Why use high voltage instead of low voltage?
To reduce electrical losses when electric power is transmitted over long distances, electrical losses are
lower if the current is low. This is obtained by using high voltage.
What is an HVDC transmission link?
An HVDC transmission link consists of three main components: a station to convert the alternating current
of the grid to direct current, the transmission equipment itself in the form of cables and overhead lines, and
another station that converts DC back into AC so that it can be used by consumers.
How does an HVDC system work?
HVDC transmission utilizes a converter station at either end of the system.
A mercury arc valve or solid-state valve (thyrister) is used for the conversion of AC and DC current.
The valve at the beginning of the system converts alternating current to HVDC, the HVDC travels to
the next location through a cable.
The valve at the end of the system converts the HVDC back to alternating current.
Energy infrastructure is an essential building block of our society. With the increased integration
of energy markets, the need to enhance security of supply and to integrate renewable energy sources, a
European HVDC grid could evolve. Over time, the point-to-point connections and the regional multi-terminal
projects could be connected with each other to more extensive grids. The first small regional systems can be
operated without DC breakers, but as the size and complexity increase, breakers will be gradually introduced.
What is an HVDC grid?
An HVDC electricity grid that can operate:
− Independently of one or several disturbances (isolate a failure)
− In different operation modes in the connected AC and DC systems
Technology gaps for the full realization include:
− Power flow control
− Automatic network restoration
− High voltage DC/DC converters
Global rules and regulations for operation are required for market acceptance.