Alstom SHPM 101, Service Manual

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SERVICE MANUAL R5888C
QUADRAMHO Chapter 2
Page 59 of 74
5.16.35 Fault locator start contacts 19A–1, 19B–1, 19C–1 and 19E–1
These contacts are provided for data logging functions such as phase selection,
starting of fault locators, fault recorders, etc. Two or more contracts close for a fault
condition, eg:
A–Ground fault 19A–1 and 19E–1
A–B Ground 19A–1 and 19B–1
A–B Ground fault 19A–1 and 19B–1 and 19E–1
A–B–C fault 19A–1 and 19B–1 and 19C–1
If a fault is detected by Zone 1 comparators, the phase information of Zone 1
takes precedence over phase information from Zone 2. This action ensures that the
closest forward fault condition detected during any simultaneous fault situation is
used for phase selection purposes. The smaller distance relay zones also offer the
best phase discrimination.
Figure 74, shows the diagram of the fault locator logic which is implemented by
software in the scheme logic microcomputer. It also shows that is a switch-on-to-
fault trip occurs due to “current and no volts” (SW1 to right) then the fault locator
logic uses the appropriate “current and no volts” information to select the fault
locator phases.
5.16.36 Zone 2 trip contacts Z2–1
This contact closes for any Zone 2 time delayed trip and may be used for data
logging purposes.
5.16.37 Zone 3 trip contact Z3–1
This contact closes for any Zone 3 time delayed trip and may be used for data
logging purposes.
5.16.38 Aided trip contact 94Y–1
Any aided trip action occurring for faults when in the permissive underreach,
permissive overreach or blocking schemes, is announced by the closure of this
contact.
5.16.39 Switch on to fault contact 98–1
A common type of fault is a close-up fault occurring on energising the line, caused
by inadvertently leaving grounding clamps on the line after maintenance work.
If line VTs are used and if the clamps are on all 3 phases, then the Zone 1 units
would fail to detect the fault. This shortcoming is due to the lack of cross polarising
and synchronous polarising signals for the Zone 1 comparators under these
conditions. The switch-on-to-fault logic (SOTF) allows other fault detectors within the
relay to trip the circuit breakers instantaneously, eliminating the dependency on
Zone 1. Should a fault be detected during SOTF conditions then the relay sends a
signal to block auto-reclosure of the circuit breakers (see Figure 73).
Two types of fault detectors are capable of detecting 3 phase zero voltage faults.
The first type is the Zone 3 comparators which can operate without voltage, owing
to their offset characteristics: however, to allow for non standard relay
characteristics, the logic is arranged so that all comparators can be used as fault
detectors in the SOTF logic. The second type uses the voltage level detectors and
low set phase current level detectors, a fault being detected if any current level
detector operates without operation of the corresponding voltage level detector.
To allow for the circuit breaker poles not all closing together, the “current and no
volts” condition (CNV) has to last for more than 20ms (see Figure 75).