Tackling the challenges of protection relay testing

—Sponsored article by Megger

Relay testing is one of those challenging areas where there never seems to be a shortage of questions. The technology adopted in both the relays themselves and in the equipment used to test them is developing rapidly.

Let’s take a look at questions Megger’s technical support team has recently been asked about relay testing:

Modern protection relays are becoming increasingly complicated and intelligent, which means that it’s often very difficult or even impossible to test them with single-phase voltage and current. But three-phase test sets are usually complicated and offer features only needed by the most advanced users. Is there a better solution?

Indeed there is! A new type of three-phase test set has recently become available which has been designed specifically to address this problem.

These instruments have essentially been designed as an engineer’s “multifunction test box,” and they combine a straightforward and intuitive user interface with extensive facilities for three-phase testing.

They provide a wide range of preconfigured virtual test instruments so that all of the most commonly used protection relay tests can be set up and performed quickly and easily. Full manual control and configuration options are also provided to cater for special testing requirements.

The instruments also offer other useful functions, which include an analogue ammeter and an analogue voltmeter together with facilities for measuring a wide range of parameters such as phase angle; active, reactive and apparent power; power factor; resistance; reactance and frequency.

Sometimes it’s necessary to test single-phase relays with higher currents or higher voltages than are directly available from a single channel of a three-phase test set. How can this be done?

The most convenient and cost-effective solution is to choose a three-phase test set that allows output channels to be connected in parallel to provide higher currents or in series to provide higher voltages. This isn’t a particularly new idea and there are several test sets on the market that offer this option.

In most cases, however, the series and parallel connections have to be made using cables. This is fiddly and time consuming and it’s very easy to make mistakes. Megger’s new easy-to-use three-phase Sverker 900 test set provides a better solution.

Series and parallel connections are set up using rigid plug-in links rather than flexible cables. The links and the sockets they plug into have a patented configuration that has been specially designed so that it is physically impossible to make an incorrect connection.

As a result, swapping from three-phase testing to high-current or high voltage single-phase testing takes only a couple of minutes and the risk of errors is completely eliminated.

This article is an edited version of the original, that appeared in Megger’s Electrical Tester March 2015 newsletter.

Megger provides testing solutions in the most critical maintenance areas including cable fault locating, protective relay testing, and power quality testing. Megger’s product offering spans 30 distinct product groups with over 1,000 specific products. To learn more visit www.megger.com

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