Schweitzer Engineering Laboratories SEL-421-4 - Figure 6.50 230 Kv Tapped Overhead Transmission Line; Kv Tapped Transmission Line Application Example

6.170
SEL-421 Relay Instruction Manual Date Code 20171021
Protection Applications Examples
230 kV Tapped Transmission Line Application Example
230 kV Tapped Transmission Line Application Example
This example shows you how to automate the complete restoration sequence,
including autoreclose and synchronism check, for the tapped 230/115 kV auto-
transformer located at Substation T. Figure 6.50 shows a one-line diagram of
the tapped 230 kV overhead transmission line.
The tapped autotransformer at Substation T has a high-side MOD (motor-oper-
ated disconnect) and two low-side circuit breakers. Whenever an internal fault
occurs on the 230 kV overhead transmission line, the SEL-421 Relays at each of
the three terminals open all of the circuit breakers, followed by the high-side
MOD at Substation T. The SEL-421 Relays replace separate line relays, discrete
reclosing and synchronism check relays, timers, latching relays, and extensive
wiring for this particular example.
Use the SEL-421 protection freeform SEL
OGIC control equations in Tab le 6.48 to
automate the following actions at Substation T:
➤ Restore tapped Substation T to service after a successful 230 kV
overhead transmission line autoreclose operation.
➤ Restore the 230 kV overhead transmission line to service after an
autotransformer failure or a low-side circuit breaker failure
operation.
➤ Restore Substation T station service and 115 kV bus continuity after
an unsuccessful automatic line reclose operation or a remote 230 kV
circuit breaker failure trip.
Figure 6.50 230 kV Tapped Overhead Transmission Line
SEL-421
SEL-421
M
IRRORED BITS MIRRORED BITS
BK1S
BK1R
BK2S
BK2R
SEL-421
115 kV
230 kV
S
R
(EHV)
MOD
BK2T
BK1T
T
(HV)