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L60 LINE PHASE COMPARISON SYSTEM – INSTRUCTION MANUAL
OVERVIEW
CHAPTER 5: SETTINGS
5
Sources, in the context of L60 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 can 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 shown.
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.
Figure 5-1: Breaker-and-a-half scheme
The following table explains how to configure the sources for full functionality.
Table 5-1: Source configuration for phase comparison
Function
CT/VT module 1 (Type 8P)
CT/VT module 1 (Type 8F)
SRC 1
SRC 2
SRC 3
SRC 4
Phase current
F1 to F3 CT channels (used for
87PC first current and Breaker
Failure 1)
Not available
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.
Sum of F1:F3 and L1:L3 (used
for distance and overcurrent)
Ground current
F1 (Ground overcurrent)
Not available
---
---
Phase voltage
Not available
Not available
---
Three-phase line VT for
distance and synchrocheck
Auxiliary voltage Not available
Not available
Single-phase bus VT for
synchrocheck
---
831786A1.CDR
Protected
line
VT2
CT2
CB2
CB1
CT1
VT1
1PH
L60
Phase
comparison
SRC 1
SRC 2
SRC 3
Distance and
overcurrent
SRC 3
3PH
Synchrocheck 1
SRC 3
SRC 1
SRC 1
SRC 2
BF 1
BF 2