Overloading your building’s wiring

The overtaxing of building electrical installations is a silent, destructive agent and little recognised.

By: Subodh Bhatia, Managing Director, Westek Electronics Pty Ltd

Take a practical installation, e.g.: a shopping mall complex. There are a large number of tenancies—everyone with fluoro lighting, lots of IT equipment, scanners, electronic cash registers, printers, etc as well climate control (HVAC).

The kilowatts consumed by these loads imply an aggregate electrical current that needs to be handled by the transformer, switchboard and wiring. The surprising thing is that the wiring, switchboard and sub-station transformer even though they have been designed to cope with the aggregate electrical load, actually don’t—or without being too alarmist, often as not are severely overtaxed.
Keeping the explanation for this as simple as possible, what happens is that the combined electrical load comprising of electronic ballasts and fluorescent lighting, IT equipment, etc draws ‘distorted current’ with very high peaks. Technically speaking, the building load is said to draw harmonic current in addition to that required for the energy needs of the aggregate electrical load. Harmonics do show up in additional heating of wiring, switchboards, and transformers. These heating effects are serious—and can very easily double or even quadruple the heating the installation has to withstand—in short, way outside the design limits of the electrical installation assets.
There have been a number of instances of switchboard failures, fires and catastrophic occurrences as a result of harmonics. One thing can be stated clearly: the overtaxing of building electrical installations is a silent destructive agent and little recognised. Spending money on hardware to correct the overload situation needs to be balanced against the costs involved in breakdowns, catastrophic failure (costs of interruption to business—danger to personnel) and of course, the cost of electricity.

There is also the matter of the possible avoidance of additional capital investment when expansion of the electrical facility is dictated by commercial opportunities bearing in mind that harmonics derate the electrical plant. The solution can be the installation of active harmonic filters Active harmonic filters—as their name implies—filter out the harmonic current contribution and are able to ‘roll with the punches’ adapting to rapid changes in the harmonic load as is typical of many installations. They basically function by measuring the harmonic components, and then ‘sucking up’ just that part of the load current.

Is you electrical installation up to the job?

A great deal depends on the electrical loads in the facility. Offices, shopping centres and hospitals—in fact everything rather than factories where mitigation measures are now more frequent, are all trouble areas. Quite apart from the problem of overtaxing electrical installations there is the increasing attention power companies are paying to harmonics—they cause disharmony in their electrical supply systems through voltage distortion. They are becoming more and more stringent in their demands that customers adhere to Australian Standards relating to the so called ‘point of common coupling (PCC) permissible level of harmonic distortion.

For this reason alone, harmonic filtering may be well become mandatory in the not too distant feature. Westek’s role Westek supplies the range of Reinhausen MR active filters that have been proven throughout developed world as a highly effective answer to harmonics mitigation. We have built up considerable experience over the years of specialising in harmonics mitigation and are therefore in a good position to discuss mitigation solutions with you. Although we sell the hardware, we recognise that you buy the solution—so that is where we are coming from—effective solutions that provide safety and cost-effectiveness.