Siemens 6MD85 Manual page 699

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Figure 7-101
Legend for Figure 7-101
Stage ▶:
▶, ◀:
If you are using a communication channel, the protocol-transmission methods detect if the channel is inter-
rupted. If you are using pilot wires, we recommend operation based on a closed-circuit connection. The device
uses a function chart to check and indicate if the binary input is dead for an unexpectedly long period. In
contrast with the blocking procedure, overfunction is not possible if communication is lost. Therefore, a loss of
communication is not critical where this procedure is concerned, although it must be detected and indicated.
Directional comparison protection can also be implemented as a blocking procedure. This procedure works
under all system switching states, i.e. also with infeed at one end (or weak infeed). However, to use it you
must delay the stage (typically by 100 ms) so that the blocking signal is received in time under all circum-
stances. It is also essential that you monitor the communication channel to avoid overfunction in the event of
failure followed by a system incident.
Configuration of the Stage, Function Chart
To configure the stage, proceed as follows:
•
The Directional mode parameter of both stages must be set to forward
•
The Directional comparison and Release via input signal parameters of the first stage
must be set to yes. This is so that the first stage is only released if the >Release delay & op. input
signal is active. Furthermore, the direction is indicated if a threshold value is exceeded.
•
The first stage can be set without a time delay. The second stage has to be graded
•
The information forward from the Direction signal in the first stage must be transmitted to the oppo-
site end. The routing is determined by the type of transmission
•
A function chart has to be implemented at the receive end to link the received (forward information)
and release signals, dependent upon the type of transmission.
SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017
Selectivity through Directional Comparison Protection
Stage is set in the forward direction; stage 1 is instantaneous, stage 2 is graded
If a threshold value is exceeded, the stage indicates the direction (forward or reverse)
Protection and Automation Functions
7.6 Directional Overcurrent Protection, Phases
699