Schweitzer Engineering Laboratories SEL-421-4 - Figure 6.1 230 Kv Overhead Transmission Line; Kv Overhead Distribution Line Example

Date Code 20171021 6Instruction Manual SEL-421 Relay
6Instruction ManualInstruction Manual
SECTION 6
Protection Applications Examples
This section provides detailed instructions for setting the SEL-421 Relay protec-
tion functions. Use these application examples to help familiarize yourself with
the relay, and to assist you with your own protection settings calculations. The
settings that are not mentioned in these examples do not apply.
Setting calculation guidelines are provided for the following applications:
➤ 230 kV Overhead Distribution Line Example on page 6.1
➤ 500 kV Parallel Transmission Lines With Mutual Coupling Example
on page 6.18
➤ 345 kV Tapped Overhead Transmission Line Example on page 6.53
➤ EHV Parallel 230 kV Underground Cables Example on page 6.87
Separate protection application examples are provided for the following functions:
➤ Out-of-Step Logic Application Examples on page 6.119
➤ Autoreclose Example on page 6.137
➤ Autoreclose and Synchronism Check Example on page 6.141
➤ Circuit Breaker Failure Application Examples on page 6.151
➤ 230 kV Tapped Transmission Line Application Example on
page 6.170
230 kV Overhead Distribution Line Example
Figure 6.1 shows a double-ended 230 kV line with SEL-421 protection at each
end. This example explains how to calculate settings for the SEL-421 at Station S
that protects the line between Stations S and R.
NOTE: The SEL-421-4 provides fast
and secure tripping for the line
segment but does not have the high-
speed distance elements of the
SEL-421-5.
This application example uses step-distance protection to provide high-speed
tripping for faults in the first 80 percent of the line and time-delayed tripping for
the last 20 percent.
Power System Data
Table 6.1 lists the power system data for this application example. Substitute the
values and parameters that correspond to your system when you set the relay,
using this example as a guide.
Figure 6.1 230 kV Overhead Transmission Line
SEL-421 SEL-421
Z
1L
, Z
0L
Z
1S
, Z
0S
BK1
S (Harvard) R (Princeton)
BK2
Z
1R
, Z
0R