HVAC Transmission Lines Research Articles

Analysis of electromagnetic coupling of HVAC cable section partly installed in parallel with HVDC lines in one corridor

Abstract For HVAC and HVDC transmission lines which are partially in parallel in one corridor, coupling parameters between AC and DC transmission lines can be changed due to the length of extension sections which are not in parallel. And the generated electromagnetic coupling components at the two terminals of the DC line contain the effects of line parameters of extension sections. In this paper, the coupling components on the DC line, not all of which is in parallel with the AC line are studied in detail. The DC line is longer than the AC line and it may have extension sections on the both sides. Firstly, a new methodology is presented to calculate the coupling components of HVAC line upon HVDC line in the above situation. Then, the correctness and applicability of this method is illustrated and validated through a case study. Meanwhile, the key factors affecting the coupling between the AC and DC lines are analyzed. Finally, some suggestions have been proposed to provide as a construction reference which aims to optimize the electromagnetic coupling components on the DC line.

Simulation of Power Plant Subsynchronous Resonance Possibility Based on ADPSS

The rotor shaft of a steam turbine generator consists of several masses, such as rotors of turbine sections, generator section and exciter section. When the generator is perturbed, it will cause torsional oscillation between different sections. In long-distance high-capacity transmission lines, series compensation with capacitors can enhance power transfer capability of power system, however it may cause subsynchronous resonance (SSR) between the turbine shaft and serial compensation., which produce large shaft torques can result in a reduction in the shaft fatigue life and possibly shaft failure, threatening the security of generator unit and stability of power system. In China the 1000kV HVAC transmission line with series compensation has been put in operation since 2009. Near the Nanyang substation, there has a power plant in Henan power grid. So it is necessary to model the power plant and HVAC transmission line to simulate the possibility of SSR problem. Based on the power system simulation software ADPSS developed by China Electric Power Research Institute (CEPRI), this paper built up the simulation model using the electromechanical-electromagnetic transient hybrid method, and simulated the SSR possibility between the power plant and HVAC transmission line series compensation. The simulation results showed that with the generator parameters given, there has no risk of SSR between them. This paper also gives an evaluation principle of generator SSR risk when connected into a power grid.

Simulation of Power Plant Subsynchronous Resonance Possibility Based on ADPSS

The rotor shaft of a steam turbine generator consists of several masses, such as rotors of turbine sections, generator section and exciter section. When the generator is perturbed, it will cause torsional oscillation between different sections. In long-distance high-capacity transmission lines, series compensation with capacitors can enhance power transfer capability of power system, however it may cause subsynchronous resonance (SSR) between the turbine shaft and serial compensation., which produce large shaft torques can result in a reduction in the shaft fatigue life and possibly shaft failure, threatening the security of generator unit and stability of power system. In China the 1000kV HVAC transmission line with series compensation has been put in operation since 2009. Near the Nanyang substation, there has a power plant in Henan power grid. So it is necessary to model the power plant and HVAC transmission line to simulate the possibility of SSR problem. Based on the power system simulation software ADPSS developed by China Electric Power Research Institute (CEPRI), this paper built up the simulation model using the electromechanical-electromagnetic transient hybrid method, and simulated the SSR possibility between the power plant and HVAC transmission line series compensation. The simulation results showed that with the generator parameters given, there has no risk of SSR between them. This paper also gives an evaluation principle of generator SSR risk when connected into a power grid.

Shielding Effect of HVAC Transmission Lines on the Ion-Flow Field of HVDC Transmission Lines

The HVDC and HVAC transmission lines running on the same tower is a promising technology to improve the transmission capacity of an existing corridor. The ions generated by corona discharge of HVDC transmission lines will strengthen the ground-level electric field, which may endanger human exposure. To investigate how the presence of HVAC transmission lines changes the ion-flow field, experiments are carried out on an indoor test model with bipolar dc and three-phase ac lines. The experiment results are then compared with the simulation results. The experiment and simulation results show that the HVAC transmission lines have a shielding effect on the ion-flow field from the HVDC transmission lines running above. Finally, the ground-level electric field and ion current density of the ±800-kV HVDC and 500-kV HVAC transmission lines running on the same tower are calculated.

Analysis of ion flow field of UHV/EHV AC transmission lines

In this work, the calculation method of the ion flow field of AC transmission lines based on the charge simulation method is improved. As the previous works, the problem is solved in time domain with representing the space charges as discrete line charges. In each discrete time step, the procedures of charge emission, space charge displacement, and space charge recombination are simulated. As improvements, the influence of the conductor surface field uniformity on corona discharge is taken into account, so that the ion flow field of multi-phase or bundle conductors can be simulated in this work. The corona losses of a 3-phase 8-conductor bundle HVAC transmission line is calculated. Acceptable agreement is obtained with the experimental results. The ground level total electric field of different line configurations is calculated. The influences of line configurations such as subconductor radius, bundle spacing, number of subconductors, wire spacing, and phase height on ground level total electric field are analyzed based on the calculation.

Analysis of Shock Effect Generated by Vehicles on Human Body under HVAC Transmission Lines

The shock effect has been analyzed when the human body touches different types of vehicles in power frequency electric field. It solved the problem of influence of induced voltage generated by high voltage AC Power Lines on human Body. The induced voltage value of the human body and three different types of vehicles has been calculated by the soft of ANSYS in this paper. The results indicate that the human body will be shocked by two processes of transient and steady state. The influence of shock effect of transient and steady state on human body has been selectively analyzed when the human body touches vehicles. The proposed models and algorithm has the advantages of simple calculation procedure, small calculation burden and convenient to engineering application. It can be applied to the shock effect when the human body touches metal objects with different potential in power frequency electric field. It is worth being populated.

Research on the Technology of Converting the Existing AC Lines to DC Lines

Power transmission is a key link in power system. As the increase of power supply, the transmission capacity of the lines should be enlarged too. In the developed area, the right-of-way for transmission line is hard to be obtained. And converting the existing HVAC overhead transmission lines using HVDC technology could enhance the transmission capability. There are three possible plans for different HVAC transmission lines: single-pole HVDC, bi-pole HVDC and tri-pole HVDC.

Simulation of Ion-Flow Field at the Crossing of HVDC and HVAC Transmission Lines

This paper aims at developing a simulation method for the ion-flow field when HVDC transmission lines cross over HVAC transmission lines. A time-domain 3-D method is proposed in this paper, where the 3-D finite-element method and 3-D finite volume method are used to solve the Poisson's equation and the charge conservation law, respectively. The implicit temporal discretization scheme is used to accelerate the computation. An indoor test model is set up in this work, and the simulation results agree well with the measured results from this test model, which validates the proposed method. The proposed method is then used to calculate the ground-level electric field and ion current density under the crossing of ± 800-kV HVDC transmission lines and 500-kV HVAC transmission lines. The presence of HVAC transmission lines is found to have a significant influence on the ion-flow field under the crossing.

Finite Volume-Based Approach for the Hybrid Ion-Flow Field of UHVAC and UHVDC Transmission Lines in Parallel

Sharing the same corridor of the HVAC and HVDC transmission lines can efficiently increase the power transfer capacity of the limited corridor and will be erected in East China. An accurate and efficient numerical analysis method for analyzing the ion-flow field of the ac-dc hybrid lines is helpful for engineering design. In this paper, an upwind finite volume-based algorithm for the solution of the ac-dc hybrid ion-flow field is proposed, which can take the influence of the space charges generated by corona into account. The electric field is solved by the charge simulation method and the finite-element method, while the advection and recombination effects of the space charges are solved by a time-dependent finite volume method. The reduced-scale ac-dc hybrid models are analyzed and the calculating results by the proposed approach in this paper have good agreements with the experimental ones in the literature and in this paper. Finally, the ground-level electric field and ion current density of the hybrid UHVAC and UHVDC transmission lines in parallel are analyzed, providing a reference for the engineering design.

Wideband and Narrowband HVDC Conductor Corona Test Methods for Radio Noise Prediction

Various conductor corona test methods have been used to predict corona performance of HVAC transmission lines. Due to the formation and build-up of space charge, it is unclear whether the same methods can be used for corona performance of HVDC conductors. We investigate the use of a large corona cage, a short test line, and a small corona cage at high altitude to generate RI data. Wideband excitation functions are derived using time- and frequency-domain techniques. These generation functions are compared to CISPR standard narrowband measurements as well as published empirical RI prediction formulas. We find that a small corona cage cannot be used to accurately predict the RI performance of HVDC transmission lines at high altitude.

Flashover prevention on high-altitude HVAC transmission line insulator strings

Numerical analysis, on-site measurements, and laboratory experiments are used in this paper to analyze and solve the flashover problems of 330 kV AC high altitudes transmission line middle phase glass suspension insulator strings. A sub-model approach based on a finite element method (FEM) applied in calculating the potential and electric field distribution along the insulator strings under clean and dry conditions. Using this approach, three dimensional electrostatic models (taking into account the grading rings, subconductors, tower framework, and yoke plates) are set up and investigated. On-site and laboratory measurements were also carried out to make a comparison. A relatively good agreement was obtained among the calculated, the on-site, and the laboratory measured results, which demonstrated that insulator disk nearest to the high-voltage end is required to withstand relatively high voltage according to the standard in China; in addition, the insufficient dry arc distance of the insulator strings is also proposed. Subsequently, the long insulator-string flashover tests under dry, wet, and artificial contaminated (ESDD=0.05 mg/cm/2, NSDD=0.3 mg/cm/2) conditions, considering the middle (flashover) and side phase (never flashover), respectively, are carried out to validate the proposed insufficient dry arc distance and discuss the measures for solving the flashovers. From the effective, convenient and economical standpoint for the reconstruction of the flashover lines, lowering the grading rings' position and adding a unit of insulator are considered to lengthen the dry arc distance of the middle-phase insulator string in the tests. The experimental results are compared and discussed, and it has been concluded that adding a unit of insulator is an effective and economical way to solve the flashover problems. The methods for analyzing the flashover problems are effective and can be used for other voltage-level transmission lines.

Lightning Shielding Failure Analysis of UHVAC Transmission Lines with an Improved EGM

Lightning shielding failure is an important issue in addressing the lightning performance of HVAC transmission lines. In this paper, an improved electro-geometric model (EGM) is proposed to evaluate the shielding failure outage rate of UHVAC transmission lines. In the improved model, the striking distances to phase conductors, shielding wires and the ground are differentiated, respectively. Furthermore, the influences of ground obliquity, wind deflection and instantaneous operating voltage of phase conductors are taken into account. The proposed improved EGM is applied to calculate the lightning shielding failure outage rate of a UHVAC transmission line to be built in a demonstration project in China. The simulation results show that the maximal difference of shielding failure outage rate due to the phase angle change of the conductor voltage in a period can reach 0.12 times/100 km·a. The shielding failure outage rate increases monotonously with the increment of ground obliquity and wind speed. The shield...

A New Environmentally Friendly Design Program, TLCALC 2001 for High Voltage AC Transmission Lines

Various noises produced by corona discharges from high voltage transmission lines are the important considerations in line design. HVAC transmission lines must be designed to satisfy national environmental regulations too. Therefore, it is necessary for line designers to pre-evaluate environmental problems using prediction tools. In this paper, an environmental design software, TLCALC 2001 for AC transmission lines as a comprehensive window program is introduced. It has 6 modules including audible noise, radio noise, television noise, magnetic field, electric field and conductor surface gradient module. TLCALC 2001 has solved some of the problems of the existing foreign tools and has several advantages over those. 1) It is a common tool that has solved calculating limitations of foreign formulas. 2) It has a wide application range and enhanced prediction accuracy. 3) It can be applied to almost all transmission line configurations in Korea. 4) Experienced designers can get calculation results within about 15 minutes. As the use of TLCALC 2001 is easy and practical, it will be applied to the environmentally friendly design and construction of transmission lines. It is expected that public complaints and social environmental costs will be considerably reduced by the use of TLCALC 2001 in the future.

Calculation of single phase AC and monopolar DC hybrid corona effects

Operating a hybrid HVAC and HVDC power transmission line is an option for increasing the efficiency of power transmission and overcoming the difficulties in obtaining a new right-of-way. This paper proposes a new calculation method for the study of hybrid power line corona. The proposed method can be used to calculate DC corona losses and corona currents in DC or AC conductors for single phase AC and monopolar DC hybrid lines. Profiles of electric field strength and ion current density at ground level can be estimated. The effects of the presence of an energized AC conductor on DC conductor corona and DC voltage on AC conductor corona are included in the method. Full-scale and reduced-scale experiments were utilized to investigate the hybrid line corona effects. Verification of the proposed calculation method is given.

The Effect of HVAC-HVDC Line Separation in a Hybrid Corridor

Increasing difficulties in obtaining new rights-of-way (ROW) for transporting electric power over long distances call for the development of additional transmission options to maximize the power transfer capability of a corridor. One such option is the sharing of the same corridor by HVAC and HVDC transmission lines (hybrid corridors). The proximity between HVAC and HVDC conductors causes interactions between the two line types. These interactions can produce changes in the electrical and environmental performance of a hybrid corridor from what would be expected if the two lines were acting independently. This paper presents the results of a sensitivity analysis relating the corona and field effects to the variation of the physical parameters of hybrid corridors, with the primary focus being on the separation of the two line types.

Digital generator of corona noise on power line carrier channels

A procedure is presented for the design of a digital simulator which generates a random time sequence having the statistical characteristics of the corona noise that occurs on transmission line carrier channels. The method involves the synthesis of an autoregressive filter excited by a white-noise generator is a part of the overall digital transmission system, which includes the generating and receiving sections, and the PLC (power line carrier) channel. The proposed procedure is applied to simulate corona noise on practical HVAC transmission lines.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Probability and Consequence of Gasoline Ignition Under HVAC Transmission Lines

This paper reports on an evaluation of the probability and consequences of electric field induced fuel ignition during refueling near HV transmission lines. Probability of fuel ignition is evaluated using a Monte Carlo simulation and results are applied to a sample problem to demonstrate event likelihood. A series of experiments using a specially modified vehicle provides the answer to what happens if ignition occurs. For occurrence on a typical 500 kV ROW the possibility of electric field induced fuel ignition is extremely unlikely to occur as shown in Table I. The experiments indicate that even if electric field induced sparks cause fuel ignition, this is not a catastrophic event and does not pose a safety hazard for practical situations. Figure 1 shows the typical flame from an ignited vehicle gasoline tank. Usually the flame extinguishes itself or the flame can be snuffed out with a handkerchief. If enough gasoline spilled and burned for something like ten minutes or more, then the tank could have become warm enough to become concerned about the very harzardous situation of boiling gasoline.

Measurement and Statistical Analysis of Ozone from HVDC and HVAC Transmission Lines

Measurement and Statistical Analysis of Ozone from HVDC and HVAC Transmission Lines

Switching Tests on Grounding Switches for Gas Insulated Substations

The paper deals with an investigation on the capacitive and inductive switching capability of grounding switches, as required for parallel HVAC transmission lines with one circuit carrying the current while the other is grounded at both ends. When the grounding switches are opened, they have to interrupt both the induced inductive current, and the current coupled capacitively. In addition, they have to withstand the transient recovery voltage (TRV).

High Voltage AC Transmission Lines: Reduction of Corona Under Foul Weather

Can improved conductor designs lower the corona levels (audible noise, electromagnetic interference, power losses) of HVAC transmission lines under foul weather conditions? Three types of improved conductors are considered: hydrophilic, hydrophobic and ion-shielded.