The reference voltage can be phase-neutral A, B, C or phase-phase A-B, B-C, C-A orpositive sequence (Require a three phase voltage, that is VA, VB and VC) . By settingthe phases used for SESRSYN, with the settings SelPhaseBus1, SelPhaseBus2,SelPhaseLine2 and SelPhaseLine2, a compensation is made automatically for thevoltage amplitude difference and the phase angle difference caused if different settingvalues are selected for the two sides of the breaker. If needed an additional phase angleadjustment can be done for selected line voltage with the PhaseShift setting.12.1.2.2 Synchronism check M12309-6 v10The main purpose of the synchronism check function is to provide control over theclosing of circuit breakers in power networks in order to prevent closing if conditionsfor synchronism are not detected. It is also used to prevent the re-connection of twosystems, which are divided after islanding and after a three pole reclosing.Single pole auto-reclosing does not require any synchronism checksince the system is tied together by two phases.SESRSYN (25) function block includes both the synchronism check function and theenergizing 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 adoptionto various busbar arrangements.en04000179_ansi.vsd~ ~~~ ~~ANSI04000179 V1 EN-USFigure 115: Two interconnected power systemsFigure 115 shows two interconnected power systems. The cloud means that theinterconnection can be further away, that is, a weak connection through other stations.The need for a check of synchronization increases if the meshed system decreasessince the risk of the two networks being out of synchronization at manual or automaticclosing is greater.The synchronism check function measures the conditions across the circuit breaker andcompares them to set limits. Output is generated only when all measured conditions arewithin their set limits simultaneously. The check consists of:1MRK 505 370-UUS A Section 12ControlBusbar protection REB670 2.2 ANSI 295Application manual
