Smart sensing: protecting the grid to prevent power outages

30 March 2015 (Last Updated March 30th, 2015 18:30)

Monitoring of electricity distribution lines will have to change considerably with the growth of renewable energy. Erik Christian from Tollgrade, which was named ‘Best Smart Grid Innovator’ at the UK Energy Innovation Awards, considers what challenges lie ahead. Rod James reports.

Smart sensing: protecting the grid to prevent power outages

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In 1926, British parliament passed the landmark Electricity Supply Act. The centrepiece of this bill was the proposal for a ‘national gridiron’, which would unite the UK’s disparate electricity supply networks. This meant that all connected households could receive the same voltage electricity for a regulated price, and that supply could be diverted from one location to another according to demand.

The grid has grown exponentially since then in tandem with the sophistication of its monitoring software. Models employed by the National Grid’s balancing team are so detailed that they consider factors such as the televising of sporting events and even plot lines in soap operas when, during ad breaks, vast numbers of viewers simultaneously switch on their kettles and send the mains frequency southward (though this is less common in the age of on-demand TV).

While the algorithms that drive the software are sophisticated, the hardware used to monitor the grid is actually quite simple. The network is monitored by a supervisory control and data acquisition (SCADA) system, which consists of a number of sensors in different parts of the grid that feed back data to a control centre. These sensors, known as fault passage indicators, are not enriched with functionalities.

"These [SCADA] systems take in information from wherever just happens to have monitoring capability on the grid."

Tollgrade is a network monitoring company that recently won the award for Best Smart Grid Innovator at the UK Energy Innovation Awards. Vice-president Smart Grid Erik Christian said: "These [SCADA] systems take in information from wherever just happens to have monitoring capability on the grid.

"Sometimes things like switches and recliners, which are big pieces of equipment that help shift electricity from one area of the gird to another, have monitoring capabilities. These FPIs are very basic technologies, just blinking light sensors that feed back little or no intelligence and rudimentary communications that just say ‘we saw something happen, but we don’t know what it is and we don’t know why it happened’."

Renewable resources change the game

According to Christian, the systems have worked well up to now but will become more challenging. Although the grid has grown in size and complexity, its fundaments have changed little since 1926. Whether derived from coal, gas or other fuel stock, it can be safely assumed that over its life span a power plant will be able to supply energy when and where required, except during periods of maintenance and the occasional outage.

This is not the case with renewable energy, which in line with EU targets adopted in 2009 will account for 20% of member countries’ energy output by the year 2020. Available sunlight and wind can vary from minute to minute, resulting in fluctuations in power output and requiring additional energy to balance supply and demand. In addition, these green resources are wherever they happen to be, so new transmission lines are often needed to connect renewable sites to the grid. In some cases, particularly offshore wind, cables require special technology not found in land-based lines, making such sites expensive and technically challenging to integrate.

Another significant consideration is frequency response – the ability for power generators to increase output or reduce consumption due to a decline in system frequency. When a conventional power station closes down the frequency of the power system drops but this decline is quickly countered by other generation machines helping to make up the shortfall. Although solar arrays and wind turbines can theoretically contribute to frequency stabilisation, the technology is so different to that of conventional generators that the effect of employing them is not fully understood.

Grid monitoring improves management

With a background in monitoring broadband and telecommunications networks, Tollgrade realised around seven years ago that many utilities had to deal with the same problems that telecoms companies once faced – ageing infrastructure and the need to handle new technologies being plugged into the network.

The firm created the Lighthouse unit, a collection of sensors about the size of a loaf of bread that is attached to the electricity grid and wirelessly relays data back to headquarters. These sensors are inductively powered (by the grid), unlike the battery-powered sensors prevalent now. This gives Lighthouse sensors a lifetime of around 20 years, compared to two to three years, and means that utilities firms can save considerable sums on crews, trucks and logistics related to replacing them. The unit has also been praised for its unusually accurate voltage measurements, which it is employing to help UK firms adapt to the new reality.

"Once you have renewable generation… it’s just impossible to continue to run the grid in the same way that’s happening now."

"The UK Government, to its credit, has high standards about trying to get certain [renewables] penetration rates by 2020 to migrate towards a low carbon future," adds Christian. "We are working on a couple of projects right now centred around how we cope with that future and the first part of understanding that will be making sure there’s a adequate monitoring.

"Where are the areas of the network where there is extra capacity, where is there space on the grid to add renewable energy and where are the areas on the network that are already constrained right to the very top of what the circuits and the cables can do?"

The Falcon project, carried out in partnership with Western Power Distribution, the trading name of three electricity distributors that cover the west of England, the West Midlands, and south Wales involves analysing the network to map areas that are especially able to handle input from renewable, as well as those at risk of overload. Project ARC, with Scottish Power, is similar but has the specific aim of accelerating the introduction of renewables onto the grid in areas of the network shown to have lower capacities than once thought. The eventual aim is to have enough accurate network data to be able to identify problems before they become crises.

"We are constantly amazed at how much they are able to get done with the little visibility they have," Christian says of UK network operators. "But once you have renewable generation, which will completely change the way electricity is delivered to customer, it’s just impossible to continue to run the grid in the same way that’s happening now.

"That will cause more outages and will really necessitate us, as a community of vendors and utilities, to get to situations that are not big problems before they cascade into big outages. We’ve been able to do that with some of our customers in the US and as we grow our analytics library of different events that are pre-cursors to faults it’s more and more valuable."