Faster Testing

With HIGHVOLT’s new power supply plat­form for test equip­ment, a power elec­tronic supply unit is now avail­able for the first time—marking another step forward into the future of power supply tech­nology.

Text: Martin Buschen­dorf

New devel­op­ments and tech­no­log­ical progress change our lives. Long-distance calls made from a phone booth or phones with a rotary dial are now just a chapter in the history books. Nowa­days, almost everyone uses a smart­phone and couldn’t imag­ine life without the huge range of func­tions besides phone calls that these devices offer. Another change that is familiar to us all today is the move from the combus­tion engine to the elec­tric car.

The Rein­hausen Group has seen its own fair share of developments—drawing boards for designing on-load tap-changers or testing tech­nology are yet more exam­ples of things that have been consigned to the past. In fact, tech­no­log­ical progress has taken hold across every industry, and conven­tional systems are being replaced with smart ones. As a global tech­nology leader, HIGHVOLT is also opting for intel­li­gent solu­tions for its prod­ucts. Voltage control involving a mechan­i­cally oper­ated regu­lating transformer—a method that has been around for dec­ades—is grad­u­ally being replaced by an power supply plat­form known as the elec­tronic power source (EPS).

What the elec­tronic power source does

In order to explain just how big a step this is, this article intends to provide a brief overview of what the EPS does, how it differs from the current solu­tion, and what inno­va­tions and customer bene­fits it brings with it. To achieve a test voltage of several hundred thou­sand volts, the avail­able line voltage is converted to a much higher level via trans­formers. This works in a similar way to a primary substa­tion used by a domestic energy supplier. To prevent the object that is the subject of the test from being destroyed, the output voltage needs to be regu­lated.

And there’s a little trick that can be used to do this, which involves regu­la­tion taking place straight away at the low-voltage side. The effect of the transfer ratio can then be seen at the output. To put it in simpler terms, if you have connect­­ed a system with a maximum voltage of 500,000 volts to a 400-volt grid and then set 200 volts at the input, there will be 250,000 volts at the output. Simi­larly, if 40 volts are set at the input, there will be 50,000 volts at the output, and so on.

 

Previ­ously, a regu­lating trans­former was used to achieve this. This mech­a­nism conveys a current collector across the wind­ings with the aid of a mechan­ical drive, adjusting the voltage from 0 to 400 volts as a result. The size of the struc­ture used can vary signif­i­cantly depending on the connected load and connec­tion voltage. The supply grid is loaded asym­met­ri­cally on two of three phases.

It is at precisely these points that the EPS comes in. At the grid connec­tion, there is an elec­tronic power circuit—known as the active front-end—provided directly by colleagues at MR PQ. This is used to rectify the AC volt­age from the grid and then feed it into a DC link capac­itor. From there, a specially devel­oped power inverter with IGBTs acting as semi­con­ductor switches provides a vari­able, finely adjustable output voltage between 0 and 690 volts.

The grid load is distrib­uted evenly across all three phases and the regu­la­tion proce­dure becomes much more precise and far faster—without the need for any mechan­ical moving parts. To prevent the need to manage lots of different designs, the recti­fier and the power inverter can be connected in a modular manner, and the system can be scaled simply by changing the number of iden­tical modules incor­po­rated into the system.

Lower oper­ating costs, shorter test times, simple expan­sion options, and quick and easy repairs — the new system delivers a whole range of bene­fits

This provides a whole host of bene­fits to customers. In addi­tion to the more precise and faster voltage regu­la­tion that has already been described, excess energy in the reso­nant circuit can now be fed back from the correspond­ing testing systems to the power grid. Of partic­ular interest is the vari­able system frequency, which can be set to be­tween 0 and 500 hertz.

This enables our customers to perform tests for the entire global market using 50 hertz and 60 hertz—regardless of their actual loca­tion and the asso­ci­ated line frequency limits in different coun­tries. Addi­tional frequency vari­a­tions can also be used to expand the test range or to take special measure­ments for the purpose of locating faults—measurements that were not possible previ­ously. In addi­tion, the system enables harmonics to be actively compen­sated or applied in specific ways.

Modular system

Essen­tially, the customer receives a system that can be extended as needed and will be well placed to meet what­ever future demands it faces. What’s more, should there ever be a problem, the indi­vidual modules can be repair­ed quickly, meaning that the system will only be out of action for a few hours.

The modular design enables customers to benefit from the full range of func­tions that the system offers from the outset and upgrade it easily at any time. A whole host of prop­er­ties that are currently deliv­ered through add-on compo­nents come already inte­grated in the EPS, such as harmonic compen­sa­tion, short-circuit detec­tion, and emer­gency shut­down.

The supply plat­form is being intro­duced in stages. Facil­i­ties with a single-phase output voltage for AC systems of type WP (trans­former-based) and type WRM (based on the reso­nance prin­ciple) will be the first to be equip­ped with the EPS. This will be followed by the adap­ta­tion for modular DC test equip­ment. The devel­op­ment of the three-phase EPS means that trans­former test systems for low-voltage and medium-voltage trans­formers will soon be avail­able with the new EPS feature too. The func­tions provided by the system are constantly being expanded.

Customer bene­fits

The biggest chal­lenge when it came to devel­oping the EPS was achieving a low noise level. Tests can only be done if what is known as the partial discharge back­ground noise level is much lower than the signal being measured. The experts at HIGHVOLT have succeeded in reducing this noise level to < 1 pC (pico­coloumb), meaning that it is below the level of conven­tional feed-ins.

Despite the exten­sive enhance­ments the EPS offers, it does not cost customers any more to purchase and even saves them money during oper­a­tion thanks to shorter test times, simple expan­sion options, and quick and easy repairs. Not only that, but customers also benefit from a much wider range of func­tions that they can select based on their needs.


YOUR CONTACT


Do you have any ques­tions about the elec­tronic power source?
Martin Buschen­dorf is here to help:
M.Buschendorf@highvolt.com