5.9
Date Code 20171021 Instruction Manual SEL-421 Relay
Protection Functions
Current and Voltage Source Selection
ESS := 2, Single Circuit Breaker Configuration—Two Current Inputs
Set ESS to 2 for single circuit breaker applications using two current sources.
Figure 5.6 illustrates this application along with the corresponding current and
voltage sources. The relay uses current source IW for line relaying and current
source IX for Circuit Breaker 1 failure protection.
ESS := 3, Double Circuit Breaker Configuration—Independent Current Inputs
Set ESS to 3 for circuit breaker-and-a-half applications using independent current
sources. Figure 5.7 illustrates this application along with the corresponding cur-
rent and voltage sources. This selection provides independent circuit breaker fail-
ure protection for Circuit Breaker 1 and Circuit Breaker 2.
ALINEV Alternate Line Voltage Source (VZ, NA) NA
ALTV Alternate Voltage Source (SEL
OGIC Equation) NA Hidden
a
Hidden when preceding setting is NA.
Table 5.6 ESS := 1, Current and Voltage Source Selection (Sheet 2 of 2)
Setting Prompt Entry Comments
Figure 5.6 ESS := 2, Single Circuit Breaker Configuration
Table 5.7 ESS := 2, Current and Voltage Source Selection
Setting Prompt Entry Comments
NUMBK Number of Circuit Breakers in Scheme (1, 2) 1
LINEI Line Current Source (IW) IW Automatic
ALINEI Alternate Line Current Source (IX, NA) NA
ALTI Alternate Current Source (SEL
OGIC Equation) NA Hidden
a
a
Hidden when preceding setting is NA.
BK1I Breaker 1 Current Source (IX) IX Automatic
BK2I Breaker 2 Current Source (NA) NA Hidden
IPOL Polarizing Current (NA) NA Automatic
ALINEV Alternate Line Voltage Source (VZ, NA) NA
ALTV Alternate Voltage Source (SEL
OGIC Equation) NA Hidden
SEL-421 Relay
BUS
CB1
3
1
3
IW
IX
VAZ
VY
3
Analog Input
IW
IX
VY
VAZ
Function
CB1 protection, line protection
CB1 breaker failure
Line protection
Synchronism check
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