Renewable Voltage Regulation And The Transformer Tapping Trade-Off

Load-tap-changing (LTC) transformers provide voltage regulation in subtransmission and distribution networks, but these expensive devices can only tap so many times before they fail. Fluctuations due to renewable energy can cause excessive tapping, accelerating aging. We address the question of how voltage regulation at renewable sources influences tapping frequency. In particular, we show that loose regulation results in excessive downstream (distribution) transformer tapping, while tight regulation causes upstream (subtransmission) tapping. We use yearlong simulations of a simple test network to generate tap trajectories and trade-off curves, illuminating the trade-off between subtransmission and distribution transformer wear. The paper concludes with a description of future work based on joint minimization of upstream and downstream tapping operations.