In this paper, the Radial Basis Function(RBF) network based sheath fault detection and location technique is presented for underground power transmission cables. A three-phase, six-section power transmission system has been simulated using the ATP(Alternative Transient Program) software. The rms(root mean square) values of zero sequence sheath current were calculated and applied to the RBF network. After successful training, the network will be able to accurately indicate which section the fault is on. This technique is suitable for both the low impedance and high impedance single sheath to ground fault.