Reliability Of Power Supply System Research Articles

The Estimation of Wind Power Station on the Basis of Fuzzy Regression Model to Forecast the Speed and Direction of the Wind

To forecast the wind speed and the angle of its direction, it is suggested to use autoregression based on the concept of fuzzy system, which is recognized as a fairly convenient modeling tool. The main goal of fuzzy regression analysis is to find a regression model that satisfies all the observed fuzzy data within specified optimality criterion. According to this method, the regression coefficient is fuzzy numbers, which can’t be expressed as a number of the interval with membership values. In this work, the wind speed and direction are predicted for the Far Eastern coast. It is shown that on this basis the power and generation of a wind power plant with the possibility of covering its load schedule, and the function of energy storage can be determined. High introduction of wind power plants into system leads to some inconveniences in the operation of operator systems, primarily due to unpredictable and volatile nature of wind speed, and wind power generated, respectively. Despite fact that the power generated at the wind form is not regulated by the system operator, accurate prediction of wind speed and the angle of its direction could solve this problem, thereby making a significant contribution to improving the reliability of power supply systems

A study of the reliability of a solar-wind power supply system

The growing demand of agricultural consumers for autonomous energy generating systems based on renewable energy sources leads to a need for an evaluation of the reliability of electricity supply. In this regard, the present study is devoted to considering approaches for the reliability evaluation of a solar-wind power supply system taking into account the changeability in the power of solar and wind energy flows, as well as methods for calculating the parameters of its reliability. As a result of a theoretical study, a mathematical model was developed to estimate the reliability of a solar-wind power supply system. This paper presents the obtained reliability parameters of the power supply system for a dwelling house on the basis of a solar-wind installation.

Decentralized Suppression Strategy of Circulating Currents Among IPOP Single-Phase DC/AC Converters

To increase the power rating and improve the reliability of the single-phase power supply system, the input-parallel output-parallel (IPOP) single-phase dc/ac converters (SDACs) are widely used. However, among the IPOP SDACs, there are complicated circulating currents which will increase the current stress on the switching devices and influence the safe operation of the system. But, the detailed quantitative analysis of the circulating currents is not well developed and the corresponding suppression strategies are not very comprehensive. Focusing on these problems, this paper pays attention to the detailed mathematic model and effective suppression strategy of circulating currents among IPOP SDACs. First, the detailed mathematic model of the circulating currents is established. Based on this model, it is found that there are various types of circulating currents existing in the IPOP SDACs, including circulating currents within the single SDAC and circulating currents among the multiple SDACs. At the same time, the influence factors are also analyzed, and it is first revealed that the asymmetry of impedances in different sides will cause circulating currents with different frequencies components including the dc, fundamental, and second frequencies. Second, after the detailed analysis, a decentralized control method composed of the common mode (CM) and differential mode (DM) control is proposed to suppress the complicated circulating currents. The control method is comprehensive and can suppress circulating currents caused by diverse influence factors. All the theoretical analyses are verified by the real-time hardware-in-loop (HIL) tests.

<b>Recent Topics on Power Supply Technology</b>

In order to ensure that the railways remain a sustainable transport mode into the future, it is essential to improve the reliability and stability of train operations and railway systems. Functional failures in power supply systems significantly affect train operation: the RTRI has therefore been tackling the issue of improving reliability of power supply systems. This paper describes recent power supply technology research focusing on research geared to contribute to reducing failures and accidents on the railway system.

Анализ сенсорных элементов схемы и выявление слабых мест в сетях генераторного напряжения

Large industrial enterprises use own electrical and thermal energy sources in addition to external power systems. Therefore, ensuring the stable operation of both the auxiliary power plants supply mechanisms and the main technological equipment of an enterprise is an important task in the electric networks design and reconstruction. The reliability of the power supply system can be carried out in various ways, one of which is the identification and analysis of sensory (sensitive) circuit elements in order to further eliminate weak units. Thus, the paper considers a complex generator voltage network of an industrial enterprise that is connected to the system through high and extra high voltage substations. This network features thermal power plants with auxi­liary and high-voltage industrial consumers of the enterprise and pumping stations. A series of electromechanical transients calculations was performed in the simulation of short circuits in the network using KATRAN 10.0 software package to identify the sensory elements of the circuit. Based on the results of the calculation, the stability of synchronous and asynchronous motors is estimated by determining the level of their operational parameters deviation. Based on the calculation results, it is concluded that the power plant mechanisms of auxiliary needs have the highest sensitivity, and the maximum deviation of the mode parameters is achieved during short circuits at high voltage levels. Analyzing the sensor elements of the system allows for the higher reliability of the industrial enterprise power supply system with strong disturbances in the network.

Modeling of reliability of power supply systems with autonomous energy source

The methodology for calculating the reliability of power supply systems with autonomous and mixed energy sources has been considered. Autonomous sources are widely used in industrial power supply systems as primary, backup or emergency sources. The functioning and interchangeability of these systems has features that affect the reliability of power supply. The proposed methodology is based on the method of semi-Markov random processes and can be used for comparative analysis of the reliability of options for power supply systems. The methodology has been brought to software implementation and is accompanied by an example of calculating the reliability of the power supply system for stationary marine oil production platforms.

Features of Estimation of Structural Reliability of Power Supply Systems

Development and operation of modern power supply systems of consumers which are the part of distributed generation (DG) systems with their communication with electric power system (EPS) and renewable energy sources (RES) demand changes in estimation of their reliability indicators on the basis of corresponding mathematical apparatus. It is shown that DG systems refer to structures with several overlapping zones of action, which determines their peculiarities, which are represented by some integral characteristic - efficiency of operation, which characterizes the degree of expediency of use of the DG system in different modes. The approach based on evaluation of effectiveness of such systems is offered. Examples of calculation of relatively simple structures of DG systems performing several tasks simultaneously are given.

Reliability Evaluation of a Metro Traction Substation Based on the Monte Carlo Method

The study of a metro traction power supply system reliability makes a significant contribution to researching on new power supply principles and configuration, and also providing a reference for system design and operation. According to the power supply structure and operation mode of the metro traction substation power supply system, based on the internal equipment, the reliability evaluation model of the traction substation is established by the block processing fault tree. An improved sequential Monte Carlo method is used to realize the quantitative reliability evaluation of the metro traction substation power supply system. The conclusions show that the reliability model and the sequential Monte Carlo simulation method proposed in this paper can obtain rich reliability indexes. Through visual simulation and theoretical calculation, the reliability of the metro traction power supply system can be effectively evaluated.

Identification of interturn faults in power transformers by means of generalized symmetrical components analysis

The paper deals with experimental identification of transformer internal faults, an important factor in reliability and sustainability of power supply systems. Task of identification of transformer internal faults requires increasing sensitivity of relay protection by calculation of components most sensitive to interwire faults from transformer current. In order to study internal faults in transformer, the model in Simulink MATLAB was developed on the basis of transformer constitutive equations. Transformer with short circuited wires was simulated as a multiwinding transformer. We provide the calculation of transformer parameters. Model was applied for analysis of transients in power transformers, such as interwire fault, transformer inrush, and fault in transformer connections. Analysis of power transformer internal faults by means of time-dependent symmetrical components of currents is provided. These symmetrical components were calculated for the first harmonic of current by means of discrimination of firs harmonic by low-pass filter and compensating elements implementing phase shift. Described method allows calculation of symmetrical components during transient and under non-sinusoidal conditions. Simulation results showed the advantage of instantaneous symmetrical components of other direct values. Those components were implemented in relay protection algorithms for identification of internal faults in transformers.

TRANSMITTING THE ACCURATE TIME USING THE PTP PROTOCOL FOR AN INTELLECTUAL SMART GRID NETWORK

In the integrated power supply systems SMART-Grid, energy effici-ency, reliability, and survivabilityare ensured, to some extent, by continuous monitoring of the stability of parameters with reference to real-time signals. In accordance with the ІЕЕЕ С37-238-2017 standard, in order to provide power supply system with the time stamps, it is necessary, with respect to the concept of intelligent power sys-tem SMART Grid, to develop and implement the means for reproducing accurate time stamps with a microsecond accuracy. A protocol, which is capable to meet these re-quirements and does not require the development of a dedicated power system is the PTP protocol. The developed state standard of Ukraine DSTU IEC / IEEE 61850-9-3: 2018 defines a number of characteristics of the PTP protocol for both energy and other profiles. A full standardization of PTP protocol in Ukraine requires a development and adoption of the following document-based standards as the state’s ones: IEEE Std 1588 ™ — 2008 or IEC-61588: 2009, IEEE C37.238-2017. The appropriate schemes have been developed for testing a domestic complex of the US-1588M and US-1588S devices with the use of PtpMon2 software. During the tests, it is envisaged to perform short-term and long-term measurements of time cha­ -racteristics of the synchronization signals generated at the output of US-1588S de-vice. The measurement results are presented as the Time Interval Error (TIE) and Maximum Time Interval Error (MTIE), which is calculated as a maximum value of the TIE array at a given measurement interval by using v1 of the PTPmon2 software. Also, we investigated the complex US-1588, which provides the transmission of accurate time stamps’ signals using the PTP protocol. According to the results of experimental studies, the obtained accuracy of time stamps transmission does not exceed 1 μs, which meets the requirements of the IEEE S37-238-2017 standard to the energy profile of PTP.

Interactive Multi-energy Complementary Island Microgrid Ecosystem

Reliable and stable island power supply system is an important guarantee for the development of the island. Based on the island connected to the main network by cable, this paper proposes an interactive multi-energy complementary microgrid consisting of new energy generation, electric energy interaction, electric vehicle charging and discharging, home photovoltaic system, power distribution and emergency rescue. The electricity generated by the residents themselves can be used by themselves, and the excess can be sold back to the main network. This system makes full use of the characteristics of electric vehicles energy storage and mobility and participate in grid dispatching, which can improve the popularity of new energy power generation, balance the peaks and valleys of island electricity consumption and reduce the cost of electricity for residents.

Forecasting Electricity Consumption Using Time Series Model

Electricity demand forecasting is important for planning and facility expansion in the electricity sector. Accurate forecasts can save operating and maintenance costs, increased the reliability of power supply and delivery system, and correct decisions for future development. Universiti Tun Hussein Onn Malaysia (UTHM) which is a developing university in Malaysia has been growing since its formation in 1993. Thus, it is important for UTHM to forecast the electricity consumption in future so that the future development can be determined. Hence, UTHM electricity consumption was forecasted by using the simple moving average (SMA), weighted moving average (WMA), simple exponential smoothing (SES), Holt linear trend (HL), Holt-Winters (HW) and centered moving average (CMA). The monthly electricity consumption from January 2011 to December 2017 was used to forecast January to December 2018 monthly electricity consumption. HW gives the smallest mean absolute error (MAE) and mean absolute percentage error (MAPE), while CMA produces the lowest mean square error (MSE) and root mean square error (RMSE). As there is a decreasing population of UTHM after the moving of four faculties to Pagoh and HW forecasted trend is decreasing whereas CMA is increasing, hence HW might forecast better in this problem.

Forecasting Electricity Consumption Using Fuzzy Time Series

Electricity consumption forecasting is important for effective operation, planning and facility expansion of power system. Accurate forecasts can save operating and maintenance costs, increased the reliability of power supply and delivery system, and correct decisions for future development. There is a great development of Universiti Tun Hussein Onn Malaysia (UTHM) infrastructure since its formation in 1993. The development will be accompanied with the increasing demand of electricity. Hence, there is a need to forecast the UTHM electricity consumption for future decisions on generating electric power, load switching, and infrastructure development. Therefore, in this study, the Fuzzy time series (FTS) with trapezoidal membership function was implemented on the UTHM monthly electricity consumption from January 2011 to December 2017 to forecast January to December 2018 monthly electricity consumption. The procedure of the FTS and trapezoidal membership function was described together with January data. FTS is able to forecast UTHM electricity consumption quite well.

Technological and operational reliability of power supply system

The article is devoted to choosing ways to improve the technological reliability of regional electric network (REN) to ensure reliable power supply. At the operational stage, the task of increasing operational reliability is assigned to the enterprise asset management system of the territorial network organization (TNO), as a REN operator. Technological reliability is ensured by an operational dispatch control system, which uses the existing reserves in the network to support the technological process of electricity supply to electricity consumers in case of network equipment failures. The relevance of improving the technological and operational reliability of power supply system (PSS) requires the development and improvement of methods for analyzing and assessing the TNO's readiness to provide power transmission services. The indicators adopted in Russia reflect the level of technological reliability of PSS. However, these indicators do not reflect the technical condition of the equipment, or identify causal relationship between an equipment failure and an interruption of power supply. The research is aimed at identifying “bottlenecks” from the technological reliability standpoint and substantiating maintenance and repair, and technical re-equipment and reconstruction measures to improve operational reliability. A PSS model is proposed reflecting the technical condition of the network equipment, the operational readiness of automation systems, the availability of structural, functional and load redundancy in the REN. A method is suggested for calculating the PSS reliability indicators, where the developed indices reflect the degree of development of the network technical potential and the role of the aforesaid nodes in the PSS. The method makes it possible to identify the network parts, where it is necessary to introduce new technologies. In contrast to a well-known method, which is based on expert estimates of probabilities of different circuit-mode states of the network and on the calculation of normal and post-emergency modes, a less timeconsuming formalized procedure for analyzing and evaluating the network structural and functional reliability is proposed. The results obtained allow to increase the validity of the decisions made both at the operational stage and the design stage.

Reliability assessment for traction power supply system based on Quantification of Margins and Uncertainties

The traction power supply is a crucial part of high-speed rail network. A failure of the traction power supply system may lead to delay or outage of high-speed trains that will not only have direct impact on the entire operation schedule but will also cause tremendous losses. Therefore, the reliability assessment of the traction power supply system is extremely important to ensure the transportation quality of high-speed trains and improve the economy. This paper presents a reliability evaluation method for the traction power supply system based on Quantification of Margins and Uncertainties (QMU). Firstly, the characteristics of the traction power supply equipment and system are combined to establish the observation list and then the performance channel for the equipment and system is determined. Finally, the confidence factor is calculated and the reliability of the equipment and system quantified by the quantification of the performance margin and uncertainty. In order to validate the effectiveness of the proposed method, simulations are conducted using practical operation data from a China traction power supply system. The simulation results demonstrate that the proposed reliability assessment method can account for the uncertainty and quantify the system reliability index. The proposed method has good applicability and can be used to effectively evaluate the reliability of the traction power supply system.

Combined Way of Diagnostics of Reinforced Concrete Conical Structures

Reinforced concrete conical structures are the basis of safety and operational reliability of railways power supply systems. The article presents optimal methods for diagnostics of reinforced concrete structures, which allow recommending the sequence and amount of repair work aimed at restoring or maintaining the required state of reinforced concrete conical section structures (contact-line supports, power transmission line supports, etc.). A design scheme is proposed for determining the residual bearing capacity of the support in the presence of cracks and corrosion of the reinforcement.

ENHANCED EFFICIENCY OF PROTECTION OF RAILWAY POWER NETWORK SECTIONS BY SECTIONING POSTS WITH DISCONNECTORS

ABSTRACT The article considers features of a scheme of protection of sections of a power network with disconnectors at a sectioning post (SP), its advantages and disadvantages are shown. A solution is proposed that allows improving the scheme under study and enhancing reliability of a traction power supply system. The power circuit of a two-track section of the catenary with disconnectors and a switch at SP, schedules of selectivity of protection of switches of adjacent traction substations and switch of SP, and also their time characteristics are shown. The sequence of actions connected with supplying current to the disconnected section of the network under the proposed protection scheme is considered. Keywords: railways, power network, catenary, sectioning post with disconnectors, traction power supply, short circuit, non-selective protection system, cross-link protection system, time delay.

STATE OF THE ISSUE OF THE POWER SUPPLY SYSTEM'S RELIABILITY

The electric power system of the Russian Federation was most developed in the 80-90s of the last century, after which there was an almost twofold decline in the generation and transmission of electrical energy in the system with subsequent growth. The main problem of fuel and energy complexes is the progressive aging of fixed production assets in conditions of increasing energy consumption requirements, which is a source of increased risk of major accidents. In this case, negative disturbances can arise both in the system itself and be external to it and can lead not only to a low quality of electrical energy but also to interruptions in power supply. The studies carried out to date are devoted to a quantitative assessment of the reliability of power supply systems and their equipment and do not take into account the effects of electrical equipment failures on the characteristics of production processes and the operation of technological machines. To consider the reliability of power supply systems in isolation from the operation of other systems (technological, relay protection, automation, ventilation, dewatering, etc.) means not to use the whole range of measures aimed at improving the reliability of electricity supply, as a result it is impossible to ensure the optimum level of reliability of electricity supply. Reliability of the power supply system must be evaluated taking into account the interaction of electrical equipment with the equipment of all production systems. The problem of increasing the efficiency of the functioning of industrial enterprises by optimizing the parameters of the reliability of power supply systems is topical and of great economic importance.

ELECTRIC SUPPLY OF UNDERGROUND CONSUMERS OF DEEP ENERGY-INTENSIVE MINES

The increase in the capacity of cleaning and construction vehicles for highcapacity and energy-intensive mines calls for an increase in the supply voltage of cleaning and tunneling combines, as well as transport systems: from a voltage of 660 V switched to 1140 V, and now to 3300 V. This allows improving technical and economic indicators for clearing and access areas, as well as improving the reliability of local Power Supply Systems (PSS). However, this trend prevents the supply of underground electric networks with a voltage of 6 kV, in connection with which the problem arises of increasing the voltage of supply networks. To date, it has become possible to apply the 10 kV voltage to the operation, which is most acceptable for the use of electrical equipment for electrical networks and protection devices. Leading educational, research and design organizations were engaged in research on this issue. An analysis of the results of the research showed that switching to 10 kV voltage is justified and timely. At the same time, 35 kV voltage is not removed from the agenda, which is technically feasible and economically justified, but there are problems with the safety of its operation in underground workings, which requires appropriate refinement. This level of voltage will improve the quality of electricity.Conclusions: 1. Application of 35 kV voltage in the underground power supply system of coal and ore mines is advisable at a depth of more than 1000 m with a maximum load of at least 1000 kVA at the level of the stem cables.2. Application of 35 kV voltage in underground electrical networks will allow to significantly improve the quality indicators of voltage, reliability, and economy of the system due to the current unloading of the most important element of SES, such as stem cables.3. Analysis of the main parameters and characteristics of electrical mine electrical equipment gives reason to believe that it allows implementing a trend of 35 kV deep input to deep horizons of mines (mines) and placement of 35/6 kV substations on working horizons.

Influence of failures of overhead lines on reliability of autonomous power supply system

We research influence of failures of overhead lines on reliability of autonomous power supply system with distributed generation in the given article. Simulation of failures of overhead lines are done on the base of long-term data of exploitation distributing electricity networks. Considered autonomous power supply system consists of wind and solar power stations. Diesel generators are emergency sources of electricity in the system. For adequacy estimation of electricity supply we many times simulated and analyzed of random states of autonomous power supply system. Results of experimental research confirm that detailed accounting of statistics of real failures of overhead lines increases of quality of reliability analysis.