To understand the partial discharge characteristics and gas production of turn-to-turn insulation（TTTI）of the oil-immersed high-voltage shunt reactor（HVSR）

a partial discharge model of TTTI of HVSR wasconstructed. A number of tests were conducted by the step voltage rising method and the constant voltagemethod

and the partial discharge signals and oil samples were acquired and analyzed. The results show that thepartial discharge which accelerates the TTTI aging process can be divided into

inception stage

developmentstage and approaching breakdown stage according to the statistical characteristics of the partial discharge signals.The main characteristic gases by TTTI partial discharge are H

2

CO and CH

4

and there are also a few C

2

H

2

C

2

H

4

and C

2

H

6

. All the characteristic gases increase with the development of insulation defects

and inapproaching breakdown stage H

2

CO and CH

4

increase sharply. In actual operation process of the high-voltageshunt reactor

continuous monitoring of partial discharge and oil dissolved gases facilitates determination ofinsulation defects

which can provide the reference for its operation and maintenance.