电力变压器第25部分:中性点接地电阻器

[中文适用范围]： 本标准适用于电力变压器中性点接地电阻的设计、制造和测试。主要内容包括电阻器的额定环境温度、额定电阻、最大电阻变化、额定时间、额定电压、额定绝缘水平、额定短时电流、额定连续电流、额定频率等技术要求，以及电阻器的设计、构造、测试和验收标准。 [外文原描述]： IEC 60076-25:2023 applies to dry type natural air-cooled resistors, for neutral grounding of transformers and generators, in order to limit the earth fault current in power systems by means of metallic resistive elements. For the purposes of this document, the resistor can be: used alone or in combination with other electrotechnical products not covered by this document, such as (but not limited to): a step-down single-phase transformer, an open triangle or zig-zag transformer (where the neutral point is not available) and a Petersen coil reactor (in order to increase active power contribution to the fault or reduce time constant for proper protection operation or both); designed, manufactured and verified on a one-off basis or fully standardized and manufactured in quantity. Both terms "neutral grounding resistor" (NGR) and "neutral earthing resistor" (NER) can be used. However, for the purposes of this document and in order to avoid any confusion with "neutral earthing reactor" (NER), the term "neutral grounding resistor" (NGR) is used. This document specifies: the characteristics of the NGR; the service conditions requirements for NGRs; the tests and test methods for confirming that these conditions have been met; the requirements relating to marking for NGRs. Annex A provides guidance on how to consider the effect of resistance variation with temperature.