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TB MRF3 04.01 E
6.5
Primary injection test
Generally, a primary injection test could be carried
out in the similar manner as the secondary injection
test described above. With the difference that the pro-
tected power system should be, in this case, con-
nected to the installed relays under test "on line", and
the test voltages should be injected to the relay through
the voltage transformers with the primary side ener-
gized. Since the cost and potential hazards are very
high for such a test, primary injection tests are usually
limited to very important protective relays in the power
system.
Because of its powerful combined indicating and
measuring functions, the
MRF3
relay may be tested in
the manner of a primary injection test without extra ex-
penditure and time consumption.
In actual service, for example, the measured voltage
and frequency values on the
MRF3
relay display may
be compared phase by phase with the concerned in-
dications of the instruments of the switchboard to verify
that the relay works and measures correctly.
6.6
Maintenance
Maintenance testing is generally done on site at regu-
lar intervals. These intervals vary among users depend-
ing on many factors: e.g. the type of protective relays
employed; the importance of the primary equipment
being protected; the user's past experience with the re-
lay, etc.
For electromechanical or static relays, maintenance
testing will be performed at least once a year accord-
ing to the experiences. For digital relays like
MRF3
,
this interval can be substantially longer. This is be-
cause:
•
The
MR-
relays are equipped with very wide self-
supervision functions, so that many faults in the relay
can be detected and signalised during service. Im-
portant: The self-supervision output relay must be
connected to a central alarm panel!
•
The combined measuring functions of
MR-
relays en-
able supervision the relay functions during service.
•
The combined TRIP test function of the
MR-
relay al-
lows to test the relay output circuits.
A testing interval of two years for maintenance will,
therefore, be recommended.
During a maintenance test, the relay functions includ-
ing the operating values and relay tripping times
should be tested.
Summary of Contents for MRF3
Page 1: ...MRF3 Frequency Relay...
