Date Code 20011112
Line Current Differential, Distance, Out-of-Step, Overcurrent,
3-75
Voltage, Synchronism Check, and Frequency Elements
SEL-311L Instruction Manual
If the voltages are static (voltages not slipping with respect to one another), the two synchronism
check elements operate as shown in the top of Figure 3.54. The angle settings are checked for
synchronism check closing.
If the voltages are not static (voltages slipping with respect to one another), the two synchronism
check elements operate as shown in the bottom of Figure 3.54. The angle difference is
compensated by breaker close time, and the breaker is ideally closed at a zero degree phase angle
difference, to minimize system shock.
These synchronism check elements are explained in detail in the following text.
Synchronism Check Elements Settings
Table 3.13: Synchronism Check Elements Settings and Settings Ranges
Setting Definition
Range
25VLO
low voltage threshold for “healthy
voltage” window
0.00–150.00 V secondary
25VHI
high voltage threshold for “healthy
voltage” window
0.00–150.00 V secondary
25SF
maximum slip frequency
0.005–0.500 Hz
25ANG1
synchronism check element 25A1
maximum angle
0°–80°
25ANG2
synchronism check element 25A2
maximum angle
0°–80°
SYNCP
synchronizing phase
VA, VB, VC, VAB, VBC, or VCA
TCLOSD
breaker close time for angle
compensation
OFF, 1.00–60.00 cycles
BSYNCH SEL
OGIC
control equation that blocks
synchronism check
Relay Word bits referenced in
Tables 9.3 and 9.4
Accuracy
Voltage Pickup:
±
1 V and
±
5% of setting
Voltage Transient Overreach: < 5% of setting
Slip Pickup:
±
0.003 Hz
Angle Pickup:
±
4°
Summary of Contents for SEL-311L
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