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Insulator string member is fixed to the insulating power plants, substations and high voltage power transmission line conductor.In the case of operation due to internal mechanical stress, electrical and mechanical loads, and air pollution generated by various defects.These defects can gradually develop in the operation, if not timely detection of replacement, will inevitably lead to an accident at work voltage and over-voltage long-term effects, affecting the safe operation of the system.
Insulator failure There are some situations:
Insulator insulation resistance degradation, divided into two types: low and zero values Insulator Insulator.Insulator low, due to the combined effects of long-term mechanical loading and high voltage caused by deterioration of the breakdown voltage which will make Insulator declining current dropped to a low value called dry Insulator smaller than the creeping flashover voltage.Insulator zero value, the limit of low Insulator, i.e. internal breakdown voltage is zero.
Insulator surface contamination, failure of performance due to serious environmental pollution caused by surface leakage current increases.
Insulator breakage, or mechanical reasons arc burns, Insulator crack fault occurs, resulting in longitudinal cracks or transverse temperature abnormality.
Insulator string normal voltage distribution depends on Insulator its own capacitance, the stray capacitance of the wires.Regardless of the value of insulation resistance, and exhibits an asymmetric distribution of the saddle, and therefore, when put into operation, the temperature rise performance Insulator string saddle asymmetric distribution, i.e., the temperature at both ends of the string Insulator high, middle and gradually reducing the temperature of continuous distribution.
Insulator performance deterioration when the insulation resistance is reduced, the voltage distribution and the degree of heat resistance decrease with a corresponding change occurs.Studies have shown that normal Insulator insulation resistance ≥300MΩ (corresponding to point a in FIG.), Then the distribution voltage Insulator constant, and is independent of the resistance, the surface temperature with respect to ambient atmosphere is also approximately constant Δθ1; starts to deteriorate when the resistance drop when 10 ~ 300MΩ (ca section corresponding to FIG.), which is greater than the heating power of the heating power Insulator normal, higher than the normal temperature Insulator; 5MΩ less when the ohmic drop, which the distribution voltage is low, the heating power is less than the normal Insulator heating power, temperature is lower than normal Insulator.Thus the cap of steel exhibits low Insulator force center high temperature thermal image (bright as lantern); a value of zero adjacent Insulator presenting as a dark tone (negative temperature) compared to a good thermal image Insulator.
Insulator surface when severe contamination, because the surface of insulator layer of the surface contamination resistance is lowered significantly increased creepage current leakage through the porcelain surface, thereby causing increased surface temperature Dish.Thus, a serious contamination Insulator wherein Dish thermal imaging temperature higher than the thermal image without contamination of the temperature Insulator Dish.Typically, the temperature rise due to a failure Insulator very small, conventional thermal imager is difficult to accurately identify, have high sensitivity thermal imager and image analysis methods such as fault detection means.
Insulator anomalies, such as dirty surface, cracks, degradation, etc., can be determined by the temperature difference, the high voltage is determined more apparent Insulator.Monitor subtle changes in temperature, ready determination hidden defect, convenient and timely elimination of maintenance.
Insulator insulation resistance degradation, the effect of lowered.
Detection: Porcelain Insulator steel or glass cap temperature is high, the surface temperature difference exceeds 1k, a low value Insulator.
Porcelain Insulator steel or glass cap temperature is low, the surface temperature difference exceeds 1k, a zero value Insulator.
Insulator Surface of serious temperature abnormality caused by the partial discharge, the surface leakage current distribution uneven.
Detection: Porcelain Insulator glass or high local temperature, the temperature difference exceeds 0.5-1k, possible causes surface contamination resulting in a leakage current due to the increase Insulator.
Insulator breakage, transverse or longitudinal cracks caused abnormal temperature.The reason is mechanical damage and arc burns.
Detection: no surface temperature anomalies, large temperature difference between horizontal and vertical comparison, it is determined that the initial crack defect.By comparison reasons also, the temperature difference between white, than 2K, cracks.