Ultrahigh-voltage direct current transmission equipment reaches new heights

2012-12-31 - The newly developed 1,100 kilovolt DC power transmission equipment stands at up to 26 meters above the ground, equivalent to a standard seven story building.
By ABB Communications

1100 kV UHVDC Coupling Capacitor
Most utilities would jump at the chance to purchase a transmission system that could carry billions of volts of electricity. This is because the higher the volts the lower the amps required to deliver the same power, and since reducing the amps lowers the losses, more power can reach the paying customer.

ABB is striving to develop all the components required for a 1,100 kilovolt (kV) or 1.1 million volt UHVDC (ultra-high voltage direct current) power transmission system, which represents the biggest capacity and efficiency leap in over two decades. Such a system could deliver approx. 10,000 MW of power across several thousands of kilometers with minimal transmission losses.

To develop the system many technical challenges have been overcome and these achievements have followed hot on the heels of ABB’s recently announced world’s first 1,100 kV ultrahigh-voltage direct current (UHVDC) converter transformer, a key enabling component of the system.
Today other components are also available including ultrahigh-voltage by-pass switches, surge arresters, coupling capacitors and capacitor filters.

1100 kV UHVDC Surge Arrester
These parts are as important as the converter transformer in UHVDC networks since they form vital elements for the safe transmission of UHVDC power. The by-pass switches are required to rapidly by-pass or insert the HVDC converters back into the network after maintenance or reduced voltage operations. The coupling capacitors are used as radio interference filters, the surge arresters are a vital element for the overvoltage protection of equipment, and the capacitor filters ensure power quality by mitigating harmonics and other electrical disturbances.

To develop UHVDC networks the equipment must be capable of enduring high-voltage stresses and must maintain a high degree of electrical insulation. For example, all the ultrahigh-voltage components described above have been designed and tested for a switching impulse withstand level of >2.1 megavolts (MV) or 2.1 million volts, and for a lightning impulse withstand level of >2.5 MV, the highest ever for products within this category. The protection levels of the arresters have been optimized to give a sufficient operational margin with respect to these levels. This has been made possible through the careful design of equipment to ensure excellent thermal performance and the use of high-quality ZnO varistors.

By increasing the ground to earth clearance between live parts, the insulating properties of air can be used to enhance the insulation performance of 1,100 kV UHVDC products. This means that much of this equipment stands high above the ground, with capacitor filters at 26 meters (m), bypass switches at 14 to 16 m, surge arresters at 16 m and coupling capacitors at 18 m. These physical constraints have placed further requirements on the design of UHVDC products, which must be capable of withstanding seismic activities and associated mechanical load combinations.

UHVDC transmission is a development of HVDC, a technology pioneered by ABB more than 50 years ago. ABB is a world leader in HVDC transmission technology, with many pioneering achievements and over 70 such projects around the world with a combined transmission capacity of around 60,000 MW.

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UHVDC 1100 kV transformer