Experts’ Q&A: low-voltage switchgear

October 10th, 2014, Published in Articles: Vector

 

Paul Louw

Paul Louw

Vector’s Peter Adams speaks to Paul Louw from ABB about low-voltage switchgear, its purpose, communication and the dangers of using outdated switchgear, and shares a number of tips on the selection, installation and use of LV switchgear.

What is the main purpose of LV switchgear today?

To put it in simple terms, modern LV switchgear must do more than simply protect installations and people; energy efficiency management is a new and essential function. In the old days, LV switchgear was not “smart”. It performed a straightforward protective function. Today, it is an essential part of an energy management system. It must facilitate lighting control, control circuits on demand, measure load at various centres and provide surge protection and condition information, among other functions.

Does modern switchgear have communication abilities?

This is one of the factors that makes quality switchgear so valuable. In the modern environment, end-users demand steady, uninterrupted power in spite of constant changes to the load. So, switchgear must be able to “talk” to other devices, balancing load and isolating faults to preserve the quality of the main supply. This means switchgear manufacturers must have a new design approach – control parameters are much more extensive these days. Switchgear must keep people and equipment safe and ensure that the power supply is managed for optimum efficiency.

How does this affect LV switchgear specifiers and installers?

It is important to gain an overview of an installation and to know what, if anything, has already been installed. Because the components “talk” to each other, the installer or specifier must be careful to ensure that every element in a modern installation is compatible with all the other elements. It is very unwise or even dangerous to follow a “mix and match” approach. This may work under circumstances where the system is not under undue stress but when problems arise, it could lead to expensive and even catastrophic results.

Many buildings have switchgear installed many years ago. Can it still be included in an updated system?

I have seen switchgear installed during the 1970s in various commercial buildings, many with unclear service history! No-one knows if it will perform to the levels required by current legislation. In case of a serious fault which causes those antique breakers to trip, they would be unable to be re-set. If you were to try and install modern switchgear alongside these museum pieces, you would be asking for trouble! But those installations also provide an opportunity for specifiers and installers – you can show your customer how money can be saved by retrofitting modern equipment which provides the potential to improve electrical efficiency significantly.

In an industrial setting, switchgear’s ability to provide arc-fault protection is essential. Even in a low voltage (say, 690 V) environment, a full-power arc can prove fatal for service personnel or operators. The danger is far greater than most people realise. The IEC international standard governing LV installations dictate that anyone working on such installations must wear specified personal protection equipment (PPE). Many arc-faults occur when breakers are racked in and out during service interventions.

Why are there more demands on electrical supply systems these days?

We live in a time where the number of electronic devices is increasing at an unprecedented rate, both in the home and at work. Many of these devices are “mission-critical” – they must be kept operational at all times, otherwise the consequences can be devastating. So it falls to the switchgear to manage the increased loads, and loads that vary frequently. This is not to mention multiple factors which the switchgear’s protective function must manage, to ensure that the system operates safely and efficiency.

What message would you like the contractor/installer to remember?

There are several points:

  • The electrical contractor or switchgear installer should be very careful when selecting a panel builder. It is very important to appoint a panel builder with the necessary access to high performance products, expertise and facilities.
  • The contractor should check the panel builder’s certification, both for enclosures and contained switchgear – the panel builder must have the correct certification levels for the job at hand.
  • Never forget that the testing requirements are extremely onerous and that all tests must be passed before the relevant certificates can be issued.
  • One practice which was allowed in times past is that of partial type-testing – this is no longer permissible within the IEC 61439 regime.
  • A modern switchgear panel is an intricate space demanding high levels of expertise from those working on it.
  • The contractor is not let off the hook, however – he must know enough about IEC 61439 to know when his panel builder is not fully compliant.
  • In short, the demands on switchgear are increasing and the wise contractor will make sure he keeps up-to-date with developments. Where there is any uncertainty, contractors or installers can approach their switchgear manufacturers or suppliers for help and advice.

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