Testing power factor corrections panels against IEC 61921

Capacitor banks, otherwise known as power factor correction panels (PFC panels), are used to avoid inefficiencies in power distribution networks associated with large electrical motors similar loads with a low power factor. Testing these products require specific knowledge, expertise and facilities.

Although most of the international standards for this equipment (IEC 61921) refers to the IEC 61439-2 standard, there are also some critical differencies with respect to temperature rise testing. DEKRA can support you in testing these panels. The major differences are described below.

Increasing the load current
One major difference is that temperature rise testing should be performed at increased load current. Several options for increasing the load current in the circuits of the PFC panel are described in IEC 61921 - in clause 7.2.1 You can: a)increase the voltage, b)increase the frequency, c) increase the capacitance, and/or d) superimpose harmonics.

At DEKRA, we can perform testing according to several of the above options. In most cases, we will discuss the perferred method with the manufacturer. Henk Kormelink, Project Manager at DEKRA, comments: "We think that a very realistic way of testing would be a combination of increasing the frequency and increasing the voltage. A higher test frequency (from 50 Hz to 60 Hz) can be used to deliver part of the load current (1.2 times) and increasing the test voltage can be used to achieve the final load current if required. Only increasing the voltage may overstress the control circuits. A disadvantage of only increasing the capacitance may be that this does not reflect the worst-case scenario, as the capacitors are not loaded up to the current as specified. We think that a combination of increasing the frequency and increasing the voltage is most realistic without the need to change the test object (capacitors and/or control circuits) and/or to use more costly components."

To make testing as realistic as possible, an inductive load bank is used. For manufacturers this is an advantage because there is no need to adapt the test sample to control the capacitor banks. This can be easily controlled, using the standard functionality of the control circuit of the PFC panel.

Full line voltage
Another major difference is the fact that temperature rise testing should be performed at nominal line voltage. Testing to IEC 61439-2 is normally done at low voltages. However, for PFC panels the standard requires testing at nominal line voltage. Safety conditions during testing are, of course, a critical element. Our test laboratories are fully equipped to make the appropriate measurement ans to ensure that these tests are done safely.

Testing at higher ambient temperatures
In areas with a hot climate, e.g. in the Middle East, additional testing at higher ambient temperatures than those specified in the international standards is required. To meet this demand DEKRA is able to test in a unique and new climate-controlled test laboratory, where we can test equipment at 15 - 60°C. DEKRA engineer Thijs van Gemen comments: "This automatically controlled climate chamber assures that the elevated ambient temperature of e.g. 50 or 52°C is kept stable during the complete test. This is of course important for manufacturers and end-users
witnessing these tests as fluctuations during testing may lead to discussions on the outcome". Temperature rise testing of a PFC panel is one of the critical tests as the lifetime of capacitors reduces drastically at higher temperatures. Accurate measuring and stable conditions during testing is in that respect of vital importance.

Case study
We recently tested a PFC capacitor bank panel at 52°C for Comar Condensatori of Italy. Sales & Marketing Manager Claudio Romagnoli commented: “We chose DEKRA because they can test over an extended temperature range. We greatly appreciated their support during the test programme and we will return for further testing.” These tests were witnessed by a delegation from the end-user of the panel, the Kuwait Ministry of Electricity and Water.

Testing the incoming circuit
As per the requirement of IEC 61439-2 the incoming circuit should be tested. An MCCB or a switch disconnector as an incomer should therefore be subject to testing. For an incomer MCCB an ICC test is required and for the busbar system an ICW test is required. In case the incomer is a switch disconnector an ICW test is required to test the incoming circuit.

We trust that the above information will help you prepare for testing a PFC panel. At DEKRA we have the right people, the right facilities and the right expertise to support you. Our experienced engineers are familiar with the requirements for specific markets and ensure that your equipment will be tested quickly and efficiently. Our facilities assure accurate outcomes and create
 realistic test methods. On top of that, we think that testing should be an informative experience for you as a customer and our people take time to explain details and explain test methods.

For more information, please contact us.

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