ICMflex - partial discharge detector, partial discharge fault locator, and loss factor measurement system

PD measurements are a reliable and accurate method for determining the service life and quality of stator bars and stator windings in high voltage generators and electric motors, but up to now there is no international standard that defines acceptance levels for partial discharges during factory acceptance tests for these types of high voltage components. Where PD acceptance tests lack standardization, this is not the case for tan delta measurements thanks to IEC 600034-27-3, published by the International Electrotechnical Commission in 2015. This standard defines the acceptance criteria for form-wound stator bars with slot corona protection and a nominal voltage of 6 kV or higher. So, the accuracy and efficiency of a high -frequency off-line PD measurement complements a low -frequency tan delta measurement and, therefore, combines the best of both worlds. 

The ICMflex can be used with any fixed or portable high voltage power supply, such as transformers, hi-pots, resonant test systems, motor/generator sets, and VLF systems. 

Building high voltage equipment requires using insulation material. Commonly used insulation materials show losses due to resistive currents or polarization currents of dipoles. Often, the magnitude of these losses can be used as an indicator for the quality of the insulation. In the case of assessing the quality of aged insulation, increased dissipation indicates oil or paper decomposition (transformers), humidity, electro-chemical processes (water -trees in polymeric cables),or heavy partial discharge. With an ideal capacitor (C), the resistance of the insulation material (dielectric) is infinitely large. When an AC voltage (V) is applied, the current (IC) leads the voltage by exactly ϕ = 90 °. A component close to this ideal capacitor with a negligible resistance should be used as standard (or reference) capacitor for the reference branch of a dielectric loss analyzer. Technical insulation systems are usually built of less than perfect insulation material, resulting in a small current (IR) in phase to the supplied voltage (V). This current can be described by a parallel resistor (R) to an ideal capacitor (C). The phase difference between the real current (I) and the ideal current (IC) can be described as phase angle: ‘deltaδ’.  Because P = Q · tan deltaδ, the losses, which are proportional to tan deltaδ, will usually be given as a value of tan deltaδ to express the quality of an insulation material. Therefore, the angle ‘delta’δ is described as ‘loss angle’ and tan deltaδ as ‘loss factor’. With a good insulation of low-loss capacitors (tan deltaδ ~ 0° and ϕphi ~90 °), the ideal current (IC) is approximately equal to the real current (I); resulting in a negligible deviation of the values tan deltaδ and cos phiϕ. In Europe, the dissipation factor tan delta is mostly used to describe the dielectric losses, while in North America the power factor (PF = cos phiϕ) is commonly used. The software of the ICMflex displays both values, together with the calculated capacitance, the voltages, and the frequency.