SERVICE MANUAL R5888C
QUADRAMHO Chapter 5
Page 9 of 24
and for reverse reach ground faults is:
(K1 + K2 + K4 + K5 + K6) (K35 + K36) K33 x K37
ohms
I
n
The phase fault loop impedances required are; for forward faults:
2 x (K1 + K2) (K31 + K32) K33
ohms
I
n
and for reverse phase faults:
2 x (K1 + K2) (K35 + K36) K33 x K37
ohms
I
n
The reach checks should be made for each element of the relay and the
appropriate outgoing contacts checked.
Note: The fault locator contacts do not operate for Zone 3 trips. For the reverse
reach an additional tolerance of ±15% is allowed.
4.8 Resistive reach check (if quadrilateral characteristic is fitted, see Figure 5)
Checks are done using resistive faults, thus in the forward direction all zones will
be seen to operate at the same loop impedance.
The required loop fault resistance is:
K3
ohms
I
n
The checks should be done for all phase to ground faults and results should be
within ±15% of the selected setting.
4.9 Zone 1 operation times
Zone 1 operation times should be checked by applying a fault at 50%
(approximately) of the Zone 1 reach.
An interval timer should be started when the fault is applied and stopped from the
contacts brought out on the left hand side terminals 7 and 8 of the 1Z test plug.
The following points should be noted:
i) To obtain “fast” operating times it is essential to use dynamic tests starting with
all phase-neutral voltages above the level detector setting, when connected for
phase faults do not have resistors fitted which tie down the neutral point, check
phase-neutral voltages with 100% potential setting. If this is not done filters in
the voltage circuits will already be switched in and the operation times will be
slower.
ii) If the polarising quantities are not correctly provided by the test set some slower
times may be measured.
iii) The times vary with the point on wave of fault application. It is thus suggested
that 10 operations be done for each type of fault.
iv) Times vary with the type of characteristic being used and the SIR.
v) Typical times expected are:
a) Shaped mho characteristic 15 – 30ms
b) Quadrilateral characteristic 20 – 35ms
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