Shunt Reactor Research Articles

Experimental Investigation of Switching Overvoltages of Shunt Reactor

Experimental Investigation of Switching Overvoltages of Shunt Reactor

An adaptive three-phase reclosure scheme for shunt reactor-compensated transmission lines based on the change of current spectrum

In this paper, a new three-phase adaptive reclosing scheme for transmission lines with shunt reactors is proposed to identify fault nature and determine the arc extinction time under the single and double-phase-to-ground faults. According to the fact that the faulted phase currents of shunt reactors contain only one oscillating frequency before the fault extinction and contain other two different oscillating frequencies when the fault is extinguished, this change of current frequency can be used to distinguish transient faults. When sampling rate is an integral multiple of the faulted phase current frequency of shunt reactors under permanent faults, an abrupt increase of currents even harmonics which is caused by spectral leakage of the DFT algorithm under non-synchronous sampling can lead to identify transient faults and three-phase reclosing. Electromagnetic Transient Program simulation results verify the correctness of the frequency spectrum characteristic analysis of the faulted currents of shunt reactor. The feasibility of the proposed scheme is also tested under different fault condition.

Improved control algorithm for shunt reactors using fuzzy logic

The task of provision of the efficiency of fuzzy controller action, regulating the power of shunt reactors, is considered for the stabilization of the voltage values in high-voltage buses, as well as to increase the regime reliability of the power grid. A new algorithm is proposed for controlling the power or inductive resistance of reactor depending on the load resistance, rate of change and voltage on the network buses. The results of the designed experiment based on computer simulation confirm the effectiveness of the proposed control algorithm.

Impact of Shunt reactor to DFIG Connected to Series-Compensated Power System on Sub-synchronous Oscillation Characteristics

The shunt reactor will affect the sub synchronous oscillation characteristics of the wind power system, and there is no paper that analyse this aspect. To this end, in the DFIG via series compensation transmission power system, use impedance scanning method to measure the total equivalent impedance of system side and DFIG side, the mechanism of the influence of the installation position and capacity of the shunt reactor on the sub synchronous oscillation characteristic of the system is analysed. The analysis results show that the larger capacity of shunt reactor, equivalent impedance effect is larger, the installation position that is very near the fan can reduce the resonant frequency and increase the resistance of resonance point, being far from the fan will increase the resonant frequency and the absolute value of the negative resistance in the resonance points, besides, the effect of parallel capacitor on system impedance is very small. Finally, the correctness of the theoretical analysis is verified by the time-domain simulation.

Optimizing the switching time for 400 kV SF6 circuit breakers

This paper presents real-time voltage and current analysis for optimizing the wave switching point of the circuit breaker SF6. Circuit Breaker plays an important role in power systems. It provides protection for equipment in embedded stations in transport networks. SF6 Circuit Breaker is very important equipment in Power Systems, which is used for up to 400 kV due to its excellent performance. The controlled switching is used to eliminate transient modes and electrodynamic and dielectric charges in the network at manual switching of capacitor, shunt reactors and power transformers. These effects reduce the reliability and lifetime of the equipment installed on the network, or may lead to erroneous protection.

Influence of Hybrid Reactive Power Compensation on the Secondary Arc of Ultra-High-Voltage Transmission Lines (May 2018)

Hybrid reactive power compensation (HRPC) which consists of series compensation and a stepped-controlled shunt reactor will see use in China's future ultra-high-voltage (UHV) transmission system. As a result, some new characteristics of the secondary arc during a single-phase-to-ground fault on UHV transmission lines with HRPC may be raised. In this paper, the secondary arc characteristics during the single-phase auto-reclosure (SPAR) operation have been simulated with regard to the UHV AC system installed with HRPC. Based on the UHV system model with HRPC and its secondary arc model, the influence mechanism of HRPC on secondary arc current is theoretically derived with the simulated waveforms and the Fourier analysis. Besides, the relationship among the secondary arc current, the arcing time with different HRPC compensation degrees, neutral reactance, as well as the grounding fault locations have been investigated in detail. Finally, an improved time sequential control strategy of bypass breaker and SPAR has been put forward. The research presented in this paper will provide necessary theoretical basis and technical support for the future application of HRPC in UHV transmission lines.

PROBLEMS OF REACTIVE POWER COMPENSATION OF 110 KV LINE CABLE

Construction of 110 kV cable systems, where the line length exceeds ten kilometers requires compensation of reactive power generated by the cable capacitance. The compensation can be realized with the application of shunt reactors, whose selection seems to be an easy task. The presented considerations deal with a problem, whose source are the below listed facts. Both the 110 kV cable and the shunt reactor to be applied are custom made and their quality parameters are subject to random variability, whose source are manufacturing processes. Construction of a cable system and manufacturing of a customized shunt reactor are realized at the same time and hence it is not possible to have the reactor matching the already existing and tested cable line. Taking into account that cable and reactor parameters are of random character, the shunt reactor selection process exhibits features of a stochastic process. The article presents the Monte Carlo simulation results obtained for various parameters of the analyzed HV cable line – shunt reactor system. Various forms of the random variable distribution have been obtained and the random variable is the operation compensation costs. The performed analyses make it possible to select optimal inductance for the shunt reactor. The highest value of the probability that operation costs of the reactive power compensation will not exceed a certain predefined value has been assumed as the selection criterion. Article DOI: https://dx.doi.org/10.20319/mijst.2017.32.163172 This work is licensed under the Creative Commons Attribution-Non-commercial 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.

Protection schemes for turn-to-turn faults within control windings of TCT-CSR and impacts of power regulation

The commonly used protection scheme for turn-to-turn faults detection of shunt reactors lacks sensitivity when applied to thyristor controlled transformer-type controllable shunt reactor (TCT-CSR), especially when TCT-CSR is working almost at its rated power and the short-circuited turn ratio is small. Based on the analysis and comparison of the characteristics under internal faults and external faults, this paper proposes zero-sequence overcurrent protection with zero-sequence voltage blocked to detect turn-to-turn faults within control windings. The impacts of power regulation on the proposed protection scheme is investigated in depth. The results indicate that the proposed protection scheme may mal-operate during power regulation. As a solution, the approach of increasing the resistance of control windings is proposed in this paper. The value of resistance and its impacts on the performance of the proposed protection scheme during power regulation are discussed in detail. Finally, the optimal value of the resistance of control windings is recommended as the reference for the future design of TCT-CSR after the comparison of simulation results under different scenarios.

Appropriate selection of shunt compensation reactor in parallel transmission lines: A case study

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.

Adaptive single-phase auto-reclosing method using power line carrier signals

This paper proposes a new method for adaptive single-phase auto-reclosing (ASPAR) that improves the rate of successful reclosing actions after the occurrence of a transient single-phase fault and prevents unsuccessful reclosing. After the occurrence of a fault, the only faulty phase is disconnected by the protection system (e.g., distance relays and circuit breakers). The proposed method deploys power line carrier (PLC) signals for determination of the secondary arc extinction time and releasing the reclosing signals to the circuit breakers. Despite the growing use of new communication systems (e.g., fibre-optic links), PLC systems are still widely used, and may not be considered for replacement in near future. Therefore, the proposed method can be utilized as an auxiliary application of PLC systems to enhance the resiliency of power grids. The simulation studies are carried out using EMTP-RV and MATLAB, and the advantages and disadvantages of the proposed method are discussed and compared with the existing ASPAR methods. According to the simulation results, the efficiency of the proposed ASPAR method is negligibly influenced by the following factors: fault location, faulty phase, system loading, transmission line transposition, shunt reactor, PLC carrier frequency, PLC operating mode, and the noises.

A noncommunication adaptive single phase auto-reclosure of transmission lines using phase space based criteria

This paper presents two phase space (PS) based criteria, and then on the basis of which it illustrates the preparation of a new non-intelligent and noncommunication adaptive single phase auto-reclosure (ASPAR) scheme to detect the secondary arc extinction for reclosure of transmission lines after self-clearing of transient faults. This scheme, which is fed by local voltage signal, can accurately distinguish between transient and permanent faults in transmission lines. Moreover, in the case of transient faults, the secondary arc extinction can be detected by the proposed algorithm within 8ms and under effective operational and structural conditions, including different fault locations, load amounts, number of circuits, ideally transposed, partially transposed and un-transposed circuits, existence of shunt reactors and measurement noise. Besides, the presented PS based algorithm can be implemented sample by sample and does not need complicated integral computation, which connotes that it can be embedded in reclosing relays in transmission systems.

Assessing the Future Trends of Reactive Power Demand of Distribution Networks

In the last decade, the transmission system operator (TSO) in Great Britain has seen an acute declining trend of reactive power demand during periods of minimum load. Reactive power traditionally being absorbed by distribution networks is now in many cases injected to transmission. This not only results in significant voltage regulation challenges to the TSO but may also trigger future requirements for distribution network operators (DNOs) to manage these reactive power exchanges. Nonetheless, for the TSO and DNOs to adopt suitable investment strategies, it is crucial to first quantify the extent of this decline in the near future. This study proposes a methodology to identify trends of reactive power demand using historical DNO monitoring and network data. Multiple scenarios are also considered to cater for potential changes in demand, generation, and networks. The methodology is demonstrated on real British distribution networks, from the transmission–distribution interface to primary substations. The assessment reveals the significant effect of demand trends in primary substations on the overall transmission–distribution exchanges. It was also found that the potential use of shunt reactors in distribution networks would require significant investment, highlighting the importance of understanding reactive demand trends in planning cost-effective solutions.

ON THE SIMULATION OF MODES ОF ELECTRIC POWER SYSTEMS WITH FACTS

Power flow control is an important task of development of electric power systems. It is necessary to reduce the power loss, improve the reliability and quality of power supply and increase the power transmission. Currently, on the basis of modern power electronics effective FАСТS devices for flexible control of power system operation modes have been developed. FАСТS devices are able to simultaneously influence the voltage, the reactance, the angle between the voltages. As it is known, the calculations of the established modes of electric systems are the most frequently performed tasks at all the territorial and time levels of control and planning operations. These calculations are significant by themselves, being also an integral part of software systems of calculation of losses of power and energy in electrical networks, calculation of optimal modes and also sustainability. The need for multiple mode calculation imposes high requirements to the methods of calculation of the established modes in real time in terms of performance and reliability of the results of the solution being obtained under operating conditions of electric power systems. In traditional calculations of the established modes of electrical networks, shunt reactors, current-limiting reactors, capacitor banks, longitudinal compensation devices were accounted in the simulation as passive elements. In regard with the introduction of FACTS devices in power systems, there is an arising need to develop appropriate algorithms and implement them in the form of software for analyzing and controlling the established modes of power systems. The methodology and software for calculation of the established modes of electric networks with consideration of FACTS devices have been developed. The software makes it possible to obtain practically acceptable solutions in three outer iterations. Based on the results of numerical simulation of modes of the power system of the “Azerenergy” JSC it was determined that the application of FACTS devices can significantly increase the transmission line active power, improve voltage levels and reduce losses of active power. The dependences of flows and power losses on the control parameter of FACTS devices have been derived.

Limitation of Transient Recovery Voltage When Using Shunt Reactors in 110 – 220 kV Networks

In design practice there often arises the problem of assessing the feasibility of installing shunt reactors (SR) when observing conditions of the occurrence of admissible transient recovery voltages at circuit breaker contacts during switching action. A simplified design methodology for this purpose is proposed for calculating the defining parameters of the SR connection circuit, making it possible to define the feasibility of its use in the analyzed circuit.

TCSR Features Facilitating Safe Testing of 500 kV Power Transmission Lines

Reasons are examined for failures of gas-insulated circuit breakers on lines with shunt reactors that provide a level of line compensation close to 100%. It is shown that using a TCSR as a linear reactor makes it possible to eliminate the reason leading to failure of the circuit breaker in line testing.

An optimal/adaptive reclosing technique for transient stability enhancement under single pole tripping

This paper presents an integrated autoreclosure scheme (IAS) for transmission networks. The IAS operation is based on merging the functional advantages of the adaptive reclosing technique (ART) and the optimal reclosing technique (ORT). The ART identifies the nature of the fault, transient or a permanent fault, and determines the fault persistence time of a transient fault by analyzing the harmonic of the fault phase voltage using wavelet packet transform (WPT). The ORT is dependent on the load angle of the generators that minimizes the systems oscillation. The resulted information from the adaptive reclosing and the optimal reclosure timing units can effectively settled to achieve the optimum reclosing strategy that able to enhance power system stability. The proposed IAS is merited by an adaptive threshold level while needed information are captured from single end only. The IAS performance assessment compared to conventional reclosing schemes is carried out by using proposed voltage and speed indices. Examination of the proposed IAS is successfully achieved at different fault scenarios that involve various fault locations, inception angles, and representation of secondary arc characteristics. Added to that, the capability of the proposed scheme is confirmed considering the effects of shunt compensators, reactors and capacitors. Numerous simulation studies are emulated using MATLAB/SIMULINK on two test systems with different configurations. Simulation results indicate that the proposed reclosing method can enhance the transient stability.

Evaluation of controlled energization of shunt reactors for minimizing asymmetric DC component of charging current with circuit breaker having pre-insertion resistors

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 765kV have been presented which clearly depicts mitigation of asymmetric dc component.

A High-Speed Adaptive Single-Phase Reclosing Technique Based on Local Voltage Phasors

In this paper, a new adaptive single-phase reclosing method for high-voltage transmission lines is proposed. This method employs local voltage magnitude and angle of the faulted phase. It is shown in this paper that the proposed method is able to quickly identify the fault type and the arc extinction if the fault is transient. This method is effective for various system configurations, including ideally and partially transposed transmission lines, untransposed lines, as well as transmission lines with or without a shunt reactor. Superior performance of the proposed method has been verified using 550 case studies simulated in PSCAD and Matlab and a real case related to a 765-kV transmission line.

CALCULATION OF CFD-THERMAL MODELS OF OIL-COOLED TRANSFORMER EQUIPMENT

The purpose of the study is to ensure designing of full-function and stable CFD-simulation procedure for integrated thermal models of the transformers and the reactors, as well as to receive the approval of method of quality and abilities using the calculation examples of full-scale models of the equipment, along with autonomous models of coil-type windings having various design versions of heat-transfer intensification. Research Methods. Computational Fluid Dynamics (CFD) method of mathematical simulation of nonlinear processes as concerns hydrodynamics and heat transfer in the transformer equipment using finite-element analysis is employed. The results obtained. The paper presents the main elements of technique for creation of mathematical models; it also contains the examples of CFD-calculations as referred to axisymmetrical integrated models of furnace transformer and gapped-core shunt reactor, as well as the models of windings having design approaches of heat exchange intensification owing to «labyrinth» (partitions) and «alternation» (of number and locations) of axial cooling ducts. Scientific novelty. Scientific value of applied methodological approach lies in the fact that the developed models are the integrated ones, i.e., they consider geometry, loss, thermal parameters not only of the windings, but also of the main structural elements and cooling system. This ensures the quality and the accuracy of simulation of heat-and-mass transfer processes in complex structure of oil ducts and coils in the windings, enables to avoid erroneous «zigzag» oil flow movement through the groups of coil regular structures (without labyrinth and «alternation» of number and locations of axial ducts under conditions of transformer oil natural cooling as was deduced in the certain studies. Practical significance. Integrated models ensure calculation of oil temperature distribution within active part, including winding fields, oil temperature field between the tank and the windings, temperatures at oil outlet from the tank (top) and oil inlet into the tank (bottom). Calculations allow estimation of mean temperature distribution over the crosssection of winding coils, mean winding temperatures by means of averaging of the temperatures within the coils, detection of location and maximum temperature on the surface of conductors relevant to the most heated coil. The latter is treated as winding hot spot temperature (HST) and used to evaluate the aging of the contacting insulation. Determination of winding hot spot locations and temperatures (HST) is used as support data for installation areas of fiber optic probes for measurement during type testing, as well as in operational monitoring systems of the equipment. The results presented above are practically applied for industrial designing and testing of transformers and reactors.

Adaptive single‐phase reclosure scheme for transmission lines with shunt reactors based on current inner product

In this study, two current inner products have been defined to implement adaptive single-phase autoreclose for high-voltage transmission lines with shunt reactors. The inner product of fault phase current in shunt reactor and the current in the neutral point reactor is defined as initialisation inner product, and the inner product of the derivative of fault phase current in shunt reactor and the current in the neutral point reactor is defined as compensation inner product. In case of permanent faults and transient faults in the second arc stage, the initialisation inner product will keep bigger than compensation inner product. As for transient faults after arc extinction, low-frequency oscillation is observed in both curves of current inner products which have 90° phase differences; and two curves will have points of intersection. According to this phenomenon, the intersection of two current inner product curves is used to identify fault nature and detect the arc extinction. The proposed algorithm needs no threshold and no calculation in frequency domain. The electromagnetic transients program simulations have verified its correctness and effectiveness.