The valve room is the place where electricity is transformed from alternating current to direct current, and vice versa, to enable it to be transmitted across long distances.
The technology used to convert the energy is based on the use of a thyristor. This is a simple electronic device similar to a power valve, hence the name of the room, which can be set to “ON”, where it acts as a conductor through a control signal, or “OFF”, where it blocks the current.
To make a simple analogy, the huge devices in the valve room work in much the same way as a mobile phone charger which uses mains electricity to charge the device with an output that is around 50 million times more powerful. Thyristors are water-cooled and comprise the four-way valves, 14-metre-high structures usually suspended from the ceiling of the valve room (to comply with safety distance and seismic resistance requirements), weighing a total of 24 tonnes.
The four-way valves form the converter, a gate that connects the “alternating” and “direct” parts of the system, composed of insulators connected to the cables of the grid.
During normal operation, the electrical output, which varies between 0 and 600 MW, as well as the direction of energy flow, is set and communicated by the remote-operation centre. The system is usually automated, and in particular the thyristors of the converter are controlled by computer via over 40 kilometres of fibre-optic cable. Adjacent to the valve room there is often another building that houses the control system, which also manages the cooling and monitoring equipment.
