Distance Transmission Lines Research Articles

Measurements of microwave transmission mode in HL-3 tokamak relevant ECH corrugated waveguides transmission line

The transmission modes of high-power millimeter wave in corrugated waveguides transmission line (TL) are crucial, especially for the long-pulse operation for long-distance TL. The microwave transmission mode in the TL on HL-3 tokamak relevant the electron cyclotron heating system are studied for the purpose according to the phase retrieval method based on intensity distribution measured by an infrared camera at several different locations away from the outlet of TL. A specific high power test platform with about 40-meter TL is established and the mode contents in the middle and the end of the TL are analyzed. In the middle of the TL, the proportion of main transmission mode LP01 mode is about 97 % and other high-order modes contents are <3 %. In the end of the TL, the main mode purity is about 94 %, and the high-order mode, LP11 even mode is excited about 4.6 %. These mode analysis results indicate that the high-power and long-pulse millimeter wave corrugated waveguides TL are designed and machined well, and the alignment method for long distance transmission line installation is highly useful for high-purity wave mode transmission.

Modeling and Simulation of Mho Type Distance Relay for High Voltage Transmission Line Protection

Abstract-This paper describes the opportunity of implementing a model of a Mho type distance relay with three zones by using MATLAB/SIMULINK package. SimPowerSystem toolbox was used for detailed modeling of distance relay, transmission line and fault simulation. The proposed model was verified under different tests, such as fault detection which includes single line to ground (SLG) fault, double line fault (LL), double line to ground fault (LLG) and three phase fault, all types of faults were applied at different locations to test this model. The results show that the relay operates correctly under different locations for each fault type. Keywords- Distance relay, Single line to ground fault (L-G), Double line to ground (L-L-G), Line to Line fault (L-L), Three phase fault (L-L-L), MATLAB/SIMULINK.

Emerging Trend in Power Generation and Utilization

Power generation technology has been evolving ever since Edison put up his first generating station. It started with generation near the load center. To capitalize on the economics of scale large power plants were set up near the energy centers like the coal mine heads. This led to development of long distance transmission lines and the grids. Then came the restructuring of the rules and regulations governing the power system. With the issues of pollution and Global warming coming to the fore a paradigm shift is noticed in the generation of electrical power. Large number of renewable energy sources (RES) based small generators started getting connected to the distribution system. The concept of microgrid evolved to control and regulate the RES based generations. In order to effectively use these RES based generation and to capitalize from the electrical energy trading the concept of Virtual Power Plant and Community microgrid have started taking shape.

Fast excitation control strategy for typical magnetically controllable reactor for reactive power compensation

Though the magnetically controllable reactor (MCR) has been used in dynamic reactive power compensation of high voltage long distance transmission lines, its dynamic compensation performance is restricted by the imperfection of its slow response in the transition process. Hence, based on the typical structure and working principle of MCR, a novel fast excitation control based on rapid magnetization and demagnetization (RMDM) strategy, which only needs to add augmented boost circuit in the control winding of an MCR, is proposed to improve the dynamic response characteristics of MCR. The mathematical model of the novel proposed RMDM strategy is built and analyzed, based on which, the associations between the estimated transition time and the parameters of the typical MCR structure with auxiliary circuit are considered. Furthermore, the simulation model of the RMDM strategy is established by PSCAD/EMTDC, and simulation findings indicated that the transient time of magnetization and demagnetization of the typical MCR is improved from 0.5sec and 1.0sec to 0.3 sec and 0.1 sec respectively, while the transient time of the reactive power compensation is improved by half. These results substantiate the precision of the theoretical analysis and efficacy of the proposed RMDM strategy of typical MCR.

Open‐phase temporary overvoltage before and after an intermediate subsation accessing a long distance transmission line

In transmission lines, shunt-reactors are commonly applied to counteract the “Ferranti effect.” However, in highly compensated lines, hazardous overvoltage may occur during unbalanced open-phase conditions. In addition, when a new substation is put into operation, π circuit can be selected by accessing an existing transmission line and the original shunt-reactor configuration is maintained. Severe overvoltage may occur on the shunt-reactor side of the newly installed transmission line. In this study, we analysed the effects of compensation, neutral-reactor, and system frequency on open-phase overvoltage. The maximum deviation of system frequency is <±0.5 Hz, therefore, we suggested maximum critical compensation of the shunt-reactor under different proportional coefficients of neutral-reactor. We analysed the impact of line division, when an intermediate substation is accessed, and a risk range in which the substation located may cause severe overvoltage was proposed. Finally, according to an actual line division project, we optimised the original configuration scheme of the shunt and neutral-reactors. We used electromagnetic transient simulation to verify whether severe overvoltage occurred before and after the power station is accessed. The study results may provide guidance for selection of the π circuit accessing point and for optimising the configuration of the shunt and neutralreactors.

Analysis of power loss on the addition of new networks in Malang transmission system

Power loss problems in Malang transmission line system can occur due to high voltage drops in a long distance transmission lines and can be attributed to large loads resulting to high current flowing in the lines. Not only this setback can contribute to the decrease power transfer in the demand side, but it also can impair the conductor line over time owing to the excessive heats. To mitigate this problem, new networks or current distribution scheme are offered to reduce the excessive power loss and additionally to meet the load demands. This study aims to investigate and calculate the power losses in the transmission system before and after the networks are employed. The mathematical analysis of the power loss is presented in this paper and subsequently verified through simulation. The data used in this study are obtained from the State Electricity Utility (PLN) of Malang Raya. The results of this study indicate that before the addition of the network, Malang Transmission System experienced a significant power loss that is equal to 598.2 kW in six lines, including Bus 1 – LW at 125.5 kW, Bus 1 – PKS 164 kW, PKS – KA 1 kW, LW – KA 12.1 kW, KA – SKL 50 kW, and STM – KA 245.6 kW. After the addition of four new networks, the power loss is considerably reduced to 355.7 kW in 10 lines, including Bus 1 – LW 67.9 kW, Bus 1 – PKS 52.6 kW, PKS – KA 1.6 kW, LW – KA 0.3 kW, SKL – KA 0.1 kW, STM – KA 88.3 kW, LW – SKL 0.4 kW, PKS – LW 0.2 kW, STM – PKS 57.2 kW, and STM – SKL 87.1 kW.

Improved subsynchronous oscillation detection method in a DFIG-based wind farm interfaced with a series-compensated network

The use of series capacitors in long distance transmission lines leads to subsynchronous oscillation (SSO), which affects the stability and safety of power systems. The accurate detection of the SSO phenomenon within a short time is a necessary to avoid the harmful effects of SSO on power systems. This paper first presents an overview of previous SSO detection methods. An effective, secure, and improved SSO detection method based on the voltage signal is proposed and consists of two stages, namely, analysis and decision. In the analysis stage, the voltage magnitude signal passes through a first-order bandpass filter (fast filtration in the time domain) to only pass the subsynchronous frequency, and a new method for detecting the oscillation is added to avoid erroneous judgments and to make the method secure. In the decision stage, the best decision is taken (SSO detection, instant trip, or normal trip) based on the received data from the analysis stage. The robustness and speed of the improved SSO detection method are tested with the induction generator effect (IGE), subsynchronous control interaction (SSCI), and torsional interaction (TI). Simulation results indicate that the improved method can effectively and quickly detect the SSO phenomenon. The improved method is compared with the traditional method with different SSO types (IGE, TI, and SSCI) and is proven to be faster than the traditional method in all cases. In this study, the IEEE first benchmark model is adapted with a doubly fed induction generator (DFIG) wind farm to study the SSO phenomenon. MATLAB/SIMULINK software is used to validate the results.

Influence of Series Compensation Degrees on Secondary Arc Current Characteristics under the Different Series Compensation Mode

AbstractThe high compensation degree series compensation has a broad development prospects in long distance and large-capacity UHV transmission lines. But it is generating secondary arc current contains low frequency components with high amplitude when the single-phase grounding fault occurs in the series compensated transmission line, which is not conducive to rapid arc extinguishing. To solve this problem, this paper based on the mechanism of generating secondary arc by series compensation transmission lines, and using ATP – EMTP electromagnetic transient program to establish the simulation model of UHV series compensation device. And the suppression effects of small resistance short connection fault series compensation and linkage bypass series compensation measures on secondary arc current and recovery voltage under different series compensation layout mode are studied respectively. The results show that the attenuation speed of the secondary arc current is related to the series compensation arrangement modes and the time when the series compensation device is short connected or bypassed. Series compensation device short connected or bypassed before circuit breaker tripping which can accelerate the arc extinction speed, and the suppression effect is better when the series compensated double platform segmentation layout is distributed on both sides of the line. The results can be used as a reference for the engineering design of UHV with large capacity and long distance and high compensation series compensation transmission lines.

Harmonic transmission characteristics for ultra-long distance AC transmission lines based on frequency-length factor

Distributed parameter characteristics of Ultra-long Distance Transmission Lines (UDTLs) are prone to cause harmonic amplification. Amplified harmonic components deteriorate the quality of energy delivery, and consequently affect the safety and operations of a power grid. This paper proposes a method based on Frequency-Length Factor (FLF) to investigate the harmonic transmission characteristics (HTCs) for UDTLs, including Half-Wavelength Transmission Lines (HWTLs). The proposed method considers the impact of line loss and reveals the comprehensive effects of line length, operation mode, and frequency on HTCs analysis for UDTLs. It is proved that only inter-harmonics can be amplified and cause resonance in lossy standard HWTLs propagation. Using the proposed method, the severity of harmonic amplification is quantitatively calculated. Additionally, this paper provides a fast evaluation approach for potential resonance frequencies of UDTLs, mitigating power quality issues caused by harmonic amplification. The effectiveness of the proposed method is verified by PSCAD simulation.

Modelling and Simulation of Mho Type Distance Relay for High Voltage Transmission Line Protection Using MATLAB Software

Transmission lines are an important part of a power system. Transmission lines have high power transmission capacity and they are prone to faults of larger magnitudes. Various faults occur in transmission lines. Therefore, protection relays are necessary to protect transmission lines. The purpose of protection system is to interrupt the faulty section from the healthy section because the fault currents may damage the electrical equipments. One of the protection relays is distance relay and it is mainly used in transmission line. Sometimes these relay are used for backup protection. Distance relays for determining the impedance need the voltage and current. Transmission lines are typically protected by distance protection relay. Distance relays are considered of high speed class and can provide transmission lines. Nowadays, numerical distance relays have been used instead of using electromechanical and static distance relays. The proposed model was verified under different tests such as single line to ground (L-G) fault, double line to ground (L-L-G) fault, line to line (L-L) fault and three phase (L-L-L) fault. SimPower System was used for modelling and simulation of distance relay, transmission lines and faults. The simulation results were obtained from MATLAB software shows the feasibility of analysis of transmission line protection with mho type distance relay for single line to ground fault, double line to ground fault, line to line fault and three phase fault at different location of transmission lines. The difficulties understanding on operation of distance relay can be cleared by using MATLAB/SIMULINK software.

Optimization Strategy of SVC for Eliminating Electromagnetic Oscillation in Weak Networking Power Systems

The central Tibet AC interconnection project (CTAIP), which connects the Tibet power grid and the Sichuan power grid through a long distance transmission line of more than 1400 km, has a significant problem of voltage regulation. In order to improve the voltage regulation performance, six sets of ±60 Mvar static VAR compensators (SVC) were installed in the CTAIP. However, the SVCs may lead to electromagnetic oscillation below 50 Hz while improving voltage regulation capability. In this paper, the electromagnetic oscillation modes and the sensitivity of control parameters of SVC are analyzed. Then, the characteristics and influencing factors of the oscillation are discussed. It was found that there is an inherent electromagnetic oscillation mode below 50 Hz in the ultra-long distance transmission system. The employ of SVCs weaken the damping of this mode. Large proportional gain and integral gain (PI) parameters of SVCs can improve the voltage regulation performance, but weaken the electromagnetic oscillation mode damping. Therefore, a suppression method based on SVC PI parameters optimization is proposed to damp the oscillation. The essential of this method is to use the rising time of voltage response and setting time of SVCs as performance indicators of voltage regulation, and take the damping level of the electromagnetic oscillation mode as the performance index of SVC electromagnetic oscillation suppression ability. Combining the two indicators to form a comprehensive optimization index function, an intelligent optimization algorithm is applied. The process of SVC parameter optimization and the steps of multi-SVC parameter optimization in large power grids is proposed. Finally, PSCAD and real-time digital simulation (RTDS) simulation results verified the correctness of the proposed method. The optimization strategy was applied to CTAIP. The artificial grounding short circuit experimental results proved the effectiveness of the proposed strategy.

Учет промежуточного отбора мощности в математической модели полуволновой линии электропередачи

The paper studies the mathematical model of the half-wavelength transmission line with intermediate power take-off. The methods of direct calculation of parameters of an equivalent circuit and a four-terminal network are used for the development of the mathematical model of the half-wavelength transmission line with intermediate power takeoff. The calculations are carried out using MathCAD. The presented results demonstrate the features of accounting the individual elements of the mathematical model of the half-wavelength transmission line, which are included in the appropriate power transmission nodes, and their effect on regime parameter calculation. It is shown that the wave character of line parameters variations should be taken into account for the complete and reliable calculation of the regime parameters in any point of the half-wavelength transmission line. Otherwise, the calculation results are contradictory. At the same time, the calculation of regime parameters in the intermediate points should consider that the parameters of long distance transmission lines have a distributed character while the nature of the included element parameters is concentrated.

Evaluation of Capacitive Current Compensation Strategies to Current Differential Protection for Long Distance Transmission Lines

In UHV and EHV, distributive capacitive current to current differential protection has serious problem. Nowadays, to deal with the problem of distributed capacitive current a stimulating modern technology is being used in current differential protection with high operating threshold. Many schemes have been used into current differential protection for capacitive current compensation, which was based on shunt reactor, phasor compensation algorithm, Bergeron method. Those techniques were also reducing operating speed and sensitivity of current differential protection. To solve the problem of distributed capacitive current of the line, novel principle of current differential protection is described in this article. Current calculated from set point to both the ends give rise to a differential criterion. Differential protection is launched under the phenomenon of low sampling frequency to improve the expediency of the criterion. The calculation of set point distributed current is achieved at low sampling frequency by adding an interpolation point at each sampling interval. The point is set in the middle of the line and the calculation for magnitude of the current is done with half data window absolute value integrals, for improved the operating speed of the current differential protection.

Application of piezoelectric transducer in energy harvesting in pavement

Mechanical energy appears everywhere in the nature, road vibration energy created by the vehicle will not only do damage to pavement structure, but also is difficult to collect. Utilizing electromechanical conversion characteristics of piezoelectric material, gather the vibration energy when vehicle passing on the pavement, and design the piezoelectric transducer package box, for traffic lights along the roads, signs, and so on. Save the cost of laying long distance transmission line, also take full advantage of the loss of energy. Experiments of piezoelectric boxes has been conducted in pavement to prove the effectiveness of this product. This study shows that utilize piezoelectric technology in road energy harvesting is feasible and has a bright future.

Value of pumped hydro storage in a hybrid energy generation and allocation system

Transition from fossil fuels to renewable sources is inevitable. In this direction, variation and intermittency of renewables can be integrated into the grid by means of hybrid systems that operate asa combination of alternative resources, energy storage and long distance transmission lines. In this study, we propose a two-stage stochastic mixed-integer programming model for sizing an integrated hybrid energy system, in which intermittent solar generation in demand points is supported by pumped hydro storage (PHES) systems and diesel is used asan expensive back-up source. PHES systems work asa combination of pumped storage and conventional hydropower stations since there is also natural streamflow coming to the upper reservoirs that shows significant seasonal and inter-annual variability and uncertainty. With several case studies from India, we examine the role of high hydropower potential in the Himalaya Mountains to support solar energy generation in the form of pumped hydro or conventional hydro system while meeting the demand at various scales. We show that pumped hydro storage can keep the diesel contribution to meet the demand less than 10%, whereas this number can go up to more than 50% for conventional systems where the streamflow potential is limited compared to the demand. We also examine the role of pumped hydro systems in both isolated and connected systems (through inter-regional transmission lines) and show that the benefit of pumped hydro is more significant in isolated systems and resource-sharing in connected systems can substitute for energy storage. In addition, with the help of the proposed model, we show that the upper reservoir size of a pumped hydro system could be lower than the reservoir size of a conventional hydropower system depending on the demand scale and streamflow availability. This means that, most of the current conventional hydropower stations could be converted to pumped hydropower stations without needing to modify the upper reservoir, leading to a significantly reduced diesel contribution and lower system unit cost.

The Analysis of Overvoltage on 220kV Transmission Line in Single-phase Reclosing

Because of line-to-line inductance and capacitance, overvoltage may occur in single-phase reclosing process when breaker is reclosed on unloaded 220kV long distance transmission line. The paper establishes a model system of single generator to infinite bus power system with PSCAD simulation software, analyzes overvoltage in reclosing operation of 220kV long distance transmission line, studies the influence factors as reclosing phase angle, system equivalent impedance, transmission line parameters etc. It shows that reclosing phase angle and zero sequence line parameters have large effects to overvoltage, as the system equivalent impedance has lower effects.

Hybrid damping adaptive control scheme for grid‐connected inverters in a weak grid

The distributed generation system (DGS) located far away from load centres leads to the existence of long distance transmission lines and several transformer devices. Consequently, the equivalent impedance is introduced to a grid, which is called a weak grid and shows high impedance characteristic. A weak grid will affect the control loop stability of grid-connected inverters in DGS. To study the effects of a weak grid, the small signal model of single-phase LCL-type grid-connected inverters is first derived in this study. Then, the stability of grid-connected inverters caused by the grid impedance is analysed. Second, two common control schemes of passive and active damping are further studied. Then, the effects of the grid impedance on the damping coefficients under different damping options are analysed in quantity. A novel hybrid-damping control scheme is thereby proposed. Meanwhile, an adaptive control scheme of grid-connected inverters based on the hybrid damping is introduced in combination with the grid impedance online measurement, which ensures the stable performance of grid-connected inverters with different grid impedances. Finally, a prototype is built to verify the effectiveness of the proposed adaptive control scheme.

Design of low-power, low-voltage, differential I/O links for High Energy Physics applications

This work presents the design of a low-power, differential signaling, input/output data link in a 65 nm CMOS process for high energy physics (HEP) experiments. The proposed driver, able to operate at 320 Mbps or 640 Mbps with a normalized power dissipation of 3.125 mW/Gbps, is meant to drive short distance (between 2 and 10 cm) transmission lines located to the module hybrid circuit. A de-emphasis technique has been adopted to reduce the impedance mismatch effects between the driver output and the transmission line. This paper will discuss in detail the solutions implemented in the design and will describe the simulation results.

Electric field analysis on the insulation design of the stop joint box for DC HTS power cable

DC HTS power cable is a promising electric power transmission line for the future of smart grid, and it has been competitively investigated at many research institutes all over the world. For the commercialization of DC HTS cable, higher power transmission capacity and longer length for long distance transmission line should be prepared. In order to meet the needs of long distance DC HTS cable, a joint box should be developed for the connection of cable components. As for AC HTS cable, a number of patents of nominal joint box have been already reported. However, any conceptual designs of the joint box for DC HTS cable have not been suggested yet. One of the reasons is that the cryogenic high voltage insulation design, especially in DC environment is not fully investigated yet. Conventional normal joint box for AC HTS cable could not be directly applied to DC HTS cable because different electric field distributions compared to AC electric field which requires totally different electrical insulation design concepts. In this paper, in order to establish the basic insulation design of the stop joint box (SJB) for DC HTS cable, three kinds of SJB models were designed and electric field analyses have been conducted both considering AC and DC environment. And the critical factors affecting the DC insulation design of the stop joint box were analyzed. From the simulation results, it was observed that the electric field distribution was totally different both in AC and DC operating conditions. And it was possible to find the weakest regions in the insulation design of the SJB. Consequently, based on the DC electric field analysis, the insulation design criteria and the desirable configurations were suggested for the insulation design of the stop joint box for DC HTS cable.

Optimal Location of Shunt Facts Devices For Power Flow Control

Power flow control, in an existing long transmission line, plays a vital role in Power System area. This paper employs the shunt connected compensation (STATCOM) based FACTS device for the control of voltage and the power flow in long distance transmission line. The proposed device is used in different locations such as sending end of the transmission line, middle and receiving end of the transmission line. The PWM control strategy is used to generate the firing pulses of the controller circuit. Simulations were carried out using MATLAB Simulink environment. The suitable location and the performance of the proposed model were examined. Based on a voltage-sourced converter, the STATCOM regulates system voltage by absorbing or generating reactive power. Contrary to a thyristor-based Static Var Compensator (SVC), STATCOM output current (inductive or capacitive) can be controlled independent of the AC system voltage. The simulation results reveals that the reactive power generated is better at the middle of the transmission line when compared with the other ends of the transmission line and also the voltage is controlled at the middle of the line. Henceforth the location of STATCOM is optimum when connected at the middle of the line.