SPAU 341 C1-AA SPAU 341 C Voltage regulator

Product Description

The voltage regulator SPAU 341 C is intended to be used for regulating the voltage of power transformers with on-load tap-changers in distribution substations. The connections required for a simple voltage regulating function is the measured phase-to-phase voltage U12 and the raise and lower output contacts. If the line drop compensation, the minimizing circulating current or the overcurrent blocking feature is to be used, one or more phase currents have to be measured. If only one phase current is measured, it is always connected to the terminals of the phase current I L1, and the current to be measured is selected with the software switches SGF2/6 and SGF2/7 of the automatic voltage regulating module SPCU 1D50.

The purpose of the regulator is to maintain a stable secondary voltage of the power transformer. The basis for this operation is the reference voltage, which is set by the user. By adding
or decreasing various compensation factors, the regulator calculates a control voltage from the reference voltage. Hence, the control voltage is the desired transformer secondary voltage to be maintained by the regulator. Then the control voltage is compared with the voltage measured and the difference between these two forms the regulating process error.
Since the tap-changer changes the voltage in steps, a certain error has to be allowed. This error, called bandwidth, is also set by the user. If the measured voltage fluctuates within the bandwidth, the regulator is inactive. Should, on the other hand, the measured voltage be outside these bandwidth limits, an adjustable delay T1 starts. This delay T1 remains active as long as the measured voltage is outside the hysteresis limits of the bandwidth. The factory setting of the hysteresis limits is 90%.
Should the measured voltage still be outside the hysteresis, when the delay counter T1 reaches its setting value, the raise or lower output relay is activated and the motor drive of the tapchanger is operated. If, on the other hand, the measured voltage falls within the hysteresis limits, the delay counter is reset.
Should one tap-changer operation not be enough to regulate the transformer voltage within the hysteresis limits, a second adjustable delay T2, usually with a shorter time setting than T1, starts.
The delays T1 and T2 can be selected either with definite or inverse time characteristic. Inverse time characteristic means, that the delay is inversely proportional to the regulator error, i.e the delay is inversely proportional to the difference between the control voltage and the measured voltage.
The voltage regulating function will be described more in detail in the document 1MRS 750111- MUM EN.