​MANAGING VOLTAGES IN FAST-CHANGING NETWORKS

Managing voltages is set to become an increasing challenge for all network operators. In this article, Fundamentals examines why fluctuating voltages are a growing problem – and we explore the opportunities and solutions available for tackling the issue, including wholesale voltage reduction.

We are entering an era of unprecedented change in the way electricity is generated, transmitted, distributed, stored and consumed. Every change will have knock-on effects for network operators of all shapes and sizes – and nowhere more so than in the area of managing voltages.

The voltage management issue comprises a combination of challenges and opportunities, but the bottom line is that voltages outside set parameters waste energy and produce excessive carbon. They also damage many types of plant, equipment and appliances, lead to poor customer service and complaints – and may lead to penalties from the regulator. Conversely, well managed voltages are carbon-efficient, reduce financial costs and ensure good customer service. So, let us consider some of the key causes, effects and solutions.

VOLTAGE VARIATION CAUSES

Existing networks were designed for centralised generation and passive consumers served by transmission and distribution networks. That is changing fast. As SP Energy Networks said recently: “Historically, distribution networks were not designed to accommodate the large number of Low Carbon Technologies (LCTs) that are now becoming a critical part of our fight against climate change. The uptake of LCTs such as photovoltaics and electric vehicles is expected to create a sizeable strain on the low voltage distribution network and lead to costly network reinforcement.”

We will come back to the issue of network reinforcement later. First, let us look at some more examples of why networks are coming under increasing strain.

On the Isle of Jersey, a significant number of residents have installed ground heat pumps. Good news environmentally in principle, but many are ‘fast start up’, springing into action at the same time in the morning when people are using power showers, kettles and stoves. The result has been massive spikes in load, with consequent effects on network voltages. Given that there is growing pressure to replace gas boilers with heat pumps across the UK (if not on a wholesale retrofit bases, then at least on new builds as part of revised building regulations), Jersey may serve as a warning of one of the changes on the horizon.

Even without the impact of heat pumps, increasing affluence means that more people are running more power-hungry appliances and devices at the ends of old, weak networks which were not designed to cope with them. This clearly exacerbates the simple fact that voltage falls as networks increase in length.

The voltage management problems associated with the growth of distributed generation are worthy of a whole new set of articles, not least because distributed generation on LV raises the effective impedance, compounding voltage problems. It is certain that distributed generation of all shapes, sizes and types will increase – from domestic rooftop solar to giant offshore wind farms, not to mention tidal, wave, geothermal and biomass. All will bring their own issues for network operators, but the experience of Australia with rooftop solar is a good example of what can happen when network operators launch into unexplored territory.

In summary, some Australian operators invested heavily in reinforcing their networks to cope with a combination of increased demand on weaker networks, plus a massive uptake of rooftop solar generation (some estimates claim solar is already producing 25% of Australia’s load). Costs of reinforcement were passed on to consumers in higher standing charges, which caused many customers to complain of profiteering, buy battery storage and go off-grid. This shot the operators’ investment and revenue strategies full of holes. In addition, the problems of managing voltages where people are connecting substantial solar arrays to the networks are a growing headache. For example, voltage fluctuations are causing customers’ solar inverters to fail, leading to more complaints and compensation claims.

EVs AND BATTERIES

This brings us to the question of batteries, which are very much a two-edged sword for network operators. On the one hand, battery storage looks set to play an increasingly vital role in managing load (and hence voltage) on smart networks. Batteries, including those in electric vehicles, have the capacity to act as energy storage buffers. On the other hand, new battery technologies could prove to be massively disruptive. The era of lithium ion batteries, together with the whole charging infrastructure built to support them, could be made redundant at some point by emerging technologies. We do not know when or how fast this will happen – only that change is on the way.

Carbon ion batteries (alias dual carbon or dual graphite) are just one example of a plethora of potentially game-changing electricity storage innovations appearing over the horizon. A new carbon ion battery has been developed by ZapGo Ltd., claiming to enable an EV to take on a 100kWh charge in 35 seconds – enough for a 350-mile (500 km) range. That is faster than filling up with petrol or diesel. The company reports it is working on a project in Norway which will provide a similar range for 18 wheeled trucks in 60 minutes. It also claims to be working on solutions for ferries and buses.

The good news is that carbon ion batteries (and other technologies in the pipeline) are allegedly cheaper, safer, longer lasting and greener than lithium ion. The bad news is that existing electricity networks will be hopelessly inadequate to power thousands of new 350kW to 1,500 kW charge points needed to support millions of carbon ion EVs.

One solution is that new grid-powered charging stations will have to be built at or very near primary substations. The alternative is the creation of enormous power banks on the sites of charging stations, presumably topped up from the electricity grid overnight.

The impact of EVs may seem a long way off in the UK, where their market share is still only in low single figures. But in Norway, EVs topped 60% of new car sales in 2019, even without a fast-charge revolution – or the prediction by some industry watchers that battery prices will fall so fast that EVs will be cheaper than internal combustion engine variants within a few years. Impossible? Well, when PCs were launched in the early 1980s, memory cost around £100 per megabyte. Now it is less than £100 per terabyte (a million megabytes). Such is the pace of change.

VOLTAGE VARIATION EFFECTS

As mentioned in the introduction, uncontrolled variation in voltages create numerous adverse effects for generators, network operators, customers and the wider environment. The possibility of penalties for allowing voltages to stray outside permitted limits is certainly a driver for voltage management. So too is the ability of smart meters to monitor voltage levels, which can provide valuable voltage data that enables operators to adjust levels accordingly (see ENW’s Smart Street example below).

Drax Lead Engineer Gary Preece recently summarised the problem at the generating end as: “Keeping the voltage steady requires careful management. A deviation as small as 5% above or below can lead to increased wear and tear of equipment – and additional maintenance costs. Or even large-scale blackouts. Power stations such as Drax can control the voltage level through reactive power.

“If voltage is high, absorbing reactive power back into the generator reduces it. By contrast, generating reactive power increases the voltage.

“As the generators continue to produce active power while absorbing reactive power, the conditions begin to reduce efficiency and, if prolonged, begin to damage the machines. The changing nature of Britain’s energy supply means voltage management is trickier than ever. Voltage creeps up when power lines are lightly loaded.

“Where once the challenge lay in keeping voltage high and enough reactive power on the grid, today it’s absorbing reactive power and keeping voltage down.”

At the other end of the network, increasing demand on over-loaded wires lowers voltages – and domestic solar and wind feeding into the network complicate matters further.

Specifically, the EU operating range is 230V +10%/-6% i.e. 216V to 253V. All equipment must be designed to operate at 230V +10%/-10%. In order to operate in this range, most products are designed at the lower end. In many cases, higher voltages will result in increased losses, inefficiency and earlier failure.

Or as the IEE Wiring Regulations state: “A 230V linear appliance used on a 240V supply will take 4.3% more current and consume almost 9% more energy. A 230V rated lamp used at 240V will achieve only 55% of its rated life.”

VOLTAGE OPTIMISATION

All the above makes a very strong case for active management, to keep voltages within statutory limits. It also makes a strong case for reducing voltages across the network, in order to lower costs and carbon emissions, while increasing the service life of equipment. Indeed, Capenhurst-based power engineering specialists EA Technology completed a number of voltage optimisation (i.e. voltage reduction) projects for UK supermarkets including Tesco more than a decade ago. They demonstrated an average 1% energy saving for every 1% voltage reduction, across all lighting, heating and cooling equipment, without loss of operational performance, and with the bonus of potentially longer service life for equipment. Average energy/cost savings were around 5%.

VOLTAGE MANAGEMENT SOLUTIONS

Wholesale network reinforcement is one of the options for managing loads and voltages – but only in some scenarios, with high costs and disruption: and as the Australian example above demonstrates, it can result in unintended consequences.

There are increasing numbers of innovations from UK network operators, which address the issues more creatively. For example, Electricity North West’s CLASS project (Customer Load Active System Services) deploys Fundamentals’ SuperTAPP SG smart voltage control relays in primary substations, linked to the company’s control centre. They control network transformers and interface with a Schneider Advanced Network Management System, providing immediate load, voltage and VARs responses to support the needs of the National Grid. It’s a future-proof solution, which both improves service to the Grid and generates revenue from ENW’s existing assets.

ENW’s four your Smart Street trial of voltage management measures in its substations saw customer electricity consumption reducing by between 5% and 8%, alongside a 7% to 10% fall in carbon emissions.

Northern Powergrid is also using our SuperTAPP SG voltage control relay in primary substations, to enable the roll out of an increasing number of distributed generation systems, EV, and STOR (Short Term Operating Reserve) connections.

LV Engine is a flagship innovation and Smart Grid project lead by SP Energy Networks, bringing Smart Transformers (ST) to the distribution network for the first time. The five-year project involves extensive trials of Smart Transformers at secondary substations, with the aim of facilitating the growth of low capacity infrastructure, without the need for costly network reinforcement. Key functionalities include: Phase Voltage Regulation, Reactive Power Control, Power Flow Control, Low Voltage DC Supply, Active Harmonic Filtering and resonance damper in LV networks. The Smart Transformer may also improve flicker and voltage fluctuations, fault isolation between the 11kV and LV networks, and phase balancing.

SP Energy estimates there is the opportunity to deploy 7,817 Smart Transformers by 2030 and 36,270 (still only 16% of existing UK substations) by 2050. It further estimates that deployment of STs across the whole of Britain would save consumers up to £528 million by 2050 and a large amount of carbon.

There are numerous other strategic initiatives across the UK involving smart voltage management, either being deployed now or in the pipeline. But what about the demand for immediate solutions for voltage problems which are causing customer issues and need fixing right now?

 For example, Pacific Volt’s Low Voltage Regulator (LVR-30) above is a cost-effective series voltage regulator for maintaining voltage compliance in applications typically including local networks impacted by the integration of solar generation and EVs, together with rural situations involving long high impedance feeders. Fundamentals can supply the unit with simple plug-and-play installation, which enables engineers to set voltages at the point of supply. It can be deployed as a temporary fix pending network reinforcement, or left in place permanently.

CONCLUSION

Voltage management is a growing opportunity as well as a growing challenge for the electricity industry. New voltage management initiatives and technologies hold out the promise of enabling networks to embrace new patterns of electricity generation, distribution, storage and consumption, while minimising carbon emissions and delivering excellent customer service reliably. However, the pace of change can only accelerate, with disruptive technologies such as ultrafast-charging EVs making for a future which is difficult to chart with certainty. Only one thing is certain: there has never been a more exciting time to be part of the electricity industry.