How flood defences help build resiliency in distribution networks and lower grid outages.
Hurricane Matthew, which in September/October of last year left a trail of destruction across the Caribbean and the US East Coast, resulted in widespread outages that affected more than one million homes and businesses.
Once again, the potential consequences of these extreme weather events are highlighted as decision makers continue to search for solutions that will lessen the impact these events have on distribution network companies and our daily lives.
Outages are the most significant electrical events utilities and their customers face. They’re bad enough when planned, but they’re even worse when unplanned. The majority of such interruptions generally relate to minor network issues that utilities can rectify promptly with limited customer impact. However, when outages last more than five to 10 minutes, they start costing customers real money, estimated in the US at more than $26bn per year.
For individuals, loss of power for electronic devices, appliances and heating or cooling systems affects their ability to work and their personal comfort. Moreover, industries are unable to function and businesses are unable to make sales.
New smart grid technologies are bringing innovations, such as 24/7 monitoring and condition-based maintenance, which can reduce the likelihood of sudden equipment failures and the subsequent outages.
However, what isn’t so predictable is the increasing prevalence of the extreme weather events, which by their nature can do considerable damage. Strong winds can bring down a power infrastructure either directly or for example from falling trees, while heavy rains can cause flooding. A recent report from the World Energy Council found extreme weather to be one of the top three ‘mega risks’ of concern to energy leaders.
Since the so-called Superstorm Sandy, which caused devastation across the US Northeast in October 2012 and left tens of thousands of homes without power for weeks, state authorities have placed much effort into building resiliency into the grid to reduce the adverse effects of such events. For example, the efforts of several East Coast states, including New York, have given a boost to the development of microgrids.
The risk of flooding was a key consideration for the Brazilian utility Cemig when it decided to install underground HV distribution switchgear as part of a major grid upgrade in 2012. For this project, S&C Electric Company supplied 450 of its Vista Underground Distribution Switchgear units for installation across Cemig’s service territory.
In an interview at the time, Cleverson Takiguchi, then General Manager of S&C in Brazil, explained that the switchgear, along with automation, sensors for monitoring and theft detection and communications were being installed in flood resistant enclosures. The advantage of this over standard submergible equipment is that the control systems can be included, making the system truly ‘smart’ even during flooding conditions.
Tropical countries, with their more extreme climates, have always tended to be prone to flooding. In other parts of the world, such as the UK, the increased occurrences and more widespread effects of flooding are a more recent phenomenon, thought to be caused primarily by climate change and the growth in housing developments.
Following floods in the summer of 2007 that affected more than 55,000 homes and businesses across the UK, Ofgem called on the distribution network operators (DNOs) to review their measures to mitigate flood risk. Based on their plans, Ofgem approved £112m of investment into distribution network flood mitigation for the 2010-15 price control period.
In its recent performance review of DNOs following the end of the price control period, Ofgem found that the proportion of substations in the one in 100 year flood risk category, which exceeded 50% in 2010, dropped to about 20% in 2015, while the number of substations in the ‘1/1000’ category doubled to 70% from about 35% previously.
At the customer level, this corresponds to a drop in the number of customers supplied by ‘1/100’ risk substations over the price control period, from approximately 3.3m in 2010 to approximately 1.1m in 2015.
Among the specific investments, Electricity North West spent £7.3m to build flood defences, install pumping equipment and waterproof specific vulnerable equipment in 31 substations. UK Power Networks allocated £2m toward a concrete flood barrier wall around a 132kV/11kV substation in West Ham to safeguard supply should the River Thames flood barrier fail, which would be a 1/1000’ event.
“Protecting our electricity system is central to a quicker recovery from flooding because the loss of a major substation would hamper the recovery from a natural disaster,” said UKPN senior project manager, John Nagle. “Thankfully, while the risks of the River Thames flooding are relatively small, due to the Thames flood barrier, this project will mitigate a known risk.”
As a result of these additional investments by network companies in the UK, no significant transmission or distribution network energy infrastructure was affected by flooding during extreme weather events in 2013 and 2014.
With the risk of flooding, protection must be an ongoing concern for distribution companies, not only for existing equipment but also for the new assets being installed in the move to a smarter and more decentralised grid.
For example, Western Power Distribution designed its recently completed Lincolnshire Low Carbon Hub project to test a variety of new technologies for renewable integration. As part of the project, S&C installed a suite of products, including a 3.7MVAr PureWave DSTATCOM Distributed Static Compensator, to provide fast-acting voltage support to the network to aid power quality at a wind farm in Trusthorpe.
S&C Project Engineer Tim O’Leary said the project – a first for the UK mainland – had to be adapted to the customer’s needs and to the location of the DSTATCOM, which is on a floodplain. “This brought many challenges during the construction and resulted in placing the unit on a raised platform,” he said. “This indicates the versatility of these solutions.”
S&C is now working with other DNOs in the UK to promote this and its other flood protections solutions, such as the one deployed by Cemig in Brazil, which are suitable for all types of environments. The fully submersible HV switchgear (including controls) is designed to improve network resilience and allow full remote control during flooding conditions. Such features allow the distribution companies to better manage the system, which can be critical to keep the lights on and ultimately result in fewer customer outages during these harsh weather conditions.
With flooding set to be a problem well into the foreseeable future, waterproofing costly assets is the smart way forward and key to the distribution companies in fulfilling their role of keeping the networks operating.