GE L60 Instruction Manual page 134

5.1 OVERVIEW
Sources, in the context of L60 series relays, refer to the logical grouping of current and voltage signals such that one
source contains all the signals required to measure the load or fault in a particular power apparatus. A given source may
contain all or some of the following signals: three-phase currents, single-phase ground current, three-phase voltages and
an auxiliary voltages from a single-phase VT for checking for synchronism.
To illustrate the concept of sources, as applied to current inputs only, consider the breaker-and-a-half scheme below. Some
protection elements, like breaker failure, require individual CT current as an input. Other elements, like distance, require the
sum of both current as an input. The phase comparison function requires the CT currents to be processed individually to
cope with a possible CT saturation of one CT during an external fault on the upper bus. The current into protected line is the
phasor sum (or difference) of the currents in CT1 and CT2, depending on the current distribution on the upper bus.
5
The following table explains how to configure the sources for full functionality.
Table 5–1: SOURCE CONFIGURATION FOR PHASE COMPARISON
FUNCTION
Phase current F1 to F3 CT channels
(used for 87PC first current
and Breaker Failure 1)
Ground current F1 (Ground overcurrent)
Phase voltage
Auxiliary voltage
5-6
CT1
VT1
1PH
BF 1 BF 2
L60
SRC 1 SRC 2
Phase
comparison
SRC 1 SRC 2
SRC 1 SRC 3
Distance and
Synchrocheck 1
overcurrent
SRC 3 SRC 3
Figure 5–1: BREAKER-AND-A-HALF SCHEME
CT/VT MODULE 1 (TYPE 8P)
SRC 1 SRC 2
Not available
Not available
Not available Not available
Not available Not available
L60 Line Phase Comparison System
CB1 CB2
CT2
3PH
VT2
Protected
line
CT/VT MODULE 1 (TYPE 8F)
SRC 3
L1 to L3 CT channels
(used for 87PC second
current and Breaker
Failure 2). This source is
configurable only if a
second CT/VT module is
ordered.
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Single-phase bus VT for
synchrocheck
5 SETTINGS
831786A1.CDR
SRC 4
Sum of F1:F3 and L1:L3
(used for distance and
overcurrent)
---
Three-phase line VT for
distance and
synchrocheck
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GE Multilin