Microprocessor Protection Research Articles

The Use of Emergency Components as Input Information Signals for Microprocessor Protection

The Use of Emergency Components as Input Information Signals for Microprocessor Protection

Dependability factors of microprocessor protection software

Dependability factors of microprocessor protection software

ОГЛЯД МЕТОДІВ РОЗРАХУНКОВОЇ ПЕРЕВІРКИ ТРАНСФОРМАТОРІВ СТРУМУ, ЯКІ ПРАЦЮЮТЬ В КОЛАХ РЕЛЕЙНОГО ЗАХИСТУ

Systematized existing methods of calculation verification of current transformers that work in the circuits of modern relay protection devices. The requirements of the Ukrainian rules for the arrangement of electrical installations differ from the requirements of the standard of the International Electrotechnical Commission IES 61869-2. The difference concerns the absence of contact vibration and not exceeding the maximum allowable current error of 50% in the case of an internal short circuit is a separate case of the requirements for electromechanical protections and these requirements cannot be used for microprocessor protection devices. For any relay protection device, there is no concept of the permissible value of "voltages at the current inputs". The voltage at the terminals of the secondary winding and the voltage at the "input of the relay protection device" are two completely different voltages. There are no methods for calculating errors in the case of switching on protection based on the sum of the currents. Companies producing microprocessor relay protection devices specify in their instructions individual requirements for current transformers for each individual device. Compliance with these requirements guarantees the correct operation of the relay protection even for large values of the time constant of the primary network. Leading manufacturers of microprocessor relay protection devices develop and recommend software tools for checking the correct selection of current transformers. But they are not freely available. To increase the accuracy of the calculation of the limit multiplicity, it is advisable to use complex supports of the secondary winding and load of current transformers. Depending on the initial data and conditions, the permissible load resistance can be calculated using four methods. The question of whether the allowable load of a current transformer can exceed its nominal load requires further research. The scientific novelty is consists in the systematization of existing methods of calculation verification of current transformers that work in the circles of modern relay protection devices. The practical significance of the work is that checking current transformers that are connected to microprocessor relay protection devices do not need to check the maximum permissible current error of 50%; to check the correct operation of microprocessor relay protection devices, it is advisable to use the instructions for the requirements for current transformers of device manufacturers; for a more accurate calculation of the limit multiplicity, it is advisable to use complex supports of the secondary winding and load of current transformers.

Improving of Functioning Stability of Current Measuring Elements in Microprocessor Protections

In the measuring elements of the current of microprocessor protection, the controlled values are usually the effective values of the fundamental harmonic of the currents. They are determined by the orthogonal components of the input signals, which are formed by digital Fourier filters. Due to the inertia of these filters, the time for obtaining reliable effective values is one or more periods of the input current, which mainly determines the speed of the measuring element. When the frequency of the input signal deviates from the nominal value, its effective values become oscillatory. As a result of this, unstable functioning of the specified organ may occur at current values that are close to the operation and return areas. To increase the speed of the measuring body, it is proposed to determine the effective value of the current by multiplying its value obtained using the orthogonal Fourier components by a correction factor. To ensure the stable functioning of the current organ, it is recommended to filter the effective current value using a digital moving average filter. Evaluation of the effectiveness of the proposed solutions has been carried out by the method of computational experiment using thedynamic simulation environment MATLAB-Simulink. The proposed solutions provide an increase in the speed of the current measuring organs and their stable operation when the frequency deviates from the nominal. As a result of the research, it has been found that the proposed digital current measuring organ in comparison with an organ based on the Fourier algorithm has a speed of 1.4-2 times greater. In addition, it functions stably both under the condition when the tripping current is less than the fault current, and in the case when the indicated currents are comparable when the frequency deviates from the nominal by ±2 Hz. The proposed digital measuring body can be used in many microprocessor-based current protection of electric installations.

POSSIBILITY OF BUILDING MICROPROCESSOR RELAY PROTECTION DEVICES ON OPEN ARCHITECTURE

"The article analyzes the structure of relay protection devices of various designs. Based on the Unified Electric Power System of the Republic of Kazakhstan prediction on the electric energy balance the plan to increase the generation of electricity due to the commissioning of new capacities was revealed In addition, the international market of the energy sector and a preliminary forecast for the total demand for energy separeted into the declared scenarios and the scenario of sustainable development of electricity generation, cumulative average annual growth rate, electric capacity by countries, continents and regions were studied. It is determined that the type of power generation system and the fuel used affect the features of building and updating relay protection systems. The hypothesis of the study is the replacement of existing closed solutions on the market of relay protection systems with open hardware and software, which allow developing and applying then various power supply systems, including FPGAs. Within the framework of the study, solutions for building a microprocessor relay on an open architecture were proposed: a block diagram and a developed laboratory stand “relay protection microprocessor on an Arduino board”; «Relay protection microprocessor using FPGA». Comparative data on the characteristics of the boards are presented, where the FPGA board is more effective in all respects. The program was developed in the Quartus Prime 21.1 Lite Edition environment. Based on the results of the work, it can be noted that aim of the further research will be the expansion of the microprocessor relay protection devices based on an open architecture use. Keywords: relay protection, open architecture, FPGA, microprocessor protection, FPGA, automation, control"

Microprocessor protection of electrical motors against phase failure in external power supply network

Nonsymmetrical modes in the external power supply network during operation can be caused by several reasons: phase failure due to strong wind or glaciation of overhead power lines, wire burnout due to persistent short circuits, open phase automatic reclosing. In case of open phase condition, the external power supply network, synchronous and asynchronous electric motors are powered along the two phases that are in operation. It leads to the negative sequence current, which poses maximum danger for electric motors, since it causes additional heating and, as a result, premature damage. Therefore, the currently important goal of the project is to study transient processes of the motor load when an open phase mode occurs in the external power supply network and to design microprocessor protection of electrical motors against phase failure in the supply network. To achieve the goal, a computer simulation method is used, based on mathematical models of the elements of electrical network presented as the systems of differential equations in a three-phase coordinate system. The regularities of the flow of transient processes in synchronous and asynchronous electric motors in case of open phase modes in both the internal and external power supply networks have been established. Thus, it is possible to develop an algorithm of the operation of microprocessor protection of electrical motors against phase failure in the external power supply network. The proposed algorithm is based on monitoring the negative sequence current level and the absence of current in one of the phases at the section input. The obtained results show that the proposed algorithm to protect electrical motors against open phase modes in an external power supply network has a high selectivity. Its use as a starting element of the fast-acting automatic transfer switch device allows you to provide uninterrupted power supply for enterprises with a continuous technological process.

Comprehensive Automation of Microprocessor Protection Relay Terminals Operated on AC Railways

The article discusses the possibility of a potential reduction in the number of operations of microprocessor relay protection of feeders of the contact network of AC railways TsZA-27.5-FKS (FTS) for unknown reasons. Real statistics on the number of microprocessor relay protection operations at the Buryatskaya traction substation are presented, simulation of the real train situation (in accordance with the regime maps of the throughput capacity of the sections of the Trans-Baikal railway) was carried out in the specialized software complex “KORTES”. Based on the results of the analysis of simulation modeling, the process of forming a unified template of settings using neural network technologies is considered, which characterizes only this specific regular train situation. To protect objects in the event of pre-emergency and emergency modes of operation of the traction power supply system, a variant of changing the standard operation algorithm of the TsZA-27.5-FKS (FTS) terminal by introducing additional blocks for calculating the predictive functions of current and voltage has been proposed.

Automation of the Process of Measurement of Electrical Parameters in Microprocessor Devices of Relay Protection

The article continues a complex research of the operation of standard microprocessor protection of feeders of the AC overhead contact system DPA-27.5-TNF operated at the Zabaikal’skaya railway in regards to the possibility of obtaining the array of information in the online mode on the magnitudes of start-up and transient currents that flow in the traction network in different recurring modifications of the train schedule (TS). In the future, it would reduce the number of relay protection tripping events due to undetermined causes, thereby increasing its selectivity.

MODERN MICROPROCESSOR PROTECTION OF POWER TRANSFORMERS

The purpose of the present study was to understand what advantages and disadvantages in the operation of microprocessor devices in the RZA, to analyze the main series of microprocessor protection, their advantages, disadvantages and features, to review microprocessor protection in the labor market. Based on this, conclude the relevance and acceptability of microprocessor protection in general. The study examined several companies that are engaged in microprocessor protection. Comparing microcontrollers is challenging. Usually, each crystal manufacturer offers its own tests, developed personally by him, showing that its microcontroller is the best. Therefore, their comparison was also made taking into account the characteristics of the relay protections themselves based on microprocessor data.

DEVICE FOR DETERMINING THE VALUE OF THE STEADY-STATE ELECTRICITY IN THE PRIMARY CIRCUIT USING A REED SWITCH AND A MICROPROCESSOR

This article discusses an innovative device designed to determine the value of the steady-state current in the primary circuit of electrical installations using reed switches and a microprocessor without the use of current transformers. The typical structure of relay protection devices is considered. The main elements are presented. When choosing a primary converter, a reed switch was taken, because it has certain advantages over current transformers. As part of the research, experimental installations for measurements were assembled. They made it possible to emulate the real conditions in which the relay protection devices have to function, unnecessary and to depict the characteristics of future devices. The code is presented that allows the microprocessor device to function according to the laid down algorithm. A device on a reed switch and a microprocessor is presented, which allows transmitting a certain amount of current in the primary circuit in digital form (binary code) to the microprocessor protection. The presented measuring device made it possible to implement a method for determining the magnitude of the steady-state short-circuit current.

Development of universal algorithm of voltage circuits detecting faults of microprocessor protection and automation devices

Reliability, along with response speed, sensitivity, and selectivity, is the key requirement for relay protection (RP) devices. The reliability of modern RP digital terminals is understood as protection operation for all estimated failure modes and failure of protection equipment to operate in all other modes, in which this protection is not provided. Analysis of the secondary voltage schemes and algorithms of detecting faults in these circuits reveals several disadvantages of the implementation of blocking in case of faults in voltage circuits. All existing algorithms and blocking schemes in case of faults in voltage circuits suffer from several disadvantages. In this regard, it is relevant to develop a universal relay protection terminal, which can be used with any types of voltage transformers. The MatLAB Simulink is used to simulate the primary failure of secondary circuits for the connection schemes of the voltage transformer load on phase and electric line voltages. The authors propose the algorithm that allows us to create a typical universal RP terminal, which can be used with any type of voltage transformers. To detect the neutral conductor interruption of the «star» circuits, it is proposed to create an artificial asymmetry at the input voltage circuits of the relay protection and automation (RPA) terminal and develop a group of fault detectors that analyze the position of the offset neutral on the voltage complex plane. Using a simulation model of various types of failure of voltage transformer secondary circuits and the logic diagram of the unit that implements the proposed algorithm, the authors graphically show that the detection of a break in the neutral wire is possible due to monitoring the zero-sequence voltage spike (triggering of the pulsed dU0 fault detector) with neutral displacement to the complex plane area, which is set by the setpoints. The results obtained allow us to implement a universal scheme of blocking faults in voltage circuits. This scheme does not depend on the voltage transformer secondary load connection method and exclude the disadvantages of existing solutions discussed in the article. This algorithm allows us to develop a typical universal RPA terminal. Due to its connection scheme and functional and logical implementation, this terminal can be used with any types of voltage transformer without reprogramming. Also, the proposed algorithm fully complies with the requirements of the current regulatory and legal documents.

Formation of Orthogonal Components of Input Currents in Microprocessor Protections of Electrical Equipment

The methods used in the microprocessor protection of electrical equipment for forming orthogonal components of input currents ensure their reliable isolation after changing the mode followed by one or more periods of the fundamental frequency. This is due to the inertia of the functional elements, in particular, digital frequency filters, as well as the saturation of the steel magnetic cores of current transformers. To increase the speed of the selection of orthogonal components of the input currents, it is proposed to form them as equivalent ones in terms of the cosine and sine components obtained using digital Fourier filters by multiplying by the resulting coefficient. The method that has been developed for determining the specified coefficient provides compensation for the delay caused by the inertia of digital filters, as well as the saturation of the steel of magnetic cores of current transformers. The proposed method of forming orthogonal components is highly effective in the modes of strong saturation of the magnetic core with a complex input action in the presence of an aperiodic component with a large damping time constant. The evaluation of the efficiency of the proposed method was performed using a complex digital model implemented in the dynamic modeling environment MatLab-Simulink. As a result of the performed studies, it was found that in the absence of saturation of the magnetic core of current transformers, as well as in the presence of a small and medium degree of saturation, the proposed method for forming equivalent orthogonal components of input currents has dynamic properties close to the ones of those that had been previously proposed. With a strong saturation of the magnetic core of current transformers, the speed of obtaining reliable values of these components is increased by 1.5–2 times.

Improvement of Algorithm for Formation of Orthogonal Components of Input Quantities in Microprocessor Protection

The use of orthogonal components (OC) underlies the construction of measuring elements of modern protection and automation devices. In most microprocessor-based protections, the orthogonal component of the input signal is extracted using a discrete Fourier transform (DFT). The DFT disadvantages are its low speed, which is more than one period of the fundamental frequency, as well as the sensitivity to the free aperiodic component, which creates significant conversion errors depending on the time constant of its decay. Such a settling time of the true output signal is often unacceptable for the design of high-speed measuring devices. The paper proposes to form the OC of the equivalent signal according to the values of the cosine and sine OC of the fundamental harmonic, formed using the DFT by multiplying them by the resulting correction factor. The developed algorithm for the formation of orthogonal components of input signals in microprocessor protections is characterized by high speed in transient modes and it has wide functionality. So, the proposed digital device for forming the orthogonal components of an equivalent signal, in comparison with digital filter based on the DFT, has an increased operating speed both in the mode of occurrence of a short circuit and during the decay of the monitored signal, while maintaining the same characteristics as in the DFT in other modes. A block diagram of the proposed digital device for forming the OC of an equivalent signal has been developed, all blocks of which can be implemented on a microelectronic and microprocessor element base. A digital model of the specified device has been developed in the dynamic modeling system MatLab-Simulink in accordance with the structural diagram. As a result of the calculations, a significant (up to two times) increase in the performance of the proposed digital device for forming the OC in transient modes has been established in comparison with the shapers based on the DFT.

Microprocessor protection terminals of traction substations: Study of connection variants

Microprocessor protection terminals of traction substations: Study of connection variants

Дослідження роботи дистанційного захисту в розгалуженій секціонованій лінії 10 кВ

The article investigates the parameters of setting up adjacent remote protections with remote start-up, taking into account the peculiarities of operating modes and operating conditions of partitioned branched distribution lines. The influence of parameters and modes of operation of such lines on the range of adjustment of settings on resistance and time of operation at the end of a zone of action and requirements to linearity of time characteristics that allows to define distances to a place of short circuit on operation time is defined. The results for setting up remote protections of partitioned lines with sources of distributed generation are obtained: the conditions for adjusting the protection settings for resistance to operation are determined taking into account the parameters of the partitioned lines and the limits of adjusting the settings for resistance to secondary values are determined. The conditions for adjusting the settings by the time of operation and the limits of the time of operation of protection for most lines are determined. For selective operation of protection at the selected settings on time of operation unambiguity of time characteristics at change of sizes of working currents of protection on condition of ten percent accuracy of work of protection on resistance of operation is provided. The conditions for ensuring the selective operation of adjacent protections in the selected range of settings by the time of operation, taking into account the ratio of resistances and the difference in the time of operation are determined. The initial time of protection protection is substantiated for debugging of protection on time of operation against operation of overvoltage limiters and against burnout of fusible insert of fuses of branches and unsoldering at short circuit directly behind the fuse. The use of modern microprocessor protection devices will ensure, on the one hand, the accuracy of the resistance, linear and unambiguous dependence of the operating time on the resistance of the short circuit at different levels of currents and voltages, etc., and on the other hand - ease of maintenance.

Идентификация элементов измерительной части цифровой релейной защиты по времени ее срабатывания

The purpose of the study is to develop an identification method of a specific implementation of the elements of the measuring part (intermediate converters, analog filters) and partially computational-logical part (digital filters) of a microprocessor relay protection by the signal actuation time, which, unlike the existing approaches allows to identify and exclude the delays introduced by the executive protection elements. The method of directed graphs is used to form a mathematical model of the measuring part of the microprocessor relay protection. The solution formed as a result of differential equations is implemented using the method of analog implicit continuous integration. The time delays introduced by the input protection circuits are determined as follows: identical signals are fed to the terminal and the mathematical model of protection; signal actuation time is recorded, where the time starting point is the moment the input signal reaches the setpoint and the end point is the moment of the actuation signal occurrence. Having studied 144 different combinations of measuring part elements (intermediate converters, analog filters) and digital filters with a finite impulse response of microprocessor relay protection, the most “optimal” combination has been chosen, which features the least deviation from the response time of a real device in all studied modes as compared with other combinations. The proposed identification method of input circuit elements of microprocessor (numerical) protection is the main way to bring the model closer to a real device. It also enables to receive a table of “typical” response times of protections with the different structure of the measuring part and depending on the specific type of protection terminal choose in practice a predetermined “optimal” internal composition of protection used when setting up protection using their mathematical models.

Increase of operation speed of digital measuring elements of microprocessor protection of electrical installations

Increase of operation speed of digital measuring elements of microprocessor protection of electrical installations

Reducing the Impact of the Frequency Change on the Formation of Orthogonal Components of the Relay Protection Input Signals

Digital filters made with the use of discrete Fourier Transform are applied in most microprocessor protections produced both in the home country and abroad. When the input signal frequency deviates from the value to which these filters are configured, a signal is generated at their output with oscillation amplitude that is proportional to the deviation of the signal frequency from the specified one. The article proposes an algorithm for compensating the oscillations of orthogonal components of the output signals of digital filters implemented on the basis of a discrete Fourier transform, when the input signal frequency deviates from the nominal one. A mathematical model of the proposed digital filter with an algorithm for compensating the oscillations of its orthogonal components, as well as a signal model for reproducing input effects, is implemented in the MatLab-Simulink dynamic modeling environment. The digital filter model is provided with two channels, viz. a current channel and a voltage channel, which makes it possible to simulate their operation in relation to protections that use one or two input values, for example, for current and remote protection. Verification of the functioning of the digital filter model with compensation for fluctuations in its output signal was carried out with the use of two types of test effects, viz. a sinusoidal signal with a frequency of 48–51 Hz (idealized effect), and the effects that are close to the real secondary signals of measuring current transformers and voltage transformers in case of short circuits accompanied by a decrease in frequency. The conducted computational experiments with deviation of frequency from the nominal one, revealed the presence of undamped oscillations at the output of standard digital Fourier filters and their almost complete absence in the proposed digital filters. This makes us possible to recommend digital filters based on a discrete Fourier transform supplemented by an algorithm for compensation of fluctuations in the amplitudes of the output signals for the use in microprocessor protection.

Creation of a learning microprocessor system for protection of contact network feeders using adaptive parametric identification methods

Handling of high-weight trains, double trains, packet traffic schedule, recuperation on electric locomotives often leads to false protection relays, downtime of trains and increased wear of power switching and protective equipment of traction substations. The paper proposes methods to improve the selectivity of microprocessor relay protection of feeders of AC traction substations contact network by increasing the accuracy of extraction of the first current and voltage harmonic based on phase locked circuits, integration of learning subroutines by fixing the electric parameters and creating the sets of dynamic setpoints in accordance with the current train situation and adaptive parametric identification of dynamic assessment of current electric parameters of the traction network. It also analyzes structural diagrams of hardware and software of the proposed microprocessor protection system of contact network feeders.

MIKROPROCESORSKA ZAŠTITA ELEKTROMOTORA

U radu se razmatratraju savremeni mikroprocesorski zaštitni uređaji čija je funkcija da zaštite električne motore kao najzastupljenije električne mašine u elektroenergetskom sistemu. Cilj je da se pri­kažu prednosti i različite pogodnosti primjene ovakve vrste zaštite koja omogućava pouzdanost, te detaljnu ana­lizu i predvidviđanje opasnih stanja u cilju njhovog spre­čavanja. Razmatranja su izvršena na primjeni zaštitnog uređaja tipa „Sepam M61“ za zaštitu elektromotora.