GE T60 Instruction Manual page 553

CHAPTER 5: SETTINGS
The synchronism check function supervises the paralleling of two parts of a system that are to be joined by the closure of
a circuit breaker. The synchrocheck elements are typically used at locations where the two parts of the system are
interconnected through at least one other point in the system.
Synchrocheck verifies that the voltages (V1 and V2) on the two sides of the supervised circuit breaker are within set limits
of magnitude, angle, and frequency differences. The time that the two voltages remain within the admissible angle
difference is determined by the setting of the phase angle difference ΔΦ and the frequency difference ΔF (slip frequency). It
can be defined as the time it takes the voltage phasor V1 or V2 to traverse an angle equal to 2 × ΔΦ at a frequency equal
to the frequency difference ΔF. This time is calculated by:
where
ΔΦ is phase angle difference in degrees
ΔF is frequency difference in Hz
If one or both sources are de-energized, the synchrocheck programming can allow for closing of the circuit breaker using
undervoltage control to bypass the synchrocheck measurements (dead source function).
— This setting selects the source for voltage V1 (see the Notes section that follows).
SYNCHK1 V1 SOURCE
— Selects the source for voltage V2, which must not be the same as used for the V1 (see Notes).
SYNCHK1 V2 SOURCE
— Selects the maximum primary voltage difference in volts between the two sources. A primary
SYNCHK1 MAX VOLT DIFF
voltage magnitude difference between the two input voltages below this value is within the permissible limit for
synchronism.
— Selects the maximum angular difference in degrees between the two sources. An angular
SYNCHK1 MAX ANGLE DIFF
difference between the two input voltage phasors below this value is within the permissible limit for synchronism.
SYNCHK1 MAX FREQ HYSTERESIS
condition becomes satisfied when the frequency difference becomes lower than
Synchrocheck element has operated, the frequency difference must increase above the
sum to drop out (assuming the other two conditions, voltage and angle, remain satisfied).
MAX FREQ HYSTERESIS
— Enables the dynamic mode of synchrocheck. When it is enabled, the location of where the present
SYNCHK1 SYNC CLOSE
V2 vector will be arriving to synchronize (shown as V2' in the figures here) with breaker close time being taken into account
will be predicted based on the measured slip frequency so that breaker close command can be issued in advance to
ensure the synchronism at the time when the breaker is actually closed.
T60 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
— Specifies the required hysteresis for the maximum frequency difference condition. The
Figure 5-198: Synchrocheck plot for slip > 0 (slip = F2-F1)
CONTROL ELEMENTS
. Once the
SYNCHK1 MAX FREQ DIFF
SYNCHK1 MAX FREQ DIFF + SYNCHK1
Eq. 5-56
5
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