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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]

In a power system, the transmission network is the backbone of electricity delivery from power plants to load centers; hence, it becomes a critical issue for electrical engineers to shorten the service restoration time after a fault occurrence on the transmission line. This application paper integrates the two- and three-terminal hybrid transmission line fault location algorithms based on synchronized phasor measurements into the proposed cloud-computing-based fault location system to inspect the feasibility and practicality of our algorithms for the real transmission-line incidents. The computing results are performed via Google Map for authorized personal computers and the application for intelligent mobile devices is developed to assist engineers in acquiring the fault-event information immediately as well as in figuring out the fault position intuitively and quickly due to its visualization and navigation. Last but not the least, the suggested fault location system has already been applied to the practical 345- and 161-kV transmission networks of Taiwan Power Company for achieving the combination of theory and practice. Up to the present, the proposed system still yields excellent performance verified by realistic fault data. [ABSTRACT FROM AUTHOR]

This letter presents a fault location technique for three-terminal hybrid AC transmission lines with one off-service line branch by using synchrophasor data obtained from buses which are connected to in-service line branches. The proposed method adopts the two-terminal fault location technique to identify the faulted line branch and locate the fault point when a fault exists on the in-service line branch. Contrarily, if a fault exists on the off-service line branch, the apparent reactance that is obtained from synchronized voltage and current phasor sets of the junction point P, and sequence networks are both chosen to calculate the exact fault point. The performance evaluation shows that the proposed idea has high accuracy under different fault types and resistance. [ABSTRACT FROM AUTHOR]

A power-failure event occurred at the third nuclear power plant (TNPP) in Taiwan in 2001. A chain of events began at 09:36 p.m. on March 16 due to insulation failure associated with flashovers on the 345-kV transmission line. As a result, the 4.16-kV engineered safety features (ESF) buses at the TNPP experienced a loss of power for 2 h and 8 min. This accident was a class 3 emergency (e.g., a class 4 emergency will lead to an overall evacuation of local residents) based on the declared class of emergency in Taiwan. The purpose of this paper is to describe and analyze the chain of events leading to the loss of electrical power. Conclusions on the causes of the outage are drawn and modifications of the system structure are made to improve safety and reliability in a nuclear power plant. [ABSTRACT FROM PUBLISHER]