Siemens 6MD85, Manual

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Figure 7-101 Selectivity through Directional Comparison Protection
Legend for Figure 7-101
Stage ▶:
▶, ◀: 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)
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.
Protection and Automation Functions
7.6 Directional Overcurrent Protection, Phases
SIPROTEC 5, High-Voltage Bay Controller, Manual 699
C53000-G5040-C015-9, Edition 11.2017