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Capacitive Voltage Transformers

Capacitive voltage transformers of type ECF are used in high-voltage switchgears from 72 to 550 kV.  They transmit voltages to standardized, equivalent values for meters, measuring and protective devices.

The capacitive voltage transformer consists of one condenser unit and one electromagnetic measuring unit (EMU).  The condenser unit is located in the insulator and consists of one capacitive mixed dielectric which is impregnated with insulation liquid.  This active art is hermetically sealed to the outside.  For volume compensation of the oil there is a stainless steel expansion tank in the head section.  The operating pressure can be visualized via a monitoring unit.  Depending on customer specifications, creepage distance or voltage level, the condenser unit consists of up to 3 parts.  In order to avoid field distortions, a shielding electrode is used from a voltage level of 420kV.  A high-grade composite or porcelain insulator can be used as an insulator.  According to the contamination classes of common standards, different creepage distances can be selected.  The EMU is an inductive intermediate voltage transformer which is housed in the foot case of the transformer.  It allows the safe transmission of measurement signals.  A damping unit ensures increased safety against relaxation oscillation.  By using proven materials the converter is temperature and precision-stable over the entire service life.  On request, the converter can be designed in such a way that it can be used as a coupling capacitor for carrier transmission in high-voltage lines.

All metallic housings and flanges consist of a special aluminum alloy and can be painted in various colors.  The generously sized terminal box is equipped with a lid that is to be opened sideways.  This allow for easy connection of secondary cable.  The terminal box is equipped with a blind flange.  On request, cable glands or individual safety instructions can be built-in.

Advantages of Capacitive Voltage Transformers

  • Cost-effective and reliable design for high and very high voltages
  • Expandable for the transmission of high frequency signals (TFH)
  • Fabrication-internal reconciliation of the precision classes, no reconciliation required on site
  • Temperature and precision stable over the entire service life
  • Increased safety against relaxation oscillation due to attenuators

 

High and very high voltage

 

  • Simple and safe mounting on site for transformers which consist of multi-piece condenser units
  • High temperature and precision stability over the entire service life
  • Compensation of transient over-voltages in the grid, caused by circuit breakers

Tone frequency (TFH) couplings

 

  • Expandable for tone frequency (TFH) couplings
  • Extendable for the installation of the audio frequency suppressor

Easy-to-fit terminal box

 

  • The terminal box with the lid to be opened sideways is secured by captive screws.  Apart from terminals, fuses, surge arresters, additional contacts, spark gaps and sealable cover can be built in.
  • By default, the terminal box is equipped with a blind flange.
  • On request, the capacitive voltage transformer can be equipped with an additional terminal box.