ABB RELION REX640 Operation Manual page 154

Maintenance and Periodical Testing
documentation is up to date and test records from the pre-commissioning and
commissioning tests are available. Periodical testing should not be seen as a
reconfirmation of commission stage testing, but as a stage where the installation's
possible impaired performance is detected, documented and also corrected.
REX640 protection and control relay is a vital part of the complete protection and
control scheme, but it's not the only one. The other devices within the scheme shall
be considered as well. Depending on the actual installation these might include all
or just a part of the following list:
• Circuit breaker primary part
• Circuit breaker trip coils, one or several
• Measurement transformers or sensors and related wiring
• Arc flash detection sensors
• Other protection relay(s) as a part of the complete scheme
• Interpanel wiring
• Interpanel communication for binary and/or analogue signals
• DC auxiliary voltage supply
• Station level Scada/monitoring system
• Process control system
• Remote level Scada system
The following is mainly concentrating on the REX640 as a part of the overall system,
but other devices will be shortly discussed where seen necessary.
8.1.2.1 Method of Testing
Important aspect in periodical testing is to secure that at the end of the testing
all parts of the installation are restored to the original state. For example, if
some test requires disconnecting relay voltage measurements from busbar voltage
transformer secondary circuits, the connections must be reestablished at the end
of that testing. It's highly recommended that the test engineer keeps a record of all
possible temporary modifications within the installation, to help him/her to revert
to the original set-up.
In general, a good rule is to perform the tests using a method which is as close as
possible to the normal operational conditions of the installation. This is one way
to reduce the risk of leaving some temporary connection or setting unrestored to
original position at the end of the testing.
Periodical testing is performed with the protected feeder de-energized, circuit
breaker truck withdrawn to test position or in case of a fixed circuit breaker,
bus- and line-disconnectors in open position. In case the other feeders within the
installation remain energized and supplying loads, it's important to isolate the relay
under testing from the rest of the system to avoid accidentally sending upstream
trip commands during the testing.
Protection relay periodical testing is normally carried out as secondary injection
testing. The currents and voltages normally measured via sensors or instrument
transformers are replaced with adjustable analogue signals from the test set. In
case the installation is equipped with relay test blocks, the separation of the
relay from the measurement and trip circuits happens automatically when the test
adaptor is inserted into the test block.
If test blocks are not present, the connection point of the test set is the LV-
compartment's terminal blocks. These terminal blocks typically offer the possibility
to open the terminal mid bridge connection and that way separate the relay under
154
1MRS759118 D
REX640
Operation Manual