Communications Media; Pictorial Comparison Of Operating Modes - GE MiCOM P40 Agile Technical Manual

P44x/EN AP/Hb6
(AP) 5-130
Permissive
Blocking
The requirements for the three channel types are represented pictorially in Figure 95.
Figure 95: Pictorial comparison of operating modes
This diagram shows that a blocking signal should be fast and dependable; a direct intertrip
signal should be very secure and a permissive signal is an intermediate compromise of
speed, security and dependability.
5.6.1.3

Communications Media

InterMiCOM is capable of transferring up to 8 commands over one communication channel.
Due to recent expansions in communication networks, most signalling channels are now
digital schemes utilising multiplexed fibre optics and for this reason, InterMiCOM provides a
standard EIA(RS)232 output using digital signalling techniques. This digital signal can then
be converted using suitable devices to any communications media as required.
Note:
The EIA(RS)232 output may alternatively be connected to a MODEM link.
Regardless of whether analogue or digital systems are being used, all the requirements of
teleprotection commands are governed by an international standard IEC60834-1:1999 and
InterMiCOM is compliant with the essential requirements of this standard. This standard
governs the speed requirements of the commands as well as the probability of unwanted
commands being received (security) and the probability of missing commands
(dependability).
channel isn't seen as being a valid signal. In other words, an intertripping
channel must be very secure.
In permissive applications, tripping is only permitted when the command
coincides with a protection operation at the receiving end. Since this
applies a second, independent check before tripping, the signalling
channel for permissive schemes do not have to be as secure as for
intertripping channels.
In blocking applications, tripping is only permitted when no signal is
received but a protection operation has occurred. In other words, when a
command is transmitted, the receiving end device is blocked from
operating even if a protection operation occurs. Since the signal is used
to prevent tripping, it is imperative that a signal is received whenever
possible and as quickly as possible. In other words, a blocking channel
must be fast and dependable.
The MiCOM P442/P444 relays only use electrical connections (EIA(RS)232, port
SK5)
Application Notes
MiCOM P40 Agile P442, P444