Area of Application
Medium and high voltage systems can be equipped with carrier transmission installations which are used for communicating measurands, control signal , and telephone connections between the substation and individual installations.
The high frequency signal generated in the HF-equipment must be coupled to the lines by the carrier transmission apparatus.
The main component of this apparatus is the coupling capacitor. The high frequency modulated voltage is generated in the PLC terminal and routed via the coupling filter and protection device to the coupling capacitor and finally to thehigh (or medium) voltage line.
Up to 25 kV line voltage we manufacture coupling capacitors in steel case , with one or two identical bushings and in porcelain or composite insulator housing too .
For high voltage lines ( 110 kV...500 kV) we manufacture porcelain or composite insulator housing capacitors.
Depending on the voltage level each capacitor comprises one to three superimposed units.
The capacitor core is a stack of ecological oil impregnated (SAS 60E) flat rolls, made of two or three biaxially orientated hazy polypropylene films between aluminium foil electrodes.The foils are extended.
The roll stacks are placed horizontally in the steel cases and vertically in porcelain or composite insulator housings.
The steel case capacitors have welded type bushings.
Low dissipation factors (0.0001...0.00015) and low partial discharges are the characteristic of ISOFARAD coupling capacitors.
This is due to exellent all film dielectric.The surface of the hazy film is roughed , which ensures spotless , perfect impregnation even without paper.
The impregnating material (SAS 60 E) is a synthetic aromatic hydrocarbon fluid having very good partial discharge characteristic and low viscosity even at low temperature.
The all film dielectric is stable even in the case of impulse voltages , which is an important property of coupling capacitors.
The dielectric keeps its original permittivity at high frequencies and its loss factor does not increase dramatically in these ranges.
In the 20-500 kHz range generally used for coupling the equivalent series resistance of the capacitor remains low, so the signal is coupled with low loss.