Keeping the Lights On - Electrical System Maintenance and Inspection
P.Eng., PE, CRP, Loss Control Engineer
Email : firstname.lastname@example.org
Power is easily the most important utility at any facility. We like to take it for granted until we are sitting in the dark with a candle waiting impatiently for the lights to come back on. During those rare moments we get to see how little gets done in the absence of electricity.
Electrical systems can be complex and can require significant inspection and maintenance to operate in peak condition. Serious fires, mechanical failures and lost production can occur if these critical systems are ignored. Some services to consider at your facility include the following:
Transformer Rupture and fire in a residential vault
Transformers may contain significant quantities of insulating oil, designed to provide insulation and cooling for the windings. The physical properties of the oil as well as the presence of water, solid contaminants, and a variety of gases (ethylene, acetylene, methane) can be used to determine the operating condition of the transformer. This is a test known as Dissolved Gas-in-Oil Analysis or DGA. It can allow for problems to be diagnosed far in advance of any ruptures and potential fires involving the transformer(s) and the oils contained inside.
A lack of testing can lead to premature failure, arcing ignition and even oil explosions in tranformer units. Replacement times for transformers vary by size but can require weeks of downtime to repair and replace. Annual sampling, testing and trending of dissolved gases is recommended for primary transformers.
All electrical systems produce heat. The resistance of connections, conductors and other elements cause passing current to heat up those particular areas. Too much heat can be a problem for any component as it can lead to decreased life expectancy of the part as well as act as an ignition source.
Loose or corroded connections, unbalanced phases and other electrical faults are easily diagnosed with infrared scanning. Special cameras that “see” in the infrared spectrum are used to measure and display the heat of objects. For example, in the images below, no problem is apparent in the “visible” light spectrum. Switching to infrared, the second image clearly shows that the disconnect switch in the top left corner is overheating due to a poor connection.
Visible light image of disconnects | Infrared image of same panels showing hot spot.
It is advisable to perform infrared testing on medium and low voltage residential and commercial power systems at least every three years.
Dual Radial Vaults
In many urban centers, power is provided on a radial cable system. This arrangement allows for switching of power feeders between a primary running circuit and a ‘standby’ circuit. The advantage of this system is that loads can be switched between the two circuits to overcome outages due to planned maintenance or failures.
For instance in Vancouver, if you have a dual radial vault and you have not completed your three year maintenance, BC Hydro is prohibited from operating your vault due to WorkSafe BC regulations (similar regulations might be in force in other provinces or territories). This exposes you to non-compliance status that could leave your building without power for a considerable period following any outages. The entire electrical system has to be isolated, inspected and tested prior to any circuit switching in a non-compliant vault. You must arrange for you vault service during your prepared maintenance “window” to maintain your compliance and avoid prolonged power disruptions.
Other Vault and Electrical Service
Radial vaults are not the only vaults and electrical switchgear that need attention. The following items apply to regular vaults, switchgear, power distribution centers and motor control panels:
- Physical inspection/mechanical testing of switches and protection equipment (Annually)
- Cleaning and vacuuming enclosures (Annually)
- Relay calibration and coordination of protection elements (Every three years)
- Current injection and other testing on breakers
- Load testing emergency generators (Annually)
- Ground testing and earth resistance (Annually)
- Ground fault circuit testing
A safe and effective electrical system is easily maintained with proper maintenance. Contact licensed professionals for your electrical service needs and keep your systems in peak condition. Either that or stock up on candles on ghost stories to pass all that downtime.