SELOGIC
®
Control Equations 4-25
SEL-300G Instruction Manual
Date Code 20000616
Setting Descriptions
Enable Synchronism Checking (Y, N) E25 = Y
Set E25 = Y to enable synchronism checking elements. If synchronism checking is not
required, set E25 = N. When E25 = N, the 59VP, 59VS, GENVHI, GENVLO, GENFHI,
GENFLO, VDIF, 25A1, 25A2, 25C, CFA, and BKRCF Relay Word bits are inactive and
the following relay settings are hidden and do not need to be entered.
Synch-Check Phase (VA, VB, VC, VAB, VBC) SYNCP = VA
Set SYNCP to indicate which phase the synch voltage VT is connected to. You may use
phase-to-ground or phase-to-phase connected VT, regardless of whether open-delta or four-
wire wye VTs are used on the generator.
Voltage Window, Low Threshold (20.0 to 200.0 V) 25VLO = 58.3
Voltage Window, High Threshold (20.0 to 200.0 V) 25VHI = 69.7
Maximum Voltage Difference (OFF, 1.0 to 15.0%) 25VDIF = 3.3
The 25VLO and 25VHI settings define the acceptable system (VS) voltage magnitude
window prior to closing the generator breaker. 25VHI must be a higher voltage value than
25VLO. The system and generator voltages must both be greater than 25VLO and less than
25VHI for the synch-check outputs to operate. The 25VDIF setting defines the maximum
acceptable percentage magnitude difference between the system and generator voltages
prior to closing the generator breaker.
Generator Voltage High Required (Y, N) GENV+ = Y
If your synchronization practice requires that the generator voltage be higher than the
system voltage prior to closing the generator breaker, set GENV+ = Y. If not, set
GENV+ = N.
Voltage Ratio Correction Factor (0.500 to 2.00) 25RCF = 1.000
Use the 25RCF setting to null minor differences between the system and generator voltage
transformer ratios. Normally, the 25RCF setting should be very close to 1.000. Use the
instructions below to determine whether a nonunity setting should be used in your
application.
Minimum Slip Frequency (-1.00 to 0.99 Hz) 25SLO = 0.05
Maximum Slip Frequency (-0.99 to 1.00 Hz) 25SHI = 0.10
The 25SLO and 25SHI settings define the acceptable slip frequency between the system and
the generator prior to closing the generator breaker. 25SHI must be greater than 25SLO.
The SEL-300G Relay defines slip frequency greater than 0 Hz when the generator frequency
is greater than the system frequency.
Transformer Compensation Angle (0, +30°, -30°) COMPA = 0
Use the COMPA setting to compensate for the phase angle shift introduced by a generator
step-up transformer connected between the generator terminals and the open generator
breaker. When there is no transformer, set COMPA = 0. When there is a transformer
andthe system phase-neutral voltage phase angle leads the generator phase-neutral voltage
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