AC power systems have to continuously balance generation and consumption in order to maintain a stable system frequency. The mismatches between the electricity generated and consumed have to be compensated by means of ancillary services, usually provided by conventional power plants. However, the recent developments in power distribution and automation will allow some of those services to be provided by distribution networks. Therefore, in this paper voltage control, at distribution substations, is used in connection with demand response (DR) for aiding system support in the Netherlands. The available capacity, which could be accessible by applying active voltage control, is evaluated and quantified as a function of supplied load over time. The DR capacity is estimated and the implications on power system imbalances are demonstrated in a case study for the Netherlands. In addition, the impact on the network losses is addressed and evaluated.