Alstom SHPM 101, Service Manual

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SERVICE MANUAL R5888C
QUADRAMHO Chapter 5
Page 11 of 24
These impedances must be prepared as A–B phase faults.
The boundary may be determined either by momentarily applying the fault or by
gradually decreasing the impedance until the voltmeter reading fails. For the
reverse reach an additional tolerance of
±
15% is allowed.
Note: Ensure that C–N post-fault voltage is maintained at greater than 70% of
63.5V. If this condition is not met, PSB will be blocked by the ‘Any Pole
Dead’ feature. See Figure 60 Chapter 2 of this manual.
It should be possible to meet the above condition by manipulating fault
and source impedances on the test set.
4.12.2 50ms timer check
The voltage out of the monitor point box has been chosen so that the digital timer
will treat it as a contact, the voltage present being treated as an open contact.
An impedance should be presented to the relay approximately midway between
Zone 3 and Zone 6, start the timer when it is applied and stop it when the voltage
on the monitor point box terminals 2–7 falls. (On the timer terminal 2 must be
connected to the common on the timer and the timer set for normally open to start
and stop).
The time measured will be that of the Zone 6 comp 50ms + processing
time; the comparator will vary with point-on-wave of fault application.
Take five timings, find the average and subtract x ms which should give 50ms
(
±
10ms).
Where x = 25ms for quad/mho version
30ms for mho/lenticular version
Note: Each phase to ground pre-fault voltage must be greater than 70% of
63.5V. If this condition is not met, 240ms is added to the measured time.
This can be seen from Figure 60 in Chapter 2.
4.12.3 Simulated power swing with blocking checks
It is now necessary to simulate a power swing for the A–B element of the relay.
Set the power swing blocking switches Z1, Z2, Z3 to the right. Press the indicator
reset, apply an impedance just outside Zone 3 and reduce the impedance without
switching off (say 1% steps) until power swing indication is obtained (this should
be when the Zone 3 boundary is crossed). Check that the alarm contact operates
(C19 to C20).
Still maintaining the fault, set K11 and K21 to
∞
, then in turn check (starting with
Z1) that removing the blocks enables the correct LED indications after the
appropriate time delays.
Put the blocking switches to their required positions.
Make sure the correct settings are put back on K11 and K21. If the optical isolator
input for inhibiting power swing blocking is to be used, check that putting the
required volts on terminals A5–6 inhibits the feature.
4.13 Voltage transformer supervision
Operation occurs when zero sequence voltage above a set level is detected
without any zero sequence current being detected above a set level. If set for
indication only, instantaneous indication will be given if operation conditions are
satisfied and a comparator is operated, otherwise time delayed indication will be