Fernanda C. L. Trindade

Fault Location in Distribution Systems Based on Smart Feeder Meters

This paper proposes a fault-location method based on smart feeder meters with voltage sag monitoring capability. The main idea is to explore voltage measurements from monitors placed in different buses of distribution systems to estimate the fault location. The estimation is achieved by relating the voltage deviation measured by each meter to the fault current calculated based on the bus impedance matrix, considering the fault in different points. In order to improve the method accuracy, the loads are represented by constant impedance models and included into the bus impedance matrix. The performance of the proposed method is demonstrated by using a real distribution system. Sensitivity studies results show that the method is robust since it has good performance for different values of fault resistance, quantity, and location of the smart meters.

Investigation on Voltage Sags Caused by DG Anti-Islanding Protection

This paper investigates the voltage sag caused by distributed generation anti-islanding protection. This is a new power-quality concern associated with distributed generation expansion. Anti-islanding protection aims to disconnect distributed generators immediately after the opening of a recloser. As a consequence, after the reclosing operation, voltage sag will occur in some parts of the distribution system, since the loads are energized immediately but the generators are no longer present. In this context, this work presents the findings on our investigations about this problem. The results show that the resulting voltage sag level can violate power-quality limits. Thus, a set of indices has been introduced to characterize the severity of the voltage sag, and a load flow-based method has been proposed to predict the phenomenon. Sensitivity studies are also conducted in order to identify some key factors that influence this type of voltage depression.

Analysis of the harmonic distortion impact of photovoltaic generation in Brazilian residential networks

In Brazil, in spite of the outstanding solar irradiance levels, the installed amount of photovoltaic (PV) generation was practically inexistent until two years ago. This scenario started to change with the publication of resolution #482/2012 by the Brazilian Electricity Regulatory Agency, which establishes the main technical and commercial rules for residential power generation. This paper presents an overview of the current and near future scenarios of residential PV generation in Brazil, including regulatory aspects. The largest Brazilian field project on PV integration (about to start in 2014) is described. Since PV arrays use power electronic inverters, the imminence of a high PV penetration has raised utilities attention to its potential impacts on system harmonic distortion levels. In such context, this paper also identifies, through extensive simulations, the key factors influencing PV impacts on harmonic distortion level. It is found that the most important factors are: network loading level; PV connection point; and PV power factor.

Control systems analysis of industrial plants with synchronous generators during islanded operation

This work presents a methodology that permits to show, in a graph, the maximum allowable time for changing the distributed synchronous generator excitation system and speed governor control modes after the occurrence of an islanding, for a wide range of values of power unbalances between load and generation. The visualization of this parameter becomes interesting when the conflict between the synchronous generator control modes for grid connection operation (parallel) and for islanding operation is taken into account. At the point of view of practical implementation, this time is desirable to be sufficiently high, so that the decision of altering the control mode does not result in a false detection of an islanding situation. From another perspective, changing the generator control mode needs to be sufficiently fast in order to avoid the operation of voltage and frequency relays used in the generator protection.

Low Voltage Zones to Support Fault Location in Distribution Systems With Smart Meters

This paper proposes to combine the voltage monitoring capability of smart meters with impedance-based fault location methods to provide an efficient fault location approach improving service restoration. The first step of the proposed methodology is to apply an impedance-based method to obtain a rough estimation of fault location. Since the result is an estimated distance to the fault, multiple branches can be indicated due to the typical distribution systems topologies. Therefore, the challenge is: how to recognize the actual fault location? To solve this problem, voltage measurements from smart meters are used to build the low voltage zones (LVZs). The main contributions of the proposed fault location technique are to decrease the multiple estimations associated with impedance-based methods, to propose a systematic approach to build the LVZs, and to explore the presence of smart meters for fault location. The proposed method was tested through intensive and extensive simulations in a real distribution system, proving its efficiency.

Fault location in distribution systems based on smart feeder meters

Summary form only given. This paper proposes a fault-location method based on smart feeder meters with voltage sag monitoring capability. The main idea is to explore voltage measurements from monitors placed in different buses of distribution systems to estimate the fault location. The estimation is achieved by relating the voltage deviation measured by each meter to the fault current calculated based on the bus impedance matrix, considering the fault in different points. In order to improve the method accuracy, the loads are represented by constant impedance models and included into the bus impedance matrix. The performance of the proposed method is demonstrated by using a real distribution system. Sensitivity studies results show that the method is robust since it has good performance for different values of fault resistance, quantity, and location of the smart meters.

Mitigation of Fast Voltage Variations During Cloud Transients in Distribution Systems With PV Solar Farms

Since photovoltaic (PV) generators have no mechanical inertia, fast solar irradiance changes associated with cloud transients cause instantaneous variations in PV power output, resulting in rapid and possibly significant voltage changes in systems with high penetration of PV generators. In addition to characterizing this emerging power-quality issue, this paper proposes and investigates techniques to mitigate these fast voltage variations caused by cloud transients in distribution system with PV solar farms. The investigated approaches are based on the PV inverter capacity for fast reactive power compensation without the need to oversize the inverter or curtail the active power by using only the available reserve. Real measurement data characterize the issue and time-series power-flow simulations evaluate the mitigation techniques.

A transmission line two-end fault location approach based on mathematical morphology

This paper presents a fault location method for transmission lines. The proposed approach is based on voltage traveling waves sampled in both line terminals. A morphological filter called Simplified Multi-resolution Morphological Gradient (SMMG) is proposed. Because of its simplicity and low computational load, the SMMG is suitable for real time applications. The SMMG is used to detect the instant of arrival of the first wave front at the line terminals. Using these instants and the waves propagation speed, obtained from line parameters, the fault location is calculated. Tests based on a real transmission line show the robustness and the good precision of the proposed approach.

Investigation of infrastructural solutions to mitigate the impacts of EV recharging at LV networks

Due to environmental and economic incentives, the use of plug-in Electric Vehicles (EVs) is growing in several countries. The batteries of the EVs are recharged by being connected to distribution networks, and the power and energy required during the recharges are high compared to the typical loads. Consequently, the load levels can increase considerably, incurring in negative impacts to the distribution networks. In this paper, infrastructural solutions, which are part of the daily practices of utility engineers, are used to solve the impacts of 25,000 LV networks of a real Brazilian utility. A Monte Carlo algorithm is proposed for the analyses providing the engineers an estimative of the required solutions for a given penetration level of EVs and the required investment per EV. The results obtained for the analyzed networks and the prices practiced in Brazil show that the infrastructural solutions can cost about R

Potential solutions for minimizing voltage sags caused by DG anti-islanding protection

180.00 (US