Seeing through switchgear

2013-01-28 - By using radiography to inspect switchgear for wear and defects in a fleet of 26 circuit breakers, ABB has saved a US customer 38 man-days of maintenance downtime at a cost of less than half that of traditional maintenance.

By ABB Communications

Inspecting switchgear the traditional way is not a simple matter. Downtime has to be planned and coordinated, the equipment has to be disconnected and earthed, and circuit breakers filled with SF6 gas have to be degassed and the gas collected and recycled.

Only then can dismantling and subsequent reassembly begin. This phase brings with it the risk of human error and the introduction of defects that were not previously present. Parts can be lost, damaged or incorrectly fitted, and debris can enter the equipment. Disassembly for inspection is time consuming and costly, and not always effective.

In view of the importance of switchgear in the delivery chain of electrical energy, utilities cannot afford not to inspect their switchgear regularly. An unexpected malfunction can cause blackouts. At the same time, in order to plan maintenance and replacement effectively, knowledge of the condition of switchgear is vital.

With radiographic inspection, ABB can see inside equipment without having to disassemble it. As with manual inspection, the switchgear must be taken out of service, disconnected and earthed. But the subsequent steps are replaced by the far simpler and much less invasive approach of radiography. This cuts downtime from days to hours and significantly reduces costs.

Outage times
Circuit breaker type
Traditional invasive internal inspection
Radiography
38 – 145 kV
2 days
2 hours
242 kV
3 days
3 hours
362 kV
4 days
3 hours
550 kV
5 days
4 hours

Table: Typical time savings achieved with radiography

One customer who benefitted greatly from ABB’s radiography approach is Call Henry Inc., the high-voltage onsite service contractor at the NASA Glenn Research Center in Cleveland, Ohio in the United States.

A review of the center’s switchgear revealed that many of its circuit breakers were 10 to 14 years old, with one having completed 2,700 operations during its lifetime. Call Henry Inc. invited ABB to conduct a health check of the 26 SF6-filled circuit breakers.

ABB performed external diagnostics testing and radiographic inspections. Of the 26 breakers radiographed, one required entry to repair a hardware problem and seven required reduction of the SF6 gas moisture content. The remaining 19 were spared entry and intrusive maintenance.

As a result, 38 man-days of intensive internal inspections were avoided and NASA’s fleet was restored to reliable operating status for less than 50 percent of the cost of traditional maintenance.

These and other examples show that radiographic inspection saves both time and money, by reducing the amount of work required in comparison with traditional invasive inspection, and in terms of disruption and downtime for the customer.

ABB performs radiography on both its own and legacy equipment and on the products of other third-party suppliers.

Click here to read a longer version of the article and to learn how ABB radiography led to major savings for a leading US electric utility.


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