Novel 'tap-changer' development and concept demonstration

Close-up of a microscope with a dark background.

The novel tap-changer addresses the challenge of voltage control in low voltage (LV) local distribution networks with increasingly uncertain and rapidly varying loads. It can provide high fidelity voltage control where currently this is a fixed ratio with any balancing being performed at a much lower resolution at higher voltages further up the network chain.

Our aim

Electricity distribution network operators must ensure that voltages delivered to customers are close to nominal values, for example, 230 V @ +10% & −6%.

They have to do this for all customers, and on all timescales, from seconds to years. The difficulty is that there are tiny voltage drops throughout the network itself: the cables and overhead lines each have some impedance (combination of resistance and reactance), which causes a slight drop in the voltage whenever a current flows.

Voltages are balanced at much higher voltages in the electrical system, meaning there can be significant variability at the low voltage side when uncertain and unsteady loads are drawn, i.e., local feed-in energy distribution from photo-voltaic cells and charging of electric vehicles.

The project aimed to develop a compact and low-cost tap-changer based on the sponsors' established patent to address the issue of voltage control in LV networks. It can provide control of the secondary distribution transformers that feed 'local' networks and provide much greater control of voltages delivered to customers in the presence of much more significant local load uncertainty. Many distribution network operators are considering introducing voltage control mechanisms to their LV networks due to these uncertain loads that are becoming larger and much more unpredictable.

Our research

This project has developed from a theoretical concept through various stages of modelling and design to create two generations of prototype demonstrators.

Our outcomes

The demonstrator/prototype has shown that the patented concept that this project is based on is feasible.  This has been demonstrated through dynamic modelling in simulation, mechanical design and, subsequently the construction of a demonstrator in the laboratory.

Project lead: Dr Chris Ward


This project has enabled a private investor to tap into the research expertise in the Control Systems Group and develop an idea from concept through to demonstrator. The next step is to test the tap-changer in a real-world environment.

Dr Chris Ward