Overvoltage Characteristics Research Articles

Mechanism and suppression of breaking overvoltage of DC circuit breakers

AbstractThe occurrence of breaking overvoltage in a DC circuit breaker (DCCB) poses a potential threat to the safe operation of a DC grid. Based on the structure of the ±10 kV three‐terminal DC distribution network, this paper sets up the medium‐voltage DCCB and formulates a fault protection strategy. Additionally, a simulation model of the system is developed to analyse the overvoltage characteristics within the DC distribution network across different nodes and fault conditions. By examining the factors that influence breaking overvoltage, this paper unravels the fundamental mechanisms associated with DCCB‐related overvoltage generation. Furthermore, the paper suggests measures to alleviate DCCB overvoltage. These insights provide a theoretical and technical basis for the design and operation of DCCBs within DC distribution networks.

Capacity Planning Method for Wind–Solar–Thermal-Storage Bundled HVDC Sending System Considering Transient Overvoltage Constraints

High-voltage direct current (HVDC) sending systems have been the main means of renewable power cross-regional sharing and consumption. However, the transient overvoltage problems restrict the transmission capacity and renewable energy accommodation. The allocation of wind–solar–thermal storage capacity has become an important factor affecting the safety and stability of renewable energy sending. A capacity planning method is proposed for a wind–solar–thermal-storage bundled HVDC sending system considering transient overvoltage constraints. Firstly, based on quantile regression analysis and Gaussian mixture modeling, the typical scenario generation method is proposed to depict the uncertainty of renewable energy. Then, the transient overvoltage characteristics of the integrated HVDC transmission system are analyzed. The relationship between the power output of power sources and the system short-circuit capacity is derived. Meanwhile, the calculation method of the minimum short-circuit capacity of the HVDC system is proposed. Based on the calculation method, the transient overvoltage constraint corresponding to the voltage support strength is constructed. Finally, considering the transient overvoltage constraints, the capacity planning model of the wind–solar–thermal storage is established. The upper-layer model optimizes the configuration scheme of the wind–solar–thermal storage to minimize the total system cost. The lower-layer model optimizes the operation scheduling under the typical operation scenarios of renewable energy and delivery load. The optimal capacity planning scheme for the wind–solar–thermal storage is determined through the coordinated optimization of the two-layer model. The feasibility and effectiveness of the proposed method are verified through a case analysis. The results show that the proposed planning method can effectively maintain a higher short-circuit ratio and improve the voltage support strength under the premise of completing the sending plan.

Interference Characteristics of Electromagnetic Transient Overvoltage on Secondary Equipment of UHV Fixed Series Capacitors

This manuscript addresses the issue of electromagnetic radiation interference experienced by secondary equipment in ultra-high voltage (UHV) fixed series capacitors (FSCs) under electromagnetic transient overvoltage conditions, which cannot be easily determined. To tackle this, a simulation and analysis method for the electromagnetic interference characteristics of secondary equipment is proposed. First, a primary system simulation model of UHV FSC is established, including modeling the platform’s multi-conductor system. The electromagnetic transient overvoltage signals between the low-voltage busbar and the high-potential platform are then simulated and analyzed under two conditions: spark gap triggering and disconnector operation. Next, a finite element model of secondary equipment is created to simulate and analyze the electric field distribution of different materials in the area of the measuring box. The shielding effectiveness of the measuring box is calculated using the overvoltage signals at the measuring box location as excitation. This method allows for the simulation of the electric field distribution in the measuring box area for different materials and calculates the shielding efficiency of the measuring box. It effectively simulates the complex electromagnetic environment of secondary equipment, assesses the electromagnetic shielding efficiency of the measuring box, and provides a theoretical basis for analyzing and improving the anti-interference characteristics of the measuring box.

Research on Ultra-Fast Transient Overvoltage Characteristics of Electric Locomotive

Operating overvoltage occurs when the pantograph or main breaker of an electric locomotive is operated, which is prone to causing insulation failure of high-voltage equipment. The HXD1 electric locomotive is taken as the research object in this paper to explore the characteristics and influencing factors of operating overvoltage. Under pantograph lifting, main breaker closing, main breaker opening, and pantograph dropping, operating overvoltage waveform in the high-voltage system is recorded by a high-speed oscilloscope and resistance–capacitance voltage divider to analyze the overvoltage characteristics and distribution law. Tested data show that the amplitude of operating overvoltage is in the range of 80 to 330 kV with ultra-high steepness, which is similar to the Very Fast Transient Overvoltage (VFTO) in power systems. The maximum overvoltage during the entire test occurred during the main breaker closing and its amplitude is 328.60 kV with a steepness of 4.21 × 104 kV/μs. The max overvoltage of the other operations (pantograph lifting, main breaker opening, and pantograph dropping) are 280.60 kV, 194.73 kV, and 305.56 kV with ultra-high steepness. High-amplitude overvoltage is predominantly located at the pantograph, while the low-amplitude sort is mainly observed around other high-voltage equipment. The result indicates that operating overvoltage belongs to ultra-fast transient overvoltage and its amplitude and steepness are higher than existing research.

Simulation on Operating Overvoltage of Dropping Pantograph Based on Pantograph–Catenary Arc and Variable Capacitance Model

When the electric locomotive pantograph is dropping, the interruption of pantograph catenary contact causes electromagnetic oscillation and arcing. The frequent arc burning that occurs due to charge accumulation results in the amplitude of overvoltage increasing gradually, posing a threat to locomotive high-voltage equipment. However, the physical mechanisms and characteristics of overvoltage are still unclear. This paper proposes a simulation model of operating overvoltage due to a dropping pantograph based on the pantograph–catenary arc and variable capacitance. Distributed RLC electromagnetic oscillation is considered, which allows the real-time calculation of arc resistance and capacitance. Under the same working conditions, the error between the simulation and test results is less than 4.0%, which proves the credibility of the model. The variation law of overvoltage under different dropping speeds or catenary phases was investigated, which shows the max amplitude is 298.20 kV and steepness is 2096.80 kV/μs at 0.30 m/s speed. The waveform shows the characteristics of high amplitude and high steepness, similar to very fast transient overvoltage (VFTO). There is a sinusoidal relationship between the catenary phase and overvoltage amplitude. The closer the catenary phase to 90°, the higher the overvoltage amplitude. The research has important guiding significance for the overvoltage formation mechanism of a traction power supply system and the insulation coordination design of high-voltage equipment.

Simulation analysis of overvoltage caused by grounded short circuit in the collection system of far-offshore wind farms

Abstract As the distance from the shore of offshore wind farms increases, MMC-HVDC technology is gradually gaining attention in its grid connection schemes. A broadband electromagnetic transient model of offshore wind farms with a total capacity of 800 MW connected to the grid via a flexible direct current transmission system is developed. After three types of grounded short circuit faults occur at different fault positions within the power collection system, the characteristics of overvoltage are obtained and they are analyzed on the basis of considering the low voltage ride-through capability of the direct-drive permanent magnet wind power generator. Combining the two factors of range and amplitude, the results show that the overvoltage phenomenon is the most serious when a two-phase grounded short circuit occurs at the converging busbar, which can be the focus of the study when setting up overvoltage protection.

Study on fast transient overvoltage characteristics of substation under UHV disconnector operation

Abstract Due to the short duration of fast transient overvoltage in the substation, the suppression effect under the control strategy of traditional optimization equipment and switches is not good. Therefore, the characteristics of fast transient overvoltage in substation under the operation of a UHV disconnector are proposed. The fast transient condition of the substation is analyzed, the corresponding simulation method is set, and it is simulated. The elimination operation is carried out by using the reverse sequence backtracking formula, and the relevant parameters of the fast transient condition simulation of the substation are obtained. The inductance of the substation is calculated in the fast transient process, the potential in the equivalent circuit is obtained by using the capacitance and inductance, and the reactive power compensation capacity on the electromagnetic transient model of the fast transient process is comprehensively considered, so as to calculate the rapid transient overvoltage of the substation and realize the research on overvoltage characteristics. The method in this paper can ensure the rapid transient overvoltage level decline, successfully realize the automatic voltage regulation, effectively maintain the stability of voltage, and effectively restrain overvoltage to keep it within an acceptable range.

Single pulse lightning and multiple lightning intrusion overvoltage in 500 kV GIS substation

Abstract Lightning intrusion wave is a key factor threatening the safe operation of substations. This paper uses electromagnetic transient simulation software to calculate and analyze the overvoltage characteristics and influencing factors of lightning intrusion waves in GIS substations. It studies the effects of lightning current waveform, corona effect, and multiple lightning strikes on the lightning overvoltage. The results show that with the same amplitude of lightning current, the longer the duration and lower the steepness are, the lower the peak and steepness of lightning overvoltage invading the power station will be. As the distance between the lightning strike point and the substation increases, the attenuation effect of corona on lightning overvoltage shows a “not obvious-significant-saturation” pattern. When multiple lightning strikes occur, the peak and steepness of overvoltage caused by the first lightning strike are the highest, and the temperature rise of the lightning arrester varies linearly with the number of lightning strikes.

A case study on transformer ferroresonance for subsea cable connected 230 kV substations using PSCAD

This research paper presents a comprehensive procedure on how to perform a ferroresonance study in a system dealing with the addition of subsea cable interconnector-2 between two 230 kV substations which is previously linked by subsea cable interconnector-1. Addition of a subsea cable interconnector-2 needs to be investigated for ferroresonance in planning and designing stages itself since the interaction between cable capacitive reactance and power transformers-magnetizing core which is a non-linear inductance may cause ferroresonance. The investigation is conducted in three stages namely energisation, de-energisation and stuck pole conditions of circuit breaker. Each stage concentrates on the overvoltage patterns as ferroresonance is characterized by overvoltage. The analysis is conducted in PSCAD/EMTDC software and the modelling of entire study network is done according to the CIGRE WG C4.307. The maximum overvoltage for each stage is found by performing 200 cases of statistical simulation and it is compared with the rated withstand voltage of the equipment. Through a rigorous analysis of overvoltage characteristics under different scenarios, suggestion has been given whether the subsea cable interconnector-2 can be safely operated during the studied cases without the risk of ferroresonance.

A Control Method for Output Voltage Stability of Proton Exchange Membrane Fuel Cells

The widely used PEMFC (Proton Exchange Membrane Fuel Cell) analysis found that when the REMFC load is changed, its instantaneous output voltage fluctuates, and it causes voltage loss. The main reason is that it is activated by activation. The characteristics of the three-proton exchange membrane fuel battery characteristics of Ohm overvoltage and thickness cause voltage loss. By using the corresponding empirical formula in the Matlab / Simulink environment, the study designs the PID and the Fuzzy PID Controllers. After the established dynamic model of PEMFC, it controls the hydrogen supply module, changes the ratio of hydrogen and oxygen input, and indirectly controls the output voltage. Through experiments, it was found that Fuzzy PID Controller can achieve faster and smoother voltage stability than an ordinary PID Controller and less overshoot when load change, The controller can control the system voltage to reach a set point and to stabilize the supply voltage for the load.

Study on the Simulation of the EMU Body Operating Main Breaker Overvoltage and High-Voltage Side Suppression Method Based on the 3D Structure

Current circuit simulation research on EMU (Electric Multiple Unit) overvoltage has focused on overvoltage amplitude distribution and the oscillation frequency of the operating main circuit breaker overvoltage. However, when studying the suppression method, the overvoltage amplitude and frequency characteristics must be considered simultaneously, and few studies have reported on the overvoltage frequency distribution. In this paper, a new simulation model of train-operational main breaker overvoltage based on the 3D structure of the EMU body was proposed, which provided guidance for the study of overvoltage suppression in operational main circuit breakers. This model simulated the transient overvoltage characteristics and distribution of the vehicle body when the train operated the main circuit breaker. The simulated results showed that the first vehicle had the highest operating overvoltage amplitude, and the fourth vehicle had the lowest. The overvoltage amplitudes of vehicles 1–4 were all above 1 kV, and the main overvoltage oscillation frequencies of each vehicle were at 0.70 MHz and 1.30 MHz. The accuracy of the distribution characteristics and spectral characteristics of the operating main breaker overvoltage was verified by static tests on trains, and the simulation was considered to be in agreement with the test. Aiming at the problem that there was no universal suppression method for the operating main breaker overvoltage, a general suppression method for the overvoltage on the high-voltage side of the EMU was studied, and an overvoltage suppression device based on a grounding inductor was proposed. The inductance parameter requirements of the suppressor were theoretically analyzed, and the validity of the design of the inductance suppressor was experimentally verified.

Study on switching overvoltage characteristics of VSC-HVDC grid with multiple topology

VSC-HVDC grid with multiple topology technology has broad application prospects in new energy grid connection. However, due to the various topologies, the overvoltage characteristics of DC line are quite different from the terminal-to-terminal DC systems. Based on the seven-terminal power grid of Zhangbei VSC-HVDC project in long-term planning and by combining theoretical analysis and simulation calculation methods, switching overvoltage characteristics of flexible MTDC grids with various topologies have been researched in this paper. The overvoltage amplitude generated on the fault line of the DC grid by DC circuit breaker tripping and clearing fault is relatively high. And, in the closed-loop topology, the overvoltage amplitude is lower than that in the open-loop topology. The overvoltage amplitude decreases when adding branch line. The overvoltage generated on fault-free pole line by single-pole grounding fault is less affected by the topology, and the overvoltage level of each line is not much different. In general, after the DC line is formed into a network, the switching overvoltage of DC line is lower and the distribution tends to be uniform, which is beneficial to insulation coordination of the DC line.

Modeling and Experimental Analysis of Overvoltage and Inrush Current Characteristics of the Electric Rail Traction Power Supply System

High-speed EMUs (electric multiple-units) frequently pass through the phase-separation zone during operation. Overvoltage generated during the operation of the vehicle-mounted circuit breaker has a long duration and high waveform steepness, which accelerates the service life of the vehicle-mounted equipment and is likely to cause insulation failures. For the above-mentioned problems, the operating overvoltage characteristics of high-speed EMU were obtained by traction substation-catenary-EMUs system (SCES) analysis and experiments, thus deriving the influences of the closed phase angle and the residual magnetism of the vehicle-mounted transformer on operating overvoltage. The results showed that the voltage phase of the catenary significantly affected the operating overvoltage, and the closed switching overvoltage was small at 0–40°, 140–210° and 320–350°. The voltage on the primary side of the vehicle-mounted transformer was 60.78 kV, with the transient impact of high-frequency oscillation overvoltage of 22.71 kV, and an initial period of oscillation of 0.01 ms. Then, the period became longer, and it took 0.5 ms for the high-frequency oscillation from attenuation to disappearance. Finally, a scheme of series reactance suppression devices was proposed to protect vehicle-mounted voltage transformers. This work is to provide data support for the insulation design and system protection of a traction power supply system.

Prediction of Breakdown Voltage of Equipotential Live-Line Work Air Gaps in Transmission Lines: A Computational Discharge Model

Equipotential live-line work (EPLW) is an indispensable technology to ensure the power supply. Due to the huge risks of the strong electric field, the distance of the EPLW air gap should be greater than the minimum approach distance (MAD). MAD is determined by calculating the hazard probability according to the characteristics of the switching overvoltage and the 50% breakdown voltage of EPLW gaps. Currently, the 50% breakdown voltage is obtained by a great many actual-size discharge tests, which costs a large amount of time and workforce. In this article, a computational discharge model was presented to solve the problem. First, the discharge process of EPLW air gap was analyzed based on the test experience. Subsequently, according to each stage of the discharge process, a computational discharge model for predicting the 50% breakdown voltage of EPLW gaps was presented. Finally, the computational discharge model was applied to EPLW air gaps of ±800 kV UHVDC and 1000 kV UHVAC transmission lines. The calculated results agreed well with the test results, and the errors did not exceed 6%. This research can provide theoretical support for the transmission line design and lineman safety protection.

Characteristics of overvoltage and approaches to encounter overvoltage suppression for DC submarine cable of VSC-HVDC transmission system powered by large-scale offshore wind

Wind power generation is one of the most mature and commercial power generation methods in the field of renewable energy utilization. With the continuous consumption of coastal wind power resources, the development and utilization of offshore wind power resources is an inevitable trend. VSC-HVDC transmission is the best technical means for the collection and transmission of offshore wind power far away. The transient overvoltage of DC submarine cable is the decisive factor of equipment insulation level, manufacturing difficulty and project cost. Based on the practice of offshore wind power transmission through VSC-HVDC project, this paper studies the transient overvoltage characteristics and overvoltage suppression measures of DC submarine cable when AC and DC faults occur, and completes the simulation verification. The results show that the overvoltage suppression measures can effectively reduce the transient overvoltage level of DC submarine cable by more than 13%. The overvoltage suppression measures improve the safety margin of DC submarine cable and enhance the reliability of DC system. The research results have been applied in Rudong project, the first VSC-HVDC transmission system powered by offshore wind power in China.

Study on Dynamic Characteristics of Single-Phase Grounding Fault of 1000 MW Hydro Generator under Different Grounding Modes

The continuous operation of 1000 MW large hydro generators in China is of great value to the implementation of “double carbon strategy” and power grid safety. However, with the continuous increase of single unit capacity of the hydro generator, the problems of unit fault grounding current and neutral point voltage drift become more and more prominent, and the traditional analysis methods cannot accurately obtain the fault dynamic data. Therefore, starting from the neutral point grounding mode of the large hydro generator, taking a 1000 MW hydro generator as the research object, this paper establishes the single-phase grounding fault model under the condition of three-phase parameter asymmetry of stator winding and analyzes the dynamic characteristics of fault current, transient overvoltage, and neutral point voltage drift under different grounding modes by using transient analysis method; the influence of frequency offset on neutral voltage drift and the dynamic characteristics of single-phase grounding fault of the large hydro generator under different grounding modes are also obtained. Finally, according to the analysis results, the selection and optimization method of neutral grounding parameters are proposed, which provides a reference for the selection of neutral grounding mode and the research of protection strategy of the large hydro generator.

Configuration of suppression schemes against high-frequency transient reignition overvoltages caused by shunt reactor switching-off in offshore wind farms

It is crucial to protect offshore wind farms from overvoltages because of bad accessibility and high maintenance costs. During the process of switching-off a shunt reactor with a 40.5 kV vacuum circuit breaker, high-steepness reignition overvoltages may occur. In order to reproduce this reignition overvoltage accurately and further determine a suitable mitigation scheme, this paper proposes a new quantitative evaluation framework, which comprehensively considers its magnitude and steepness. Firstly, main component models of a typical offshore wind farm are developed in PSCAD/EMTDC, which consider their high-frequency transient characteristics. Subsequently, the transient characteristics of reignition overvoltages at the 35 kV side of shunt reactors are analyzed. Then, for the sake of investigating the mitigation performance of different overvoltage protective schemes, a quantitative evaluation is conducted. Simulation results show that switching-off shunt reactors in offshore wind farms can cause high-frequency transient reignition overvoltages characterized by a high amplitude and a high steepness at its terminals. It is found that a resistor-capacitor filter or a new scheme combining a surge arrester with a smart choke can be installed on the terminals of shunt reactors to decrease both the magnitude and the steepness of reignition overvoltages.

Research on overvoltage characteristics and arrester operation under typical failure of Ultra High Voltage DC project

Accurately predicting the overvoltage level under typical faults and operating condition in the UHVDC (Ultra High Voltage DC) transmission project is not only beneficial to the insulation coordination design of the system, improving the security and reliability of the system, but also helping to reduce the project cost. Based on the circuit transient simulation platform, this paper builds a UHVDC transmission system simulation model, analyzes the typical overvoltage sources, compares the overvoltage characteristics of the system under 3 types and 12 typical operating faults including the inverter side, rectifier side, and DC line side, and analyzes the operation of the arrester under fault conditions. Results show that when the midpoint of the line is ground faulty, an overvoltage of 1791kV will appear at the midpoint of the non-faulty DC line, which is the most serious overvoltage of the DC line, and when a ground fault occurs at the outlet of the DC line on the rectifier side or the inverter side, the overvoltage amplitude of the DC valve top on the corresponding side is the highest, which respectively are 1324kV and 1190kV. The research results provide a reference for the insulation coordination of the UHVDC transmission project.

Research on over-voltage characteristics of ultra high-voltage direct current transmission system

Load dumping overvoltage has a significant effect on insulation coordination of direct current (DC) transmission system. Based on the PSCAD/EMTDC electromagnetic transient simulation programs, this paper has built the electromagnetic transient calculation model of ultra high-voltage direct current (UHVDC) transmission system. Respectively, we have done comparative research on the overvoltage during load dumping under three rated-load operations, which are the bipolar operation with ground return, unipolar operation with metal return, unipolar operation with ground return, concluding that alternating current (AC) load dumping on the inverter side under these three operations can result in overvoltage no less than 50% on the DC polar line, DC valve top, as well as both ends of the converter transformer valve and the upper six pulses bridge also produce a large overvoltage. Besides, we observed a similar overvoltage level between unipolar ground return operation and unipolar metal return operation. These conclusions can provide suggestions for insulation coordination in various operations.

Research on overvoltage characteristics and influencing factors of converter station under grounding fault

In grounding fault of DC system, overvoltage will appear on equipment nodes in converter station. Due to different operation mode and equipment type, it is very different from overvoltage in AC system. Based on Shanghaimiao–Linyi​ ±800kV Ultra High Voltage Direct Current (UHVDC) transmission project, this paper studies the converter station overvoltage characteristics under the conditions of DC pole line grounding, DC bus grounding and converter transformer valve side grounding fault, then analyzes the influence of smoothing reactor, filter capacitor and grounding pole line on overvoltage. In grounding fault at DC pole line near the converter station, the maximum overvoltage occurs on the inductance of DC filter, which is 592.75kV; In grounding fault at the top of the high voltage converter valve, the maximum overvoltage occurs on the neutral bus, which is 272.17kV. Increasing the inductance or capacitance of the smoothing reactor and filter capacitor, shortening the length of grounding electrode wire can significantly reduce the amplitude and steepness of overvoltage. The calculation results provide a reference for the internal overvoltage suppression of DC converter station with layered access at the inverter side.