11.1.2 Voltage control of Parallel TransformersIn parallel operation, each transformer protection IED must be connected to the stationcommunication bus for data exchange. The following procedure assumes that thenecessary pre-configuration in the Parameter Setting tool and the Signal Matrix toolhas been performed and tested to enable data exchange between IEDs or betweeninstances of voltage control in the same IED.For parallel operation, it is also recommended to confirm the setting for the generalparallel arrangement of transformers in Main menu/Settings/Setting group N/Control/TransformerVoltageControl(ATCC,90)/TR8ATCC:x/ParCtrl.General parallel arrangement of transformers are defined by setting TnRXOP to On orOff. The following rules are applicable for the settings of T1RXOP – T8RXOP.• In each instance of TR8ATCC, set all TnRXOP parameters corresponding to theconnected IEDs to On except the parameter corresponding to the IED itself. Forexample, do not set T1RXOP to On in IED T1 or T2RXOP to On in IED T2.For example, if IEDs T1, T2 and T3 are connected,• In instance 1 of TR8ATCC, set T2RXOP and T3RXOP to On.• In instance 2 of TR8ATCC, set T1RXOP and T3RXOP to On.• In instance 3 of TR8ATCC, set T1RXOP and T2RXOP to On.11.1.3 Minimum Circulating Current (MCC) methodVoltage control of parallel transformers with the circulating current method meansminimizing the circulating current at a given voltage target value. The busbar voltage(UB) is measured individually for each transformer in the parallel group by itsassociated TR8ATCC function. These measured values are then exchanged betweenthe transformers, and in each TR8ATCC block, the mean value of all UB values iscalculated. The resulting value UBmean is then used in each IED instead of UB for thevoltage regulation.1. Check the overcurrent blocking level (Iblock) in Main menu/Settings/Generalsettings/Control/TransformerVoltageControl(ATCC,90)/TR8ATCC:x/TCCtrl/Iblock.2. Check that the circulating current blocking (OperCCBlock) is set On, and thecheck the correct settings for circulating current limit (CircCurLimit) in Mainmenu/Settings/General settings/Control/TransformerVoltageControl(ATCC,90)/TR8ATCC:x/ParCtrl/CircCurrLimit.1MRK 511 360-UEN A Section 11Primary injection testingBay control REC670 2.1 IEC 193Commissioning manual
