYER
E
E-5
Advertisement
Table of Contents
