Feeder Section Research Articles

Resiliency Assessment in Distribution Networks Using GIS-Based Predictive Risk Analytics

A new predictive risk-based framework is proposed to increase power distribution network resiliency by improving operator understanding of the status of the grid. This paper expresses the risk assessment as the correlation between likelihood and impact. The likelihood is derived from the combination of Naive Bayes learning and Jenks natural breaks classifier. The analytics included in a geographic information system platform fuse together a massive amount of data from outage recordings and weather historical databases in just one semantic parameter known as failure probability. The financial impact is determined by a time-series-based formulation that supports spatiotemporal data from fault management events and customer interruption cost. Results offer prediction of hourly risk levels and monthly accumulated risk for each feeder section of a distribution network allowing for timely tracking of the operating condition.

Predictive Risk Management for Dynamic Tree Trimming Scheduling for Distribution Networks

This paper introduces a predictive method for distribution feeder vegetation management based on a risk framework. The state of risk is calculated for each feeder section using a variety of factors extracted from network parameters and historical outage data, historical weather data and weather forecasts, and a variety of vegetation indices. The framework implements the spatiotemporal correlation of all the collected data. The prediction model used is the Gaussian conditional random field, which takes into account spatial interdependencies between different feeder sections. This enables better prediction accuracy, and also offers the capability to deal with missing and bad data. Based on the calculated risk, the dynamic optimal tree trimming schedule, which minimizes the overall risk for the system under a given predetermined budget, is developed. Results obtained on a real utility network show that optimal tree trimming based on the developed risk framework for vegetation management could significantly decrease the overall risk of the feeder outages without increasing the budget.

Probabilistic Analysis of PV Generation Impacts on Voltage Sags in LV Distribution Networks Considering Failure Rates Dependent on Feeder Loading

The impact of photovoltaic distributed generation (PVDG) in the voltage sag indices of low-voltage distribution systems is assessed in this paper. A sensitivity study of these indices in relation to the penetration level of PVDG is performed considering the effect of the feeder sections loading on their failure rates. It is showed that, when this dependence is neglected, the indices are predicted with errors, especially for scenarios with large integration of PVDG. This study was performed using clustering techniques to model the uncertainty of solar irradiation, and the state enumeration method (SEM) is used to evaluate voltage sags indices. The results obtained by the clustering method and SEM were compared with those obtained with Monte Carlo Simulation based on the beta probability density function (pdf) model for solar irradiation. This comparison showed that the clustering model can obtain indices with precision comparable to those obtained with the beta pdf model, but with a significant reduction in CPU time.

Evaluation of lightning-related faults that lead to distribution network outages: An experimental case study

Lightning activity is often one of the major causes of voltage transient disturbances and interruptions in distribution networks. Although important researches have been performed on the correlation of lightning-related events and faults in distribution networks, there is still an open question about in which situations will a lightning-related fault self-extinguish or evolve to a sustained short-circuit that will lead to a power outage. This study aims to show, based on an analysis using data from a real monitored distribution system and high-voltage laboratory tests, that the conditions for sustained arc-formation from a lightning-induced fault depend on the utility infrastructure construction patterns and the characteristics of the distribution equipment available. The distribution feeder was modeled based on laboratory test results and the digital simulations are validated by comparing calculated and actual measured overvoltages. This paper presents an analysis of lightning-related faults in power distribution feeders, integrating experimental data and digital simulations. The proposed method is promising in predicting the effects of lightning on distribution networks, especially in identifying the feeder sections most prone to failures.

A new single end wideband impedance based fault location scheme for distribution systems

This paper proposes an improved impedance based fault location scheme based on system analysis at non-fundamental frequencies. The fault is treated as a voltage source that injects high frequency components into the system and the analysis is carried out using these injected components. The proposed method only requires local measurements at the substation and therefore is classified as a single end method. The new contribution is that the proposed method uses the distributed parameter line model to account for inductive and capacitive effects of the line. It has been evaluated on the IEEE 34-bus feeder which is based on an actual distribution system which has the typical features such as non-homogeneous feeder sections, asymmetrical line configurations, unbalanced loads and single and three-phase laterals. The fault point, fault resistance and fault inception angle have been varied to check their influence on the accuracy of the method. The simulation results demonstrate the accuracy of the proposed method where for most cases, the error in fault location is less than 50m.

Differential Frequency Protection Scheme Based on Off-Nominal Frequency Injections for Inverter-Based Islanded Microgrids

Protection is considered one of the major challenges associated with the operation of islanded microgrids with high penetration of inverter-based distributed generation (IBDG). As stated in the IEEE Std. 1547.4, due to the limited injected fault current levels by IBDG, conventional overcurrent relays might not be capable of detecting and clearing faults. Thus, this paper proposes a novel protection strategy for inverter-based islanded microgrids which relies on injecting an off-nominal frequency, through the DG interface, during fault conditions. A differential protection scheme that is based on the differences in the current frequency components, measured at both ends of a feeder section, is proposed to detect and isolate faults. This paper also presents the structure and control logic of the proposed relay for differential protection. The proposed protection scheme is implemented and tested on a distribution system equipped with IBDG, modeled to operate in an islanded mode. Simulation results are presented to highlight the effectiveness of the proposed protection scheme in detecting and isolating faults for inverter-based islanded microgrids.

Influence of rooftop PV generation on net demand, losses and network congestions: A case study

This paper presents a practicable methodology allowing the impact of rooftop photovoltaic (PV) panels on distribution networks to be thoroughly assessed. Based on granular information (both in space and time) about the network and the demand, and a minimum but realistic set of assumptions concerning the available rooftop surface, hourly scenarios of PV production and consumption are created for increasing PV penetration levels. A load flow solution provides, at the feeder level, the voltage profile, the net power flowing through each feeder section and the total losses. The methodology is then applied to a real case study comprising over 80,000 customers from urban and rural areas, with an annual consumption of 460 GWh and served by over 3600 km of MV&LV lines/cables, large enough to safely extrapolate the attained conclusions to the general case. In a nutshell, network losses increase with respect to the base case scenario, and network congestions begin to show up, when the PV penetration exceeds 30% of the maximum installable power, which is roughly equivalent to 45% of the PV power that yields zero net demand all year round.

Optimal economic-driven planning of multiple DG and capacitor in distribution network considering different compensation coefficients in feeder’s failure rate evaluation

The main aim of Distribution Companies (DISCOs) is to satisfy end user demand with quality and reliable supply of power at all possible locations in the distribution network. Since majority of loads connected to the distribution network are inductive in nature, there exists possibility of higher energy loss and lower reliability in the distribution feeder sections. In this study optimal planning of Distributed Generation (DG) and capacitor is investigated considering maximization of total cost benefit as main objective. Here, the cost benefit due to DG and capacitor installation is attained by minimizing energy purchased from the substation including energy loss and by reducing Expected Interruption Cost (ECOST) of the system. Moreover, a detailed analysis is carried out in the DG and capacitor planning problem considering different compensation coefficients in feeder’s failure rate evaluation so that the compensation coefficient resulting in enhanced net cost benefit is identified. Furthermore, a hybrid combination of Weight Improved Particle Swarm Optimization (WIPSO) and Gravitational Search Algorithm (GSA) called hybrid WIPSO-GSA algorithm is proposed to solve the optimal DG and capacitor planning problem in the distribution network. The proposed methodology is tested on standard 33-bus and Indian 85-bus distribution systems. The superiority of the proposed hybrid algorithm is also illustrated by comparing the results with other optimization techniques.

Rapid assessment of maximum distributed generation output based on security distance for interconnected distribution networks

Security distance provides a quantitative approach to assess the N-1 security and its margin of distribution systems. In order to support system N-1 secure operation, distributed generations (DGs) should be used in terms of capacity credit (CC). Considering the conductor thermal constraints and voltage constraints after a substation transformer or feeder N-1 contingency, this paper proposes a rapid maximum output assessment method for DGs. With the proposed method, the system operators can better guarantee system security in the presence of active management. The concept of security distance for distribution networks is primarily decomposed into two parts: feeder security distance (FSD) and transformer security distance (TSD). Considering the correlation between the wind speed and illumination intensity, the combined output characteristics of DGs are achieved using the defined wind-photovoltaic conversion coefficient based on coordinate conversion. Then, the initial maximum DG output on each feeder section is approximately calculated by initial FSDs and TSDs. On these bases, the maximum output assessment method is proposed under uncertainties associated with DGs, loads and contingencies. Moreover, several related issues are further discussed: (a) discussion of the proposed use of DGs in terms of CC, (b) consideration of demand response in the proposed method, and (c) feasibility of the proposed method to N-2 contingency analysis. In the end, the proposed method is successfully applied to the expanded IEEE RBTS-Bus4 and a real urban distribution networks and the results verify its high performance when compared to the normal optimal method from static and dynamic views.

Computational geometry‐based methodology for identification of potential islanding initiators in high solar PV penetration distribution feeders

Accidental disconnection of a live feeder section is a major concern accompanying large distributed solar photovoltaic (PV) generation integration. High localised penetration can alter power flows leading to anomalous occurrences. Load-inverter power balance during grid-side disturbances, for different load models, may cause unique situations that can trigger the interconnection point protective devices. One such phenomenon, identified as a potential cause of unintentional islanding on radial feeder models (a modified IEEE feeder in simulation and verified on a laboratory-hardware network), has been used in this work. A pre-emptive detection strategy has been implemented to identify such islanding initiators among other power system transients. Computational geometry concepts have been utilised to create an optimisation-derived feature extraction methodology for effective training of a classifier module realised in a Raspberry Pi microcomputer. This module predicts the class labels of test data points transmitted from simulations carried on a personal computer for the feeder model. The proposed pre-emptive islanding detection strategy can trigger an appropriate change in a PV inverter's operating mode before a feeder protective device is tripped by such island initiating anomalies. The online classification accuracy and speed indicate a possible integration of the proposed methodology and strategy with the inverter's control circuitry.

Automatic Faulted Feeder Section Location and Isolation Method for Power Distribution Systems Considering the Change of Topology

The increasing use of modern measuring devices, such as Feeder Terminal Units (FTUs), on power networks can provide multiple types of information for fault location on distribution systems. Using these devices, in this paper, a novel automatic matrix-based algorithm for the identification and isolation of faulted feeder sections on distribution systems is proposed. The algorithm works in two stages: the first stage automatically identifies the radial feeders that make up the whole system and represents the feeders’ topology in matrix form; and the second stage automatically identifies the faulted section of the identified feeder and opens the relevant switches to isolate it. The algorithm can be applied to single and multiple faults, as it operates using measuring device information and detecting the status of switch devices. It does not require any electrical parameters and it is not affected by the fault type or fault resistance. The algorithm was thoroughly tested using a large distribution system and was found to efficiently identify and isolate the faulted feeder section in each case.

Prioritizing the Restoration of Network Transformers Using Distribution System Loading and Reliability Indices

A method is proposed to prioritize the repair or replacement of out-of-service transformers that feed a heavily meshed secondary grid. Priority assigned to the restoration of a specific transformer is based on the risk reduction that results from this replacement. Risk is defined as the reduction in the probable number of customers out of service should the transformer return to service. This measure of risk addresses the possibility of network collapse following feeder failures (occasioned by load-induced failure of transformers or feeders) and local customer impact on the secondary network. The prediction of risk makes extensive use of load predictions for feeder sections, network transformers, and secondary mains. A software tool has been developed to implement the equations proposed in this paper. This software gives system planners and operators the ability to quickly and economically select the next transformer to be repaired or replaced.

Optimal Installation of Different DG Types in Radial Distribution System Considering Load Growth

In power distribution network, the gradual increase in system load is a natural process, and it results in increased real and reactive power losses and reduced voltage profile. In this paper, optimal single and multiple installations of different types of distributed generation (DG) units are used to handle annual growth in system load, while satisfying system operational constraints. For load growth study, a predetermined growth in system annual load is considered. Minimization of system total real power loss is taken as the main objective, and optimal location and sizing of different DG types are determined using a hybrid configuration of weight-improved particle swarm optimization (WIPSO) with gravitational search algorithm (GSA) called hybrid WIPSO-GSA algorithm. The effect of load growth is studied using standard 33-bus radial distribution system, and the results illustrate significant reduction in system real and reactive power losses, enhancement in system voltage profile, and improvement in load carrying capacity of distribution feeder sections. Moreover, the economic benefits of DG on system annual load growth are also established. Also, the effectiveness of the proposed algorithm is demonstrated by comparing the results with other evolutionary optimization techniques.

Representation of Magnetic Coupling in Distribution System Feeders using BW/FW

This letter presents a new method for representing the mutual coupling between feeders or sections of feeders in distribution systems using a backward/forward sweep method. Two distribution systems with magnetic coupling between the feeders are used to test the method and to show the impact of mutual coupling between feeders. Features of computational convergence are also analyzed.

경부고속철도 회생 에너지 저장시스템 성능 분석

Recently, various researches are conducted in the application of regenerative energy produced during the operation of an electric locomotive. Regenerative energy is produced by a generator in the brake procedure. The generator is operated by kinetic energy of an electric railroad using an electric motor. The process of producing regenerative energy varies with the current type of a railroad and its running condition. The quality of electric power can be improved and electric energy can be utilized effectively, especially in the use of an energy storage system (ESS). Thus, it is necessary to apply ESS into AC section and high speed railway. This study analyses the composition of the regenerative ESS equipment installed in Yong-Jeong sectioning post, operational principle, charge and discharge algorithm and energy efficiency. The analysis shows that CO2 emissions can be reduced about 0.5 ton per a day. In addition, ESS helps saving the energy and the compensation of the voltage drop caused by the operation of high speed train when it is installed at the end of the feeder section. The number of high speed train will be increased continuously related to the electrification rate. Therefore, applying the ESS to high speed railway is expected to solve the instability of the feeder voltage and the equipment capacity problem caused by the high speed trains.

Study of Resonances in 1 × 25 kV AC Traction Systems

AC traction systems are 1 × 25 or 2 × 25 kV 50-Hz single-phase, non-linear, time-varying loads that can cause power quality problems. One of the main concerns about these systems is voltage distortion, because adjustable-speed drives for trains may inject harmonic currents of frequencies below 2 kHz. Since the presence of parallel resonances in the contact feeder section of the traction circuit worsens the scenario, traction system resonance phenomena should be analyzed to prevent problems. Several works addressed these phenomena, but they only drew weak numerical conclusions based on the frequency scan method. This article studies 1 × 25 kV traction system resonances at pantograph terminals and provides more effective analytical expressions to locate them and determine the impact of traction system parameters on them. These expressions are validated from several traction systems in the literature.

Ranking of feeder sections of distribution systems for maintenance prioritization accounting distributed generations and loads using diagnostic importance factor (DIF)

Abstract This paper presents an algorithm for deciding preferences in maintenance activities for feeder sections of distribution systems. A component importance measure, known as diagnostic importance factor (DIF), has been used for this purpose. A methodology has been developed to compute a newly framed weighted cumulative diagnostic importance factor (WCDIF) for each feeder section which represents quantitatively relative significance for prioritization of maintenance activities. The developed methodology includes the effect of distributed generations (DG) and loads. It has been implemented on two sample distribution systems and ranking lists of feeder sections for maintenance activities have been obtained.

Smart Meter Data Analytics for Distribution Network Connectivity Verification

Many utilities have the data quality problem with the geographical information system (GIS) records at distribution level. This affects many business functions of a utility, including asset management, outage response, and workforce safety. For correcting connectivity errors in the GIS representation of the distribution network topology, BC Hydro has developed an in-house algorithm. The algorithm leverages smart meter interval measurements and identifies the neighboring meters by voltage profile correlation analysis. It also predicts customers’ upstream and downstream location relationship by voltage magnitude comparisons. The output of the algorithm is then compared with the existing GIS records to correct any errors in it. This paper presents in detail the algorithm and the promising testing results within the practical BC Hydro system. Challenges for underground services are demonstrated. The algorithm’s potential use for phase detection by collectively leveraging smart meter and feeder meter data is explored. It shows encouraging results when applied in a downstream section of a large feeder.

Inspection–Repair based Availability Optimization of Distribution Systems using Teaching Learning based Optimization

This paper describes a technique for optimizing inspection and repair based availability of distribution systems. Optimum duration between two inspections has been obtained for each feeder section with respect to cost function and subject to satisfaction of availability at each load point. Teaching learning based optimization has been used for availability optimization. The developed algorithm has been implemented on radial and meshed distribution systems. The result obtained has been compared with those obtained with differential evolution.

Modifications of fault components of currents and voltages

The development is given of ideas regarding the fault components of electrical quantities and about the corresponding pure fault process. The specificity is shown of fault components of currents and voltages monitored in different places of the controlled object. Each fault component can be separated into two parts. There are several variants of separation, because the first components are created by half of the observed values: from every point of observation of current and voltage, one is selected. In accordance with the principle of compensation, selected values are introduced as known sources of voltage or current to the model of the passive undamaged object. The first components are determined as the reaction to the action of these sources. The second components are created by unknown sources of a pure fault process occurring operates in the location of a fault of an unknown object. The corresponding active model of a damaged object is open or closed in the places of observation. It is short circuited where a voltage source has previously acted and open wired where a current source was. The theory of fault components is applied to solution of the problem of locating a feeder fault on both observed sides. The objective function is the standard deviation of the second component of fault components of the two voltages, which are determined in an arbitrary position of the feeder as a result of its observations on different sides. Feeder sections that are to the left and right of the determined fault location are described by long line difference equations. Samples of the second component of each of the two voltages in the determined fault point are calculated from lagging and leading samples of the second component of the current in the corresponding place of observation. Different line equations consider losses as lumped resistances. In the considered example, the required accuracy is provided by two resistances at the ends of each feeder section.