No-load Line Research Articles

Analysis of Switching Overvoltage and Suppression Measures in UHV Transmission Lines

As the ultrahigh-voltage (UHV) projects are rapidly developing, it is necessary to investigate the problems involved in overvoltage and insulation, thereby providing a technical basis for future UHV projects. The switching overvoltage of closing no-load lines was simulated and analyzed here using two kinds of typical UHV network structures: the power plant to the grid system and the grid-to-grid system. Different factors, such as line length, mode of operation on the power plant side, and short-circuit capacity, are considered. It is possible for lines shorter than 60 km to eliminate the closing resistor, determined by calculating the probability of flashover. We analyzed the phase selection closing in depth to inhibit the switching overvoltage and considered the factors such as phase deviation and the length of the line. Finally, the applicability of phase selection closing is put forward for lines of different lengths.

Analysis Model for VFT Considering the Effect of Nonuniform Distribution of Residual Charge

The magnitude and distribution of residual charge have a significant effect on very fast transients (VFTs) in gas-insulated substations (GISs). So far, as we know, references for researching the effect of a nonuniform distribution of a residual charge on VFT have not been found. Considering the effect of a nonuniform distribution of a residual charge, a hybrid method is presented in this manuscript by combining the finite-element method (FEM) and finite-difference time domain (FDTD) for analyzing VFT. In this method, the distribution of residual charge along a no-load line may be first analyzed at the moment before the arc starts by using the FEM. And then, based on transmission-line theory and considering the residual charge as an initial value, VFT is analyzed by using FDTD. The validation of the method was performed in comparison with the 3-D-Maxwell model-based transient simulation. On the point of setting initial voltage, the proposed analysis process is more practical to actual VFTs than the Electromagnetic Transients Program and COMSOL analysis in references, and it is better to deeply research the mechanism of VFT generation, especially the effect of the initial phase of operation on VFTs and the suppression of VFT overvoltage in GIS.

Close-Operation Overvoltage of No-Load Transmission Line with Fault Current Limiter

The comprehensive impacts of series resonance type fault current limiter (FCL) on power system need further investigation and verification. With regard to switching on 500kV EHV no-load transmission line, the instantaneous peak value, the free component oscillation frequency, the fundamental component amplitude and free component amplitude of terminal overvoltage waveform are simulated with and without installation of FCL considering different switching times. The relationship curves of free component oscillation period, the fundamental component amplitude and free component amplitude are gotten respectively by simulation results. The law of the influence of different fault current limiting reactance on terminal voltage of switching on no-load line is also summarized. The analysis results show that the installation of FCL is benefit for switching on no-load line.

Study on Very Fast Transient Overvoltage of Closing No-load China UHV Transmission Demonstration Project Jindongnan-Nanyang-Jingmen 1000 kV Transmission Lines

When the ultra high voltage (UHV) substation used the gas insulated switchgear (GIS) system to switch lines with capacitive current, the pre-breakdown and multiple reignition will occur between switching contacts. Because of discharge characteristics of SF6 and special structures of GIS system, the variations of the electromagnetic transient process and very fast transient overvoltage (VFTO) are very fast and extremely complex. The development process and characteristics of VFTO remain to be dealt with to seek effective suppression measures. The overvoltage of closing no-load long lines on GIS system is analyzed in detail. The simulation model of the very fast transient process of closing no-load long lines on UHV GIS system is established. The VFTO of closing no-load China UHV transmission demonstration project Jindongnan-Nanyang-Jingmen 1000 kV transmission lines is analyzed using electromagnetic transient simulation software ATP-EMTP. The VFTO of closing no-load long lines on UHV GIS system is simulated and calculated, when the system has no additional closing resistors and lightning arresters, additional single stage closing resistors, additional multistage closing resistors, lightning arresters in two terminals of lines, lightning arresters in two terminals and the middle of lines, and additional multistage closing resistors and lightning arresters in two terminals and the middle of lines. The simulation results show that the additional multistage closing resistors and lightning arresters in two terminals and the middle of lines can effectively restrain the VFTO of closing no-load long lines on UHV GIS system.

Research on the Influence of 500kV Power Engineering Materials Line Parameters to EFT/B

In this paper, the influence of 500kV power line engineering materials parameters to EFT/B is discussed. When the 500kV line isolation switch cut off no-load line, arc would generate between the disconnecting switch. This paper mainly discussed the influence that disconnecting time on the electrical fast transient burst. At the time of the current zero-crossing, if the arc gap dielectric strength is less than the arc gap recovery voltage, the arc gap will be broken-down and the arc reignites. This paper analyses the influence on EFT/B caused by different power line engineering materials parameters including the moment of arc reigniting, transformer inductance and capacitance of power line. Through this research we can effectively reduce the disconnecting time by change the power line engineering materials parameters and improve the state of EFT/B.

Adaptive Neural Subtractive Clustering Fuzzy Inference System for the Detection of High Impedance Fault on Distribution Power System

High impedance fault (HIF) is abnormal event on electric power distribution feeder which does not draw enough fault current to be detected by conventional protective devices. The algorithm for HIF detection based on the amplitude ratio of second and odd harmonics to fundamental is presented. This paper proposes an intelligent algorithm using an adaptive neural- Takagi Sugeno-Kang (TSK) fuzzy modeling approach based on subtractive clustering to detect high impedance fault. It is integrating the learning capabilities of neural network to the fuzzy logic system robustness in the sense that fuzzy logic concepts are embedded in the network structure. It also provides a natural framework for combining both numerical information in the form of input/output pairs and linguistic information in the form of IF–THEN rules in a uniform fashion. Fast Fourier Transformation (FFT) is used to extract the features of the fault signal and other power system events. The effect of capacitor banks switching, non-linear load current, no-load line switching and other normal event on distribution feeder harmonics is discussed. HIF and other operation event data were obtained by simulation of a 13.8 kV distribution feeder using PSCAD. The results show that the proposed algorithm can distinguish successfully HIFs from other events in distribution power system DOI: http://dx.doi.org/10.11591/ij-ai.v1i2.425

Research on Microcomputer Relay Protection Anti-Interference of 500kV Transmission Line in MATLAB

This paper established a 500kV microcomputer protection model with EFT/B generator. The generator was built based on the mechanism of arc forming and distinguishing when cutting off the no-load transmission line. The according parameters were set by the arc estimating formula and test data. The simulations shows that the traditional disincentive measure is limited for high voltage line and the arithmetic is still sensitive to the disturbance and made the relay set false operation. A comprehensive measure is put forward and tested by the microcomputer protection arithmetic.

Development of a fuzzy inference system based on genetic algorithm for high-impedance fault detection

A novel method for high-impedance fault (HIF) detection in distribution systems is presented. Using this method HIFs can be discriminated from isolator leakage current (ILC) and transients such as capacitor switching, load switching (high/low voltage), ground fault, inrush current and no-load line switching. Wavelet transform and principal component analysis are used for feature extraction/selection. A fuzzy inference system is implemented for fault classification and a genetic algorithm is applied for input membership functions adjustment. HIF and ILC data was acquired from experimental tests and the data for other transients was obtained by simulation of a real 20 kV distribution feeder using EMTP. Results show that the proposed procedure is efficient in identifying HIFs from other events.

Circuit-breaker requirements for alternative configurations of a 500 kV transmission system

This paper describes a study made to assess the electrical stresses imposed on line circuit breakers of a new 500 kV AC expansion of the FURNAS transmission system, to be possibly installed in the Brazilian central region. The study has considered three configurations of the transmission lines, two of which assume the use of compact towers. In one of these two cases, the lines would have high surge-impedance loading. Digital simulations have been made with the aid of the Alternative Transients Program (ATP) to calculate the switching transients appearing as a result of line energization and reclosing, clearing of terminal and short-line faults, no-load line opening in normal and faulted conditions and out-of phase switching. Four alternatives have been considered for the limitation of overvoltages on closing, assuming either the sole use of surge arresters on each line end or the use, in addition to the arresters, of pre-insertion resistors, synchronizers or time relays to provide a staggered closing of the breaker poles. The stresses obtained were compared with those applied by the standard IEC tests or with the maximum admissible levels usually considered by the utility for its transmission branches at the planning stage.

Switching Surge Test on No-Load 187-kV Transmission Line

Descriptions are given of measurements of switching surge generated by air blast breaker switching of charging current on no-load transmission line of the 187-kV effectively grounded system, with one-step insulation reduction, belonging to the Shikoku Electric Power Company, Japan. Measurements have been made on phase-to-ground surge overvoltages and phase-to-phase overvoltages at the sending end and receiving end, corresponding to various breaker operations, including high-speed reclosing. To examine the effect of system configuration upon switching surge, tests have been made on two system configurations. Maximum values of switching surge overvoltages which are likely to occur in the test system have been calculated by means of computer, and, making due reference to the measured results, insulation coordination has been examined.