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Insulation resistance and insulation system sections
The article deals with disadvantages of often recommended connections and order of measurements for measurement of the insulation resistance of two and three-winding transformers. If there is any failure in the dielectric, the place of damage should be well localized. The calculation of resistance of partial sections (R1 to R3, or R1 to R6) is affected not only by the measurement error, but also by other methodical errors due to change of poles or repeated charging of some sections in cases when the adequate time needed for discharge of the insulation was not kept. The author of the article proposes a method of direct measurement of partial sections of the insulation system, because the possibility of change of poles in unmeasured sections is eliminated in case of adherence to the order of measurements and at the same time better conditions for discharging of insulation are created. In addition, the unwritten principle that the measured section is supplied by the negative pole of the measurement appliance on a side of higher voltage winding against lower voltage winding, to which the positive pole is connected, is observed.
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