Automated Coordination and Optimization Tool of Protection Devices for Distribution Systems

The major aim of any power system is the continuous provision of safe, quality and reliable electric power to the customers. One of the greatest challenges to meeting up with this goal is the failure of components in the system. In this article, the frequency of outages caused by failure of different components in the distribution system was investigated to ascertain the ones that are more susceptible to failure by comparing their proportions in the entire failure events. The outage data obtained from Irrua Transmission Station comprising Ehor, Ubiaja and Uzebba 33kV feeders were analyzed using Microsoft Excel while the hazard rates were measured using the failure rate index. Findings revealed that 93.77% of all the forced outages in the distribution subsystem in the power sector are caused by the high exposure rate of the bare aluminum conductors used in the construction of the various overhead feeders. Subsequently, the yearly failure rates of aluminum conductors, cross arms, relay, insulators, fuses, electric poles, breakers, transformers, isolators, cables lightning surge arresters were found to be 836.0, 17.5, 17.0, 10.3, 4.3, 2.0, 1.5, 1.3, 1.0, 0.5 and 0.3 respectively in the studied network. A comparison between this study and a related work showed that the rural feeders are more prone to faults as compared to the ones in the urban areas. It was therefore recommended that regular tree trimming along the network corridor should be done. Proper conductor size should be used in every subsequent construction and every segment with undersized conductor should be replaced with the appropriate size. This study will help the power system engineers in the design, construction, maintenance and operation of the distribution power system for optimum and improved system performance.

The circuit breakers, reclosers, and fuses are the main protective devices in the power distribution systems. However, due to the high penetration of wind generators in the existing distribution systems, the protective devices are exposed to high current levels, which may deteriorate the protection coordination performance and even can cause major blackouts in the distribution systems. This paper proposes the Sliding Mode Controller (SMC) based bridge type fault current limiter (BFCL) for the protection coordination of the protective devices in the distribution network. The protection coordination operation is investigated through some case studies of the Memphis Light, Gas and Water (MLGW) division's distribution test feeder with the presence of a wind farm. The performance of the proposed SMC has been compared with that of the fuzzy logic controlled (FLC) BFCL. Extensive simulations have been performed by using the Matlab/Simulink software. Simulation results for different fault situations in the test feeder indicate that the proposed SMC can maintain the protective relay coordination well and the performance of the proposed SMC based BFCL is better than that of the FLC based BFCL.

Optimal placement and coordination of protective devices in distribution networks considering fuse saving by genetic algorithm.

Introduction. In recent years, the development of high-voltage power systems has received a boost due to the need for infrastructural support for priority development areas. Universal models and algorithms are required to implement processes in power components and identify their optimal parameters. However, there are no such solutions. Accordingly, there are no ready-made subsystems with control and optimization algorithms adequate to the tasks under consideration. The objective of the presented research is to develop an optimization subsystem for the design of control and measurement components of power distribution systems.Materials and Methods. Methods for constructing automated design systems, optimization, system analysis, mathematical modeling, and adaptive control were used. When selecting methods, we proceeded from the fact that the components of power distribution systems consisted of a finite number of elements. The synthesis of a power system includes tens or hundreds of sequential operations. This was taken into account in the developed models and algorithms.Results. The possibilities of managing and monitoring manufacturing processes (MP) for the production of components of low-voltage power distribution systems were shown in terms of checking the operability and correct functioning of processing equipment. A modular structure was created to allow the integration of CAD output files into the manufacturing processes of energy distribution system components. A functional diagram of a subsystem for control and monitoring of the manufacturing processes of the production of components of power distribution systems was developed. The proposed schematic diagram of production control showed how the data collection subsystem, management system, and operating mechanisms were involved in the control of operations. The multi-level optimization module model created within the framework of this research sequentially optimized the service intensity of the i-th block, the input flow separation coefficients, and the priorities of the original data flows that form the input flow of the i-th block.Discussion and Conclusion. The combined application of modeling, system analysis, and optimization methods maintains control of the accuracy of the generated power components. The algorithm for controlling electrical loads opens up opportunities for creating a mathematical model of a power supply system that combines management, control, and monitoring, which ultimately leads to an improvement in the quality of electric power. The solution can be in demand in the development of power systems of priority development areas.

Performance of electrical load degrades if they are subjected to power quality disturbances. Voltage sags are the most frequently occurring disturbances in power system. In a three-phase, four-wire neutral grounded distribution system, due to an unbalanced nature of load, zero-sequence component also occur in system. These zero-sequence components are undesirable as they can cause the terminal voltage imbalance for the balanced three-phase loads connected on same feeder and high insulation cost in distribution network. This paper proposes a control strategy for Dynamic Voltage Restorer to correct voltage sag as well as to mitigate the zero-sequence components in distribution system. Synchronous reference frame theory along with hysteresis control is implemented in this paper to mitigate sag and unbalance of distribution network using Dynamic Voltage Restorer. MATLAB/Simulink environment is used to for simulation of the system.

Plug-in hybrid electric vehicles (PHEVs) are an increasingly attractive response to the future transportation challenges because of their potential economic and environmental benefits. When integrating PHEVs into the distribution system, it is necessary to evaluate the impact of PHEVs on distribution system reliability from the perspective of system adequacy. This paper develops a probabilistic reliability model for integrated distribution and PHEV systems. A comprehensive and time sequential Monte Carlo simulation method is applied to generate the artificial operation history for each component of a residential distribution system, and a complete simulation procedure considering the PHEVs integration is proposed. The IEEE-34 feeder system is utilized as the residential distribution network in case studies, and simulation results are presented and discussed.

This work describes the study of distribution system overcurrent protection through a probabilistic approach. Conventional approaches for overcurrent protection do not consider the probabilistic nature of the main variables involved, such as fault location, fault type and fault impedance for faults involving the ground. In this case, for instance, it is very difficult to assess the impact of situations where full coordination cannot be attained for some reason. The probabilistic approach, on the other hand, allows quantifying the risk of two adjacent protective devices operating in a non-coordinated way. This information is extremely valuable for electrical engineers at design level. In this work, the proposed methodology is illustrated through a few detailed application studies, including various sensitivity analyzes for assessing the influence of model parameters on the coordination of protective devices.

Real-time simulation of distribution system is challenging due to its' complex structure consisting of DGs. In this literature, a real-time simulator for distribution system with DG integration based on the field programmable gate array (FPGA) is realized for hardware emulation. The overall framework and asynchronous multi-rate interface method between DG with high nonlinearity and distribution system is proposed. The models of main components in distribution system are designed in FPGA. The hardware parallelism and highly pipeline design is utilized to guarantee real-time simulation, which has strong generality and flexibility. The simulator uses a floating point arithmetic calculation to achieve high accuracy. To validate the new simulator, a photovoltaic-battery hybrid generation system and a typical distribution system integrated with PV generation system are emulated in the hardware. The time-step of DG system and distribution system reach 1.096μs/1.696μs and 2μs/2μs respectively. The captured waveforms show excellent accuracy in comparison to the offline simulation in PSCAD/EMTDC. The time-step is less than RTDS which indicate a higher precision. The resource consumption of FPGA also show advantage compared with RTDS.

The connecting of distributed generation (DG) to the distribution network has numerous advantages. However, in the presence of DG some problems in coordination of protection devices will occur, due to changes in short-circuit levels at different points. Fault current limiter (FCL) is applied to limit the fault current levels and the effect of DGs on coordination of overcurrent (O/C) relays during the faults. The use of DG and FCL in distribution networks causes to some transient currents during fault conditions. Steady-state coordination methods do not result in accurate settings in such networks. A new method is proposed for coordination of O/C relays by considering the transient behaviour of the network. This method is based on the genetic algorithm and uses the dynamic model of O/C relays instead of the fixed characteristic curves. For this purpose, transient behaviour of DG and FCL are simulated and the relay operating status is calculated for all primary and backup relays to achieve the optimal settings of relays in transient condition. Simulations are carried out on a sample network and the results demonstrate that the method gives feasible and effective solutions for optimal coordination in the practical power system networks in comparison to the previous steady-state methods.

Network theory is rapidly changing our understanding of complex systems, but the relevance of topological features for the dynamic behavior of metabolic networks, food webs, production systems, information networks, or cascade failures of power grids remains to be explored. Based on a simple model of networks, we offer an interpretation of instabilities and oscillations observed in biological, ecological, economic, and engineering systems. We find that most networks display damped oscillations, even when their units - and linear chains of these units - behave in a non-oscillatory way. Moreover, networks of damped oscillators tend to produce growing oscillations. This surprising behavior offers, for example, a new interpretation of business cycles and of oscillating or pulsating processes. The network structure of material flows itself turns out to be a source of instability, and cyclical variations are an inherent feature of decentralized adjustments. In particular, we show how to treat production and networks as transport problems governed by balance equations and equations for the adaptation of production speeds. The stability and dynamic behavior of networks is investigated for different topologies, including sequential chains, supply circles, supply ladders, and supply hierarchies. Moreover, analytical conditions for absolute and convective instabilities are derived. The empirically observed bullwhip effect in chains is explained as a form of convective instability based on resonance effects. An application of this theory to the optimization of production networks has large optimization potentials.

Protection of a power system is an extremely important aspect as the duality and scheme of protection decides system reliability, controllability and stability. This paper concentrates on the protection of a distribution system in the light of developments in distributed generation (DG). The conventional distribution system is radial in nature, characterized by a single source feeding a network of down-stream feeders. The protection system has traditionally been designed assuming the system to be radial. After connecting DG, part of the system may no longer be radial, which means the coordination might not hold. The effect of DG on coordination will depend on size, type and placement of DG. This paper explores the effect of DG on protective device coordination such as fuse-fuse, fuse-recloser and relay-relay. In each case, depending on size and placement of DG, there are some margins in which the coordination may hold and certain cases, where no margin is available. These conditions are identified for each case through coordination graphs.

A significant factor for properly designing the protection scheme of a microgrid is the fault current contribution from the converter-interfaced distributed energy resources (CI-DERs). The fault current direction and magnitude is difficult to be defined, since the currents injected by the CI-DERs affect it considerably. The fault situation is even more complicated, considering the case of islanded looped microgrids with conventional protection devices. In such microgrids, all protection devices are settled to the same rated current. In order to overcome these issues, this paper proposes a new method for detecting and clearing faults, without utilizing any communication means. The fault identification process is carried out by measuring indirectly the microgrid impedance, while each CI-DER adapts the internal control method and injects a fault current proportional to the sensed impedance. Therefore, the source being closer to the fault injects relatively larger currents enabling the selective coordination of conventional protection devices. In order to enhance even more the selective cooridnation of the protection devices, a time delay is also incorporated in the fault control. The proposed strategy is validated in a looped microgrid, protected by simple overcurrent relays.

A new era of the electrical grid began due to the high integration of the inverter-based resources. Typically, resources are connected to the electrical grid using grid-following control techniques. Overall system inertia reduces as these resources replace rotating synchronous machines. Grid-forming control is one of the solutions introduced to overcome the challenges in the electrical grid due to the increase in inverters. With the increase of inverter-based resources in both transmission and distribution networks and the introduction of new inverter controls, it is important to understand how power system voltage and frequency dynamics are affected. In this paper, a 100% inverter-based resource electrical network is studied across both transmission and distribution networks while considering different inverter control configurations and different methods of current limiting. Moreover, the increasing penetration of inverter-based resources poses challenges to transmission planning as the dynamic interaction between distribution and transmission can no longer be ignored. In this regard, an aggregated distribution network model is proposed for transmission planning studies to accurately represent the distribution network's dynamic behavior at different grid-forming and grid-following inverter ratios.

The traditional distribution systems are radial and have unidirectional power flow. The overcurrent protection system of these networks is negatively affected by Distributed Generation (DG) units. The time and current coordination of protection devices of these systems is the most important concern in the case of high DGs penetration. Actually, DGs connection and disconnection change the short circuit level of feeders and disturb the coordination of protection devices. So, new protection schemes should be proposed which must not to be affected by DGs and should work properly in both islanded and grid connected operation modes of the micro-grid. In this paper, an adaptive protection scheme, based on fault location, is proposed for smart micro-grids. The functionality of each protection device is adaptively selected based on detected network topology and fault type. The proposed solution is simulated in the SimPower software. The results show the efficiency of the proposed protection scheme which cannot be affected by DGs.

As the energy demand increases due to the developing electric power industry, the fault current becomes higher during the fault time. A new approach is needed to reduce a fault current in a power distribution system, since the fault currents influence other protective devices’ operation. To decrease the fault current, the superconducting fault current limiter (SFCL) has been suggested. The SFCL has no power loss with no effect on a power distribution system because the SFCL impedance only occurs during the fault time. However, the SFCL can reduce the fault current; it causes the trip time delay of the over current relay (OCR). Compensation methods for the balanced fault have been invented in previous studies, while research on unbalanced ground fault compensation are few. In this paper, the compensation method configured with impedance components of a power distribution system is introduced to eliminate the influence of the SFCL on the OCR. In addition, the components of the SFCL impedance are removed from the characteristic equation of the OCR. To verify the effect of the impedance compensation method, fault simulations are carried out in 3 types of ground faults using PSCAD/EMTDC.