A novel transmission line test and fault location methodology using pseudorandom binary sequences

A novel pulse echo test methodology, using pseudorandom binary sequence (PRBS) excitation, is presented in this paper as an alternative to time domain reflectometry (TDR) for transmission line fault location and identification. The essential feature of this scheme is the cross correlation (CCR) of the fault response echo with the PRBS test input stimulus input which results in a unique signature for identification of the fault type, if any, or load termination present as well as its distance from the point of test stimulus injection. This fault identification method can used in a number of key industrial applications incorporating printed circuit boards, overhead transmission lines and underground cables in inaccessible locations which rely on a pathway for power transfer or signal propagation. As an improved method PRBS fault identification can be performed over several cycles at low amplitude levels online to reject normal signal traffic and extraneous noise pickup for the purpose of multiple fault coverage, resolution and identification. In this paper a high frequency co-axial transmission line model is presented for transmission line behavioural simulation with PRBS stimulus injection under known load terminations to mimic fault conditions encountered in practice for proof of concept. Simulation results, for known resistive fault terminations, with measured CCR response demonstrate the effectiveness of the PRBS test method in fault type identification and location. Key experimental test results are also presented for a co-axial cable, under laboratory controlled conditions, which substantiates the accuracy of PRBS diagnostic CCR method of fault recognition and location using a range of resistive fault terminations. The accuracy of the method is further validated through theoretical calculation via known co-axial cable parameters, fault resistance terminations and link distances in transmission line experimental testing.