Issue link: https://fhpublishing.uberflip.com/i/846256
NETWORK / 18 / July/augusT 2017 increased role of distributed generation rendering networks more exposed to rapid changes in current – when cloud cover dras- tically alters the contribution of solar power, for example. One technology that is set to play a criti- cal part in enabling this new method of pro- tection is the solid state circuit breaker, says Cameron. "The solid state circuit breaker operates roughly 20 times faster than a con- ventional circuit breaker. What that allows you to do is catch current peak before it gets to its peak and puts your equipment over into fault level rating." As well as detecting potential problems much faster than traditional breakers, the latest tranche of solid state breakers also come with sensors and communication technologies that enable them to work in tandem with other equipment on the network. Enhanced communication between cir- cuit breakers and other parts of the network are also enabling networks to better predict when a fault might occur, with a range of online monitoring platforms enabling a more detailed understanding of what is go- ing on in the network. "All of the protection and control devices can talk to each other, that helps with a range of things," explains Brazier. This advance not only enables communication and online monitoring, but also delivers significant savings through stripping copper from substations and enabling individual components to be switched out without replacing the entire system. Networks are also investing in – and rolling out – power electronics on the low-voltage networks to overcome the new challenges they face. Capitalising on the conductivity of semiconductors, power elec- tronics enable networks to control voltages along individual distribution lines rather than the network as a whole. In terms of protection, this offers network operators a critical tool to deal with the increased variability brought on by an increase in distributed generation. The age of power electronics Installing power electronics has enabled UK Power Networks to connect parts of its network that would not normally have been connected. "It allows us to balance networks where they may not have been balanced before," explains Cameron. "It allows us to balance by phase, so you might have one phase of a certain network overloaded, and by putting power elec- tronics between them you can actually balance them across the three phases and between networks." Although the adoption of power electron- ics offers new opportunities and greater control to the networks – enabling a ef- fective and quick method to connect new generation assets to the network – it also brings new operational complexities. "More and more generators are connect- ing to the networks via power electronics and that means that sometimes you don't get much fault current from the genera- tors when there's a short circuit," explains Taylor. "That might sound like a good thing but if that means that you can't detect a fault because there isn't much fault current flowing, that can mean the protection sys- tem just thinks that everything is fine when actually there's a fault on the network, and that can be dangerous." To overcome this, network operators are turning to monitoring equipment installed across different parts of the network to help them better understand what's going on – installing more intelligent relays that can have more sophisticated and variable settings. With the advances in circuit breakers, power electronics and monitoring of the network, network operators are trialling and adopting new ways to protect the network from the new stresses being placed on it. But there are also other approaches being taken to protect against faults. One such approach is islanding, in which a protection system identifies that an area of the network has become disconnected from the grid and switches to a secondary power source to restore operations. Because of the growth in distributed generation across the networks, the potential for solar PV or wind power to be used to keep a network area operational has increased significantly. "Where we are going with that is that people are starting to question more and more why they need to shut everything down if they become islanded," says Taylor. "You need to think how you can run as an island and keep the generators connected, allowing areas of the network to run as an autonomous standalone system for a while – but that requires a protection system that ensures the island stays safe." Even further down the line than the widespread use of islanding, but poten- tially offering the best way to cater for the challenges brought on by distributed generation, is to stop monitoring fault levels altogether and instead attempt to detect them by other means. Cameron believes this approach holds much promise for the future, and suggests that networks will instead monitor the shapes of waveforms, inspecting whether the harmonic wave looks right and develop- ing algorithms to determine whether or not to trip. "Now that's a world away," he says, "but that then leads us to an opportunity to protect instead of being reactive when things are out of tolerance – monitoring proactively. When you do that, you can see disturbances starting to occur, because faults usually start to manifest themselves in strange waveform shapes, so you could start to move your network around, away from that type of circuit. And if that fault does occur, the impact is lower." As the rise of distributed generation con- tinues, the challenges faced today in terms of protection and control will only get big- ger. However, from new technologies such as the latest breakers and power electronics to new methods of detection and monitor- ing, the networks are already working to overcome them. N AutomAtion, protection And control