FEATURE NON-CONTACT MEASUREMENT & INSPECTION


GOING LIVE with electrical system inspection


With the inspection of live electrical systems a risky process, switchgear


manufacturers are being encouraged to build a toolkit of techniques into their products that allows maintenance teams to check the health of an


energised system while it remains in a closed and guarded condition. Martin Robinson, CEO of IRISS, comments


Motor current analysis tap off ports


and voltage detection ports can be considered, a concept which also includes continuous monitoring and online systems such as vibration and air partial discharge analysis. Another option is Delta T Alert, which acts as an early warning system if the temperature in the electrical enclosure exceeds a pre-set threshold and provides trending temperature data.


T


he National Fire Protection Association (NFPA) in the US


operates internationally to reduce the effects of fire; while Occupational Safety (OSHA) addresses other hazards in the workplace. Their codes and standards are important benchmarks worldwide, with their studies giving an understanding of how much damage is caused by an arc flash incident. Phase to phase or phase to ground


‘shorts’ will cause a rapid expansion of air up to 16,500˚C, three times the surface temperature of the sun. As a result, metal components go from a solid to a plasma state instantaneously – copper, for example, will expand 67,000 times its original volume. The maintenance team will therefore be in the direct line of fire for not only this but also huge sound and pressure waves. The safety incident pyramid commonly


used by health and safety professionals suggests that for every 100,000 hazardous tasks, there are 10,000 near-miss incidents, 1,000 first aid cases, 100 recordable injuries, 10 disabling injuries and one fatality. Compared with a similar pyramid for arc flash and the ratio of incidents to fatality rises to 85:1, of which 20 are third degree burn injuries and six are incurable burns over half the body. While organisations advise that live


electrical systems are kept closed, in order to determine the nature and severity of the fault, maintenance


26 JUNE 2014 | INSTRUMENTATION


teams need to open up systems for repair and take measurements whilst they are energised.


MINIMISE RISK To address the problem, a hierarchy of control is now commonly used which spells out the steps every company needs to take, in order of priority, to minimise risk. The first is to eliminate the


hazard altogether, which is clearly not possible in all cases; and the second is to incorporate electrical maintenance safety devices (EMSDs) and other data collection points into basic systems designs. This move is supported by the IEEE


whose ‘Recommended Practice for Electrical System Design Techniques to Improve Electrical Safety’ (P1814), provides a framework for safety to be addressed at OEM level. That, however, doesn’t preclude installed systems from being made safer too. A wide range of EMSDs are now


available that can be retrofitted to any panel to provide vital maintenance data while the system is live and closed. For example, a dedicated port allows an ultraviolet camera to see corona when the air gap is starting to break up around the electrical connection – the first sign of failure. An infrared window can then be employed so a thermal imaging camera can see the problem and quantify its thermal profile.


AVOIDING DOWNTIME Lost production costs industry millions of pounds each year and much of this downtime could be avoided with more robust electrical maintenance programmes with Electrical Maintenance Safety Solutions (EMSS). Comparing an energised survey by


firstly removing panels and secondly using IR windows for thermal inspection gives a good example. The manpower per inspection of one panel is typically 3.3 hours, but factor in PPE suit-up time and this increases to 4.8 hours. However, thermal inspection via an infrared window, including PPE suit-up, is 0.2 hours per panel. By using just one EMSD,


the accumulative cost savings on inspection time are significant. Costs are also saved by minimising downtime. With every EMSD added to the solution, there are more opportunities to discover the fault before it becomes critical – all without compromising personnel safety.


IRISS T: 01245 399713 www.iriss.com Enter 666


/ INSTRUMENTATION “The manpower per inspection of one panel is


typically 3.3 hours, but factor in PPE suit-up time and this increases to 4.8 hours. However, thermal inspection via an


infrared window, including PPE suit-up, is 0.2 hours per panel”


A wide range of EMSDs are now available that can be retrofitted to any panel to provide vital maintenance data while the system is live and closed


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