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EMTP models for simulation of shunt reactor switching transients
Abstract
Long EHV transmission lines are generally compensated by means of shunt reactor sets. Reactor failures have directed attention to the transient overvoltages generated by reactor switching. 750 kV site measurements have shown that arrester operations or breaker restrikes could cause particularly dangerous steep reactor voltages. The paper introduces a comprehensive EMTP-type model of the reactor and the surrounding system (busbar, breaker, arrester, transformer, supply side network). The computer model has been tested by field experiments. A similar computer model has been elaborated for the study of transients, caused by de-energising reactors connected with the 18 kV tertiary winding of the 420/132 kV autotransformers. The model has been validated using a pushing into service test of a new air core shunt reactor, equipped with SF6 circuit breakers. The computer models are easy to use for case studies, as well as in simulations to predict those variables which were not, or can not, be measured in the field tests. This paper introduces elements of the elaborated EMTP model, some steps of the model testing and verification. This paper contains the results of the computer analysis and of the field experiments.
... The effective reactance of a TCR is controlled continuously by partial conduction control (firing at different angles) but in TSR the effective reactance is controlled by full or zero reactance (no partial conductance by firing at variable firing angle). Several models [10]- [14] of TCR have been used for simulation in EMTP and the most commonly applied models are described in this section. ...
... 1) Simplified ATP Model of TCR [10]: Shunt reactor current interruption produces extremely high over-voltage due to the interruption of inductor current before its natural zero crossing. In order to investigate the turn-to-turn over-voltages a comprehensive computer model of the reactor and the surrounding network needs to be considered. ...
... 2) Detailed ATP Model of TCR [10]: The simplified model fails to provide any information about the internal stresses of the reactor and it would not be able to predict the local overvoltages accurately. Therefore, a comprehensive EMTP model is shown in Fig. 3(b) that is based on part inductively coupled elements. ...
This paper documents electromagnetic transient simulation models for conventional flexible AC transmission systems (FACTS) that do not employ voltage-sourced converter (VSC) technology. The FACTS controllers included in this document are classified into four categories: (1) shunt controllers (2) series controllers (3) combined shunt and series controllers (4) auxiliary controllers. Modeling techniques of these controllers are reviewed and the key aspects of each model are summarized. A comprehensive list of references is also included in this paper to provide further detailed information to the readers.
... However, today, shunt reactors are used for steady-state voltage control [9]. Therefore, during low load or no load periods, the reactors are normally connected to the lines and should be considered in the transmission lines energization studies [10]. In [11] and [12], studies on shunt reactors focus on transient states followed by energization and deenergization of the reactors. ...
... In Figure 14, the trapped charge voltage is smooth before the CB closing. This is because, according to Eqs. (10) to (14), the frequency spectrum of the PTCS has been determined so that the line voltage to be smooth before closing. As shown in Figure 15, the values of overvoltages are slightly higher in the presence of a shunt reactor due to the power frequency overvoltages. ...
Insulation coordination studies are of great importance in power grid reliability. In this paper, a new method is proposed for modeling trapped charge sources (TCS) in switching transient studies. The TCS is used to take account of the voltage stored in line capacitors during reclosing operation after fault occurrence. The proposed model is designed based on the active filter concept, so it does not have the limitations of conventional TCS for simulating transient states in EMTP/ATPDraw. Given the natural frequencies of the transmission line to which the proposed TCS (PTCS) is connected, the PTCS injects the appropriate frequencies and eliminates voltage oscillations, which limit the use of TCS. To verify the efficiency of the PTCS, it is implemented in a real system with a shunt reactor, and the results are then compared with field measurements. A comparison of the results shows that the PTCS eliminates the voltage oscillations in the simulation before closing and provides a smooth voltage with the desired amplitude. Using the proposed model, the maximum line switching overvoltage is correctly calculated; this, in turn, results in a more accurate transmission line insulation design, which is technically and economically beneficial.
... Thereby, especially the first windings of the transformer and the shunt reactors may be damaged. For a voltage stress distribution through the windings, detailed modelling of the transformer and shunt reactor is needed [7]. The DSO normally does not have this information during the project planning phase, but has to guarantee a safe operation throughout the years. ...
... For uchop = 0 (current chopping near current zero crossing) it results to (7). With the surge impedance Zw, it is obvious that with lower Cload (e.g. ...
In high voltage grids with a high amount of underground cables, the voltage limits might be exceeded due to the rising demand of reactive power. A common compensation method is the installation of shunt reactors, which are connected at the tertiary side of transformers or directly at the high voltage busbar. This article discusses the main influence factors of transient overvoltages during switching of these shunt reactors and analyses their effects on the equipment by transient simulations. Furthermore, the essential criteria and challenges for the design of circuit breakers and components regarding transients are shown. For safe operation, the transient stress must be below the maximum limits of all equipment and therefore different mitigation methods are introduced. In the end, a commonly used mitigation method, a so-called RC-Snubber, is designed for the tertiary side of transformers in a practical application.
... Studies were carried out using MATLAB/Simulink. In our studies we used the simplified grounded wye connected model of the 160 MVAR shunt reactor with the following parameters [4]: R = 12 M Ω/phase, L = 5.3 H/phase, r = 30 Ω/phase, C = 14 nF/phase. ...
... where U max -maximum operating phase-to-phase voltage of the SR (RMS); R -resistance of closing resistor; t -operation time of the closing resistor. The price of power resistors and CB installed in the neutral is in turn determined by the thermal stability in the case of SR load current flow (4). The load current is much smaller than the short circuit current. ...
The application of shunt reactors (both controlled and uncontrolled) on HVAC overhead transmission lines improves operational characteristics, but at the same time it brings the line closer to the resonance. Operation of the shunt reactor-compensated transmission line that is close to the resonance, causes a large number of problems which in particular can be solved by temporary tripping of the reactor(s). The article focuses on some aspects of the SF6 shunt reactor circuit breaker operations during one-phase and three-phase auto-reclosing. In particular, the problem of accident-free shunt reactor tripping, as well as possible ways to solve it are discussed.
... There have been and continues to be substantial research investigations into shunt reactor switching. Computer modelling of shunt reactors and other connected components has been studied in [3]. The study presented a comprehensive shunt reactor model which takes into acount both self and mutual inductances of the reactor. ...
... A timecontrolled switch with a chopping level of 10 A at each pole is used to model the circuit breaker. This model is regarded as the most simple alternative to breaker modelling and can be used to represent the air-blast type breaker and the SF 6 insulated breaker [3]. Furthermore, a capacitance element is placed across the switch to represent the grading capacitors of the circuit breaker. ...
This paper presents an analytical solution and computer simulations of switching transient overvoltages during the disconnection of shunt reactors. The interruption of reactor current provokes excessive overvoltages particularly across the reactor and the circuit breaker grading capacitor. The magnitude of these overvoltages may exceed 2 p.u. which, consequently, may jeopardise the insulation of the reactor and accelerate the ageing of circuit breaker grading capacitors. In this work, the transient overvoltages were computed using ATP/EMTP simulations and analytical solution of the equivalent circuit during switching. For different switching times the distribution of overvoltages and the influence of switching angle is presented.
... In [1] In addition to using surge arrester and RC snubber to address the problem of overvoltages, the effect of their installation position has also been investigated, and finally, after field testing, the performance of the solution has been proven. Articles [2][3][4][5][6] have examined switching overvoltages issues at the HV level. Given that the approach of this paper is to investigate the switching problem in MV reactor, studies on this voltage level have been of particular importance. ...
Abstract—Overvoltages related to shunt reactor switching is
one of the most important phenomena that has challenged the
operation of medium voltage circuit breakers. In the present
article, the overvoltages caused by switching of shunt reactor by
a 20 kV vacuum circuit breaker (VCB) are investigated and
some efficient solutions to control them are presented. This
study was performed on a real power network and the results
were presented for various considerations. Surge arresters and
RC snubbers are the most common and efficient tools for
controlling switching overvoltages. The use of these types of
equipment in different conditions has been studied and
compared with each other. This comparison has been performed
in two cases with and without the phenomenon of multiple reignitions. For a more practical study, compliance with the
requirements and related common standards is also included in
this study. Also, the effect of the switching instant on the level of
overvoltages and the phenomenon of multiple re-ignition has
been investigated. Finally, according to the conclusions of
various studies, a practical and appropriate solution for
controlling overvoltages is introduced.
... Often, the reactors are switched on and off several times a day due to changes in loads and transits on the electrical system. The study of the switching of shunt compensators and of the relative transient has been already discussed in [4][5][6]. ...
Stringent environmental constraints make the construction of new transmission overhead lines more and more difficult. Alternatively, today it is possible to use cable lines for high (HV) and extra-high (EHV) voltage systems. The configuration of the so-called mixed lines can create some problems in the operation of the electrical system, both during steady-state and transient conditions. In particular, the system stability is one of the main concerns when analyzing the dynamic response of power systems. In this paper, the study of angular stability of a system containing a mixed line is presented: a specific control logic applied to the shunt reactors of the mixed line is proposed as improvement of the overall system stability. The proposed switching logic is first discussed from a theoretical point of view and validated with two different testing systems. Then, the existing overhead-cable lines connecting Sicily to the rest of continental Europe 400 kV power system are taken as case study for the application of the proposed switching strategy. Several simulations are performed in the power system analysis software NEPLAN360: the results show the fundamental role of the timing of the control actions applied on the shunt reactors in helping the system to keep the stability. The proposed control proves to be an effective support to the system subjected to critical contingencies, contributing decisively to avoid the angular separation between areas and therefore to preserve the stability of the system.
... By this way, following the line disconnection, it is possible to trip the reactors out and eliminate the steady-state resonance overvoltages occurrence completely. It should be noted that this approach does not resolve the short-term phenomena such as reclosing problem due to capacitive coupling of adjacent lines and capacitive voltage drops [20]. ...
Shunt reactors are widely deployed as effective compensation means against the capacitive behavior of high voltage transmission lines. Subsequent to load rejection or light load conditions, a resonance phenomenon is highly potent due to remarkable capacitive feature of these lines. Reactor failure, threatening the interior insulation of high voltage equipment connected to the line, and early aging of insulations are some of the main concerns regarding resonance voltages. To study the phenomenon, different cases including complete disconnection of the transmission line, single and double pole operation of breakers, and short circuit faults on the de-energized line are simulated with two different knee points of reactor saturation. A sensitivity analysis is also conducted considering the soil resistivity and corona phenomenon. Different solutions such as neutral reactors and resistors, complete transposition of the circuits, capacitor bank and replacing the ground disconnector switches with breakers are examined in the worst case to limit the resonance overvoltage. In contrast to previous contributions, it is shown that when the shunt compensation reactor is not appropriately determined, none of the solution methods alone can resolve the resonance phenomenon. Hence, an exact and carefully-selected compensation level is of great significance.
... This includes various parameters such as the internal resistance of the reactor winding (r), the capacitance of reactor (C L ), a bus bar (C BB ) and bushings (C B ) along with the series inductance of the reactor (L). The details of these parameters are given in Appendix A section (Shunt reactor data) and they are referred from [25][26][27]. The presentation of different connection configurations of the shunt reactor (Yg, Y, and D) have been given in Section 4.2.1. ...
Generally, Controlled Switching Device (CSD) is used during de-energization as well as energization operations of shunt reactors. However, for substations configured with One-and-Half Breaker (OHB) or line connected to non-switchable reactor scheme, the Pre-Insertion Resistor Circuit Breaker (PIR-CB) might be used during switching of shunt reactor. This paper presents optimized controlled switching strategy to minimize the level of asymmetric dc component of charging current during energization of a shunt reactor using CSD with PIR-CB. This is achieved by optimizing the insertion instant, value and Electrical Insertion Time (EIT) of PIR. The validity of the proposed technique has been evaluated by generating a large number of simulation cases in PSCAD/EMTDC software package by changing rating & configuration of shunt reactor, EIT, insertion & removal instant and the value of PIR. The simulation results suggest that the proposed methodology maintains the level of asymmetric dc component in charging current of the order of 1.02, 1.11, 1.11 p.u. for grounded star (Yg), un-grounded star (Y) and delta (Δ) configuration of shunt reactor. At the end, field results of energization of 240 MVAr shunt reactor with PIR-CB for line application at 765 kV have been presented which clearly depicts mitigation of asymmetric dc component.
... L = Inductance of reactor phase winding. NGR = Reactance of neutral grounding reactor.1 st IEEE International Conference on Power Electronics, Intelligent Control and Energy Systems (ICPEICES-2016)[3]If the decay of DC offset is assumed negligible till the moment of first peak of inrush current then ...
This paper presents an overview of transient phenomena occurring during energization of shunt reactor at EHV substation. Unsymmetrical phase currents during shunt reactor energization are analyzed and its effects on protective devices are discussed. High DC offset inrush currents with very high time constant during energization of reactor can cause mal-operation of zero sequence ground relays. High value of DC offset in the current might lead to current transformer saturation. Error in phase difference of the currents of saturated CTs at HV and LV side of shunt reactor leads to spurious trip of differential protection relay. This case study is done for 1200/765/400/200 kV Wardha substation of Power Grid Corporation of India Ltd, Western region, 1, India. Simulations are carried out using Alternate Transient Program/Electromagnetic Transient Program (ATP/EMTP) software.
... For series reactors, there is a capacitance from the terminal to ground and from terminal to terminal. More sophisticated models may be developed for determining internal stresses [83]. ...
An overvoltage is a voltage – between one phase and ground or between two phases – having a crest value exceeding the corresponding crest of the maximum system voltage. Standards distinguish several classes and shapes of overvoltages:
1. Temporary overvoltages: These are undamped or weakly damped oscillatory phase-to-ground or phase-to-phase overvoltages of relatively long duration (seconds, even minutes). Temporary overvoltages are originated by faults, load rejection, resonance and ferroresonance conditions or by a combination of these factors.
2. Slow-front overvoltages: These are unidirectional or oscillatory highly damped overvoltages, with a slow front and a short duration. They are caused by switching operations, fault initiation or remote lightning strokes.
3. Fast-front overvoltages: These are caused primarily by lightning strokes, although they can also be caused by some switching operations or fault initiation.
4. Very-fast-front overvoltages: In general, these are the result of switching operations or faults. They are usually associated with high-voltage disconnect switch operation in gas insulated substations (GISs), and with cable-connected motors.
Standards also include continuous power-frequency voltages, which are originated when the system is under normal operating conditions. For systems whose maximum voltage exceeds that given in the standards, the actual maximum system operating voltage should be used.
This chapter presents the main causes and methods for limitation of overvoltages, also detailing the analysis and calculation of those typical overvoltages. Modelling guidelines are provided to be used with any class of overvoltage, and a description of the phenomena that cause overvoltages and some illustrative cases.
... Shunt reactor switching is a long-time issue addressed in literature [3] [4], and the related transients are well known. When a reactor is de-energized, the chopping of the current and subsequent possible reignitions can results in significant transient overvoltages. ...
The growing sensibility to environment issues contributed in recent years to the erection of barriers in the construction of new overhead transmission lines. One of the solutions to overcome these problems is the use of cable lines for high (HV) and extra-high (EHV) voltage. However, the coexistence of overhead and cable lines in transmission systems, in the so called “mixed” lines, raises a number of issues regarding the behaviour of such systems both in transient and steady state. In particular, the definition of angle or transient stability of a system plays a strategic role and provides the actions of design and planning of the system. The purpose of this study is to investigate the angle stability of a system containing a mixed line: a control strategy of shunt reactors, located to compensate reactive power request of cable line, will be proposed as countermeasure to severe disturbance and then as improvement of power system stability. The analysis, based on detailed time simulations, will show that the timing of control actions of shunt reactors is critical for the success of emergency control: in particular, the size and the timing of reactive power involved in switching operation determine whether these control actions play positively or not in avoiding angular separation and system instability.
... Reactors are normally disconnected at heavy load and are connected to the lines at periods of low load. As a result, frequent switching is a significant property of shunt reactors because they can react to the changing system load condition [1], [2]. As is well known, the interruption of a sinusoidal current of an inductive element before the natural current zero can result in the high overvoltage of an oscillating nature. ...
This paper presents an approach for switching overvoltages reduction during shunt reactor energization. Radial Basis Function Neural Network (RBFNN) has been used to evaluate optimum switching condition. The most effective method for the limitation of the switching overvoltages is controlled switching since the magnitudes of the produced transients are heavily dependent on the closing instants of the switch. This work presents a harmonic index whose minimum value corresponds to the best case switching time. Artificial Neural Network (ANN) is trained with equivalent circuit parameters of the network, so that developed ANN can be applied to every studied system. In order to ascertain the effectiveness of the proposed index and accuracy of the ANN-based approach, two case studies are disussed.
The main cause of reactor failure is the virtual current chopping over-voltage caused by the re-ignition of the first interruption phase when the shunt reactor is disconnected. At present, the traditional controlled interruption strategy based on vacuum circuit breaker with permanent magnet actuator has obvious effect on restraining the re-ignition of the first interruption phase, but the virtual current chopping problem, which is the root cause of the three-phase simultaneous interruption over-voltage, can not be effectively solved. Aiming at the existing problems of controlled strategy, an asynchronous controlled interruption (ACI) strategy based on fast vacuum switch is proposed in this paper. Considering the factors such as switching speed, current chopping level, mechanical dispersion and characteristics of arc extinguishing chamber, the effects of the above factors on the probability of re-ignition and virtual current chopping and over-voltage level of common vacuum circuit breakers and fast vacuum switches are compared and analyzed. The PSCAD/EMTDC simulation model based on the actual parameters of 220 kV substation and the results of field interruption experiment show that the virtual current chopping problem can be solved by the proposed interruption strategy fundamentally, which has a significant suppression effect on the switching over-voltage of shunt reactors.
Purpose
The purpose of this paper is to solve the reactive power adjustment and the overvoltage suppression problems in the extra high voltage (EHV) long distance grid, which often appears transient overvoltage, light load loss and other issues.
Design/methodology/approach
One 800 kV EHV magnetically saturation controllable reactor (MSCR) used self-power supply control system is designed. The structure and the working mechanism of the novel MSCR are analyzed in detail. Then the control and capacity step adjustment characteristics are obtained by experiments. The harmonic characteristic is studied by theoretical analysis and low voltage test.
Findings
To solve the problem of harmonics in the working current of nets windings, the fifth and the seventh filers are equipped between the compensation windings and the control system. The effectiveness of the harmonic suppression method is proved by simulation and experiments.
Originality/value
It proves that the 800 kV EHV MSCR design in this paper can achieve the purpose of the reactive power continuous linear adjustment, and the capacity adjustment is sensitive. After filtering, the harmonics level of the working current meets the standard of the EHV grid.
In this paper, the simulation of inter-turn protection for high-voltage (HV) shunt reactors is studied by using Simulink. Expound that when the closing angles of the three-phase circuit breaker are different, the zero-sequence current and zero-sequence voltage will occur in the system. Demonstrated that during such time, the protection criterion of inter-turn protection will be satisfied in some cases, and thus, the false tripping will occur possibly. Finally, some suggestions are given to avoid the false tripping in the inter-turn protection.
Shunt reactor interruption by circuit breakers may produce current chopping and cause severe overvoltages. The four-legged reactor interrupting transients were elucidated with equivalent circuit analysis, and the mechanism of beat frequency oscillation was also characterized, further, a 3-D portfolio of the beat frequency, specifically regarding shunt reactor interrupting with either a short line distance or a long transmission line, was given to describe the variation trend versus the shunt reactor's parameters. Based on the available parameters from an installed 750kV transmission line in China, simulations of the four-legged reactor interruption process were carried out with adoption of an appropriate arc model for SF6 circuit breakers, and the scenario of the switching overvoltages was presented for two different kinds shunt reactor interrupting. The research results present useful reference for future construction and operation of the extra high voltage(EHV) and ultra high voltage(UHV) transmission lines.
The controllable shunt reactor (CSR) is one of the key elements used in an extra-high voltage (EHV)/ultra-high voltage (UHV) transmission system for reactive power control. In contrast to conventional CSRs, EHV/UHV CSRs are at a higher voltage level and with a larger capacity, which makes higher requirements on the indices such as response speed, harmonic distortion, reliability and the corresponding techniques. An overview is made of domestic and foreign developments in four key techniques of EHV/UHV CSR, including body structure design, electromagnetic transient modeling, protection configuration research and control system design. The advantages and disadvantages of different technical schemes are discussed. Key issues of the four techniques are pointed out, and the trends in application and development are projected.
To ensure the safety of substation expanding and new shunt reactor operation, we researched the overvoltage of shunt reactor during switching-on process by theoretical analysis, tests and simulations, and theoretically analyzed the reasons of the overvoltage from two aspects, namely, mechanism of transient prebreakdown of SF6 breaker and reflection and refraction of wave. Moreover, we established a SF6 breaker prebreakdown model in ATP-EMTP to simulate the field tests. Tests and simulation results showed that the specific overvoltage on the reactor during process of switching-on could reach 4.0. However, simulation results showed that, with resistance and capacitance absorption equipment, the specific overvoltage could be decreased to 1.68 in the same condition. Simulation results indicated that the absorption equipment could be an effective measure for overvoltage limitation, which not only decreased the systematic overvoltage but also restrained systematic harmonics. The pre-breakdown phenomenon introduced in this paper could be referred for protection of shunt reactor operation in substations.
This paper presents a methodology for obtaining the current-limiting air-core series reactor model suitable for the transient recovery voltage (TRV) studies, which is constructed from the reactor geometry, accounting for the winding design and disposition, as well as the insulating material properties. The model is based on the ladder connection of frequency-dependent lumped-parameter reactor winding elements (representing partial capacitances, resistances, inductances and conductances). A frequency-dependent equivalent admittance matrix is formed for the ladder network, which is further processed using the vector fit technique, resulting in a Foster-type network suitable for a direct incorporation within the EMTP–ATP environment. A parametric analysis is provided in the paper as well, featuring different impacts that the variation of reactor design properties produces on the inherent TRV response.
This paper deals with the computation of secondary arc in different 400-kV transmission systems that differ from each other in their configuration. Two technologies overhead line (OHL) and power cable are implemented worldwide to transfer energy for longs distances at extreme high voltage (EHV) level. Long EHV lines are generally compensated by shunt reactor. Their connection to the line, compensation level and localization are factors that could influence fault transients of the system. The representation of the secondary arc should be realistic to determine correctly the auto-reclosure performance. The secondary arc is modelled in the digital transients program EMTP/ATP. The dynamic behaviour of the arc is determined on the basis of energy balance in the arc column. Simulations with real transmission lines are very useful to understand the arcing phenomenon in particular when line consists of overhead line, cable section and shunt reactors.
One of the most important issues in power system restoration (PSR) is switching overvoltage caused by power equipment energization. This phenomenon may damage some equipment and delay power system restoration. This paper proposes an intelligent estimator which can be used to evaluate and control switching overvoltages. Transformer, shunt reactor, and transmission lines are important devices in PSR and their energization have been studied in this work. Artificial neural network (ANN) is adopted as an intelligent approach to deal with these overvoltages. Doth Multilayer Per- ceptron (MLP) and Radial Basis Function (RDF) structures have been analyzed. Five learning algorithms, backpropagation (DP), delta-bar-delta (DDD), extended delta-bar- delta (EDDD), directed random search (DRS), and quick propagation (QP) were used to train the MLP. In the cases of transformer and shunt reactor energization, ANNs are trained with the worst case scenario of switching angle and remanent flux which reduce the number of required simulations for training ANN. Also, for achieving good generalization capability for developed ANN, equivalent parameters of the network are used as ANN inputs. The simulated results for a partial of 39-bus New England test system show that the proposed technique can estimate the peak values and duration of switching overvoltages with good accuracy and EDDD algorithm presents best performance.
This bibliogrphy was prepared by the Modeling and Analysis of Systems Transients Using Digital Programs Working Group of the General Systems Subcommittee and Transmission and Distribution Committee. The bibliography covers the subjects of electromagnetic transients and the application of digital programs for the analysis of these transients. It is not limited to a specific period. General Bibliography includes references related to background information. Solution Methods covers computing algorithms and techniques for the digital solution of electromagnetic transients including transient solution, numerical oscillations, initialization and control systems. Modeling of Power Components covers model development and usage of for overhead lines, cables, transformers, arresters, network equivalents, machines, circuit breakers, and protection systems. Modeling Guidelines includes references related to the application of component models for system analysis. Simulation Tools includes references related to digital electromagentic transient simulation programs. Application and Case Studies covers the application of digital programs for system studies and analysis, including overvoltage and transient recovery voltages, secondary arc, subsynchronous resonance, power electronics, and power quality. All references listed in the bibliography are written in or translated into English. Recognition is given to members of the Working Group who participated in compiling this bibliography.
Overvoltages caused by switching operation of power system equipments
might damage some equipment and delay power system restoration. This
paper presents a comparison between transmission line (TL) models for
overvoltages study and investigates which TL model is most proper for
every case study. Both simulation time and accuracy factors of TL models
are considered for selecting best TL model. Various cases of switching
of transformer, shunt reactor, capacitor bank, and transmission line are
investigated and simulation results for a partial of 39-bus New England
test system, show that the proposed TL model evaluation increase
accuracy and reduce simulation time (accelerate power system
restoration) properly.
This paper presents an intelligent approach to evaluate switching
overvoltages during power equipment energization. Switching action is
one of the most important issues in power system restoration schemes.
This action may lead to overvoltages that can damage some equipment and
delay power system restoration. In this work, transient
overvoltages caused by power equipment energization are analyzed and
estimated using artificial neural network (ANN)-based approach. Three
learning algorithms, delta-bar-delta (DBD), extended delta-bar-delta
(EDBD), and directed random search (DRS), were used to train the ANNs.
In the cases of transformer and shunt reactor energization, ANNs are
trained with the worst case scenario of switching angle and remanent
flux which reduce the number of required simulations for training ANN.
Also, for achieving good generalization capability for developed ANN,
equivalent parameters of the network are used as ANN inputs. The
simulated results for a partial of 39-bus New England test system,
show that the proposed technique can estimate the peak values and
duration of switching overvoltages with good accuracy and EDBD
algorithm presents best performance.
The shunt reactors located on both line terminals and substation bus-bars are commonly used on long extra high voltage (EHV) transmission systems for controlling voltage during load variations. In a small power system that appears in an early stage of a black start of a power system, an overvoltage could be caused by core saturation on the energization of a shunt reactor with residual flux. The most effective method for the limitation of the switching overvoltages is controlled switching since the magnitudes of the produced transients are strongly dependent on the closing instants of the switch. A harmonic index has been introduced that it's minimum value is corresponding to the best-case switching time. In addition, in this paper an artificial neural network (ANN) is used to estimate the optimum switching instants for real time applications. ANN is trained with equivalent circuit parameters of the network, so that developed ANN is applicable to every studied system. To verify the effectiveness of the proposed index and accuracy of the ANN-based approach, two case studies are presented and demonstrated.
This paper presents an approach to the study of switching overvoltages during power equipment energization. Switching action is one of the most important issues in the power system restoration schemes. This action may lead to overvoltages which can damage some equipment and delay power system restoration. In this work, switching overvoltages caused by power equipment energization are evaluated using artificial-neural-network- (ANN-) based approach. Both multilayer perceptron (MLP) trained with Levenberg-Marquardt (LM) algorithm and radial basis function (RBF) structure have been analyzed. In the cases of transformer and shunt reactor energization, the worst case of switching angle and remanent flux has been considered to reduce the number of required simulations for training ANN. Also, for achieving good generalization capability for developed ANN, equivalent parameters of the network are used as ANN inputs. Developed ANN is tested for a partial of 39-bus New England test system, and results show the effectiveness of the proposed method to evaluate switching overvoltages.
In this work, voltage evaluation after power components energization such as transmission line, transformer and shunt reactor is analyzed using artificial neural network (ANN)-based approach. Throughout the initial phase of system restoration, unexpected overvoltage may happen due to nonlinear interaction between the unloaded transformer and the transmission system. Such an overvoltage might damage some equipment and delay power system restoration. In the cases of transformer and shunt reactor energization, ANN is trained with the worst case scenario of switching angle and remanent flux which reduce the number of required simulations for training ANN. Moreover, for achieving good generalization capability for developed ANN, equivalent parameters of the network are used as ANN inputs. The simulated results for a partial of 39-bus New England test system show that the proposed technique can estimate the peak values and duration of overvoltages during network switching with good accuracy.
This paper introduces an intelligent-based method using artificial neural network (ANN) to reduce shunt reactor switching overvoltages. In power systems, an overvoltage could be caused by core saturation on the energization of a shunt reactor with residual flux. The most effective method for the limitation of the switching overvoltages is controlled switching since the magnitudes of the produced transients are strongly dependent on the closing instants of the switch. We introduce a harmonic index that it's minimum value is corresponding to the best case switching time. In addition, in this paper three learning algorithms, delta-bar-delta (DBD), extended delta-bar-delta (EDBD) and directed random search (DRS), were used to train the ANNs to estimate the optimum switching instants for real time applications. ANN is trained with equivalent circuit parameters of the network, so that developed ANN is applicable to every studied system. To verify the effectiveness of the proposed index and accuracy of the ANNbased approach, two case studies are presented and demonstrated.
Recently, in many countries EHV AC cable lines are used as means to overcome the difficulties in construction of new transmission lines. However, the coexistence of overhead and cable lines in transmission systems, in the so called “mixed” lines, raises a number of issues regarding the behaviour of such systems both in transient and steady-state. In particular, with the increment of the operating voltage of transmission systems, the behaviour of such mixed systems during switching operation becomes of special interest. The purpose of this study is to investigate the no-load energization of very long EHV mixed lines in two main configurations, both characterized by an high difference in the lengths of the first and the last stretch. The work addresses this issue from two different aspects: the switching transient and the quasi-steady state condition. The analysis will show the suitability of those configurations which have the majority of cable away from switching end, even if some important observations in transient analysis will be pointed out, especially regarding the “best end” switching issue: in particular, difference in length between the first and the last stretch affects the multiple reflections and the equivalent two-port circuit constants, then significantly influencing the opened end overvoltages.
Capacitor banks and shunt reactors are frequently
switched by circuit-breakers in medium voltage (MV)
and high voltage (HV) electricity networks. In recent
years there have been explosive failures due to circuitbreaker
restriking and reignition consequently there is a
need for monitoring techniques that will facilitate the
identification and quantification of the onset of more
severe restriking. Whilst there has been detailed analyses
of single-phase shunt reactor and capacitor bank
switching there is a paucity of information about
restriking phenomena and reignition in three-phase
circuits for the correlation of system problems with
specific waveform characteristics to develop the
necessary identification algorithms for proactive
monitoring of circuit-breakers’ condition. This paper
describes the modelling restriking and reignition
occurring during three-phase capacitor bank and shunt
reactor switching using the Alternative Transients
Program (ATP) and network data from AS 4372-1996.
Information from the ATP models and data resulting
from the simulations are examined with a view to
developing an intelligent diagnostic system with logging
and alarm features. This modelling method can be easily
applied with different data from the different dielectric
curves, circuit breakers and networks.
The work reported in this paper is EMTP simulation of reactor switching. The simulation has identified the causes of high transient overvoltage, which are produced when switching high voltage shunt reactors.
The work reports on studies, which supported the projecting, reconstruction and modification of a 750 kV, 479 km long transmission line. The changes were demanded by the technical development and the alteration of the role of the line in the power transmission. Authors analyse various ways for influencing on the interaction of the reactive power control, relaying and overvoltage protection. The possibility of the operation with incomplete, asymmetrical shunt reactor and arrester sets is investigated. The paper describes a simple way of controlled three-phase and adaptive single-phase reclosure.
When de-energizing shunt reactors with load interrupters, reignitions are likely to occur. The resulting high frequency transients have been investigated for a typical EHV installation by computer studies and field tests. These transients can be eliminated or minimized by controlling the instant of contact parting. They can also be reduced by low ohmic opening resistors. The dielectric requirements for BPA's 500-kV shunt reactor installations are discussed. It is shown that even in installations with reduced insulation levels routine switching with load interrupters does not impress excessive duties on the protective arrester. Copyright © 1979 by The Institute of Electrical and Electronics Engineers, Inc.
Switching of shunt reactors--comparison between field and laboratory tests
- S Berneryd
- C E Stlver
- L Ahlgren
- R Eriksson
Berneryd, S., Stlver, C. E., Ahlgren, L. and Eriksson, R., Switching of shunt reactors--comparison between field and laboratory tests. CIGRE Report, No. 13-04, 1976.
Devel-opment of controlled switching of reactors, capacitors, trans-formers and lines
- A Holm
- R Alvinsson
- U Akesson
- O Karlen
Holm, A., Alvinsson, R., Akesson, U., and Karlen, O., Devel-opment of controlled switching of reactors, capacitors, trans-formers and lines. CIGRE Report, 13-201, 1990.
Switching off 750 kV shunt reactors
- Prikler
Prikler, L., Switching off 750 kV shunt reactors. Proceedings of 19th European EMTP User Group Meeting, Leuven, 1990.
Controlling reactor breakers switchings in the Hungarian 750kV sub-station Albertirsa
- G Bfin
- G B~infai
- P Becker
- L Prikler
Bfin, G., B~infai, G., Becker, P. and Prikler, L., Controlling reactor breakers switchings in the Hungarian 750kV sub-station Albertirsa. Research report (in Hungarian), Dept of Power Systems, July 1992.
Modelling of voltage transformers by means of ATP at high frequency
- L B~irger
- L Prikler
B~irger, L. and Prikler, L., Modelling of voltage transformers by means of ATP at high frequency. Proceedings of 22nd European EMTP User Group Meeting, Leuven, 1992.
Controlled switching of 735 kV reactor circuit breakers at Hydro-Quebec
- R J Rajotte
- S Breault
- C Charpentier
Rajotte, R. J., Breault, S. and Charpentier, C., Controlled switching of 735 kV reactor circuit breakers at Hydro-Quebec. CIGRE Report No. 13-301, 1996.
Switching of shunt reactors—comparison between field and laboratory tests
- Berneryd
Development of controlled switching of reactors, capacitors, transformers and lines
- Holm
Controlling reactor breakers switchings in the Hungarian 750 kV substation Albertirsa
- Bán
Controlled switching of 735 kV reactor circuit breakers at Hydro-Quebec
- Rajotte
Modelling of voltage transformers by means of ATP at high frequency
- Bürger