Abstract: In order to reduce the workload of the operation and maintenance of distribution line arresters, this paper designs a frequency-dividing disconnector using double sphere gaps based on the inverse time principle, which can reliably shunt high and low frequency current. The disconnector can be separated automatically and reliably while the insulation of the arrester is damaged, and the fault section can be found. The disconnector realizes the mechanism of frequency division of leakage current by using inductance and large sphere gaps in parallel. Under the impulse or high frequency, the leakage currents flow through the big sphere gap and the disconnector would not act. While under the power or low frequency, the leakage currents flow through the inductor. When the current takes value from 40 mA to 0.5 A, resistance heating action would be utilized. When the current is larger than 0.5 A, the small sphere gap breakdown action would be adopted, which avoids the mal-operation of disconnector due to burned out resistance. In these two cases, the greater the leakage current, the faster the disconnector operates. Through the ATP model simulation, the parameters of the inductance and the operating characteristics of the large gap can be determined. The numerical simulation and experimental results show that the disconnector can operate reliably when the insulation of the arrester is damaged.