In order to early diagnose the inner latent faults and to ensure safe and stable operation of power transformer

the qualitative and quantitative analysis of power transformer oil dissolved gas are introduced.The traditional analysis of dissolved oil gas is by means of regular sampling experiment

so the equipment faults can not be found in time. In this paper

a new method of on-line diagnosis which analyzes the content of oil dissolved gas is given and some key technology

such as separating gas from oil on the spot

gas detection

data process

automatic control

long-distance data transmission

etc. are also discussed.