Synchronism Check - ABB REL650 Applications Manual

Section 11
Control
11.1.2.2
288
• The measured voltage V-Line is higher than 80% of GblBaseSelLine and the
measured voltage V-Bus is higher than 80% of GblBaseSelBus.
• The voltage difference is smaller than 0.10 p.u, that is (V-Bus/GblBaseSelBus) - (V-
Line/GblBaseSelLine) < 0.10.
• The difference in frequency is less than the set value of FreqDiffMax and larger than
the set value of FreqDiffMin. If the frequency is less than FreqDiffMin the
synchronism check is used and the value of FreqDiffMin must thus be identical to the
value FreqDiffM resp FreqDiffA for synchronism check function. The bus and line
frequencies must also be within a range of +/- 5 Hz from the rated frequency. When
the synchronizing option is included also for autoreclose there is no reason to have
different frequency setting for the manual and automatic reclosing and the frequency
difference values for synchronism check should be kept low.
• The frequency rate of change is less than set value for both V-Bus and V-Line.
• The closing angle is decided by the calculation of slip frequency and required pre-
closing time.
The synchronizing function compensates for measured slip frequency as well as the
circuit breaker closing delay. The phase angle advance is calculated continuously. Closing
angle is the change in angle during the set breaker closing operate time tBreaker.
The reference voltage can be phase-neutral A, B, C or phase-phase A-B, B-C, C-A or
positive sequence. The bus voltage must then be connected to the same phase or phases as
are chosen for the line. If different phases voltages are used for the reference voltage, the
phase shift has to be compensated with the parameter PhaseShift, and the voltage
amplitude has to be compensated by the factor URatio. Positive sequence selection setting
requires that both reference voltages are three phase voltages.

Synchronism check

The main purpose of the synchronism check function is to provide control over the closing
of circuit breakers in power networks in order to prevent closing if conditions for
synchronism are not detected. It is also used to prevent the re-connection of two systems,
which are divided after islanding and after a three pole reclosing.
Single pole auto-reclosing does not require any synchronism check since
the system is tied together by two phases.
SESRSYN (25) function block includes both the synchronism check function and the
energizing function to allow closing when one side of the breaker is dead. SESRSYN (25)
function also includes a built in voltage selection scheme which allows adoption to
various busbar arrangements.
1MRK 506 334-UUS A
Application manual