Three-phase support for substation test

—Sponsored article by Megger

Engineers whose work involves testing in substations face two important challenges. The first is having the right equipment at hand to carry out the wide range of tests that are often required, and the second is carrying out those tests safely and as quickly as possible, to minimize downtime and cost.

The recent appearance of versatile integrated substation test systems in the Megger TRAX range has done much to help hard-pressed engineers address these challenges. These high-performance test sets have been specifically-designed to offer a convenient and comprehensive solution for transformer and general substation testing.

They’re capable of performing more than 20 different test functions, including measurement of winding resistance, turns ratio, excitation current, short-circuit impedance, tan delta / power factor, capacitance, frequency response of stray losses, CT and VT testing, and circuit breaker timing and motion analysis.

Clearly, when one of these novel test sets is available, ensuring that all of the necessary test equipment is at hand is no longer a challenge!

TRAX test sets also significantly reduce the time taken to perform tests. They have an intuitive user interface that offers full manual control or guided testing using the built-in TRAX apps. Each of these apps implements a specific test function; for example, turns ratio measurement or winding resistance measurement—and automatically configures the instrument for the selected test.

All unnecessary information is removed from the display, with only information relevant to the test in hand remaining. This app-based approach makes TRAX test sets safe, fast and easy to work with as well as eliminates the need for extensive user training.

But even the best can be made better! Until now, one limitation of the TRAX test sets was that when they were being used to test three-phase assets such as transformers, it was necessary to change the test connections after testing each of the phases.

In principle this isn’t a major issue, but in practice it quickly becomes an annoyance, and the time taken to change the connections soon adds up, especially if those connections are on top of transformer and every change means climbing up and down a ladder!

Three-phase switch box
With this in mind, Megger has introduced the TSX130 three-phase switch box. Available as an optional accessory for all TRAX test sets, this new unit allows three-phase transformers to be conveniently tested without the need to reconfigure the test lead connections for each phase.

An added benefit is switching between phases is controlled by the test set, which means that test sequences can be automated. At the same time, Megger has further extended the versatility of the TRAX system by launching another invaluable accessory, the TDX120, which facilitates the use of the test sets to perform tan delta and capacitance measurements.

Despite the wide range of functions offered by TRAX test sets, they are exceptionally light and compact. The TRAX220, which has a maximum AC current capability of 200 A, is the lightest test set of its type, weighing just 32 kg in its transport case, which means that it can be transported by air as check-in luggage.

These innovative test sets can generate and measure a wide range of currents and voltages with high precision. While the TRAX220 has a maximum AC current output capability of 200 A, the TRAX280 extends this to 800 A. The output current capability of both units can be further extended to 2000 A with an optional current booster.

Other key features of Megger’s new and innovative TRAX test sets include state-of-the-art transformer winding resistance measurements with true DC test currents up to 100 A and up to 50 V compliance voltage; dynamic on-load tap changer (OLTC) measurements; and exceptional interference suppression to secure accurate readings even in high noise switchyards.

A wide operating frequency range of 5 to 500 Hz (1 to 500 Hz for tan delta measurements) is also included, as is individual temperature correction of
tan delta measurements using Megger’s patented technology; and automatic voltage dependence detection, which is another unique feature covered by Megger patents.

Today’s substation engineers are under constant pressure to work faster and more efficiently while maintaining the highest standards of safety. The new integrated substation test sets, of which the Megger TRAX instruments are the leading example, make it possible to respond positively to this relentless pressure.

Matz Ohlen is director of transformer test systems with Megger.

This article is an edited version of the original, which appears in the August 2016 edition of Megger’s Electrical Tester magazine.