This paper introduces a combined electronic current and voltage transformer（ECVT）.This transformer includes two core technologies

namely the self-excitation power supply technology and the equal potential cavum technology.The principle of voltage divider which based equal potential cavum structure and how to shield disturbance from outside electric field with balance of field and road so as to achieve precise voltage division in the electromagnetism silent environment are discussed emphasizely.It describes also how to combine two technologies and forming a new type of electronic combined transformers.The advantages of this transformer in applications and some testing records in a typical 220 kV substation are introduced as well.The practical operation conclusion indicates the combined ECVT works stably

two measurement systems are compatible

value of testing is correct

and this configuration is good for extend in applications.