IEEE Transactions on Power Delivery

In this paper, an immune algorithm-based (IA-based) optimization approach for the fault-section estimation of a distribution system is proposed. To apply the method to solve this estimation problem, each section of a power system model can be considered as an antibody. Through the immunology evolution, an antibody that most fits the antigen of concern becomes the solution. An affinity calculation has been employed in this computation process to measure the combination intensity. As this method can operate the population of antibodies simultaneously, the process stagnation can be better prevented. The proposed approach has been tested on Taiwan Power System (Taipower) through the utility data. Test results demonstrated the feasibility and effectiveness of the method for the applications.

A technique to discriminate between the line charging inrush current and the current resulting on closing or auto-reclosing a faulted EHV/UHV transmission line has been implemented on a 32-b digital signal processor (DSP) board. The technique is based on the voltage signals before switching and the current signals. This technique is proposed to be a supplement to the main protection schemes for both single-circuit and double-circuit lines. The scheme is tested on a physical model of a transmission system with a source at each end. Laboratory tests show that the proposed technique is effective for three-pole and single-pole reclosing on a faulted or healthy line.

Catastrophic equipment failures continue to occur today due to ferroresonance even though this phenomenon has been extensively studied over the past 90 years. This paper is concerned with comparing analytical nonlinear dynamics methods with a two-dimensional (2-D) brute-force bifurcation diagram for displaying safety margins in a 2-D parameter space. A simplified single-phase model is used to represent the case of ferroresonance between a transformer and circuit breaker grading capacitor. Comparisons are made between the analytical method and EMTP simulations of an actual ferroresonant event.

Electromagnetic transients on overhead transmission lines are strongly affected by the resistivity /spl rho/ of the ground return which, however, is often poorly known. Therefore, the calculation of transients with very high accuracy for a given /spl rho/ may not make good engineering sense if it entails loss of computational efficiency. The effect of /spl rho/ on the transients comes primarily via the ground return impedance. In order to judge what accuracy is reasonable, this paper derives the sensitivities of the ground return impedances for line and ground modes with respect to the resistivity /spl rho/. The results are simple and may assist decidions on the accuracy of computations in EMTP-type simulation programs.

An on-line conductor thermal overload risk assessment method is presented in this paper. Bayesian time series models are used to model weather conditions along the transmission lines. An estimate of the thermal overload risk is obtained by Monte Carlo (MC) simulation. We predict the thermal overload risk for the next hour based on the current weather conditions and power system operating conditions. The predicted risk of thermal overload is useful for on-line decision making in a stressed operational environment.

A description of the composite insulator brittle fracture phenomenon suitable to allow correct diagnosis of a failure is provided. This paper reports on the number of brittle fractures that have occurred around the world and contains specific empirical data surrounding composite insulator brittle fractures in the US. It also includes several case studies of in-service failures to inform the reader of the diversity of initiating causes. The current state-of-knowledge on the brittle fracture mechanism is presented. Based on what was learned during the study, possible actions that can be taken by manufacturers and users to reduce frequency of occurrence are suggested.

In special applications, static VAr compensators (SVCs) with thyristor-controlled reactors (TCRs) are used to balance unbalanced loads or to eliminate voltage unbalances at the terminals of the SVC. In both cases, load balancing and voltage balancing, the TCR can present a significant unbalanced behavior which produces important quantities of noncharacteristic harmonics. In this paper, the formulation and solution of the load and voltage balancing problems are developed for harmonic power flows obtained from a combination of two blocks: (1) a conventional load flow (CLF) and (2) an iterative harmonic analysis (IHA). In both blocks, the treatment of load and voltage balancing is described in detail. Load flow (LF) calculations and harmonic analysis show the presence of noncharacteristic harmonics in these two situations.