Description - GE ALPS Instruction Manual

1.9 PHASE IDENITIFIED CHANNEL SCHEMES
1.9 PHASE IDENITIFIED CHANNEL SCHEMES
1
This feature applies to the ALPS with single phase tripping model only.
NOTE
The ALPS with Single Phase Tripping models on series-compensated lines include the ability to use multiple permissive
channels in phase identified channel schemes to improve the phase selection capability of the protection. The model num-
bers that include this feature are: ALPSDA1 XXXXXXXXX and ALPSDB1 XXXXXXXXX (where X is any valid character) with
firmware version V0004.03AA21 or higher. The use of phase identified channel schemes improves the performance of the
protection scheme in single phase tripping applications where inter-circuit ("cross-country") faults are possible.
The protection of double circuit transmission lines presents a challenging problem when single phase tripping is required.
Consider the simple system shown in Figure 1–22: INTER-CIRCUIT FAULT EXAMPLE below.
For the fault condition shown, the protective relays on both lines at Station R will detect an AB to ground fault. At Station S,
the relay on the protected line will detect an AG fault, while the relay on the parallel line will detect a BG fault. Note that as
the fault location is moved away from the bus at station S, the relays at Station R will detect the correct single line to ground
fault. If suitable precautions are not taken, the condition of Fig. A-1 will result in the tripping of all three phases of both line
at Station R, and proper single pole tripping at Station S. The operation of the relays at Station R is due to the fact that they
must rely on the local phase selection to determine the fault type and which phase or phases to trip. The solution to the
problem is to use the fault type information from both the local and remote ends of the line to determine the proper tripping
mode. This solution requires multiple communications channels to transmit the information between the substations. The
ALPS relay offers two phase identified channel solutions to the problem. The first requires the use of two permissive chan-
nels with encoding; the second requires the use of four permissive channels. The operation of these schemes is described
in the following section.
a) PILOT TRIPPING
The local faulted phase determination uses the same algorithms as other ALPS relays. The permissive keying is super-
vised by the fault detecting functions (phase and ground distance, GDOC) and the local fault type determination algorithm.
The channel keying is based on the local fault type as shown in the following table.
Table 1–7: CHANNEL KEYING FOR PILOT TRIPPING (TWO CHANNELS)
LOCAL FAULT TYPE
AG, BC, BCG
BG, CA, CAG
CG, AB, ABG, 3PH
The receipt of either channel will be used as the permissive signal in the scheme logic. This allows the relay to determine
that the fault is within the protected line. In addition to the permissive signal, the receiver inputs will be compared with the
selected local fault type per the following table to determine which phase(s) to trip.
1-38
PARALLEL LINE
PROTECTED LINE
Figure 1–22: INTER-CIRCUIT FAULT EXAMPLE
1.9.3 TWO CHANNEL PHASE IDENTIFIED CHANNEL LOGIC
XMTR #1 XMTR #2
X
X
X X
ALPS Advanced Line Protection System
1 PRODUCT DESCRIPTION

1.9.1 DESCRIPTION

1.9.2 INTER-CIRCUIT FAULTS
BG
AG
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