Capacitance and Dissipation Factor Measurement
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5 Capacitance and Dissipation Factor
Measurement
Capacitance (C) and Dissipation Factor (DF) measurement is an established
and important insulation diagnosis method. It can detect:
• Insulation failures
• Aging of insulation
• Contamination of insulation liquids with particles
• Water in solid and liquid insulation
• Partial discharges
5.1 Theory
In an ideal capacitor without any dielectric losses, the insulation current is
exactly 90° leading according to the applied voltage. For a real insulation with
dielectric losses this angle is less than 90°. The angle
δ = 90° - ϕ is called loss
angle. In a simplified diagram of the insulation, C
p
represents the loss-free
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