page_title: High-voltage direct current
section_title: Converter transformers
hierarchical_section_title: High-voltage direct current / Conversion process / Converter transformers
caption_attribution_description: English: A single-phase, three-winding converter transformer of the La Grande complex, in Baie-James, Québec, Canada. The long valve-winding bushings, which project through the wall of the valve hall, are shown on the left. The line-winding bushing projects vertically upwards at centre-right. Français&#160;: L'un des transformateurs du complexe La Grande, Baie-James (Québec, Canada) Deutsch: Stromrichtertransformator, einphasige Ausführung, in Reserveposition für die Hochspannungs-Gleichstrom-Übertragung in Baie-James (Québec, Canada). Bei der Konverterhalle befinden sich drei solche Transformatoren, je einer pro Außenleiter
context_page_description: A high-voltage, direct current electric power transmission system uses direct current for the bulk transmission of electrical power, in contrast with the more common alternating current systems. For long-distance transmission, HVDC systems may be less expensive and have lower electrical losses. For underwater power cables, HVDC avoids the heavy currents required to charge and discharge the cable capacitance each cycle. For shorter distances, the higher cost of DC conversion equipment compared to an AC system may still be justified, due to other benefits of direct current links, such as interconnecting power systems operating at different frequencies.
  Most HVDC links use voltages between 100 kV and 800 kV. A 1,100 kV link in China was completed in 2019 over a distance of 3,300 km with a power of 12 GW. With this dimension, intercontinental connections become possible which could help to deal with the fluctuations of wind power and photovoltaics.
  HVDC allows power transmission between unsynchronized AC transmission systems.
context_section_description: At the AC side of each converter, a bank of transformers, often three physically separated single-phase transformers, isolate the station from the AC supply, to provide a local earth, and to ensure the correct eventual DC voltage. The output of these transformers is then connected to the converter.
  Converter transformers for LCC HVDC schemes are quite specialized because of the high levels of harmonic currents which flow through them, and because the secondary winding insulation experiences a permanent DC voltage, which affects the design of the insulating structure (valve side requires more solid insulation) inside the tank.  In LCC systems, the transformers also need to provide the 30° phase shift needed for harmonic cancellation.
  Converter transformers for VSC HVDC systems are usually simpler and more conventional in design than those for LCC HVDC systems.
caption: A single-phase, three-winding converter transformer.  The long valve-winding bushings, which project through the wall of the valve hall, are shown on the left.  The line-winding bushing projects vertically upwards at center-right
exif: {"Image ImageWidth": "1698", "Image ImageLength": "1177", "Image BitsPerSample": "[8, 8, 8]", "Image PhotometricInterpretation": "2", "Image Orientation": "Horizontal (normal)", "Image SamplesPerPixel": "3", "Image XResolution": "72", "Image YResolution": "72", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop CS5 Macintosh", "Image DateTime": "2013:01:24 12:04:04", "Image Padding": "[]", "Image ExifOffset": "2304", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "4570", "Thumbnail JPEGInterchangeFormatLength": "5156", "EXIF ExifVersion": "0221", "EXIF ColorSpace": "Uncalibrated", "EXIF ExifImageWidth": "1698", "EXIF ExifImageLength": "1177", "EXIF ImageUniqueID": "FA7639C50653446CAB0FB6789E84B99D", "EXIF Padding": "[]"}