Synchronism Check - ABB Relion Technical Manual

Section 12
Control
12.1.7.2
352

Synchronism check

The voltage difference, frequency difference and phase angle difference values are
calculated by the SESRSYN function and are available for the synchronism check
function for evaluation. If the bus voltage is connected as phase-phase and the line voltage
as phase-neutral (or the opposite), this need to be compensated. This is done by selecting
the corresponding phases for the measurement in the settings for the SESRSYN function.
In addition the phase angle difference has to be compensated for by the setting PhaseShift.
The setting scales the line voltage and adjust the phase angle equal to the bus voltage.
When the function is set to OperationSC = Enabled, the measuring will start.
The function will compare the bus and line voltage values with internally preset values
that are set to be 80% of the UBase selected for GlbBaseSelBus and GlbBaseSelLine.
If both sides are higher than 80% of the Ubase values, the measured values are compared
with the set values for acceptable frequency, phase angle and voltage difference: FreqDiff,
PhaseDiffand VDiffSC. If a compensation factor is set due to the use of different voltages
on the bus and line, the factor is deducted from the line voltage before the comparison of
the phase angle values.
The frequency on both sides of the circuit breaker is also measured. The function is only
released if the frequency difference is less than the fixed set value of +/-5 Hz.
Two sets of settings for frequency difference and phase angle difference are available and
used for the manual closing and autoreclose functions respectively, as required.
The inputs BLOCK and BLKSC are available for total block of the complete SESRSYN
(25) function and selective block of the Synchronism check function respectively. Input
TSTSC will allow testing of the function where the fulfilled conditions are connected to
a separate test output.
The outputs MANSYOK and AUTOSYOK are activated when the actual measured
conditions match the set conditions for the respective output. The output signal can be
delayed independently for MANSYOK and AUTOSYOK conditions.
A number of outputs are available as information about fulfilled checking conditions.
VOKSC shows that the voltages are high, VDIFFSC, FRDIFFA, FRDIFFM, PHDIFFA,
PHDIFFM shows when the voltage difference, frequency difference and phase angle
difference conditions are out of limits.
Output INADVCLS, inadvertent circuit breaker closing, indicate that the circuit breaker
has been closed at wrong phase angle by mistake. The output is activated, if the voltage
conditions are fulfilled at the same time the phase angle difference between bus and line
is suddenly changed from being larger than 60 degrees to smaller than 5 degrees.
1MRK 502 048-UUS A
Technical manual