kV Power Supply System Research Articles

Experimental determination of static characteristics of loads in nodes of a 6 kv power supply system

Subject of research: static characteristics of nodes of 6 kV power supply systems with asynchronous load.
 Purpose of research: experimental determination of static characteristics by active and reactive power, calculation of the reserve coefficient by static stability of a node with asynchronous load.
 Object of research: power supply systems with a complex load, which includes asynchronous motors.
 Main results of research: the results of an active experiment to determine the static characteristics of the load node are presented. The measurements were carried out using devices that record the quality of electricity. Voltage regulation was carried out by the RPN device, the current transformers on the input switch were selected as the connection point of the device. Static characteristics of active and reactive power were constructed using interpolation and extrapolation tools. The critical voltage of the load node is determined. The coefficient of static stability margin is determined.

Power flow analysis of 110kV power supply system based on PowerWorld

With the growing global interest in various economic and environmental benefits of the power system, it is essential to ensure the safe and stable operation of the power grid. The optimal power flow calculation method is studied using the PowerWorld and Newton-Ralfsnn methods. The results calculated by the Simulator LP OPF function are compared with the manual calculation of the 110 kV power supply system grid. After optimization, the total cost is saved by 623.05 ¥/h. The simulation results can directly and vividly reflect the power distribution and optimize the power supply and distribution power flow.

Series Capacitive Compensation to Increase the Railway Traction Power Supply System Transmission Capacity

The article addresses the problem of improving the numerical analysis and operation of series capacitive compensation (SCC) units in the return wire of 25 kV power supply system traction substations to increase the railway capacity. Numerical analyses of the SCC impedance for two versions are considered: according to the condition of voltage equalization in the traction substations power supply arms and according to the condition of minimizing the negative sequence voltage. It is shown that the existing regulatory documents correctly place focus on the SCC impedances determined from the condition of ensuring equal power supply arm voltages. It is also shown that for numerical analyses of SCC impedance, the connection of the 110(220) kV power supply line impedances should be taken into account. To this end, it is proposed to connect, in the equivalent analysis circuit diagrams, two adjacent substations to the external power supply system through an equivalent delta of the impedances of 110(220) kV power lines. To effectively increase the voltage in the traction network while maintaining the minimum equalizing current values, it is advisable to connect the SCCs at both adjacent substations. In so doing, the no-load voltage values should be kept at the same level to reduce the equalizing current first component, which is determined by the difference of the transformers’ no-load voltages. It is shown that the connection of the SCC does not entail a growth in the equalizing current second component, which is determined by the difference of voltage losses at adjacent substations, including the voltages across the SCCs. If the SCC is connected at only one substation of the inter-substation zone, it is advisable to introduce automated control of the transformer OLTC at the substation without an SCC with a limited number of switching operations (up to 10 per day) with increased loads in the traction network.

Модель совместной работы системы тягового и внешнего электроснабжения

Purpose: To improve record accuracy of external power supply network influence on the operation of traction power supply systems of industrial frequency AC. The article shows that existing mathematical models of traction and external power supply joint operation have sounding limitations. These limitations almost exclude the possibility of their practical use. At the same time, when projecting a new electrification, it is required to choose the most efficient external power supply scheme. At the exploitation of existing electrified sections, the necessity arises to assess equalizing current value during repairs in external power supply networks and to adopt a decision on changing power supply and sectioning schemes. Corresponding model is required to solve these tasks. Methods: Analysis of existing mathematical models and computer programs for joint calculation for traction and external power supply networks. Development of three-phase PU-generator models on the basis of EMF source behind an inductive resistance, development of three-phase and single-phase load models. Results: The article presents a description of a mathematical model implied to study the joint operation of 25 kV AC traction power supply systems and 110-750 kV power supply systems. The principles of building the model of three-phase and single-phase PU-generators on EMF source basis behind inductive resistance as well as the models of three-phase and single-phase loads are considered. Based on the given mathematical expressions, a computer model has been developed that allows analyzing the joint operation of three-phase external power supply networks and single-phase traction ones. The model is implemented in MATLAB-Simulink software package. Using this computer model, the influence of power flows through 110–330 kV network of Karelenergo and “FSK EAS” Public Companies on equalizing currents in the traction network of Knyazhaya — Idel section of Oktyabrskaya railway was analyzed. Practical importance: The reliability raise for traction power supply system operation at the expense of precise calculation of equalizing currents. Energy loss reduction in a traction network in account of traction network optimal power supply scheme choice.

On the issue of effectiveness of the oil production electrical equipment repairs management with a strategy for technical condition

PURPOSE. To consider aspects of solving the complex problem of reasonable choice and assignment of the repair management strategy for the equipment of power supply systems of oil production consumers according to the actual technical condition. To form a methodology for assessing the comparative effectiveness of repair management strategies: «By frequency, running hours» and «By technical condition». To verify the performance of the integrated methodology. Justify and demonstrate the effectiveness of the repair management strategy: «By technical condition» of the equipment on the real example of the typical scheme of the electrical supply system of oil fields.METHODS. In solving the problems set: the method of block diagrams for calculating the structural reliability of electric distribution network, including the probabilities of power supply failure in the circuit of each technological consumer, taking into account the possibility of redundancy and imposing an emergency restoration of the main element on the planned repair of the reserve, the method of hierarchy analysis for integral assessment of the actual technical condition of electrical equipment 6 (10) kV, method of calculating the mathematical expectation of damage from technological losses of oil production to assess the severity of the consequences of disruption of electricity supply to consumers of oil production, the method of expert decisions to adjust the regulatory periodicity and frequency of scheduled repairs of equipment, depending on the actual value of technical condition index.RESULTS. The relevance of the research direction is substantiated. Computational methodology of comprehensive assessment of comparative efficiency of equipment repair management strategies in oilfield power supply system «By frequency, running hours» and «By technical condition» to justify the priority of one of them has been formed. On a concrete computational example the preference of strategy choice «By technical condition» is proved as applied to the equipment of 6(10) kV power supply systems of oil fields.CONCLUSION. The developed methodology and its validation on the example of a real power supply system allows to substantiate and illustrate the effectiveness of the strategy «By technical condition» in comparison with the strategy: «By frequency, running hours» in relation to the management of repairs of oil production facilities.

Інтелектуальна система контролю та прогнозування величини струму витоку електрообладнання установок для теплової обробки і сушіння зернової сировини

One of the effective technical methods of protection against electric shock for heat treatment and drying of grain raw materials is the use of protective switching devices. The use of more advanced devices, which include a leakage current analyzer, allows you to warn and warn service personnel against electric shock and clearly reflect changes in the insulation strength of electrical equipment. The aim of the study is to analyze the existing protective equipment that operates and provides protection by controlling the magnitude of leakage currents and proposing a technical solution that will provide, in addition to protection based on leakage current control, also early warning of the possibility of insulation thresholds. To provide automated real-time control, a technical solution based on the ATmega microcontroller has been developed. The device includes a zero-sequence current transformer to the terminals of the secondary winding which is connected to a protective unit with a leakage current analyzer. The use of a protective switching device, additionally equipped with a leakage current analyzer unit, will allow monitoring the amount of leakage current, warning and informing service personnel about the appearance of dangerous leakage current in 0.38 kV power supply systems for heat treatment and drying of grain.

The Program for Determining the Optimal Location for Installation of Symmetry Facilities in 0.4 Kv Power Supply Systems with a Motor-Drive Load

The article considers the issue for development of the computer-aided program designed for determining optimal location of installation of symmetry facilities in 0.4 kV power supply systems with the motor-drive load in conditions of imbalance of voltages. The program is aimed at making electrotechnical calculations during designing, modernization and operation of electrical grids with available motor drive load. It ensures plotting of schematic circuits for 0.4 kV power supply system sections with installed symmetry facilities. The software program provides for calculating different symmetry options and selecting the most economically feasible one. Using the program in motordrive load power supply systems will enhance the asynchronous motor reliability and efficiency. The program is of interest during development of the power supply system projects for the regions with available non-linear loads

Choosing the type of equivalent circuit of traction substation when calculating short-circuit currents in 25 kV power supply system

When calculating short circuit currents in the traction network, it is necessary to take into account the input resistance of the traction substation, including the resistance of the transformers of the substation and the resistance of the power supply system. The input resistance during short circuit is determined based on the equivalent circuit of the external power supply system, of which this traction substation is an integral part. Traditionally equivalent circuit of a three-phase system has the form of a star, in which the resulting resistances in each phase are connected in series with a source of phase electromotive force, and these sources have a common point. Another equivalent circuit in the form of a triangle is possible, in which on each side the resulting resistances are connected in series with the source of linear electromotive force. It is important to note that neither one nor the other type of equivalent circuit is determined by the connection scheme of the transformer windings of the traction substation. It is only necessary to take into account the absence of a circuit for zero sequence currents. All elements of the equivalent circuit, as is known, should be brought to uniform basic conditions. If the parameters of these elements are expressed in named units, then the basic values are the effective voltage values of the main stage and the rated power of the power transformer of the traction substation. If the components of one and the other equivalent circuits are reduced to one stage of the operating voltage, for example 27.5 kV, then for the same elements of the power supply system, the resistance values in the equivalent circuit in the form of a triangle are three times larger than in the equivalent circuit in the form of a star. In this case, the input resistances of the traction substation for the one and the other equivalent circuits are absolutely identical. Therefore, in the calculation of short circuit currents of the traction network, you can use any of these equivalent circuits of the power supply system and traction substation. Formulas for calculating the resistances of the elements of the power supply system and electrical installations, given in the standards, manuals and reference books, relate to the equivalent circuit of the short circuit in the form of a star. When using an equivalent circuit in the form of a triangle, these resistances must first be tripled, and then divided by three when calculating the short-circuit currents. The meaninglessness of such an operation is obvious. The equivalent circuit of the traction substation and the external power supply system in the form of a triangle when calculating short circuits in the traction network has no advantages compared to the traditional equivalent circuit in the form of a star. The information on the linear currents on the primary and secondary windings of the traction substation transformer during a short circuit in the traction network is given, which is necessary to select the settings of its relay protection kit.

Researching and modelling of unbalanced regimes in systems of household electric power consumers

The modelling of the operation modes of the 0.38/0.22 kV power supply systems by the Monte Carlo method using the Electronics Workbench computer program is considered, and statistical processing of simulation results and testing of the Pearson distribution law hypothesis using the Mathcad program are carried out. An analysis of existing power supply systems has been carried out and an alternative, economically feasible version of the power supply system is proposed, where consumers are powered by low power transformers mounted on supports. The performed studies showed that the variation of the load currents in the segments and the losses of electric energy in an asymmetrically loaded network of 0.38/0.22 kV are subject to the normal distribution law and that the consumers who feed on the traditional power supply system have unsatisfactory quality of electrical energy.

Energy efficiency improvement of 0.4 kV power supply systems in the far North districts

The article considers the method of energy efficiency improvement of 0.4 kV power supply systems for the enterprise located in the North of the Krasnoyarsk territory. The theoretical substantiation of the necessity of reactive power compensation is presented. The method for reducing reactive power in power supply networks through the use of devices compensating reactive power is proposed. The use of this method allowed reducing energy costs, as well as decreasing the level of reactive power in the network by 48.5% and 45% for the 1st and the 2nd inputs, respectively. Also, while using reactive power compensation devices for power supply networks, the following indicators can be achieved: the increase in the throughput capacity of electric networks, the reduction in active power losses and the rational electric energy use.

Ensuring electrical safety of power supply systems of electrified AC railways for highspeed lines

Abstract. High-speed railways are fast-growing and promising type of traffic. In Russia development of high-speed railway service is associated with the solution of a number of problems, including infrastructure. Authors propose to use earth connection of the railway catenary with the help of an artificial earthing switch on currently designed high-speed line Moscow—Kazan for 2×25 kV power supply system. Taking into account requirements for electrical safety conditions for maintenance of the track and earthed catenary supports, paper justifies method for calculating allowable voltages of rail—earth points and supports of catenary. Methods takes into account structural features of ballastless track superstructure used for high-speed lines. It is estimated that the voltages admissible under the electrical safety conditions are random in nature and distributed logarithmically normal. When calculating probability of safe operation, one should take into account random nature of both permissible stresses and those actually occurring on the track. It is estimated that the probability of safe operation in traction networks of sections with ballastless track superstructure does not exceed a similar value in electrified sections with the conventional structure of a ballast prism. Feasibility of using a 2×25 kV earth system using an artificial earth connection is confirmed, recommendations on its use are given. Authors substantiate allowable values of the rail—earth voltage and catenary supports, which practically exclude the occurrence of hazardous situations for personnel maintaining the track in sections with ballastless track superstructure.

Influence of High-Speed Train Power Consumption and Arc Fault Resistances on a Novel Ground Fault Location Method for 2 × 25 kV Railway Power Supply Systems

The 2 × 25 kV power supply system is the most frequently used traction rail system to provide the huge power needed by high-speed trains. However, locating the ground fault in this power supply system is more complicated than in other configurations of electrical railway power supply due to the installation of autotransformers throughout the line section. In previous papers, the authors have described a ground fault location method with an insignificant installation cost. The method and, moreover, the location discriminate between whether the ground fault is located between a positive conductor and ground or a negative conductor and ground. The current of the high-speed train influences the accuracy of the location of the ground fault. An additional factor which influences the location method is the existence of an arc resistance between the positive or negative conductor and ground. In this paper, the influence of high-speed train currents and arc resistances are analysed to evaluate the error in the location method. The major conclusion of the paper is that the location method has an acceptable precision even taking into consideration the high-speed train current and arc resistance. The validation of the method has been performed by laboratory tests and computer simulations with satisfactory results.

Determination of optimal location for installation of symmetry facilities in 0.4 kV power supply systems with motor-drive load

This article considers the issue for creation of computer-aided program designed for determination of optimal location for installation of symmetry facilities in 0.4 kV power supply systems with motor-drive load in conditions of asymmetry of voltages. The developed program is implemented by means of C# programing language in Microsoft Visual Studio 2012 programming environment using the embedded cross-platform data base SQLite. The program is designed for making electrotechnical calculations during designing, modernization and operation of electrical grids with available motor drive load. It ensures plotting of schematic circuits for 0.4 kV power supply system sections with installed symmetry facilities. The program will enable quick and exact calculation of power capacity loss, determination of economic feasibility for taking special measures to eliminate the asymmetry of voltages, and to determine optimal application and location of symmetry facilities. Using the program in motor-drive load power supply systems will enhance the asynchronous motor reliability and efficiency.

POWER SUPPLY SYSTEM WITH THREE-PHASE TRANSFORMERS FOR HSR

[For the English abstract and full text of the article please see the attached PDF-File (English version follows Russian version)].ABSTRACT The article presents a schematic diagram of a traction substation of the 2x25 kV power supply system with three-phase transformers and a vector voltage diagram for high-speed lines. Power supply systems 2x25 kV with single-phase and three-phase transformers are compared, the power of three-phase transformers for high-speed main lines is recommended. And all this taking into account the new special technical conditions that are worked out for the design, construction and operation of Russian HSR. Keywords: railway, high-speed railway, traction substation, 2x25 kV power supply system, three-phase transformer, single-phase transformer, special technical conditions.

Software for optimal selection of places for installation of balancing devices in 0,4 kV electric power systems loaded with electric motors

This publication considers the issues of development of the software program for designing of 0,4 kV power supply systems with motor-actuated load under voltage unsymmetry conditions (using the example of the Trans-Baikal Territory). Voltage unsymmetry is practically constant phenomenon in the electric power networks of different voltage types. Voltage unsymmetry effects significantly the electric power consumers, including the supply mains itself. It has especially negative impact on the electrical equipment operation process and its lifetime. The urgency of the problem is confirmed by multiple research on the same topic and by significant number of damages suffered by the electric power consumers staying in service (especially in the Trans-Baikal Territory and in the Far-East regions). Voltage unsymmetry causes economic loss and reduction of the electromagnetic interference value by the voltage unsymmetry coefficient in negative-phase sequence (K 2 U) gives inevitable economic effect accordingly. However, the payback period for the activities aimed at reduction of electromagnetic interference, will vary from some months to several years. The more accurate value of the payback period may be obtained using the developed software program. The developed software design program is implemented by means of the programming language C# in Microsoft Visual Studio environment, using the built-in cross-platform database SQLite. The software program shall allow making quick and accurate calculation of the power losses, to determine the economic feasibility of provision special measures for removal of the voltage unsymmetry, for determination of optimal application and location of the balancing devices. The software implementation in power systems loaded with electric motors will improve reliability and efficiency of asynchronous motors. The software is of interest for developers of projects on power supply systems for regions with non-linear loads.

ANALYSIS AND FORECAST OF ACCIDENT RATE OF 6 – 10 KV DISTRIBUTION GRIDS AND POWER CONSUMERS IN THE MINING SECTOR

The main types of accidents in 6–10 kV power supply systems of mining enterprises are considered, such as short circuits, single-phase earth faults, phase failures, with their percentage relationships established. Mining enterprises are divided into three groups: open-cut mining enterprises (quarries and open coal pits); enterprises for extraction of minerals by underground method (underground coal and ore mines); mining & processing enterprises (concentrating factories, alumina plants, fertilizer production enterprises). The analysis of the accident rate of power supply systems of mining enterprises carried out for the period from 1995 to 2015 makes it possible to trace the dynamics of the above types of accidents and determine their most common form — single-phase earth fault. Over the above period, in the 6 – 10 kV power supply systems of quarries and open coal pits, underground coal and ore mines, and mining & processing enterprises, the share of single-phase earth faults was found to be within the following ranges: 65 – 76%; 60 – 69%; 58 – 67%, respectively. The greatest increase in accidents during the period under review was observed in 6 –10 kV power supply systems of quarries and open coal pits; with the total accident rate having risen with a factor of 3.21 from 1995 to 2015. The accident rate growth factor for underground coal and ore mines, and mining & processing enterprises amounted to 2.06 and 2.72, respectively. The changes are shown in specifi c types of accidents and general accident rate in the systems of electricity supply to quarries and open pits, underground coal and ore mines, and mining & processing enterprises. It is established that in the 6 – 10 kV power supply systems of the above-mentioned mining enterprises, the changes in single-phase earth faults and general accident rate are described by linear equations. On the basis of established patterns, a forecast is made of the change in the accident rates in power supply systems of the mining enterprises under consideration up to the years 2020 ÷ 2025.

Research on Centralized Short-Circuit and Leakage Protection for High-Voltage System of Underground Central Substation

According to the problems which are relay protection is difficult to adjust and when line fault occurs it will easily get override trip in the underground 6 kV power supply system in Gu Shu-yuan Coal Mine. This paper presents a centralized selective short circuit and leakage protection system. Which focuses on the analysis of the short circuit longitudinal differential protection, based on pattern recognition method of single-phase earth leakage protection principle, and completes the rapidity and selectivity of the leakage fault line selection . Through the simulation, experimental and field operation shows that the schemes can effectively improve the reliability and safety of high voltage power supply system in Gu Shu-yuan Coal Mine ,it also establishes the necessary foundation of the goal of "network relay protection" in high voltage power supply system for in China.

Failure of the London Underground's 22 kV power supply system – an exercise in logic and transport management

The power supply to the north-east sector of London Underground Ltd's Central Line, and therefore the train service, was out of service for the majority of the time between the 24th and the 29th November 1993. During this period the power system faults were investigated, identified and corrected. This incident was the most extensive power fault on London Underground's power supply system in its recent history. The key cause was identified as an earth fault on a neutral cable of an alternator, which was located several kilometres from the part of the network that became inoperative. London Underground's power 22 kV generation and distribution system is described, and the feed arrangements historically made to minimise the possibility of such an extensive outage are explained. The events leading to the loss of supply, subsequent identification and correction of the underlying main fault are described, and a model of the 150 Hz harmonic earth-return current, which was the immediate cause of tripping owing to a series resonant circuit condition, is included. The effect of the neutral cable fault was to increase the 150 Hz current to the point where it caused simultaneous multiple feeder breaker trips from earth-fault relays for the feeders supplying the north-east sector of the Central Line, resulting in loss of power to that sector. A comparison is made between the model and practically measured results.