Standard practice

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When a utility company awards contracts for a power plant project, it needs to be confident that the equipment supplied will perform reliably and safely over many years.

Manufacturers as a rule issue statements of compliance, declaring that their products conform to current safety standards. They are under no legal obligation to have product testing conducted and verified by an independent body. However, utilities the world over are increasingly insisting on third-party certification.

Craig Diack-Evans, senior international business development manager at Intertek says: "Utilities want reliable equipment and they want equipment that is safe, so they have minimum test requirements written into their specifications.

ADWEA and DEWA do it and, although they can't be specific about who the manufacturer should go to, they do give examples as you need to go to a recognised body.

There are a number of certification bodies that verify the testing of electrical power equipment, such as KEMA, ESEF, SATS, CESI and Intertek, which last year acquired ASTA BEAB certification services. Mostly, they do not carry out the testing themselves, but instead collaborate with accredited laboratories.

Shankar Subramany, manager of an accredited high power testing laboratory in Ludvika, Sweden, owned by ABB, explains.

"We are a member of SATS, which is an independent certification body, based in Norway, with several member laboratories both for high power and high voltage. We carry out the tests for SATS and those tests are supervised by inspectors from SATS, which then issues the certificate.

Even though the test laboratory belongs to an equipment manufacturer, there is no conflict of interest, as Subramany continues:

The laboratory is owned by ABB, but at the same time the laboratory is accredited to ISO/IEC 17025, the international standard for the accreditation of test and calibration laboratories.

"According to this standard, the criteria are laid down as to how the laboratory should be organised, how it should function and what kind of quality systems it should adopt and, of course, the test equipment, test and calibration methods and so on.

"And one of the most important criteria is that the laboratory should function free from the rest of the manufacturing organisation. So we are organised independently from ABB as a manufacturer, we can say we are more or less autonomous from the company.

Furthermore, the laboratory does not just test ABB products; it also conducts testing for other high-voltage power equipment makers.

Privatisation trend

Previously, utility firms often operated their own testing facilities, but because of the trend towards privatisation and the breaking up of large utilities, using independent accredited laboratories and those belonging to manufacturers is becoming more the norm.

"Most of the utilities who buy equipment today like to have third-party certification because in the past some of them owned their own laboratories and had their own competent people to do the testing," says Subramany.

"They could buy equipment from manufacturers and make their own tests, but all this has changed, a lot because of the privatisation of the utilities. Now they accept tests done in the manufacturer's laboratory, but they like to have an independent certification body to send their inspectors to supervise the test.

In the case of Intertek, the process is a little different: "We don't go and supervise the tests within our laboratories," Diack-Evans explains. "When we assess the laboratory as being suitable to test equipment for the purpose of issuing our certificates, we train one or more members of their staff to become observers.

This is an elite group of highly qualified engineers within the laboratories whose sole responsibility is to ensure that the tests are performed correctly. Their name also goes on certificate and they sign it.

"However, the certificate is rigorously reviewed before it is issued by expert Intertek engineers. When everything is satisfactory only then is the certificate signed by a senior member of the technical staff, integrally bound and sealed and sent back to the laboratory for presentation to the client.

Uniform testing

Certification bodies, operating in the field of high power testing, are usually members of the Short-Circuit Testing Liaison (STL), a voluntary organisation, which aims to harmonise the way product safety standards are interpreted and ensure that the tests are conducted and reported in a uniform manner.

An accredited laboratory will conduct any test requested by the client, but each laboratory should carry them out in the same way. "In our laboratory, we perform all kinds of short-circuit and switching tests," says Subramany. "We test all high-voltage products, that is all products rated more than 1 000 volts up to 800 kV, including transmission and distribution products, like circuit-breakers, surge arrestors, power transformers and disconnectors.

"We test for their short-circuit performance to see how they behave during an exceptional condition, when failure occurs somewhere in a network and a short-circuit is created, to see what happens when very huge currents flow through this equipment and how they withstand the effects of the short-circuit.

A short-circuit can happen anytime, but the equipment should be able to continue its normal function when the system is restored.

"We also perform switching tests to simulate certain conditions like when the circuit-breaker is called upon to switch a large capacitor bank, an unloaded line or an unloaded transformer - when the current is not so important but the switching overvoltages could be critical for the equipment.

"And of course we have some other auxiliary test facilities like temperature-rise testing and mechanical testing also in our laboratories.

To be able to carry out such tests, naturally, the laboratories need a vast amount of specialist equipment. "It requires a very large test facility in order to simulate such fault conditions in the laboratory environment," Subramany continues.

"So we have large generators to produce the very high short-circuit power for a duration of a few seconds.

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