Cable failure process is gradual and is characterized by a series of single-phase sub-cycle incipient faults with high arc voltage. They often go undetected and eventually result in a permanent fault. The objective of this paper is to develop a robust yet practical incipient fault location algorithm taking into account the fault arc voltage. The algorithm is implemented in the time-domain and utilizes power quality monitor data to estimate the distance to the fault in terms of the line impedance. It can be applied to locate both sub-cycle as well as permanent faults. The proposed algorithm is evaluated and proved out using field data collected from utility distribution circuits. The average absolute error in locating incipient faults for three underground cable failures analyzed in this paper was found to be 7.37%, 4.69% and 3.58%, respectively.

Incipient Fault Location Algorithm for Underground Cables

This paper presents a new numerical spectral domain algorithm devoted to blocking unsuccessful automatic reclosing onto permanent faults and fault distance calculation. Arc voltage amplitude and fault distance are calculated from the fundamental and third harmonics of the terminal voltages and currents phasors. The electric arc is modeled with its voltage waveshape defined numerically on the basis of a number of arc voltage records obtained in the high-voltage laboratory. From the calculated arc voltage amplitude, it can be concluded whether the fault is a transient arcing fault or a permanent arcless fault. If the fault is permanent, automatic reclosure should be blocked. The algorithm can be applied for adaptive autoreclosure, distance protection, and fault location. The results of algorithm testing through computer simulation and real field record are given.

New one terminal digital algorithm for adaptive reclosing and fault distance calculation on transmission lines

This paper presents a novel numerical algorithm implemented in a unique methodology for the control of smart single-phase autoreclosure and comprehensive fault analysis for overhead lines using synchronized measurement technology The algorithm improves on existing methodologies for adaptive single-phase autoreclosure, fault location, detailed disturbance records analysis, and fault data management It is based on line current and voltage data sampled at both line terminals and synchronized sampling of all analogue input variables is assumed in this paper The proposed algorithm is derived in the spectral domain and based on the application of the Discrete Fourier Transform The electrical arc as a source of higher harmonics is included in the complete fault model and represents the starting point for the development of the new algorithm The algorithm's distinctive feature is that it can determine both the fault arc and the fault resistance The presence or absence of an arc resistance is used to determine the nature of the fault The algorithm can be applied to both short and long lines The algorithm is thoroughly tested using electromagnetic transient simulations of an overhead line connected between two active networks, as well as with field data

Smart Overhead Lines Autoreclosure Algorithm Based on Detailed Fault Analysis

The objective of this paper is to present, discuss and compare, in some detail, the arc models used to represent an arcing fault, in order to determine which of them is the most precise for this purpose. At the beginning of the paper a brief explanation of arcing faults is given, bringing out the importance of a realistic simulation of them. A theoretical description of the black box equations to model arc is explained. The paper concludes with a comparison of the most representative arc models. Results will be useful not only in arcing fault detection but also in the design of autoreclosure schemes on transmission lines. Implementation and simulation method are based on ATP/EMTP.

Analysis of arcing fault models

This paper deals with the fault location on high voltage series compensated lines. A new approach to evaluate the fault distance is proposed. The distributed-parameter line equations are preferred to describe the overhead lines. The algorithm uses two-terminal measurements, but those data do not require synchronization. No information on the fault resistance value and on the fault type is necessary. Numerical tests with time-domain sampled measurements are carried out. The simulations are performed using EMTP-ATP. Results for various fault resistance and fault distance values, and fault type conditions, are reported.

A new unsynchronized two-terminals fault location method on series compensated lines

This paper has proposed a time domain model of a fault locator with spacial reference to fault arc nonlinearities by applying the MODELS language of the EMTP. It has been found that an impedance relay type locator is significantly influenced by the fault arc nonlinearities, while the current diversion ratio method is not influenced. This validates the advantage of the current diversion approach over the impedance approach.

Influence of fault arc characteristics on the accuracy of digital fault locators

Many fault locator algorithms were developed to be operated on digital relay data. The methods were derived from frequency domain equations and were established by a phasor simulation. The algorithms were based on the assumption that a fault arc had a constant impedance and did not show a nonlinear effect. But in practice, a fault arc in air is known to show nonlinearity due to its physical characteristic. To study the influence of the nonlinearity on the accuracy of a digital fault locator, a time domain simulation must be performed considering the characteristic of the fault arc. In the present paper, a time domain model of a fault locator and that of a fault arc are represented using the MODELS language in the ATP-EMTP. Various fault types are modeled considering constant and nonlinear fault resistances. The simulation results have shown that the impedance relay type method using one terminal voltage and currents is influenced by the nonlinear characteristic of the fault arc, while the current diversion ratio method using one terminal currents for two circuits is not. A sensitivity analysis of the locating error with respect to the model parameters of the nonlinear arc was performed for the impedance relay type method. It has been confirmed that the greater the degree of nonlinearity, the greater the location error.

M. Kizilcay

Papers

Influence of fault arc characteristics on the accuracy of digital fault locators

A study on fault arc and its influence on digital fault locator performance