Alstom SHPM 101, Service Manual

Page: 226 / 336

SERVICE MANUAL R5888C
QUADRAMHO Chapter 5
Page 6 of 24
Select test option 53 and inject current as in previous test. Determine the pick-
up; drop-off should be within 10% of the actual pick-up.
Level detector Terminals injected LED marking
A phase 1Y 1–2 Z3
B phase 1Y 3–4 Aided trip
C phase 1Y 5–6 SOFT
Note: Refer to 4.4.3(ii) as it is convenient to combine the tests.
4.4.3 Auto ranging low set and high set residual current level detectors
The auto ranging only comes into action when a minimum phase difference current
is exceeded. The residual signal is derived by summing the vectors of the voltages
in the relay which are proportional to the phase currents.
The operation level when auto ranging varies directly with the highest phase
difference current until a limit is reached. The minimum operate level varies
inversely with K1 + K2. In commissioning it is only necessary to check this fixed
level.
(i) Low-set
This is used to enable ground fault trips preventing operation of heavy close-up
phase to phase faults.
It is also used in the Voltage Transformer Supervision feature to detect the
presence of zero sequence current.
Minimum operate level =
2
x
4.8
x
I
n
amps (
±
20%)
100 K1 + K2
Select test option 43, inject current into each phase in turn (as in 4.4.2 (i))
minimum operate level as indicated by the LED marked ‘V~FAIL’. Drop off
should be within 10% of the actual pick up.
(ii) High-set
The high set is used to block phase fault comparators which may cause 3 phase
tripping during heavy close-up single phase ground faults.
The auto ranging in conjunction with the voltage level detectors permits phase
fault comparators to operate for two phase-ground faults.
Minimum operate level = 8 x low set
16
x
4.8
x
I
n
amps (
±
20%)
100 K1 + K2
Select test option 53 and inject current as for the low set and check the
“V~ FAIL” LED for operation. Drop off should be within 10% of the actual pick
up.
4.5 Zone 1 reach tests
4.5.1 Connections and preliminaries
The relay should now be connected to equipment able to supply three phase to
neutral volts and current in the correct phase relationship for a particular type of
fault on the selected relay characteristic angle. The facility for altering the loop
impedance (phase-ground fault compensation or phase-phase) presented to the
relay is essential. This may be a continuous adjustment or steps of around 1% in
the voltage or current.