Danger, danger, high voltage

Jon Hiscock, chief executive of Fundamentals, highlights the growing importance of voltage control on distribution networks in a world of intermittent renewable generation and fast-changing customer demand.

One of our clients called us recently to tackle the problem of a customer who could not charge their electric car, because the voltage they supplied was too high, tripping out the charger safety circuits. Just one example of a growing problem in the medium and low voltage distribution sector.

Our motorist’s problem was that they live in a housing development with a lot of rooftop solar panels, causing voltage surges in their local part of the network on sunny days. Atypical converse scenario affects end-of-network communities. Their distance from main substations already causes voltages to drop. With increasing demand from all manner of electrical equipment, voltages can fall to the point where they cannot function properly.

Both the above issues can usually be fixed with the addition of voltage control units locally, but these are effectively sticking plasters. The big picture is that transmission and distribution operators are having to address the growing problem of voltage control at a strategic level, across the entire grid.

Voltage challenges

Local problems are symptoms of the root causes of unacceptable voltage variations grid-wide. These are two-fold. Electricity is increasingly generated from a multitude of renewable sources, which are naturally intermittent. A cloud passing over a solar farm will cause a sudden power drop. Gusts blowing across a wind farm cause power surges. Meanwhile,growing numbers of customers need to plug in their EVs and fire up their heat pumps at the same time, causing massive and rapidly-developing peaks in demand.

The challenge of uncontrolled voltages is multi-facetted. It is a cost as well as an environmental issue, because out-of-limits voltages waste energy, increase electricity bills, cause premature equipment failure and produce excess carbon. It is a customer service issue, because consumers rightly demand reliable quality of supply. And it is a regulatory issue, because operators can be sanctioned for supplying electricity outside agreed parameters.

The grid can call on reserve generation capacity and release energy from storage systems to balance supply and demand at the national, high voltage level. But distribution network operators (DNOs) are becoming increasingly involved in controlling voltages at medium voltage and low voltage levels. This has the potential to save customers millions of pounds and cut carbon emissions, whilst minimising the disruption that can be caused to the grid by the connection of ever-growing numbers and sources of intermittent generation.

The technologies exist to drive DNOs’ progress towards better control of voltages at the distribution level. For instance, plug-and-play Automatic Voltage Controller (AVC) relays can be deployed in substations and use a combination of software and digital controls to adjust voltages instantaneously.

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