Schweitzer Engineering Laboratories SEL-751 - Figure 4.69 Angle Difference between VP and VS Compensated by Breaker Close Time (Fp < Fs and VP Shown as Reference in this Example)

4.112
SEL-751 Relay Instruction Manual Date Code 20170927
Protection and Logic Functions
Group Settings (SET Command)
Intermediate calculations:
(fP – fS) = (59.95 Hz – 60.05 Hz) = –0.10 Hz = –0.10 slip cycles/second
TCLOSD • (1 / 1000) = 0.1 second
Resulting in:
Angle Difference
= |(VP – VS) + [(fP – fS) • TCLOSD • (1 / 1000) • (360°/slip cycle)]|
= |(VP – VS) + [–0.10 • 0.1 • 360°]|
= |(VP – VS) – 3.6°|
Figure 4.69 Angle Difference Between VP and VS Compensated by Breaker
Close Time (fP < fS and VP Shown as Reference in This Example)
During the breaker close time (TCLOSD), the voltage angle difference
between voltages VP and VS changes by 3.6 degrees. This angle compensa-
tion is applied to voltage VS, resulting in derived voltage VS*, as shown in
Figure 4.69.
NOTE: The angle compensation in
Figure 4.69 appears much greater
than 3.6 degrees. Figure 4.69 is for
general illustrative purposes only.
Angle Difference
Decreasing (VS* Approaching VP)
Angle Difference
Increasing (VS* Moving Away From VP)
Angle
Difference
Angle
Difference
Angle Compensation for
Breaker Close Time
TCLOSD
Angle Compensation
for Breaker Close Time
TCLOSD
Setting
25ANG1
(or 25ANG2)
Setting
25ANG1
(or 25ANG2)
Setting
25ANG1
(or 25ANG2)
VP
VS
VS*
VS*
VP
VS
Setting
25ANG1
(or 25ANG2)