Rural Power Grid Voltage Capacitor Divider Invar-related Characteristics

Voltage transformer is to protect critical equipment and monitoring of rural power systemstable operation. With our intelligent upgrade rural power grids, the successful implementationof the new rural electrification, the rural high voltage transmission and distribution network ismoving, intelligent, high-capacity direction; traditional electromagnetic, electronic voltagetransformer for its sensing mechanism The bulky, high cost, insulation structure is becomingmore complex, such as the emergence of insurmountable difficulties, can not be applied tohigh-precision rural power grid monitoring and measurement equipment. Optical voltagetransformer for its compact structure, large dynamic range, anti-interference ability to adapt tothe requirements of the power system intelligent features, and quickly became the focus ofresearch scholars. In the power system, the optical voltage transformer through its frontcapacitive divider system high pressure into the low pressure, the use of optics to measure andmonitor the power system voltage and current signals, and therefore work under high pressurecapacitive divider directly determines the stability of the overall measurement accuracytransformer. Combining Invar material in a certain temperature range has a negative coefficientof expansion properties, Invar selection based on a cylindrical high-voltage capacitive voltagedivider for the object, of the voltage divider is an optimum diameter ratio, edge effects, and theworking state temperature changes, voltage levels, dielectric related features in-depth study ofits impact measurement accuracy.First, the basic structure of the high-voltage capacitor divider, classification andcharacteristics of various dividers were comprehensively reviewed; for capacitive voltagetransformers used in optical divider bulky, less insulation performance issues, the establishmentof a Invar capacitive divider complete system theoretical model; and capacitor breakdown fieldstrength for critical conditions deduced Invar optimum capacity cylindrical capacitive dividerdiameter ratio.Secondly, on the edge of the Invar effect cylindrical capacitive divider depth theoreticalstudy; when volume diameter ratio is constant, the marginal effect will lead to the actualmeasured value Invar cylindrical capacitor larger capacitive divider; comprehensive articleresearch results, and the capacitor in series with calculus principles anchored deduced account cylindrical capacitive divider capacitance value of the edge effect is calculated; a method byincreasing the capacitor capacitance ring edge chamfer radius edge effects weaken, and hasbeen among the best range of Invar cylindrical capacitive divider edge capacitance ring chamferradius of0.52~3.51mm.Finally, two types of cylindrical steel and brass Yin capacitive divider conductedexperimental study; error analysis model established under the divider working conditiontemperature changes, the stray capacitance, frequency voltage and other factors affect itsmeasurement accuracy, and the error synthesis; respectively voltage levels, temperaturechanges, dielectric as a single variable, brass and Invar cylindrical capacitive dividercapacitance measurement stability compared. The results show that: in the auxiliary insulatingmedium, the two cylindrical steel and brass Yin capacitive voltage divider resistance totemperature change ability, insulation performance have been improved to varying degrees,wherein the polytetrafluoroethylene Invar cylindrical capacitive division the minimum error ofonly0.0214%, the most stable capacitance measurements.