3.3 Commissioning
247
7ST6 Manual
E50417-G1176-C251-A3
3.3.5
Tests for Circuit Breaker Failure Protection
General
If the device provides a breaker failure protection and if this is used, the integration of
this protection function in the system can be tested under practical conditions.
Because of the manifold application facilities and various configuration possibilities of
the system it is not possible to give a detailed description of the necessary test steps.
It is important to observe local conditions and protection and system drawings.
Before starting the circuit breaker tests it is recommended to isolate at both ends the
feeder which is to be tested, i.e. line isolators and busbar isolators should be open so
that the breaker can be operated without risk.
Caution!
Also for tests on the local circuit breaker of the feeder a trip command to the surround-
ing circuit breakers can be issued for the busbar.
Non–observance of the following measure can result in minor personal injury or prop-
erty damage.
Therefore, it is recommended primarily to interrupt the tripping commands to the ad-
jacent (busbar) breakers, e.g. by interrupting the corresponding pickup voltage supply.
Before the breaker is closed again for normal operation, the trip command of the
feeder protection routed to the circuit breaker must be disconnected so that the trip
command can only be initiated by the breaker failure protection.
Although the following lists do not claim to be complete, they may also contain points
which are to be ignored in the current application.
Auxiliary Contacts
of the CB
The circuit breaker auxiliary contact(s) form an essential part of the breaker failure pro-
tection system in case they have been connected to the device. Make sure the correct
assignment has been checked.
Busbar Tripping
The most important thing is the check of the correct distribution of the trip commands
to the adjacent circuit breakers in case of breaker failure.
The adjacent circuit breakers are those of all feeders which must be tripped in order
to ensure interruption of the fault current should the local breaker fail. These are there-
fore the circuit breakers of all feeders which feed the busbar or busbar section to which
the feeder with the fault is connected.
A general detailed test guide cannot be specified, because the layout of the surround-
ing circuit breakers largely depends on the system topology.
In particular with multiple busbars the trip distribution logic for the surrounding circuit
breakers must be checked. Here it should be checked for every busbar section that all
circuit breakers which are connected to the same busbar section as the feeder circuit
breaker under observation are tripped, and no other breakers.
Termination of the
Checks
All temporary measures taken for testing must be undone, e.g. especially switching
states, interrupted trip commands, changes to setting values or individually switched
off protection functions.
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