Withstand Voltage Test Research Articles

Influence of test procedure on dielectric breakdown strength of alumina

Dielectric strength testing of ceramics can be performed with various setups and parameters. Comparisons of results from different sources are often not meaningful, because the results are strongly dependent on the actual testing procedure. The aim of this study is to quantify the influence of voltage ramp rate, electrode size, electrode conditioning, and sample thickness on the measured AC dielectric strength of a commercial alumina. Mean values, Weibull moduli, and failure probabilities determined in standardized short time tests are evaluated and related to withstand voltage tests. Dielectric strength values in the range from 21.6 to 33.2 kV mm−1 were obtained for the same material using different testing procedures. Short time tests resulted in small standard deviations (< 2 kV mm−1) and high Weibull moduli around 30, while withstand tests at voltage levels with low and virtual zero failure probability in short time tests resulted in large scatter of withstand time and Weibull moduli < 1. The strong decrease in Weibull moduli is attributed to progressive damage from partial discharge and depolarization during AC testing. These findings emphasize the necessity of a thorough documentation of testing procedure and highlight the importance of withstand voltage tests for a comprehensive material characterization.

Surface modification of XLPE films by CF4 DBD for dielectric properties

Cross-linked polyethylene (XLPE) is often manufactured as pipe, film and foam products and used as electric insulation material. To improve the dielectric properties of XLPE film, CF4 dielectric barrier discharge (DBD) is applied as a surface modification method. The surface of XLPE film was modified at the low pressure of 1 kPa with different treatment time (15s, 30s, 60s, 120s, 240s and 480s). Electrical and optical characteristics are observed during DBD process, including applied voltage, measured current, photograph and emission spectra. Then, the surface properties, which are hydrophobicity, chemical composition, surface morphology, trap depth, dielectric loss and AC breakdown voltage, have been measured or observed by water contact angle test, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), isothermal relaxation current (IRC), frequency domain spectroscopy (FDS) and withstand voltage test. After the surface modification, the water contact angle, trap depth and breakdown voltage increase first and then decrease with treatment time extending. Meanwhile, the dielectric loss has an opposite trend, which represents better dielectric properties. The reason is that fluorine can reduce the surface energy, which can significantly influence the water contact angle. Better hydrophobicity can restrain the accumulation of outside pollution on the surface. Moreover, fluorine has strong electronegativity, so amorphous crystalline and impurities interface trap depth become deeper and the dielectric loss becomes lower. Therefore, appropriate DBD treatment conditions can apparently improve XLPE dielectric properties.

Study on The Issue of Electric Field Concentration in Submodule of Press Pack IGBT

There is a phenomenon that the chips of press pack IGBT (Insulated Gate Bipolar Transistor) meet the requirements of withstand voltage test, but ignition sometimes occurred in the submodules of the same kind of press pack IGBT during the test. In response to this situation, this paper firstly analyzed that the difference of submodules frame lead to different level of electric field concentration. In this paper, quantitative conclusions have been drawed by modeling and simulation of the actual situation in COMSOL Multiphysics the multiphysics finite element simulation software.

Study on Influence Factors of Lightning Impulse Test Waveform of UHV GIS Equipment

The lightning impulse withstand voltage test is a test item that must be carried out for type testing, factory test or even field test of electrical equipment such as gas insulated metal-enclosed switchgear (GIS).However, the factors affecting the lightning impulse test waveform are complex and diverse. In this paper, the discharge principle of the impulse voltage generator is studied. Combined with simulation, the influence of different factors on the waveform parameters of lightning impulse test of UHV GIS equipment is obtained. The common methods and improvement measures of waveform debugging are pointed out, and the main factors affecting the parameters of lightning waves are studied.

Electric Field Calculation for Hybrid HVDC Circuit Breaker

The electric field distribution characteristic of ±535kV hybrid HVDC circuit breaker is calculated with the finite element analysis method for electrostatic. The electric field of the component and shielding system is calculated by adding the DC withstand voltage test voltage, and the electric field of valve support is calculated by adding the valve support DC withstand voltage test voltage. Calculation results show that the maximum electric field of ±535 kV HVDC circuit breaker tower is 2.748kV/mm which meets the requirements of electric control value 3kV/mm. The conclusion provides a support for insulation structure design of the ±535 kV hybrid HVDC circuit breaker, which has important reference value.

Sudden Short-Circuit Test of 22-kV YBCO Triaxial Superconducting Cable

For the power line between a power generator and a step-up transformer, isolated power bus (IPB) is generally used. The present IPB has a normal cylindrical conductor made of aluminum or copper at the center of the outer jacket and generates very huge Joule loss. To decrease it, superconducting buses have been developing. In this study, a 22-kV 3-kA triaxial superconducting bus was designed and fabricated with YBa2Cu3O7-d (YBCO) tapes and the various kinds of properties were investigated. Previously, the ac and lightning impulse withstand voltage test, critical current Ic test, and ac loss measurement were conducted and it was shown that the developed triaxial superconducting cable met the designed specifications. In this paper, a sudden short-circuit test of a 2-m-long triaxial cable was carried out by using a 200-MVA short-circuit generator. For protection, each phase of the cable was connected to a XLPE cable with a length of 3 m and a cross-sectional area of 250 mm 2 in parallel. Three-phase short-circuit current of 25 kA was applied to every phase of the cable bath-cooled with liquid nitrogen at 77 K for 2 s. As a result, the following tremendous phenomenon was demonstrated. Any phase of the triaxial cable kept a flux-flow state and did not quench. Short-circuit current was shared between the superconducting cable and the connected XLPE cable, and the branch current ratio varied even during one period of 60 Hz. The numerical simulation was also conducted to explain the phenomenon theoretically. That should contribute to the instantaneous recovery to a normal operation after a short-period interrupt of the circuit.

Development of –1 MV DC Filter and High‐Voltage DC Measurement Systems for ITER NBI

SUMMARYThis paper presents the development results of a −1 MV dc filter and dc measurement systems for an ITER (International Thermonuclear Experimental Reactor) neutral beam injector (NBI) system. High accuracy of 0.5% and fast responsivity of 3.3 μs, −3 dB are required for the dc measurement systems: both dc voltage dividers and DCCTs. Circuit design and thermal flow design were carried out to clarify and minimize their effects on the accuracy and responsivity. The validity of the established design was demonstrated by the actual‐product tests; temperature rise of each components fell below the allowable value; inner components of dc filter withstood dc −1.2 MV; each voltage divider accurately measured the voltage during the dc −1.2 MV withstand voltage test; the voltage dividers and the DCCTs were adequate to the requirements of responsivity (3.3 μs, −3 dB).

Development of DC‐1 MV Ultrahigh Voltage Generator for ITER

SUMMARYThis paper presents development results of a five‐stage DC‐1MV Ultrahigh Voltage Generator for ITER. Each generator outputs −200 kV, and the total five generators are connected in series and outputs −1 MV. In order to realize the DC‐1MV output and 1‐h continuous operation, a feasibility of both gas insulation and gas cooling for semiconductor devices was validated. A simplified structure with stud‐type diodes and heatsinks resulted in the compatibility of enough insulation distance and wide cooling surface. Withstand voltage tests and a temperature rise test were performed for the actual equipment of the rectifier and the step‐up transformer. These test results verified the validity of the proposed design.

The Application of GIS of the Same Frequency and Phase AC Withstand Voltage Test Technology

The Application of GIS of the Same Frequency and Phase AC Withstand Voltage Test Technology

Partial discharge characteristics of metallic protrusion in GIS under different lightning impulse voltage waveforms based on UHF method

The field lightning impulse withstand voltage test is an important step to ensure the safe operation of the gas insulated switchgear (GIS). The oscillating lightning impulse voltage is recommended in field test by IEC standard due to its high generating efficiency and lower impulse ratio. The insulation condition of GIS can be evaluated overall by detecting the partial discharge (PD) when conducting the field impulse withstand voltage test. In this paper, the protrusion defect was set in a 330 kV real GIS to study the PD characteristics under lightning impulse voltages, including SLI (standard lightning impulse) voltage and OLI (oscillating lightning impulse) voltages with different oscillating frequencies. The PD under impulse voltages was effectively detected by using the internal UHF sensor. The 50% probability PD inception voltage (PDIV50), maximum discharge amplitude, and discharge number were analyzed based on the measurement results. It was concluded that the PD number is significantly larger and the PDIV50 of OLI voltage is lower when the oscillating frequency is low by comparing the results of oscillating and standard impulse voltage. The PDIV50 increases and discharge number decreases with the increasing of oscillating frequency of the OLI voltage.

Development of Live-working Robot for Power Transmission Lines

Dream-I, the first reconfigurable live-working robot for power transmission lines successfully developed in China, has the functions of autonomous walking on lines and accurately positioning. This paper firstly described operation task and object of the robot; then designed a general platform, an insulator replacement end and a drainage plate bolt fastening end of the robot, presented a control system of the robot, and performed simulation analysis on operation plan of the robot; and finally completed electrical field withstand voltage tests in a high voltage hall as well as online test and trial on actual lines. Experimental results show that by replacing ends of manipulators, the robot can fulfill operation tasks of live replacement of suspension insulators and live drainage plate bolt fastening.

The Application of Surface Potential Test on Hand-making Insulation for Generator Stator End-winding

This paper presents the advantage of surface potential test on hand-making insulation for generator stator end-winding insulation detection, compared with DC or AC withstand voltage test, also details the test principle, connection method and test notes. And through the case, surface potential test on hand-making insulation proved effective for insulation quality detection after generator stator end-winding maintenance, and the experimental data is useful and reliable for the electrical equipment operation and maintenance in the power plant.

DC withstand test with partial discharge measurement of convertor transformers: Problems and suggestions for improvement

To pre-discover the insulating defects and avoid possible insulation failures, DC withstand voltage test with partial discharge (PD) measurements are routinely conducted before the operation of a convertor transformer. However, a “downward trend” of PDs under DC voltage studied in this paper indicates the limitation of the current test. According to the study, under DC voltage both PD magnitude and PD repetition rate decrease with voltage applying time. At U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pdiv</sub> =29 kV, the average charge is 105 pC in the first 10 min and 33 pC in the last 10 min. Whereas for 3U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pdiv</sub> =87 kV, the value are 2700 pC and 1561 pC separately. On the other hand, at U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pdiv</sub> , PD numbers decrease from 12 times in the first 10 min to 5 times in the last 10 min. At 3U <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pdiv</sub> , the numbers are 102 times and 83 times. When PD magnitude is higher than 1400 pC, a whitish area appears at the surface of the pressboard, accompanied by the decrease of DC withstand voltage after 2 hours' PD exposure. The results raise the question that the current test measures PDs over 2000 pC in the last 30 minutes but may introduce PDs of higher magnitude at the early stage, which will damage the dielectrics. Based on further analysis, an improved test procedure is suggested.

Application and Analysis on Frequency Conversion Series Resonance Technology in 220kV Cable Withstand Voltage Testing

AC withstand voltage test is the most severe, the most direct and the most effective test method of judging the XLPE Power Cable insulation Conditioning, It is of decisive significance in determining weather the Power Cable is measured up. Traditional test transformer is bulky, it requires high-capacity of power supply when it is used in AC withstand voltage test of high-capacity Power Cable. This paper adopted the Frequency Conversion Series Resonance Technology in 220kV Cable Withstand Voltage test program and accomplished the test successfully, Greatly reduced the capacity of the power test equipment, it also helps to promote the test quality and the work efficiency, which proved the feasibility and effectiveness in the long-distance high-voltage XLPE cables grade AC voltage test with the Frequency Conversion Series Resonance Technology.

Impact analysis of the capacitive coupling sensor on bushing external insulation

Online impulse frequency response analysis (IFRA) method is proposed and developed as a new technique to detect the winding mechanical deformation of a running transformer. The preliminary application of IFRA has been realised by using the bushing capacitive coupling sensor (CCS). However, whether the installation of the sensor affects the normal operation of the transformer is still unknown. To study above problem, this study first establishes a simulation model for transformer bushing based on the finite-element method and discusses the influence of sensor installation on the electric field distribution of capacitive bushing. The simulation proves that the installation of the CCS has minimal effect on the safe operation of the bushing. Second, the bushing withstand voltage tests are conducted in a lab, which proves that the installation of CCS meet the requirement for safe operation of capacitive bushing. Finally, the CCSs are installed on running power facilities, and the long and safe running experience indicates that the bushing and related facilities are unaffected by CCSs. The simulation analysis, withstand voltage test, and field application verify that the installation of CCS would not threaten the safe operation of high-voltage bushing, laying the foundation for engineering application of IFRA.

Breakdown characteristics of oil-impregnated paper and influential factors for damped alternating oscillation waveforms

As striking lightning impulse waveforms in power transformers are quite different from the standard lightning impulse waveform (SLIW) used in the withstand voltage tests, it is essential to identify the breakdown characteristics of oil-impregnated paper (OIP) under non-SLIW and to quantitatively compare them with those under SLIW. On that basis, the impulse insulation levels of power transformers can be rationally determined and then the insulation specifications can be evaluated to maintain high equipment reliability. In this paper, with damped alternating oscillation waveform as a representative basis, the breakdown characteristics of oil-impregnated paper were experimentally obtained by changing the frequency and damping rate of the applied voltage. All experiments were conducted using a column-column electrode model. In addition to the 50% breakdown voltages (U50), Minimum breakdown voltage Umin and V-t characteristics under different circumstances, the influence of various parameters on breakdown characteristics and the possible reasons were discussed. After comparing waveforms and corresponding results, the specific relationship between waveform parameters and U50 were expressed as a single equation. As a result, the breakdown voltage was 1.106 to 1.435 times higher than that under SLIW depending on frequency and damping rate. The steepness of the wave peak and the duration of high voltage around wave crests are considered to be two important factors affecting the breakdown voltage. An effective way was proposed to predict U50 of oil-impregnated paper as a reference for insulation specifications irrespective of wave shape. These results support the rationalization of insulation for actual lightning impulse waveforms in the power transformers.

Non-Linear Insulator Performance of Wind Turbine Blade Surface against Lightning Strike

This research work investigates the surface degradation of blade specimen which is made from epoxy resin mixed with non-linear fillers of Zinc oxide, Aluminium oxide and Sodium silicate in different ratio percentage. Test on surface trackability of each specimen according to IEC 60587 standard. Then, choose the best specimen which has achieved a high tracking resistance to test against lightning impulse voltage according to IEC 60243-3 at ± 60 kVpeak. A comparison has been made with the pure epoxy resin specimen as a controlled sample. The results showed that, the epoxy resin specimen with the ratio of 40% by weight of Aluminium oxide filler slow down the tracking process better than other specimen type. And from the result of lightning impulse withstand voltage test, it is found that all of the specimen were not affected.

The Principle and Application of AC Voltage Withstand Test for GIS without Power Cut

In order to check whether there are defects in GIS (gas-insulation-switchgear), it is necessary to do AC voltage withstand test before putting into operation. According to the standards, when doing AC voltage withstand test after GIS expansion or maintenance, the original neighboring parts should be power cut and grounded. For the double bus substation,it means that the whole substation should be power cut, which will decrease the power supply reliability of the grid and have a tremendous impact on the power grid To solve the problem, this paper presents a new AC voltage withstand test method for GIS without power cut, and explains principles and field applications of this method.

조명기기의 임펄스내전압 성능의 분석

Modern electronic circuits are becoming more vulnerable to damage by surges, and it is required to improve the impulse withstand voltage performance of electrical and electronic equipment. This paper presents the impulse withstand voltage performance of lighting equipment connected to power lines, and the impulse withstand voltage tests for fluorescent lamp, LED lamp and halogen lamp were carried out according to the reference standards under normal service conditions. To conduct performance tests against lightning surge, a combination wave (1.2/50㎲ voltage ? 8/20㎲ current) was employed. The test surge was applied between lines or between line and ground of the specimen to be measured. The test surge was applied synchronized at the peak value of the positive and negative AC voltage waves. As a consequence, some specimens satisfied the impulse withstand voltage test criteria, but lighting equipment such as 36W fluorescent lamps, 5W and 5.5W LED lamps and 50W halogen lamp were damaged at the test voltage levels between power lines. It is needed to improve the qualities of lighting equipment to satisfy EMC immunity requirements of equipment for general lighting purposes.

The Wiring Method of the Transformer AC Withstand Voltage Test

This paper briefly expounds the determination of transformer pressure value, and introduces the principles of power frequency ac withstand voltage, variable frequency series resonance withstand voltage and multi-frequency induced withstand voltage. It also expounds the ac withstand voltage wiring method, and demonstrates a simple way in withstand voltage test on low voltage winding.