Distribution transformer

immersedsubstationthree-phase

Neutral point coils (zig-zag coupling) are used to earth a neutral via high impedance.. The neutral point three-phase coils are located in the HVB/HVA source stations and connected to the MV network. Neutral point three-phase coils allow: • The creation of an artificial neutral point • The introduction of a defined impedance between this neutral point and the earth, in order to limit the current during phase-earth faults on the network. • Hermetic structure, in a mineral oil bath, for an exterior installation. • Frame supporting a crystal-oriented iron-silicon sheet single-phase magnetic circuit. • Copper coils. • Insulation made of class H metal aramid fibres. • ONAN cooling mode. • Lifting by the 2 rings located on the cover. • Operating reliability: Exceptional mechanical resistance in terms of electro-dynamic force due to coils bonded with epoxide resin*. • (*Qualification tests defined by the EDF HM-24/94/021 B specification dated 17/07/95, conducted in the Renardières Electrical Engineering Laboratory). • Endurance of inductances against thermal shocks caused by repeated neutral currents during operation (solid insulation with a thermal index > 180°)