Switchgear is one of the key components of any electrical power system – and its operating condition is vital to system reliability. In general, of course, switchgear has a proven record of reliability and performance. However if things were to go wrong, they could do so in a big way!
The UK Health & Safety Executive has identified mechanical failure, insulation failure and contacts overheating as the most common cause of operational malfunctions – and has described in graphic terms how “… results may be catastrophic: tanks may rupture and in the case of oil-filled switchgear, can result in the ejection of burning oil and gas clouds, causing death or serious injury and major damage to plant and buildings in the vicinity of the failed equipment”. ¹
“It can help to think of it in terms of the human body”, said Kerr. “To prevent illness, manage the risk of any organ malfunctioning and extend life expectancy, you not only have to treat the body well and not overload it, but take into account factors such as age, weight and medical past history, undergo regular medicals and monitor any known conditions: all as part of a comprehensive healthcare regime.”
“What we do with electrical plant is very similar! Periodic condition assessments and regular, planned condition monitoring are both essential. The objectives are straightforward: extended component life (much as we would wish for ourselves!) meaning reduced maintenance expenditure and lifecycle costs; avoidance of dangerous or environmentally hazardous conditions; and avoidance of penalties too, by predicting and preventing equipment failures.”
Siemens has been involved in the field of switchgear condition monitoring for over 30 years. Its ’i-Con’ range of solutions, for both gas-insulated (GIS) and air-insulated switchgear (AIS), is modular in design, simply-implemented in an existing substation infrastructure and easily extended to further assets if needed. It is the basis of the Siemens Integrated Substation Condition Monitoring (ISCM) system: covering all equipment in the power supply network, from the switchgear itself to the transformers, cables and overhead lines.
Typical monitoring techniques may include partial discharge detection measurements, circuit breaker and gas density monitoring: all capturing information online in real time and dramatically improving the prediction of when intervention is required and what action will be needed.
Kerr summed up the significant benefits of such a regime as “early detection of impending failure, avoidance of unplanned outages, reduced repair costs, improved availability and a more efficient, cost effective maintenance strategy”. “But,” he added – “we wanted to do even better than this”.
‘The road to RIIO’: from static data to predictive modelling
Because condition monitoring systems are focused on the present condition of an asset base, the addition of past data and the prediction and assessment of future intervention has been a complex task until now; requiring significant manual input and calculation. Siemens’ newly-launched offering, ‘Reliability Centred Asset Management – dynamic’ (RCAM-dyn) goes a step further. In particular, claims Siemens, it will offer DNOs a new tool to show how they are extending and maximising asset life, as required by Ofgem’s ‘RIIO’ obligations.
Under the banner ‘Analyse the past, monitor the present and predict the future’, Siemens initially developed and implemented its solution for a major overseas power generation, transmission and distribution company. Kerr explained it as follows:
“All elements of the solution follow a three stage assess – address – act approach and are based on ISCM standards and technology.
“Our objective in developing RCAM-dyn has been to generate value from current and historic data: analysing online monitoring data, derived either from our own i-Con condition monitoring or from alternative condition monitoring systems; along with offline data, too. These comprise some 20-22 inputs for each asset, of which up to half are now from online systems.”
Reliability-centred asset management – what makes it ‘dynamic’?
“In creating dynamic models for forecasting and risk assessment”, continued Kerr, “RCAM-dyn combines the data showing the assets’ current state, with SAP data and other manual data relating to the assets’ past performance.
“We then calculate a risk model for different asset categories: high voltage GIS (400kV and 132kV); and medium voltage AIS. RCAM-dyn analyses the data and uses appropriate algorithms to model the impact of ageing according to a set of varying condition parameters; predicting both an asset’s future health and its remaining life. This in turn allows us to compute an Asset Health Index (AHI) for each and every asset within an electrical grid.
“These AHIs take online and offline condition information into consideration and are weighted according to the asset group. They are used to calculate current and future failure probability rates for each individual asset. Reporting is based on asset clusters and a management overview is presented through an on-line dashboard function. From the AHIs, a report is calculated, where risk is expressed as [probability of failure x consequence of failure] and considered in five dimensions:
w Capex risk
w Opex risk
w Environment risk
w Safety risk
w Network performance risk.
“The overall result” he added, “is a truly comprehensive asset management approach, relevant at all stages of the energy cycle: from generation, through transmission to distribution networks. By calculating both the risk and consequences of failure, we believe we can help transform asset management decision-making and strategic planning – and in particular, because an asset no longer need be replaced automatically at the end of a given period, we believe we can really help UK DNOs fulfil their RIIO obligations.”
delivering tangible customer benefits
Siemens’ new solution is already in use: having been implemented for a significant energy customer that is active at all stages of the power generation, transmission and distribution cycle.
“Our customer wanted to radically improve their asset management and prolong the lifespan of their asset base”, said Kerr. “There were other, ready-made solutions available – and we actually considered offering one of these, but it had significantly less functionality than what we subsequently developed, and did not provide a predictive basis for future health and risk assessment.
“The deciding factor was that the nearest competing solution was not a dynamic tool, but was based on a simple Excel spreadsheet, requiring constant user input for data update and refresh. By contrast, the solution that we are now bringing to market as RCAM-dyn, with its dynamic scenario forecasting and risk assessment capability, is providing our customer with much enhanced decision-making support and a robust, comprehensive asset management platform.
“The customer can now expect cost reductions, by stretching the lifespan of their assets and focusing specifically on those that need attention. RCAM-dyn will also aid their compliance with environmental and safety obligations. And of course, they can now have significantly greater confidence in the reliability of their network. That’s quite a significant benefit package.”
‘An exciting step forward’
“In summary”, declared Kerr, “this established technology offers huge potential to UK DNOs. Asset managers can not only use it to schedule future maintenance, prevent defects developing into serious failures and extend the life of their equipment, but also as the basis of their strategic planning and to optimise their capital investments. I really believe it’s the most exciting step forward in the industry for many years – and we look forward to helping DNOs realise its potential.” ¹ Note: from ‘Keeping Electrical Switchgear Safe’ – HSE, 2002: ISBN 0 7176 2359 9