Many technologies can improve the energy efficiency of the electricity transmission process. One of them is using superconducting cables which reduce energy losses to a minimal level.
The IEC has published a brand new standard which promotes a unified approach for cable manufacturers. IEC 63075 specifies tests methods for superconducting alternating current (AC) cables. The forward-looking document is published by IEC Technical Committee (TC) 20.
Superconductors are materials which generate minimal energy losses when transmitting electrical power. Superconductivity occurs at extremely low temperatures and superconducting cables use liquid nitrogen as a coolant. The experts involved are dealing with temperatures ranging from 65 K to 80 K (-208 °C to -193 °C).
As a result of their energy-efficiency, these cables can be considered as an attractive option to replace conventional cables. They are also lighter and more compact, making them easier to install. One of the drawbacks is that they cannot be used over long distances because of the problems implicit in supplying the nitrogen they require for cooling purposes. They are also more expensive to manufacture than conventional cables.
On the other hand, their smaller dimensions and energy-efficient properties make them ideally suited for high-load centres, such as cities or dense business areas. A number of demonstration projects have already been successfully set up, in China, Japan, South Korea, Germany, the Netherlands, Russia and the US.
An example is the Ampacity project in Essen, Germany, where a medium voltage superconducting cable was used. The project linked two Essen substations with a 1 km-long cable. The analysis of the trial was published in a report issued during the summer of 2017. One of its main findings was that the technology was mature enough to operate under real grid conditions.
IEC 63075 defines a wide number of tests for cables both before and after installation. They include voltage, bending and thermal cycle tests and heat invasion of cryostat.
The new standard is the result of the work of experts from two IEC TCs, IEC TC 20: Electric cables, and IEC TC 90: Superconductivity. “Several members of the project team which developed the standard were also active in different TC 90 working groups. TC 90 took the initiative to develop the standard and TC 20 then took over as the standard is specifically related to cables,” explains Dr Mark Stemmle, who heads the IEC TC 20 project team.