Abstract: This application describes methods and apparatus for the safety and protection of capacitor units suitable for medium and high voltage applications, for instance within switching modules (400) of a voltage source converter as may be used for HVDC or FACTs. The capacitor unit (300) has a housing (201) within which is a capacitor comprising a plastic film dielectric material, for instance a winding (100) of first and second plastic films (101, 102) with metal coatings (103, 104). A pressure sensor (302) is configured to detect if the pressure in the housing exceeds a first pressure level and a pressure relief valve (304) is configured to vent gas from the housing if the pressure in the housing exceeds a second pressure level which is higher than the first pressure level.

Abstract: This application describes methods and apparatus for the safety and protection of capacitor units suitable for medium and high voltage applications, for instance within switching modules (400) of a voltage source converter as may be used for HVDC or FACTs. The capacitor unit (300) has a housing (201) within which is a capacitor comprising a plastic film dielectric material, for instance a winding (100) of first and second plastic films (101, 102) with metal coatings (103, 104). A pressure sensor (302) is configured to detect if the pressure in the housing exceeds a first pressure level and a pressure relief valve (304) is configured to vent gas from the housing if the pressure in the housing exceeds a second pressure level which is higher than the first pressure level.

Abstract: A transformer (30) comprises: first and second printed circuit board substrates, the first printed circuit board substrate (32) including at least one first substrate layer (34) having a dielectric relative permittivity of less than or equal to 3.

Abstract: A circuit breaker for high voltage direct current (HVDC) power transmission includes a module with a pair of terminals for connection to an electrical network, and four of conduction paths. Each first conduction path includes a mechanical switch connected in series with at least one first semiconductor switch to selectively allow current to flow between the first and second terminals through the first conduction path in a first mode of operation or commutate current from the first conduction path to the second conduction path in a second mode of operation. The second conduction path also has a semiconductor switch to selectively allow current to flow between the terminals through the second conduction path or commutate current from the second conduction path to the third conduction path in the second mode of operation.

Abstract: A circuit breaker apparatus for use in high voltage direct current (HVDC) power transmission is provided. The circuit breaker apparatus has one module or a plurality of series-connected modules, the or each module including: first, second, third and fourth conduction paths and first and second terminals for connection to an electrical network, each conduction path extending between the first and second terminals, the first conduction path including a mechanical switching element, the second conduction path including at least one semiconductor switching element, the third conduction path including a snubber circuit having an energy storage device and the fourth conduction path including a resistive element.

Abstract: A circuit breaker apparatus (32) comprises one module (30) or a plurality of series-connected modules (30), the or each module (30) including: first and second conduction paths (34, 36); and first and second terminals (38, 40) for connection to an electrical network (42), each conduction path (34, 36) extending between the first and second terminals (38, 40); the first conduction path (34) including a first vacuum switching element (52) to selectively close to allow current to flow between the first and second terminals (38, 40) through the first conduction path (34) in a first mode of operation, or open to block current from flowing between the first and second terminals (38, 40) through the first conduction path (34) in a second mode of operation; the second conduction path (36) including a second vacuum switching element (56) to selectively open to block current from flowing between the first and second terminals (38, 40) through the second conduction path (36) in the first mode of operation, or close to a