Safety first

Location of the switchgear is an important factor in deciding its specification and its housing.
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The continuing expansion of electrical distribution networks places pressure on the equipment that keeps them safe and reliable. Faults or failure can cause localised blackouts, damage to property, or serious injury and death to operational staff.

This is the case with switchgear, which must be selected for installation on a case-by-case basis, to ensure it will work appropriately, within the required environment. And although failures are rare, manufacturers advise against complacency. The most frequent problem is a flashover voltage when electricity jumps from one conductor to another creating an arc.

If the breaker insulation fails to absorb this arc an explosion can occur. Therefore it is imperative to inspect, test and maintain all switchgear and other substation equipment on a regular basis.

Frequent testing and monitoring can help to detect deterioration in switchgear equipment before faults occur and prevent outages. Partial discharge (PD) monitoring is the main technique used to monitor the health of high-voltage switchgear.

PD activity manifests itself through internal or surface arcing and noise, and is a sign that the insulating medium is failing. Portable detectors that record ultrasonic noise and transient earth voltage effects can indicate whether assets are working satisfactorily or whether they require further tests or urgent investigation. In addition, for gas-insulated installations regular pressure checks are vital to protect against leaks and a breakdown in the integrity of the insulation.

Checks on switchgear and substations should also include visual inspections for evidence of sooting and distortion on enclosures, the detection of smells and high temperatures, corrosion leaks and so on. The immediate environment also needs regular inspection such as external walls in case of water ingress and fences for signs of unauthorised access or interference.

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During the selection process there are several things to consider, the most important of which is safety.

“Because people are operating [the equipment] it has to be safe and it has to be reliable,” said Praveen Kashyap, manager - Technical Sales Support & Estimation for Eaton Electric. “Also, you are relying on some automation, if it is not reliable there can be some very difficult situations where protection has to work and it doesn’t.”

So, safety and reliability in switchgear product selection are absolutely essential. Looking for established performance track records are an obvious clue as to what works and what doesn’t. But apart from the performance qualities of the equipment itself, the environment in which it is placed must also be considered.

The equipment specified for any given situation will change depending upon the surrounding environmental conditions. This can make housings or enclosures for the switchgear especially important and a key consideration in the Middle East is proximity to the sea. Hot coastal locations have a brutal effect on equipment, particularly metal.

“Whether you are putting something in Ajman or Al Ain makes a big difference,” said Kashyap. “When buying equipment, you must know where it will be installed. How much moisture, heat and salt it can withstand is the deciding factor.”

Polycarbonate and glass-fibre enclosures are reasonable protective solutions, as is the possible use of stainless steel. Combinations of filters and air conditioning units included in larger installations can also keep the environment under control and regulate the temperature. The degree of protection offered can be indicated by an ‘IP’ rating.

What this all boils down to is operational sustainability. The lifecycle of the product has to be long enough to justify the cost and the long–term support must be available from the manufacturer, so replacement parts will be accessible and any regulatory upgrades can be carried out, without having to start from scratch.

Flexibility also plays a part here too. The ability to extend a switchgear installation has to be planned in at the initial installation phase. Both the selection of equipment and the allocation of space are important, if further additions or adjustments may be required at a later date. If this is a possibility, then selecting equipment that can be expanded is absolutely essential.