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1MAC309294-MB F Section 5

Control functions

RER620 331

Technical Manual

Figure 174: Angle difference when power transformer is in sychro-check 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 V_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 the

function with the Phase shift setting.

5.3.5 Application

The main purpose of the synch-check 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 synch-check function block includes both the synchronism check function and the

energizing function to allow closing when one side of the breaker is dead.

ABB RER620 Technical Manual

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