Sel 411L - Figure 3.60 Current and Voltage Source Connections for the Relay; Figure 3.61 Main and Alternate Line Current Source Assignments

P.3.107
Date Code 20151029 Protection Manual SEL-411L Relay
Protection Functions
Current and Voltage Source Selection
Figure 3.60 Current and Voltage Source Connections for the Relay
Current Source
Switching
Figure 3.61–Figure 3.63 show the basic application of some of these settings.
Figure 3.61 shows an alternate breaker that can be substituted for the main
breaker (bus switching details not shown). Normally, current IW (main
breaker) is used as the line current source. But, if the alternate breaker
substitutes for the main breaker, then current IX is used as the line current
source, instead. SEL
OGIC setting ALTI controls the switching between
currents IW and IX as the line current source (assert setting ALTI to switch to
designated alternate line current ALINEI := IX). Alternate line current source
settings ALINEI and ALTI are not used often and thus are usually set to NA.
Setting ALTI is automatically hidden and set to NA if ALINEI := NA (no line
current switching can occur).
Figure 3.62 shows combined currents IW and IX (see COMB = IW + IX in
Figure 3.60) set for line protection, metering, etc. (LINEI := COMB). In order
to combine these currents correctly inside the relay to produce the effective
line current, when the CT ratios are different, the relay divides IX by TAPX
before adding IX to IW. The relay automatically calculates TAPX from the
CTRW and CTRX setting values (TAPX = CTRW/CTRX).
Figure 3.63 shows the assignment of breaker currents for up to two circuit
breakers. These assigned breaker currents are used in breaker monitoring and
breaker failure functions. These same breaker currents can also be assigned as
line currents (e.g., line current assignment LINEI := IW in Figure 3.61).
Figure 3.61 Main and Alternate Line Current Source Assignments
Relay Rear Panel
(partial)
COMB = IW + IX
(combined
current
source
for line)
Current
Source
(for breaker
and/or
for line)
IAW IBW ICW
IW
IAX IBX ICX
IX
Current
Source
(for breaker
and/or as
alternate
for line)
VAZ VBZ VCZ
VZ
Voltage Source
(alternate)
VAY VBY VCY
VY
Voltage Source
NOTE: If a current source is set to
“combine” (e.g., LINEI := COMB),
ALINE = IX, or if BK2I = COMB, then
setting TAPX becomes visible.
IW
IX
Relay
Main
Breaker
Alternate
Breaker
LINEI := IW
ALINEI := IX