Schweitzer Engineering Laboratories SEL-700G Series, Инструкция по эксплуатации

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Date Code 20170814 Instruction Manual SEL-700G Relay
Protection and Logic Functions
Group Settings (SET Command)
The 25RCFX setting compensates magnitude differences between the
synchronism-check voltage and the generator voltage. Unmatched voltage
transformer or step-up transformer ratios can introduce magnitude differences.
Use the following equation to set 25RCFX:
After the relay has been placed in service and the generator breaker closed, you
may want to refine the 25RCFX setting to account for transformer ratio errors.
Use the procedure in the Manually Refine the 25RCFX Setting While the
Generator Is in Service on page 4.163 to refine the 25RCFX setting manually.
The 25SLO and 25SHI settings define the minimum and maximum acceptable
slip frequency for a generator breaker close. 25SLO must be set less than
25SHI. The SEL-700G defines the slip frequency as positive when the
generator frequency is higher than the system frequency.
Some large steam turbine generators require that a low, positive slip be present
when the generator breaker is closed. Setting 25SLO = 0.05 Hz and 25SHI =
0.25 Hz might satisfy that requirement.
Diesel generators may require that a zero or negative slip be present. This tends to
unload the machine shaft and crank briefly when the generator breaker closes.
Setting 25SLO = –0.25 Hz and 25SHI = 0.0 Hz might satisfy this requirement.
The SEL-700G synchronism-check function provides three methods to
supervise internal and external close signals. Relay Word bits 25AX1, 25AX2,
and 25C assert for different generator and system voltage phase angles, but all are
supervised by the voltage magnitude and difference and slip frequency limits.
The relay uses two phase-angle calculations to control the 25AX1, 25AX2,
and 25C Relay Word bits.
The first phase-angle calculation is the absolute phase-angle difference
between the generator and system voltages. The next phase-angle calculation
adjusts the absolute phase-angle difference by an angle value that is the phase
angle the system will travel through in TCLOSDX ms, assuming that the
present slip frequency remains constant. This slip-compensated phase angle
predicts the phase-angle difference when the breaker closes, if a close were
issued at this instant and if the breaker closed in TCLOSDX ms.
The 25AX2 Relay Word bit asserts when the absolute phase-angle difference
is less than the 25ANG2X setting.
Relay Word bit 25AX1 asserts when the absolute value of the slip-
compensated phase-angle difference is less than the 25ANG1X setting.
The 25C Relay Word bit asserts when the slip-compensated phase-angle
difference is equal to the CANGLE setting. When you would like to initiate a
generator breaker close, timed so that the phase angle difference equals the
CANGLE setting, supervise the CLOSEX initiation with the 25C Relay Word bit.
where
VSNOM = Nominal magnitude of VS input, secondary volts
VPNOMX = Nominal magnitude of VAX input, secondary volts (if
DELTAY_X := WYE)
VPNOMX = Nominal magnitude of VABX input, secondary volts (if
DELTAY_X := DELTA)
25RCFX
VSNOM
VPNOMX
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