In order to improve the precision of time-delays calculated from a multi-element ultra-high frequency（UHF）sensor array and reduce the cost of partial discharge detection system

we put forward a new method to estimate the time-delay. This method interpolates some values into the feature area of UHF signal sampled at a low sample rate based on interpolation cross-relation algorithm and then uses cross-correlation method to estimate the time-delay. Through simulation tests and experimental results

conclusions are obtained as follows. Firstly

compared with traditional cross-correlation method

the new method can effectively narrow the error generated by limit of the system sample rate

especially when the real time-delay is not a integer times of sampling interval. Moreover

when the number of interpolating value between two original signal points is four

the method becomes optimal and can narrow the errors below a half sample interval.