GE ALPS Instruction Manual page 49

1 PRODUCT DESCRIPTION
c) OPEN POLE OPERATION
The functional logic diagrams in Figures 1–3: POTENTIAL FUSE FAILURE LOGIC DIAGRAMS through 1–8: OSB LOGIC
DIAGRAMS do not depict all the logical interactions that occur in the software algorithms during the period that one pole is
open. Two software flags and two associated masks control the operation during an open-pole period. The single phase trip
flag, SINGPTRIP, is set when the ALPS issues a single-phase trip. The open-pole flag, OPENPOLE, is set when the pole-
disagreement logic detects that one pole is open.
A primary function of SINGPTRIP is to disable all the phase-distance function phase pairs that are involved with the open
pole. If pole A is open, then SINGPTRIP disables phase pairs A-B and C-A but allows phase-pair B-C to remain in service
for all zones of protection. This prevents inadvertent operation of the A-B and C-A distance functions during the time that
pole A is open when line-side potential is used. The SINGPTRIP mask disables the ground-distance functions associated
with the open pole.
The OPENPOLE flag is shown on all the functional logic diagrams as one input to OR30. This indicates that once the
OPENPOLE flag is set, any subsequent fault will cause a three-phase trip regardless of the fault type. The Fault Detector
(FD) measurement is modified when the OPENPOLE flag is set. With all poles closed, FD operates on the magnitude of I
and I , as well as the change in I
0
sequence currents but does not operate on the magnitude of I
level of I and I .
2 0
The Potential Transformer Fuse Failure Detection function is indicated as FFB on the logic diagrams. For a Hybrid scheme,
the weak-infeed logic is modified as shown in Figure 1–8: OSB LOGIC DIAGRAMS on page 1–15 and described above.
The operation of the Out-of-Step Blocking logic is modified as explained below. If the ground directional overcurrent func-
tions are used as part of a pilot scheme, they are disabled. The ground backup overcurrent functions, 50G and 51G, are
disabled.
As indicated on the logic diagrams, the Phase Selector function indicates the faulted phase for single-phase-to-ground
faults and produces a multi-phase output for all other fault types. Tripping for the initial fault is the faulted phase for single-
phase-to-ground faults and all three phases for multiphase faults. Subsequent faults during the open-pole period are
tripped three-phase regardless of fault type.
A single-pole relay configured for three-pole tripping requires the use of three CC inputs: 52b_A, 52b_B,
and 52b_C. This requirement is necessary for open-pole logic to function correctly.
NOTE
OUTPUT OF UV UNITS IS HIGH
WHEN VOLTAGE IS LOW
UVA
IbA
UVB
IbB
UVC
IbC
d) RECLOSE CONTROL
The ALPS includes two Reclose Initiation outputs. RI-1P picks up when the ALPS selects to trip only one of the three phase
trip outputs. RI-3P picks up whenever the ALPS selects to trip all three poles of the breaker. As shown on Figures 1–23:
OST MHO CHARACTERISTIC on page 1–42 and 1–24: OUT-OF-STEP TRIPPING LOGIC on page 1–42, the Reclose Ini-
tiation outputs of the ALPS may be blocked by the Reclose Cancel logic. The Reclose Cancel options are discussed in
Chapter 2: CALCULATION OF SETTINGS.
GE Power Management
, I , and I . When the OPENPOLE flag is set, FD operates on the change in the three
1 2 0
2
Any Voltage
Undervoltage
52b Phase A
52b Phase B 52b Phase B
52b Phase C
Figure 1–21: OPEN POLE DETECTION LOGIC
ALPS Advanced Line Protection System
1.8 PROTECTION SCHEMES
and I , since an open pole will produce some steady-state
0
All Phase
Voltages High
Phase A Open
Phase B Open
Phase C Open
1
2
Any
Phase
open
Only 1
Phase
open
All
Phases
Open
1-37