The machine stress-testing undersea power cables

The machine stress-testing undersea power cables

Cables are an important part of the infrastructure that supplies society with electricity. Before they can be buried or laid on the seabed, they must first be tested – with up to 1.5 million volts. Elektrisk Drivteknik (EDT) of Kungälv, Sweden, builds the specialised power generators that do this – ABB supplies a complete range of solutions to support EDT’s testing work, from contactors and thermal overload relays, to softstarters and Emax 2 air circuit breakers.

Final calibrations are underway for a soon-to-be-delivered, fully assembled power generator. "Everything has to be right," says EDT technician Tobias Andersson, monitoring the measurements on a screen. “There is zero tolerance on deviations.”

EDT’s customer is a manufacturer of high-voltage direct current (HVDC) cables designed to transmit electricity over long distances, for example from offshore wind farms to land. The testing takes place in huge halls, where one part of the power generator is placed on a high platform that looks like an oil rig. On the floor sits the pump unit supplying the generator with energy. A reference unit controls the current so that the temperature is kept constant in the cable under test.

The part of the cable being tested is up to 150 meters long and the finished cable can be 40 kilometers long. "A system of cables can transmit over 1000 MW – that’s enough for 10 factories or 100,000 homes," says Claes Hugoson, owner and CEO of EDT.

EDT produces between one and three of these power generators each year. Their team is involved throughout the entire process from product selection to delivery, installation, commissioning, start-up, servicing and maintenance.

Hot tests

EDT’s generators must provide reliable power to ensure the cables are safe, robust and efficient. Hugoson explains: "Our equipment heats up and tests the cables to the specified voltage, usually 525 or 800 kV, plus or minus. The impulse voltage testing is performed with a peak at about twice the voltage and opposite polarity.”

In some cases, the heating cycle must be repeated up to 300 times, in test programs that can take a year. The power generator must not fail: a single outage can result in a delay of 14 days in a facility that can cost more than $3000 a day to operate.

The first choice is ABB

To meet EDT’s performance and reliability requirements, their equipment suppliers must meet high standards. Around 90 percent of the components in their control cabinets come from ABB.

"ABB has been our first choice since we started,” says Hugoson. “I have great confidence in their people and products. We have always received the support we need. We're trying to get away from wear and tear and ABB's products are smart, safe and environmentally sustainable because they have a long lifetime. ABB is simply the best for our purposes."

“ABB loves working with companies like EDT who bring so much focus and passion to their projects,” says ABB sales specialist Anders Cullbrand. “It’s great to understand how our technologies and support helps their work – and ensures the high-voltage cables that we all rely on for energy are tested so comprehensively before they enter service.”

  • EDT uses ABB Softstarters to reduce electrical stress on the power generators
  • In EDT, a power generator is ready for delivery to the customer. The copper rails protect its interior, where Claes Hugoson's successful invention is hidden.

Text & photo: Anna Rehnberg

Facts:  ABB products in EDT's test equipment

Motors, power supplies, contactors, soft starters, motor protection, load break switches, pilot devices, signal lamps, emergency stops, miniature circuit breakers, safety relays and Relion® protection relays from the 615 series, the REM615.

Facts:  Electric Drive Technology (EDT)

EDT is a small company focused on custom-designed test equipment for customers who manufacture high-voltage cables. EDT is also a complete supplier of electric motors, generators, and control systems to customers in the energy, process, and engineering sectors.


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