Search

This paper presents an innovative fault location method for multi-terminal nonhomogeneous transmission lines by using synchronized voltage and current phasors acquired from phasor measurement units or intelligent electronic devices. We extend the previously published two-terminal and three-terminal nonhomogeneous transmission line fault location techniques developed in our lab to multi-terminal nonhomogeneous transmission lines. Specifically, a graph theory based indices and an optimal calculation data window is applied to identify the faulty line branch and to mitigate the undesirable influence caused by dc decay and the arc phenomenon of circuit breaker. The high performance of the proposed fault location method is validated by simulation results and real world utility fault data. [ABSTRACT FROM AUTHOR]

Risks from ground fault transfer (GFT) on closed-loop high-voltage (HV) underground distribution systems (UGDS) with cables running in a common route are assessed based on simulations by the Alternative Transienta Program (ATP) of the Electromagnetic Transients Program. To model the system, the configuration of a real and typical closed-loop HV UGDS is explicitly depicted. The complex connecting relationships between cable metallic shields, grounding electrodes, parallel ground continuity conductors (PGCCs), and surge suppressors at manholes and substations are clearly shown. Then, through the system modeling and simulation by ATP, the GFT characteristics (i.e., the distributions of currents and potentials on cable metallic shields and PGCCs along the cable length are analyzed). Based on the simulation results, the risks from GFT on personnel, equipment, devices, or other associated systems are assessed. Finally, the damages caused by a three-phase ground fault in a customer substation are surveyed to certify assessment result of risks and the severity of GFT on closed-loop HV UGDS with cables running in a common route. [ABSTRACT FROM PUBLISHER]

The theory and algorithms of the proposed technique have been presented in Part I of this two-paper set. In Part II of this two-paper set, the proposed technique is evaluated by considerable simulation cases simulated by the Mattab/Power system Blockset simulator. For the proposed fault detector, the trip time achieved can be up to 3.25 ms and the average value of trip times is about 8 ms for both permanent and arcing faults on transmission lines. For the proposed fault locator, the accuracy can be up to 99.99% and the error does not exceed 0.45%. Moreover, the proposed arcing fault discriminator can discriminate between arcing and permanent faults within four cycles after fault inception. It has proven to be an effective tool to block reclosing on the permanent faults in the computer simulations. The simulation results also demonstrate that the presented extended discrete Fourier transform algorithm eliminates effectively the error caused by exponentially decaying dc offset on fundamental and harmonic phasor computations. Finally, a test case using the real-life measured data proves the feasibility of the proposed technique. [ABSTRACT FROM AUTHOR]

A new fault detection/location technique with consideration of arcing fault discrimination based on phasor measurement units for extremely high voltage/ultra-high voltage transmission lines is presented in this two-paper set Part I of this two-paper set is mainly aimed at theory and algorithm derivation. The proposed fault detection technique for both arcing and permanent faults is achieved by a combination of a fault detection index |M| and a fault location index |D|, which are obtained by processing synchronized fundamental phasors. One is to detect the occurrence of a fault and the other is to distinguish between in-zone and out-of- zone faults. Furthermore, for discriminating between arcing and permanent faults, the proposed technique estimates the amplitude of arc voltage by least error squares method through the measured synchronized harmonic phasors caused by the nonlinear arc behavior. Then, the discrimination will he achieved by comparing the estimated amplitude of arc voltage to a given threshold value. In addition, in order to eliminate the error caused by exponentially decaying dc offset on the computations of fundamental and harmonic phasors, an extended discrete Fourier transform algorithm is also presented. [ABSTRACT FROM AUTHOR]