Overhead Line Networks Research Articles

High Impedance Fault Detection and Location in Combined Overhead Line and Underground Cable Distribution Networks Equipped with Data Loggers

Power distribution networks are vulnerable to different faults, which compromise the grid performance and need to be managed effectively. Automatic and accurate fault detection and location are key components of effective fault management. This paper proposes a new framework for fault detection and location for smart distribution networks that are equipped with data loggers. The framework supports networks with mixed overhead lines and underground cables. The proposed framework consists of area detection, faulty section identification, and high impedance fault location. Firstly, the faulty zone and section are detected based on the operation of over-current relays and digital fault recorders. Then, by comparing the recorded traveling times at both ends of lines, which are related to the protection zone, the faulty line is identified. In the last step, the location of the fault is estimated based on discrete wavelet transform. The proposed method is tested on a 20 kV 13 node network, which is composed of overhead lines and underground cables. The method is tested in both balanced and unbalanced configurations. The obtained results confirm the advantages of the proposed method compared with the current state-of-the art.

Quantification and visualisation of extreme wind effects on transmission network outage probability and wind generation output

An approach is demonstrated to visualise overhead line failure rates and estimated wind power output during extreme wind events on transmission networks. Reanalysis data is combined with network data and line failure models to illustrate spatially resolved line failure probability with data corrected for asset altitude and exposure. Wind output is estimated using a corrected power curve to account for high speed shutdown with wind speed corrected for altitude. Case studies demonstrate these methods' application on representations of real networks of different scales. The proposed methods allow users to determine at-risk regions of overhead line networks and to estimate the impact on wind power output. Such techniques could equally be applied to forecasted weather conditions to aid in resilience planning. The methods are shown to be particularly sensitive to the weather data used, especially when modelling risk on overhead lines, but are still shown to be useful as an indicative representation of system risk. The techniques also provide a more robust method of representing weather-related failure rates on lines considerate of the altitude, voltage level, and their varying exposure to weather conditions than current techniques typically provide, which can be used to usefully represent failure probability of lines during storms.

Decision support system for optimal location of HIFDs in real distribution network using an integrated EPSO‐fuzzy AHP model

Distribution overhead line network faults with the potential threats to public safety are of extreme importance. High-impedance faults (HIFs) occur on distribution feeders with close proximity to the population. Advanced technology has enabled power distribution utilities to detect a high percentage of HIFs. However, the application of HIF detectors (HIFDs) should meet both operational and economic requirements due to expense and a large number of distribution feeders. Installation of these devices on overhead feeders among several candidate feeders seems to be a challenging issue. Therefore, ranking of feeders is essential for equipping them with HIFDs. This study proposes a practical approach which is an improved fuzzy analytic hierarchy process (AHP), accompanied by a constrained non-linear optimisation model to extract optimal crisp priorities from fuzzified inputs, considering various criteria with a degree of inconsistency in their real data. This improved integrated model is also able to adequately evaluate both qualitative and subjective parts of the location-allocation problems. In this study, enhanced particle swarm optimisation (EPSO) is used to deal with the optimisation problem for criteria weight ratio and also finding the individual feeder preference weighting to optimally locate HIFDs in distribution feeders. The proposed model is applied on a real network and then sensitivity analysis is performed in the optimal solution.

Использование силового электронного ключа при борьбе с гололедом на контактной сети импульсно-резонансным методом

The possibility of technical implementation for deicing of double contact wires by pulse-resonance method using a high-power electronic switch is evaluated. For a specific double-track road section of overhead line network, the parameters of the necessary step-down transformer operating in pulse mode and providing heating of the contact wires to positive temperatures are calculated. A possible range of changes in the current density of the contact wires, controlled by the relative pulse duration, is determined.

Research on Single-Phase to Ground Fault Simulation Base on a New Type Neutral Point Flexible Grounding Mode

There are some problems existing in the traditional grounding mode of the distribution network. To solve them, this paper proposes a flexible grounding method for neutral point. This paper analyzes the advantages and the disadvantages of single-phase ground faults occurring at different neutral grounding points and summarizes the characteristics of several existing grounding arc elimination technologies for distribution networks. Depending on the actual data of a 10-kV substation, the ATP-EMTP was used to build a 10-kV distribution network model, and an arc model based on arc length control was used for single-phase ground fault simulation. According to the simulation results, it was known that the overhead line network of arc suppression coils was compared. Permanent ground faults occur in pure cable networks which are grounded by small resistances. Flexible grounding systems have significant benefits in suppressing the inrush currents at fault points when an intermittent arc single-phase-to-ground fault occurs, the flexible grounding system causes intermittent arcing. The voltage is clearly inhibited. The flexible grounding method has certain reference value for improving the reliability of distribution network power supply and providing the safe operation of the system.

Open-circuit fault detection in distribution overhead power supply network

AbstractCLP’s distribution overhead line network supplies electricity to its customers in rural areas. The lines exposed outdoors are vulnerable to external and environmental interferences. When op...

Simulation of the Lightning Back-Flashover for Medium Voltage Distribution Network

Lightning strikes represent a considerable cause of short interruptions in electrical overhead line networks. The over voltages caused by lightning cannot be avoided but their influence can be limited by appropriate over voltage protection. This paper presents analysis study on some factors affecting the back flashover of Egyptian 66 kV distribution lines using Alternative Transient Program (ATP). The study includes the modeling of 66 kV distribution lines, the effects of magnitude and the front and tail times of lightning wave on the back flashover voltages, the effects of the striking distance, and the using of counterpoise wires on the back flashover on the 66 kV line towers. In this paper the 66 kV lines sag is neglected and the soil ionization by the flow of the stroke current is considered.

Overhead line design considerations for conductor creep mitigation

Utilities are continuously investigating methods to economically reinforce their overhead line (OHL) networks by reconductoring with larger conductors or with novel high-temperature low-sag (HTLS) conductor technologies. To further optimise the OHL design, conductor creep ageing is calculated and mitigated at installation, which economically improves an OHLs’ performance. An already established methodology is used to investigate common and HTLS conductors ageing effect on sag and tension in order to highlight the benefits and risks that could result from existing creep mitigation methods particularly on HTLS conductors. The study aims to identify the impact of important design factors such as ice loading and emergency operation events and their frequency of occurrence on creep mitigation as well as to highlight the creep variation of the same materials used particularly on different HTLS conductors. The analysis presented here indicates that pre-tensioning could be more beneficial on soft aluminium HTLS conductors while over-tensioning can result in extensive durations of conductor over-stressing on steel supported and Gap-type conductors. Furthermore, the conductor technology majorly affects the creep of steel core which cannot be considered always as zero. The accuracy of the methodology is also re-validated using recent experimental data from Gap conductor.

Risk estimation of ageing outdoor composite insulators with Markov models

A methodology is presented which facilitates determination of the risk of flashover in an overhead line network consisting of composite insulators. The method allows consideration of environmental variation by granulation of the geography, and separates the issues of long-term ageing and the threat of short-term flashover because of environmental extremes. This is achieved by combining established statistical dimensioning principles according to the sites’ pollution severity and a four-state Markov ageing model to account for long-term ageing of the insulators. The short-term time-variant pollution severity is defined using statistical principles. Then by choosing appropriate transition probabilities between pre-defined Markov states the population of insulators at risk of flashover is estimated. Knowledge of the distribution of Markov states in the system and the pollution severity enables estimation of risk of flashover for a given number of insulators at a given point in time in a range of environments. The analysis is designed to be used to assist asset management decisions and optimise condition monitoring of overhead line composite insulators.

The economic case for RCM of overhead lines in the UK

This article describes the application of new inspection techniques, assessment methodologies and life-cycle cost analyses aimed at improving the decision-making process for the replace/repair/rebuild option on overhead line networks. The approach is based on reliability-centred power line management, pioneered in the USA. RCM provides asset life extension whilst maintaining availability and has been proven to result in a very favourable cost-benefit ratios when applied in the USA. The methods and economics for applying RCM to UK practice through collaborative work between IPEC, EDM and NORWEB are described.

Expert system aid for design of overload line distribution networks

The use of expert system techniques in power distribution system design is examined. The selection and siting of equipment on overhead line networks is chosen for investigation as the use of equipment such as auto-reclosers, etc., represents a substantial investment and has a significant effect on the reliability of the system. Through past experience with both equipment and network operations, most decisions in selection and siting of this equipment are made intuitively, following certain general guidelines or rules of thumb. This heuristic nature of the problem lends itself to solution using an expert system approach. A prototype has been developed and is currently under evaluation in the industry. Results so far have demonstrated both the feasibility and benefits of the expert system as a design aid.

Application of protective devices to radial overhead line networks

The paper reviews the need for overhead line switching equipment and its use in developing countries for the control of long radial feeders into remote districts. The requirements for pole-mounted equipment and relaying characteristics are discussed showing the need for sensitive earth fault discrimination, particularly to detect broken conductors in regions of high earth resistance. Designs of pole-mounted, autoreclosers are discussed. Sectionalising equipment is also reviewed in the context of fault management on spur lines.