Cable joint is a high fault part of cable line

it is useful to assess insulation state of the cable through the measurement of partial discharge（PD）in cable joints. The existing methods of cable joint PD measurement are mostly need to change the joint structure

or have a lower sensitivity measurement. In this paper

based on the principle of capacitive coupling

on the basis of no changing the cable joint structure

a PD measurement method which suitable for straight through cable joint has been proposed

the corresponding measurement system has been built. Through computer simulation and analysis

the correctness of the measurement method from the theoretical level is proved. A needle defect set in a real 35 kV straight through cable joint

and then

the comparison test of PD has been carried out. The test results show that

the sensitivity of PD measurement system proposed by this paper no less than 10 p C. For PD signal generated from a same defect

PRPD spectrogram generated from the PD measurement system presented in this paper and DST-4 PD detecting instrument has the similarity of up to 0.9.