| 摘要 |
FIELD: electrical engineering, in particular, overvoltage protection of electric circuits and installations. SUBSTANCE: heat-and-pollution-resistant overvoltage limiter of electric circuits and installations with an effectively grounded neutral uses a high-nonlinear, for example, zink-oxide resistor connected between the phase of the protected circuit and ground, located between the conducting flanges inside the sealed insulating cover, whose geometry, determining the effective length of leakage path, form factor, number, form and overhand of ribs, provides for electric strength of external insulation at pollutions and humidifications. The high-nonlinear resistor represents one or several parallel-connected piles built up of series-connected single high-nonlinear components. Specific transverse capacitance Cbetween the resistor pile and humidified pollution layer, equivalent convective heat transfer coefficient αreduced to the surface of actual limiter resistor pile and equivalent convective heat transfer coefficient αreduced to the surface of single-pile axisymmetric apparatus with calculated surface of resistor convective heat transfer of actual apparatus are selected from the following relation;, where m - parameter, depending on the preset level of reliable operation of heat-and-pollution-resistant limiter, and ambient temperature. EFFECT: enhanced reliability of operation and reduced mass and cost of protective apparatuses intended for use in different, both in light-duty and extreme conditions of service, concerning ambient temperature and degree of atmospheric pollution. |
