Figure 531: Angle difference when power transformer is in synchrocheck zone
The vector group of the power transformer is defined with clock numbers, where
the value of the hour pointer defines the low-voltage-side phasor and the high-
voltage-side phasor is always fixed to the clock number 12, which is same as zero.
The angle between clock numbers is 30 degrees. When comparing phase angles,
the
U_BUS
input is always the reference. This means that when the Yd11 power
transformer is used, the low-voltage-side voltage phasor leads by 30 degrees or
lags by 330 degrees the high-voltage-side phasor. The rotation of the phasors is
counterclockwise.
The generic rule is that a low-voltage-side phasor lags the high-voltage-side phasor
by clock number * 30º. This is called angle difference adjustment and can be set for
SECRSYN with the
Phase shift setting.
9.3.5
Application
The main purpose of the synchrocheck function is to provide control over the
closing of the circuit breakers in power networks to prevent the closing if the
conditions for synchronism are not detected. This function is also used to prevent
the reconnection of two systems which are divided after islanding and a three-pole
reclosing.
The Synchro check function block includes both the synchronism check function and
the energizing function to allow closing when one side of the breaker is dead.
Control functions
1MRS757644 H
1006
620 series
Technical Manual
