Download There are occasions where changes may need to be

In-Service Protection Setting changes and testing – Settings Classification
WG B5-01
1
by Pelqim Spahiu, National Grid UK (document 2)
Reasons for In-Service Protection Setting changes and testing
There are occasions where changes may need to be made to in service relay settings
for the following reasons:
i)
ii)
iii)
iv)
v)
vi)
When the numeric busbar protection is taken out of service (Central Unit
Failure for example). In such a case settings on protection (distance and
backup) protecting the circuits connected to the unprotected busbars are
changed to provide acceptable protection for busbars while the busbar
protection system is out of service.
At the request of the supplier to update the settings on the equipment. This
could, for example, happen on Current Differential Protection setting following
the changes to the telecommunication system characteristics. In such a case
non-GPS current differential protection will have to be desensitized to allow for
the time difference between ‘’go’’ and ‘’return’’ path signal delay.
Following a new, 132 kV and below, connection. In such a case, if the
settings of Overcurrent and Earth fault protections on the new connected
circuit are higher than the rest of the outgoing circuits then NG backup
protection settings will have to changed. NG backup protection settings that
will change are those on Supergrid/132 kV and lower voltage levels:
TM on the 2-Stage HV 3-phase Overcurrent protection and TM on the LV
Earth Fault (and LV Overcurrent, where applied).
Following a new generation connection into the Transmission System
busbars. Overcurrent settings for example should be changed to cater for
new load/fault levels.
Following an incident investigation if a relay setting is found to be the cause of
an incident.
Busbar Protection Central Unit will require setting/configuration change
following the introduction of a new circuit (New Bay Unit).
In relation to the tests performed to verify/confirm the changes it very much depends
whether the relay is electromechanical, electronic or numeric and in what category
the setting that has changed belongs to (see 2 below).
In general, in case of an electromechanical relay setting changes (for example reach
setting change on a distance protection) secondary injection is performed. The
injection is done with the trip links removed so that the trip relay that operates the
Circuit Breaker is not energized. In case of Numeric relay more attention is focused
on checking the readings and alarms (for example ‘’C Diff’’ level reading on the Unit
Protection or I1,I2 and I0 readings to see whether their values are as expected knowing IA, IB and IC load that the relay is ‘’seeing’’).
It has to be noted that National Grid UK tends to ask Supplier to do comprehensive
tests in the Factory before the relay is shipped to site. All of those tests are
performed with the actual specific circuit settings loaded into the relay.
2
Settings classification – categories
Settings within National Grid UK protection systems are normally categorized
as below:
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04th January 2007
1 Relay Function Selection (eg. O/C, E/F, Distance,
DAR etc)
2 Power System Measurement (i.e. V, I, Z, f, t)
3 Selectable Logic Sequence (i.e. DAR link)
4 Communication Selection (i.e. baud rate)
5 Output/Input configuration
6 Fixed Logic Sequence (e.g. DAR sequence
which is fixed at the time of Type Registration)
Power System Settings
Fixed Settings
Settings within categories 5 and 6 are normally changed in the Manufacturers
Factory and the relay is retested there before shipping it to site (again only
readings are taken and recorded on site).
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04th January 2007