A rigid approach to short circuit analysis for large-scale distribution systems is introduced. The approach uses an individual (a-b-c) phase-based system representation, a nontrivial transformer model, and includes the contribution due to load. The method can, therefore, be applied to balanced or unbalanced, radial, network, or mixed-type distribution systems. This approach is oriented toward applications in distribution system operation analysis rather than the more typical planning-oriented analysis. The solution method is an iterative compensation method, which uses a single optimally ordered factorization of the bus admittance matrix (Y/sub Bus/), commonly used in power flow analysis, to simulate the fault condition. The use of this method in a short circuit analysis program enables a factorized Y/sub Bus/ solution, resulting in many advantages. Using a common factorization, both power flow and short circuit analyses are possible in a single execution. Since the factorization is unchanged, multiple faults of various types can be simulated in one run of the program. >

Distribution system short circuit analysis-A rigid approach

Unified phase-coordinate load-flow and fault analysis of polyphase networks

A comprehensive approach to fault analysis using phase coordinates

In the last years, high penetration of distributed generation (DG) has strongly affected public MV networks. In order to improve their reliability and availability, loop operation is being tested. This solution requires the installation of new line protection devices and the identification of appropriate settings against phase-to-phase and ground faults. This study refers to an experimental loop line operated by ENEL Distribuzione, the largest Italian Distribution System Operator (DSO). The paper deals with the behavior of the currently installed line protection during cross-country faults (CCFs), occurring both in radial and loop lines. MV network response has been preliminary evaluated by approximated formula (which allow a fast check of line protection performances), and then verified by accurate simulations based on a detailed Simulink network model. CCFs occurring inside and outside the loop line have been analyzed. Obtained results show that the zero-sequence and phase directional overcurrent (Blocking-Scheme supported) are generally able to selectively identify and clear CCFs. Nevertheless, if CCFs occur in the same overhead stretch of the loop line, the adopted protection scheme may fail.

Cross-country fault protection in ENEL Distribuzione's experimental MV loop lines

Internal fault fast identification criterion based on superimposed component comparison for power transformer

A general computer program using the phase co-ordinate technique has been developed for analysing series, shunt and simultaneous faults on balanced and unbalanced polyphase electrical networks. The program eliminates the need for maintaining numerous fault analysing subroutines, one for each kind of fault, and makes the solution of many difficult and previously unsolvable problems possible. It is employed to analyse the cross-country fault involving different phases. The solution method, program outlines and postfault results of voltages, currents and apparent power of an actual power system are given.

L. Roy

Papers

Generalised polyphase fault-analysis program: calculation of cross-country fault