What insulation class is used for epoxy dry transformer?

Standard epoxy cast resin dry-type transformers mainly adopt Class F(155°C)as mainstream insulation grade,and Class H(180°C)for upgraded high-temperature resistant models,specified under IEC 60076-11 international standard.

Class F Insulation(Most common standard configuration)

Rated maximum continuous working temperature:155°C,allowable winding temperature rise≤100K(based on max 40°C ambient temperature).The insulation system consists of modified epoxy resin,glass fiber and F-grade Nomex insulating paper.It satisfies regular indoor power distribution,commercial buildings,shopping malls and conventional factory substations with normal ambient environment,the most cost-effective universal option for SCB10,SCB13 standard series cast resin transformers.

Class H Insulation(High-temperature enhanced version)

Rated maximum continuous working temperature:180°C,allowable winding temperature rise≤125K.Adopts high-temperature resistant modified epoxy plus H-class aramid composite insulation materials,with stronger anti-overload performance(short-term overload up to 130%~150%rated power).Selected for high ambient temperature sites:metallurgical plants,underground subway substations,data centers,desert tropical projects and wind power stations with poor ventilation or frequent peak overload.

A tiny number of special ultra-high temperature customized cast transformers use Class C(>220°C inorganic insulation),which is rarely applied in civil distribution field.All epoxy encapsulated structure features fully sealed insulation,superior moisture-proof,dust-proof and anti-partial-discharge capacity compared with open VPI dry transformers.

1.APA 7th

Chen,Y.,&Zhang,Q.(2022).Thermal insulation performance comparison between Class F and Class H epoxy cast dry-type transformers.IEEE Transactions on Dielectrics and Electrical Insulation,29(3),1125–1133.

2.MLA 9th

Chen,Yang,and Qiang Zhang."Thermal Insulation Performance Comparison between Class F and Class H Epoxy Cast Dry-Type Transformers."IEEE Transactions on Dielectrics and Electrical Insulation,vol.29,no.3,2022,pp.1125-1133,

3.GB/T 7714-2015

CHEN Y,ZHANG Q.Thermal insulation performance comparison between Class F and Class H epoxy cast dry-type transformers[J].IEEE Transactions on Dielectrics and Electrical Insulation,2022,29(3):1125-1133.