On-Line Independent Tap-Changing of Each Feeder Supplied by a Low Voltage Distribution Transformer

Abstract

An on-line tap-changing circuit was developed for use with low voltage transformers (10 kV/380 V, or equivalent), in which the tap positions could be set independently for each low voltage feeder. This allows for possible variation in loads and distributed generation between different feeders fed from a given transformer, allowing the line voltages to be kept within limits on all feeders. A combination of computer simulation and practical experiments was used. A model constructed in Excel gave preliminary results, which was used to specify a more detailed model in Matlab ® Simulink. A small-scale 220/380 V distribution network was constructed, with currents limited to 5 A per phase. Finally, a rotary switch was constructed, suitable for currents up to 500 A, which would be required for a full-scale low voltage distribution network. The results showed that the voltage could be kept within limits, even with a large difference in load and distributed generation from one feeder to another.

Investigation of Phase-wise Voltage Regulator Control Logics for Compensating Voltage Deviations in an Experimental Low-voltage Network

“…In addition, the current studies focus on simulation-based validation that means experimental-based validation is still largely missing in the literature. To address the aforementioned problems, several studies are performed to investigate the control performance provided by a single-phases on-load tap-changer transformer [21]- [25] and validate the OLTC control in an experimental environment [26], [27].…”

“…In [21], an OLTC circuit is developed for use with a low-voltage transformer (10/0.4 kV, or equivalent), in which the tap position could be set independently for each low-voltage feeder. To model the low-voltage system and the control logic of OLTC, the author uses two simulation tools:…”

“…In [22], phase-wise OLTC is assessed technically in Flemish LV distribution grids. Compared to [21], the proposed tapping logic considers the influence of PV in terms of active power injection. The simulation is performed in DigSilent PowerFactory, and the results showed that the phase-wise OLTC partly eliminates the violations of both voltage limits and thermal constraints.…”