HVDC stations handle direct current power. They change electricity between AC and DC forms. Big buildings called valve halls house the converter equipment. These stations use special devices to control power flow. Early equipment used mercury, but now mostly uses solid parts like thyristors. Converters are made of many smaller valves. Reactors help smooth the direct current power. Filters clean the electricity and remove unwanted signals. Large transformers increase voltage from AC lines. These need special insulation for direct current. Stations need extra power from capacitors or motors. Equipment removes annoying extra frequencies. Outdoor gear needs lightning and weather protection. These stations need lots of space, often hundreds of meters wide. Designs reduce noise and radio interference.
