Medium Voltage Feeders Research Articles

Benchmarking medium voltage feeders using data envelopment analysis: a case study

Feeder performance evaluation is a key component in improving the power system network. Currently there is no proper method to find the performance of Medium Voltage Feeders (MVF) except the number of feeder failures. Performance benchmarking may be used to identify actual performance of feeders. The results of such benchmarking studies allow the organization to compare feeders with themselves and identify poorly performing feeders. This paper focuses on prominent benchmarking techniques used in international regulatory regime and analyses the applicability to MVFs. Data Envelopment Analysis (DEA) method is selected to analyze the MVFs. Correlation analysis and DEA analysis are carried out on different models and then the base model is selected for the analysis. The relative performance of the 32 MVFs of Western Province, Sri Lanka is evaluated using the DEA. Relative efficiency scores are identified for each feeder. Also the feeders are classified according to the sensitivity analysis. The results indicate that the DEA analysis may be conveniently employed to evaluate the performance of the MVFs. The evaluation is carried out once or twice a year with the MV distribution development plan in order to identify the performance of the feeders and to utilize the available limited resources efficiently.

Control of Battery Storage Systems for the Simultaneous Provision of Multiple Services

In this paper, we propose a control framework for a battery energy storage system (BESS) to provide simultaneously multiple services to the electrical grid. The objective is to maximize the battery exploitation from these services in the presence of uncertainty (load, stochastic distributed generation, and grid frequency). The framework is structured in two phases. In a period-ahead phase, we solve an optimization problem that allocates the battery power and energy budgets to the different services. In the subsequent real-time phase the control set-points for the deployment of such services are calculated separately and superimposed. The control framework is first formulated in a general way and then casted in the problem of providing dispatchability of a medium voltage feeder in conjunction to primary frequency control. The performance of the proposed framework are validated by simulations and real-scale experiments, performed with a grid-connected 560 kWh/720 kVA Li-ion BESS.

Adaptive Decentralized Control of Residential Storage in PV-Rich MV–LV Networks

The rapid adoption of residential-scale photovoltaic (PV) systems in low-voltage (LV) networks combined with the falling prices of residential-scale battery energy storage (BES) systems is paving the way for a future in which customers could locally supply most of their energy needs. However, off-the-shelf (OTS) storage systems operate for the sole benefit of the customer (reducing grid imports). This means that charging might not occur during times of high PV generation, resulting in technical issues on LV and medium-voltage (MV) networks. This paper proposes an adaptive decentralized control strategy 1 for residential-scale BES systems to reduce voltage and thermal issues whilst still benefiting customers. With this strategy, the power charging and discharging rates constantly adapt throughout the day based on clear-sky irradiance, PV generation, demand, and state of charge; significantly reducing reverse power flows and ensuring adequate storage capacity the next morning. A real Australian MV feeder with realistically modeled LV networks is studied using smart meter data. Results demonstrate that the proposed control strategy overcomes the limitations of the OTS BES. It is also shown that it can be as effective as an ideal optimization-based approach, being able to manage all technical issues without significantly affecting customers.

A novel method for solving multi-stage distribution substation expansion planning

This paper presents a new methodology for solving multi-stage distribution substations expansion planning (MSDSEP) problem. The proposed method can determine the optimal location, capacity, associated service area and construction timing of substations with aiming to the maximum profit for supplying the forecasted demand. The objective function is of the difference between benefit and cost of expansion. The present worth of revenue from selling energy is considered as the expansion benefit while the present worth of cost from purchased energy, investment cost for installing and/or upgrading substations and the construction cost of medium voltage (MV) feeders are considered as the expansion cost. Moreover, the technical constraints consist of network radiality, voltage drop, expansion capacity and operation capacity of substations. The developed method generates the binary variables for deciding connection between load points to substations and the integer variables for deciding expansion capacity of substations. While the dynamic bacterial foraging algorithm (DBFA) process is used for searching the best binary variable and the best integer variable. The effectiveness of proposed method is demonstrated on the distribution system of Tabriz city Iran which compared with single-stage distribution substations expansion planning DSEP (SSDSEP). The results showed that MSDSEP can provide more economical solution than SSDSEP.

STUDI ANALISIS GANGGUAN PERANGKAT HUBUNG BAGI TEGANGAN RENDAH DAN UPAYA MENGATASINYA DI PLN AREA TANJUNG PRIOK

Medium voltage feeders are a means for the distribution of electricity from substations to consumers. But in reality these feeders often experience interference, among other is interference onthe low voltage network, especiallyCircuit For Low Voltage Device. Circuit For Low Voltage Device (PHB-TR) is device used as a liaison, security, and dividers electrical power from an electric power source to the customer. Over time, the PHB-TR also decreased quality of service so that should be their efforts to overcome the problems in order to maintain or restore the initial achievement level and can operate with high reliability so that the continuity of the electrical service will be achieved. The disturbances that can occur in this PHB-TR as damage to the NH fuse, corona contained in ground plate, over current and damage to the measuring instrument.Additionally by overcoming the interference can secure the assets of PLN from the interferences and reduce the cost of replacing broken tools.

Utilisation of symmetrical components in a communication‐based protection for loop MV feeders with variable short‐circuit power

Variability of the available short-circuit power also implies variation of the fault level, which can potentially cause several protection problems in the electric networks. In this study, a novel protection method that is insensitive to the fault level changes caused by variable short-circuit power is presented. It relies on utilisation of symmetrical components of the short-circuit currents and on communication between the protection relays. The proposed method addresses the single phase to ground (SPG) faults occurring in directly grounded distribution networks, with focus on closed-loop medium voltage (MV) feeders. Case studies are presented, which demonstrate that the proposed protection scheme is capable of effectively detecting the SPG faults in closed-loop feeders with variable short-circuit power.

Proactive Study and Novel Mitigation of MV Power System Damage Due to Sub-Power-Frequency Ferro-Resonance for a Gas Plant

As projects to expand the processing capacity of a gas plant located in west Texas were pursued, engineering staff observed that the planned incoming medium-voltage power feeder possessed many of the risk factors that have led to increasingly common control-power transformer (CPT) and voltage transformer (VT) failures in industry due to switching. Such failures could involve significant damage and down time. To address these concerns, a computer simulation study was undertaken. As part of initial data gathering, sweep frequency response analysis (SFRA) measurements were performed in an atypical context to establish resonant characteristics of these instrument transformers. When the remote source breaker was modeled to open, connected VTs/CPTs went into severe sub-power-frequency ferro-resonance with probable catastrophic failure. This was verified by Electromagnetic Transients Program (EMTP) simulations as well as by field measurements. The focus of this paper will be on the determination of this unique form of ferro-resonance, identification of risk factors, novel cost-effective solutions, implementation, and field measurement verification of the proposed mitigation solutions. Field measurements have shown high correlations with the EMTP simulations and have verified the effectiveness of the proposed novel mitigation solutions.

Three-Stage Distribution Feeder Control Considering Four-Quadrant EV Chargers

With the increased penetration of electric vehicle (EV) chargers in distribution systems, there is a need to understand and minimize their impact on medium-voltage (MV) and low-voltage (LV) networks. Thus, this paper proposes a three-stage algorithm to coordinate the operation of four-quadrant EV chargers with other volt/var control devices in MV and LV distribution feeders. The first stage operates on a day-ahead basis and defines the load tap changer and capacitor schedules while minimizing the peak load associated with EVs in the distribution system. The second and third stages update their operation every five minutes, to fairly allocate the aggregated and individual EV loads in the MV an LV feeders, respectively, while minimizing active power losses and voltage deviations. The proposed technique is applied to CIGRE’s North-American MV and LV benchmark systems to demonstrate its ability to properly allocate EV loads, and improve distribution system performance in terms of losses and voltage deviations.

A Framework for Optimal Coordinated Primary-Secondary Planning of Distribution Systems Considering MV Distributed Generation

Power distribution planning (PDP) approaches are evolving to new models and methods by introduction of smart grids. Distribution system is divided into two levels: 1) medium voltage (MV) as primary network and 2) low voltage (LV) as secondary network. In PDP, to have a comprehensive view, costs of primary and secondary networks must be considered coordinately. The PDP problem is exacerbated incorporating distributed generators (DG). In this paper, a single cost function is proposed, which comprises costs of LV feeders, MV substations, MV DG, MV feeders, and high voltage substations; imperialist competitive algorithm is utilized to minimize the cost function; and a greenfield network is planned for a long-term period. Results show that in PDP problem, incorporated with DG, it is required to coordinately plan the primary and the secondary network.

Distributed Control of Voltage Regulating Devices in the Presence of High PV Penetration to Mitigate Ramp-Rate Issues

A distributed voltage control scheme is proposed in an active distribution network in the presence of a large scale photovoltaic (PV) farm/plant to mitigate high ramp-rate issues. Multiple voltage regulating devices, such as on-load tap changers, step voltage regulators (SVRs), and switched capacitors banks are controlled in various ways based on either a centralized or a distributed coordination management scheme. This paper presents the relationship of the active and reactive power outputs of a PV plant in the presence of the conventional voltage regulating devices, and proposes a distributed control strategy to coordinate the SVRs with the PV smart inverter’s capability to improve power quality. The distributed voltage control schemes are tested on an unbalanced medium voltage feeder located in a California utility service territory with the PV integrated at the far end of the feeder.

A Smoothing Technique for the Multifractal Analysis of a Medium Voltage Feeders Electric Current

The current paper presents a data-driven detrending technique allowing to smooth complex sinusoidal trends from a real-world electric load time series before applying the Detrended Multifractal Fluctuation Analysis (MFDFA). The algorithm we call Smoothed Sort and Cut Fourier Detrending (SSC-FD) is based on a suitable smoothing of high power periodicities operating directly in the Fourier spectrum through a polynomial fitting technique of the DFT. The main aim consists of disambiguating the characteristic slow varying periodicities, that can impair the MFDFA analysis, from the residual signal in order to study its correlation properties. The algorithm performances are evaluated on a simple benchmark test consisting of a persistent series where the Hurst exponent is known, with superimposed ten sinusoidal harmonics. Moreover, the behavior of the algorithm parameters is assessed computing the MFDFA on the well-known sunspot data, whose correlation characteristics are reported in literature. In both cases, the SSC-FD method eliminates the apparent crossover induced by the synthetic and natural periodicities. Results are compared with some existing detrending methods within the MFDFA paradigm. Finally, a study of the multifractal characteristics of the electric load time series detrendended by the SSC-FD algorithm is provided, showing a strong persistent behavior and an appreciable amplitude of the multifractal spectrum that allows to conclude that the series at hand has multifractal characteristics.

Anti-Islanding Protection Relay for Medium Voltage Feeder With Multiple Distributed Generators

Large distributed generators (DGs) are usually connected to medium voltage (MV, typically up to 50 kV) feeders directly. Their anti-islanding protections mainly rely on transfer trips from upstream substations through communication media, which are expensive and time-consuming because of infrastructure. This paper presents a local anti-islanding protection relay (LPR) as an alternative for the traditional transfer trip in MV feeder applications. The basic idea of the proposed LPR is to short phase to neutral or phase to phase voltages by thyristors at the point of common coupling (PCC) of each DG when either of them is crossing zero; then both variations of the thyristor current and voltage harmonic distortion at the PCC are observed and measured, and they are able to indicate the operating mode of the DG unit in either grid-connected or islanding. Further, this approach is analyzed and discussed based on a single DG scenario and a complicated scenario with two DGs and one shunt capacitor bank. Finally, a lot of experiment results with different scenarios are obtained based on a scale-down testing platform, which has been built in our lab by using per-unit method from an actual MV feeder system.

Reliability and cost assessment methodology of medium-voltage feeders

The authors introduce a methodology which quantifies medium-voltage (MV) feeder reliability in the form of commonly used indices. The contribution of the proposed methodology focuses on the modelling not only of the grid itself but also of the detailed actual operational practices of the distribution system operator (DSO), taking into consideration the specific parameters of the examined network. By doing so, the influence of diverse reliability enhancement measures on different feeders can be evaluated and assessed. The method is tested using real (MV) feeders, considering as measures the installation of protection units and remote control capabilities to the switches. Furthermore, by considering the cost of protection and remotely controlled units, the proposed methodology performs techno-economic analyses to assess the trade-offs between enhancing grid reliability and increasing costs, serving as a decision-making tool for modern DSOs.

Optimisation algorithm for Earth fault location on MV distribution feeders

This study presents an earth fault location algorithm based on optimisation approach, which is developed for medium voltage (MV) distribution networks with resistance-earthed neutral. The objective function is written based on relation between voltage and current measurements at substation, line parameters, fault distance and fault resistance. The optimisation process is performed with MATLAB optimisation toolbox that gives values to the last two variables. To deal with the heterogeneity of MV feeders, fault location is carried out successively on every homogeneous section lines and the optimal points of the different sections will be compared with given final solution. The performance tests, which are performed on an MV CIGRE benchmark network, show encouraging results. In this study, impacts of load consumption uncertainty and of DG connection are also discussed.

EDP's experience in optimising in-service protection system units

With a focus on providing a higher quality of service (QoS), while minimising Capital Expenditure (CAPEX) and Operating Expenses (OPEX), EDP Distribuição (EDPD) developed a programme to optimise its current protection asset base that spans along several generations and technologies, and, consequently, with different levels of protection functions. This programme consisted of an exhaustive revision of all medium-voltage (MV) protection function settings, comprising a total of 484 substations and switching stations, and over 5100 feeders within the entire mainland Portugal distribution grid. The main goals were to ensure protection relays coordination, guarantee sensitivity for electrically distant short-circuits and minimise voltage dips duration. Firstly, EDP's Protection and Automation Department used DPlan to conduct systematic short circuit and protection studies. To optimise this process, reducing man-hours needed, EDPD and AmberTREE worked together to develop improvements within the short-circuit and reporting modules. With the newly optimised protection settings, EDPD advanced toward in-field implementation, resulting in more than 6600 protection function changes, preventing 190 potential coordination failures and reducing the voltage dips duration in 1197 MV feeders. EDPD expects to improve significantly QoS and reduce customer complaints regarding voltage dips and short interruptions by using the existing asset base, while keeping the costs low.

Receding horizon optimization-based approaches to managing supply voltages and power flows in a distribution grid with battery storage co-located with solar PV

In this paper we propose two optimization-based algorithms for coordinating residential battery storage to balance increases in daily operational savings that accrue to residential customers with the management of bi-directional power flows in the distribution grid. Bi-directional power flows are managed to improve the supply voltage for residential customers with rooftop solar PV, in addition to alleviating (potentially infrequent) congestion that occurs in the evening when PV production is unavailable. Our objectives are threefold: (1) to reduce reverse power flow leading to significant voltage rise; (2) to reduce peak loads creating sustained under-voltages and/or approaching a network thermal capacity; and (3) to increase operational savings for the residential customer. To achieve our objectives we present a Distributed-Receding Horizon Optimization (D-RHO) algorithm, wherein charge and discharge rates of residential battery storage are coordinated so as to directly influence power flows along a distribution feeder. We also present an Adaptive-Receding Horizon Optimization (A-RHO) algorithm, in which charge and discharge rates of residential battery storage are coordinated to more directly manage supply voltages. To assess the distributor benefit, both RHO-based algorithms are applied to a publicly available model of an Australian distribution region located in Elermore Vale. The results of this case study confirm that the A-RHO algorithm improves supply voltages in a low voltage network, and that the D-RHO algorithm offers a peak load reduction of 32% along the Elermore Vale medium voltage feeder.

A novel method for decomposing electricity feeder load into elementary profiles from customer information

To plan a distribution grid involves making a long-term forecast of sub-hourly demand, which requires modeling the demand and its dynamics with aggregated measurement data. Distribution system operators (DSOs) have been recording electricity sub-hourly demand delivered by their medium-voltage feeders (around 1000—10,000 customers) for several years. Demand profiles differ widely among the various considered feeders. This is partly due to the varying mix of customer categories from one feeder to another. To overcome this issue, elementary demand profiles are often associated with customer categories and then combined according to a mix description. This paper presents a novel method to estimate elementary profiles that only requires several feeder demand curves and a description of customers. The method relies on a statistical blind source model and a new estimation procedure based on the augmented Lagrangian method. The use of feeders to estimate elementary profiles means that measurements are fully representative and continuously updated. We illustrate the proposed method through a case study comprising around 1000 feeder demand curves operated by the main French DSO Enedis. We propose an application o that uses the obtained profiles to evaluate the contribution of any set of new customers to a feeder peak load. We show that profiles enable a simulation of new unmeasured areas with errors of around 20%. We also show how our method can be used to evaluate the relevancy of different customer categorizations.

System wide MV distribution network technical losses estimation based on reference feeder and energy flow model

This paper presents an integrated analytical approach to estimate technical losses (TL) of medium voltage (MV) distribution network. The concept of energy flow in a radial MV distribution network is modelled using representative feeders (RF) characterized by feeder peak power demand, feeder length, load distribution, and load factor to develop the generic analytical TL equations. The TL estimation approach is applied to typical utility MV distribution network equipped with energy meters at transmission/distribution interface substation (TDIS) which register monthly inflow energy and peak power demand to the distribution networks. Additional input parameters for the TL estimation are from the feeder ammeters of the outgoing primary and secondary MV feeders. The developed models have been demonstrated through case study performed on a utility MV distribution network supplied from grid source through a TDIS with a registered total maximum demand of 44.9MW, connected to four (4) 33kV feeders, four (4) 33/11kV 30 MVA transformers, and twelve (12) 11kV feeders. The result shows close agreement with TL provided by the local power utility company. With RF, the approach could be extended and applied to estimate TL of any radial MV distribution network of different sizes and demography.

Identification of High-Impedance Earth Faults in Neutral Isolated or Compensated MV Networks

This paper introduces novel methods for the identification and location of very high impedance one phase-to-earth faults in medium-voltage (MV) networks in order to improve the electrical safety and reduce the number and duration of outages to customers. The examination is restricted to neutral compensated and isolated MV systems which are the prevailing neutral treatment practices in Europe. The main target of the study was the development of the new method for the identification and location of earth faults up to very high fault resistances. The method is technically applicable in actual use because it utilizes standard measurements available at all 110/20 kV primary substations. No new measuring instruments or devices are needed. The major algorithm is based on the calculation of the fault resistance for every MV feeder. Field experiments in real networks have also been conducted for testing the methods. The indication method presented can identify and locate faults approximately up to 100–200 k $\Omega$ .

The Misuse of IEEE Device 52- Medium Voltage Contactors and Breakers Are Not the Same!

Many standards and specifications, related to medium voltage (MV) motor and feeder circuits, continue to center around the generic use of the IEEE Device 52 as a circuit identifier for the switching device used within those power systems. IEEE Device 52 is defined as a device that is used to close and interrupt an ac power circuit under normal conditions or to interrupt this circuit under fault or emergency conditions. Many of the current standards include detailed protection and coordination recommendations that are centered on circuit breaker protective settings. Some of these recommended protective settings can be detrimental when medium voltage vacuum contactors are used instead of ac circuit breakers to interrupt the circuit under fault conditions such as in motor and feeder applications. This paper will outline MV contactor and breaker rating differences, compare the appropriate protection variations and requirements between the two, and highlight the dangers to personnel and equipment when assuming that a medium voltage vacuum contactor can provide the same performance and require the same protective settings as a medium voltage circuit breaker.