Recorded Data And Fault Analysis - ABB SPAJ 111 C User Manual

Recorded data
and fault analysis
Secondary
injection testing
16
The data recorded in the registers of the relay
can be used both to analyze an earth-fault situ-
ation and to study the behaviour of the protec-
tion equipment.
Register 1 records the maximum measured neu-
tral current as a percentage of the rated current
I of the energizing input in use. The register
n
value is updated if:
- the measured neutral current exceeds the value
already recorded in the register
- the relay operates. At relay operation the value
at the moment of operation is recorded.
The value of the neutral current recorded in a
fault situation shows the magnitude of the fault
current. When the network's total earth-fault
current is known, the degree of development
(the fault resistance) of the earth-fault can be
determined. By means of the recorded value in
register 1 the relation between the set start
current of the relay and the real fault current can
be seen. Correspondingly the relation between
the set start current of the relay and the current
values under normal service conditions can be
determined.
Testing, both primary and secondary, should
always be performed in accordance with na-
tional regulations and instructions.
The protection relay incorporates an IRF func-
tion that continuously monitors the internal
state of the relay and produces an alarm signal on
the detection of a fault. According to the manu-
facturer's recommendations the relay should be
submitted to secondary testing at five years'
intervals. These tests should include the entire
protection chain from the instrument trans-
formers to the circuit breakers.
The secondary testing described in this manual
is based on the relay's setting values during
normal operation. If necessary, the secondary
testing can be extended by testing the protection
stages throughout their setting ranges.
As switch positions and setting values have to be
altered during the test procedure the correct
positions of switches and the setting values of
the relay during normal operation conditions
have to be recorded, for instance, on the refer-
ence card accompanying the relay.
For secondary testing the relay must be dis-
connected from the voltage transformer circuits
and other secondary circuits by means of
disconnectable terminal blocks or a test adapter
fitted on the relay.
Registers 2 and 3 contain the number of starts of
stage I > and I >> and provide information on
0 0
the occurrence of earth-faults and on the distri-
bution of earth-faults in respect of the fault
resistance. Frequent starts may indicate the pres-
ence of an imminent earth-fault or some kind of
disturbance apt to cause an earth-fault.
Registers 4 and 5 show the duration of the latest
starts of stage I > and I >>, expressed in per cent
0 0
of the set operate time. Any new start resets the
register, which then starts counting from zero.
When the stage operates, the register shows the
value 100 [%].
Registers 4 and 5 provide information on the
duration of an earth-fault, or the safety margin
of the grading times of the protection. If, for
instance, the value of register 4 of the busbar
earth-fault relay operating as feeder back-up
protection relay is 75, when the feeder relay
operates, the safety margin between the main
protection and the back-up protection is 25%.
Registers 1...5 can be reset by pressing the STEP
and RESET push-buttons simultaneously, or
with a command V102 over the SPA bus.
WARNING!
The current transformer secondary circuits
must not be opened when they are energized.
The high voltage produced by an open CT
secondary circuit could be lethal and may
damage instruments and insulation.
When the auxiliary voltage is connected to the
relay, a self-testing program is carried out auto-
matically. The self-testing program includes the
whole relay except for the matching transform-
ers and the contacts of the output relays. The
operational condition of the relay is tested using
ordinary relay test equipment. The secondary
injection test also includes the matching trans-
formers, the output relays and the accuracy of
the operate values.
When no relay test set is available the secondary
injection test can be carried out with the follow-
ing equipment:
- adjustable voltage transformer 0...260 V, 1 A
- current transformer
- ammeter, accuracy ±0.5% or better
- stop watch or counter for time measurement
- dc voltage source for auxiliary supply
- switches and indicator lamps
- supply and pilot wires
- calibrated multimeter