The hidden threat to power quality on the electric grid Surveyor engineer on the substation

It has been widely reported that unregulated electric vehicle (EV) charging could overtax or destabilise power grids yet there has been less discussion of the potentially disruptive impact on power quality. While electrification of transport will deliver many environmental benefits, we must consider and manage the full impact of this change.

By Amir Cohen

Without strict oversight and regulation, the fast chargers now connecting to the grid could cause harmonic distortion where they emit high-frequency waves that disrupt the normal ebb and flow of current across the grid. Simultaneous surges in demand from many fast chargers can have a major impact on power quality, potentially damaging the grid and many electrical appliances from motors to medical and industrial equipment. Fast chargers could also affect power quality by causing wildly fluctuating voltage levels and loads on the grid as demand swells and sags.

The problem is compounded by the fact that utilities have very limited visibility of the distribution grids where these disruptions originate. As EV chargers and other devices such as heat pumps have an increasing ripple effect across the wider grid, utilities need to expand grid monitoring, analytics and control to encompass distribution networks.

Silent source of contamination on the grid

Europe is projected to be the global leader in EV adoption and last year saw a 54% increase in public charging infrastructure including a 90% increase in bigger, faster direct current (DC) chargers. This rapid proliferation of ‘non-linear loads’ that draw in current in rapid pulses will exacerbate ‘harmonic distortion’ where devices emit high-frequency signals that disrupt the normal smooth cyclical waves of alternating current (AC) across power grids. This effectively pollutes the power supply that utilities send to homes and business, potentially breaching standards such as Europe’s EN50160 governing the acceptable consistency, reliability, and stability of electrical power.

Abundant research has shown that EV fast chargers can contribute to power quality problems unless they are regulated effectively. Because they are closely clustered in places such as service stations, fast chargers could create major hotspots of ‘harmonic pollution’ during periods of peak demand, degrading power quality and damaging nearby distribution networks or electrical devices.

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Harmonic pollution in power systems caused by EV charging could strain or damage electrical equipment, triggering excessive vibrations and torque pulses in motors or misfiring of the variable-speed drives that set machinery speeds. Harmonic pollution can even cause power loss across distribution grids by overstretching power transformers or damaging power factor capacitors and protection relays. Poor power quality can lead to equipment malfunction, data loss, reduced efficiency, and increased downtime across many other critical electrical and electronic devices from industrial machinery to medical equipment.

Rapidly fluctuating charging and discharging also causes rises and drops in voltage across distribution grids which can further reduce power quality, affecting electrical equipment lifecycles and even causing safety hazards. Sudden blips in usage of large-capacity devices such as fast chargers can also unbalance loads on the grid which strain transformers, stress power lines and create network inefficiencies. Utilities will need to respond by curtailing EV charging or encouraging flexible off-peak charging, which will require real-time visibility of the factors affecting power quality across grids.

Network blind spots

The decarbonisation and electrification of the economy will see a proliferation of appliances from electric vehicles to heat pumps with new and different load profiles or patterns of electricity use. Distribution grids were not originally designed for these devices and unregulated or unmonitored usage could have unintended consequences for the power quality on which we all depend.

This creates an urgent imperative to monitor and manage power quality at the edge of grids, bringing transparency to distribution networks. Yet utilities currently have little to no grid monitoring capability on distribution lines and therefore many have limited visibility beyond their substations. Operators often only have limited oversight of primary circuits using old-fashioned SCADA (Supervisory control and data acquisition) systems, and even less visibility of secondary circuits.

While Phaser Measurement Unit sensors are widely used to measure power performance on transmission grids, there are few if any of these on distribution networks. Advanced smart grid monitoring systems are rarely used on distribution lines. As a result, most operators only become aware of disruptions to power quality such as harmonic distortion after customer complaints. Yet we need to be on the front foot as we transition to a world where electrification is at the core of transport and the wider economy.

Bringing transparency to distribution grids

Pioneering utilities across the Middle East, US and Europe are now piloting ‘multi-sensing’ grid monitoring systems that track waves of current and voltage in real-time to spot any deviations from power quality limits. These technologies pinpoint the time and location of voltage fluctuations or harmonic distortions, identify causes, and even recommend remedial action. By identifying the site and source of problems, they could help utilities pre-emptively regulate fast charging or other devices such as heat pumps to prevent power quality issues before they arise. Future systems being developed by EU Joint Research Centre scientists will even allow grids to communicate directly with EV chargers in real-time. This could be combined with time-stamped, location-based data from grid monitoring systems to pre-emptively notify individual chargers if they are about to breach power quality standards.

Multi-sensing grid monitoring systems on distribution networks could have many other benefits for utilities too. Richer data from distribution lines could create heatmaps of common problems such as locations and causes of the worst harmonic pollution, creating smarter grids and fueling Artificial Intelligence-driven solutions. Advanced grid monitoring systems can also accurately detect the location of network faults or hazards, helping predict and prevent external risks to power quality from transient disturbances such as vegetation encroachment. These systems can monitor and analyze over 60 parameters from temperature to voltage to detect any potential factors affecting power quality from excessive demand to transient disturbances such as foreign objects touching the line. Rich, real-time data on loads across distribution grids could also give operators the opportunity to balance loads between parallel feeder lines to enhance grid reliability and flexibility.

A new approach

The electrification of transport and industry will see the electric grid becoming a single point of failure across the economy so that disruption to power quality will have wider ripple effects than before. And as distribution grids intersect with millions of new appliances from EV chargers to heat pumps, this will drive an exponential increase in harmonic pollution and other potential power quality issues further upstream. As disruptions originating downstream spill over into wider networks, this means that distribution grids must be seen as fundamental to the performance of the entire grid.

This will require a new approach where distribution grids are monitored and managed as intensively as transmission networks. Network operators will need the ability to monitor and mitigate everything from harmonic distortions to voltage variations at source and in real-time to contain any outbreaks. Ultimately, transmission and distribution grids will need to be monitored and managed as a single ecosystem where what happens in one part matters everywhere else. This will help smooth the path to a green economy powered by clean electricity.

ABOUT THE AUTHOR

Amir Cohen is the Co-Founder and CEO of Electrical Grid Monitoring (EGM), a California-based electrical equipment manufacturer.