Function description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberAutomatic voltage control for tapchanger, single controlTR1ATCCUIEC10000165 V1 EN90Automatic voltage control for tapchanger, parallel controlTR8ATCCUIEC10000166 V1 EN90Tap changer control and supervision, 6binary inputsTCMYLTC - 84Tap changer control and supervision,32 binary inputsTCLYLTC - 843.12.4.1 ApplicationWhen the load in a power network is increased the voltage will decrease and viceversa. To maintain the network voltage at a constant level, power transformers areusually equipped with an load tap changer. This alters the power transformer ratio in anumber of predefined steps and in that way changes the voltage. Each step usuallyrepresents a change in voltage of approximately 0.5-1.7%.The voltage control function is intended for control of power transformers with a motordriven load tap changer. The function is designed to regulate the voltage at thesecondary side of the power transformer. The control method is based on a step-by-stepprinciple which means that a control pulse, one at a time, will be issued to the tapchanger mechanism to move it one position up or down. The length of the controlpulse can be set within a wide range to accommodate different types of tap changermechanisms. The pulse is generated whenever the measured voltage, for a given time,deviates from the set reference value by more than the preset deadband (degree ofinsensitivity).The voltage can be controlled at the point of voltage measurement, as well as a loadpoint located out in the network. In the latter case, the load point voltage is calculatedbased on the measured load current and the known impedance from the voltagemeasuring point to the load point.The automatic voltage control can be either for a single transformer, or for paralleltransformers. Parallel control of power transformers with an IED can be made in threealternative ways:• With the master-follower method• With the reverse reactance method• With the circulating current methodSection 3 1MRK504116-UUS CIED application652Application manual
