Commissioning P54x/EN CM/La4
MiCOM P543, P544, P545 & P546
CM) 10-41
CM
8.4 Demonstrate correct relay operation – non-current differential elements
8.4.1 Protection dependencies
The pri
nciple non-differential protection elements (distance, overcurrent, and earth fault) can
be set to have dependencies the availability of the phase differential and the status of the
voltage transformer supervision function (VTS).
The distance protection can be permanently enabled, or it can be set so that it is only
enabled in the event of a failure of the protection communications channel(s).
The overcurrent and earth faults elements can be permanently enabled, or can be set so that
they are only enabled in the event of a failure of the protection communications channel(s),
or can be set that they are only enabled in the event of a VTS alarm, or can be set so that
they are enabled according to a logical combination of both conditions.
If these elements are enabled with a dependency upon the above conditions, then it will be
necessary to simulate the condition in order to test the correct operation of the protection
function.
Communications failure can be achieved by setting cell [0F13: Test Loopback] to “Disabled”
and observing that the relay raises a Comms Fail alarm.
Note: If forcing a communication failure is necessary, it will be necessary to
clear communications alarms and reset the statistics at the end of the
tests.
VTS alarm can be raised by applying a 3-phase voltage to the VT inputs and then removing
one phase voltage for a duration exceeding the VTS Time Delay setting. At the end of the
tests, it will be necessary to ensure that the VTS alarm is cleared.
8.4.2 Distance protection single-end testing
If the distan
ce protection function is being used, the reaches and time delays should be
tested. If not, skip to section 8.4.10.
Refer to section 8.4.1, check for any possible dependen
cy conditions and simulate as
appropriate.
To avoid spurious operation of overcurrent, DEF/earth fault or breaker fail elements, these
should be disabled for the duration of the distance element tests. This is done in the relay’s
CONFIGURATION column. Ensure that cells [090C: Directional E/F DEF], [0910:
Overcurrent], [0913: Earth Fault] and [0920: CB Fail] are all set to Disabled. If the distance
element is enabled without qualification of communication channel failure, then the current
differential element [090F: Phase Diff], should be disabled. If the distance protection is
enabled on communication channel failure, then the differential element should remain
enabled and the communication should be disrupted to cause a suitable failure of the phase
differential protection.
8.4.2.1 Connection and preliminaries
The relay should
now be connected to equipment able to supply phase-phase and
phase-neutral volts with current in the correct phase relation for a particular type of fault on
the selected relay characteristic angle. The facility for altering the loop impedance
(phase-to-ground fault or phase-phase) presented to the relay is essential.
It is recommended that a three phase digital/electronic injection test set is used for ease of
commissioning. If this is not available, two setting changes may need to be made on the
relay, for the duration of testing:
To Next Page
Loading...
