Estimating the load response to voltage changes at UK primary substations

The development of Smart Grid technologies and the need to defer investments for expanding and reinforcing distribution networks have attracted new attention to aspects of Conservation Voltage Reduction (CVR). Based on the fact that the demand of certain loads can change with voltage, it is plausible to envisage the active management of voltage regulation devices in order to increase/decrease the demand during certain periods for the benefit of the distribution network (e.g., peak shaving) or the whole system (e.g., fast reserves). The extent of this voltage-driven demand response is however entirely dependent on the instantaneous load composition. In order to quantify the benefits of such a scheme, this work proposes a methodology to estimate the time-varying residential load response to primary substation voltage changes whilst complying with voltage limits at low voltage. This is applied to a small UK distribution network downstream an OLTC-enabled 33kV/6.6kV substation with 351 residential, 2 commercial and 1 industrial customers (total peak demand of 932 kW). The results, only considering part of the residential loads modeled with time-varying ZIP parameters, suggest that - even considering voltage constraints- there is considerable load response that can be unlocked from residential loads. However, this is highly dependent on the time of the day.