采用植物油浸渍耐高温纸的配电变压器过载能力

During periods of Spring Festival for northern villages and summer times for Southern urban villages in China, overload capacity of some distribution transformers turn out to be insufficient. An effective method to cope with this problem is to use natural ester in conjunction with high-temperature resistant insulating paper as insulation system in distribution transformers. In this paper, temperature rises of aS13-M(B)- 400/10 transformer under a designated overload curve are calculated for mineral oil or nature ester as dielectric coolant. The highest hotspot temperature rise occurs at the end of twice per unit load. The highest hotspot temperature rise of mineral oil is 95.1K, exceeding its hotspot temperature rise limit 78K in international standard. While hotspot temperature rise of the transformer with natural-ester immersed high-temperature resistant insulating paper is 97.9K. Temperature measurements of the investigated transformer with FR3 oil and Nomex^® T910 paper are implemented with fiber optic temperature sensors installed in the transformer. The hotspot is measured for the designated overload test. The highest hotspot temperature rise is 97.4K, consistent with calculation results and meeting corresponding temperature rise limit 110K in standard for ester liquids. It is concluded that the insulation system with natural-ester immersed high-tempera-ture resistant insulating paper can be used in the distribution transformers undertaking long-time emergency loading.