Withstand Test Research Articles

Temperature and Physicochemical Properties of Abnormal Heating Composite Insulators.

Abnormal heating will reduce the insulation performance of composite insulators or even cause insulator fracture, and the abnormal heating phenomenon is more serious under high-humidity conditions. Therefore, in this paper, the voltage withstand test of abnormal heating composite insulators caused by aging and damp sheath, decay-like core rod, and contamination were carried out under different ambient humidity. The heating and discharge of composite insulators were observed by infrared thermal imager and ultraviolet imager, and its temperature characteristics were analyzed from the aspects of heating range, heating shape, and temperature difference. In addition, in order to study the abnormal heating mechanism of composite insulators, the micro-morphology, chemical groups and dielectric properties of the silicon rubber of composite insulators with aging and damp sheath and the decay-like core rod were also measured. It is found that the temperature characteristics of the three types of abnormal heating composite insulators are different, and the temperature difference increases with the increase of humidity. The deterioration of silicone rubber and core rod material is the internal reason for the abnormal heating of composite insulators, and high-humidity conditions will exacerbate the heating phenomenon.

The Effect of Air Humidity on the Performance of DC Link Capacitor Components

DC link capacitors (DCLCs) are key devices in converters. The relative humidity affects the performance of the elements of a DCLC. Currently, there are relatively few studies on the effect of relative humidity on the electrical characteristics of the elements of DCLCs during the production process. This study describes the effects and the control of the relative humidity in the production process. For this purpose, a DCLC component withstand voltage test platform and a DCLC component aging test platform were established. The voltage withstand tests were conducted during different processes and at different relative humidities, and life aging tests were conducted at different relative humidities and different storage times. The results show that after the winding and metal-spraying processes, the voltage withstand levels of the components stored at 30% RH, 60% RH, and 80% RH were very close to that of the components at 3000 VDC; after the heat-setting process, the voltage withstand levels of the components stored at 30% RH, 60% RH, and 80% RH showed a decreasing tendency compared with the level of the components at 3000 VDC. Regarding the samples, after the heat-setting process, stored at 30% RH and 60% RH for 24 h, 96 h, 168 h, 240 h, and 336 h and 2000 h of the aging tests, the capacitance decreases monotonically as the storage time is increased but never exceeds 3%, and the capacitance change decreases as the relative humidity increases. This study can provide important guidance for the humidity control of various processes in the production of DCLCs.

Hardware Testing Methodologies for Wide Bandgap High-Power Converters

Wide bandgap (WBG) power semiconductor devices are increasingly replacing silicon IGBTs in high-power and high-voltage power electronics applications. However, there is a significant gap in the literature regarding efficient testing methodologies for high-power and high-voltage converters under constrained laboratory resources. This paper addresses this gap by presenting comprehensive, hardware-focused testing methodologies for high-power and high-voltage WBG power semiconductor-based converter bring-up before the control validation phase steps in. The proposed methods enable thorough evaluation and validation of converter hardware, including device switching characteristics, driving circuit functionality, thermal management performance, insulation integrity, and sustained operation at full power. We utilized the double pulse test (DPT) to characterize switching performance in a two-level phase leg configuration, extract circuit parasitics, and validate magnetic components. The DPT was further applied to optimize gate driving circuits, validate overcurrent protection mechanisms, and measure device on-resistance. Additionally, a multicycle test was introduced to rapidly assess steady-state converter performance and estimate efficiency. Recognizing the critical role of thermal management in high-power converters, our methodologies extend to the experimental extraction of key thermal parameters—such as junction-to-ambient thermal resistance and thermal capacitance—via a heat loss injection method. A correlation method between temperature sensor measurements and junction temperature is presented to enhance the accuracy of device temperature monitoring during tests. To ensure reliability and safety, dielectric withstand tests and partial discharge measurements were conducted at both component and converter levels under conventional 60 Hz sinusoidal and high-frequency PWM waveforms. Finally, we highlight the importance of testing converters under full voltage, current, and thermal conditions through power circulating tests with minimal power consumption, applicable to both non-isolated and isolated high-power converters. Practical examples are provided to demonstrate the effectiveness and applicability of these hardware testing methodologies.

Research on Partial Discharge Characteristics of Suspension Defect in GIS under the Action of Voltage and Current

Abstract Gas insulated switchgear (GIS) is a critical component in power system, and the insulation testing is crucial before putting it into operation. Despite passing AC withstand tests, some GIS equipment exhibit insulation faults during operation. Existing AC withstand tests fall short in detecting all insulation faults in GIS equipment. To address this issue, a proposal is made to conduct a comprehensive simulation of actual GIS equipment operating conditions through a combined voltage and current boost test, aiming to address the limitations of existing tests. This study, based on a 330kV GIS test platform, compares the partial discharge characteristics of suspension defects under traditional voltage-boosting mode and the combined voltage and current boost mode. The research investigates the influence of simultaneously applying voltage and current on discharge characteristics. It is observed that the voltage and current boost combined mode significantly increase the partial discharge inception voltage (PDIV) and the corresponding apparent discharge compared to other modes. The apparent discharge quantity after a certain period of current flow during the discharge development process is greater than that observed in other modes. The current notably enhances the ultrasonic amplitude of partial discharge. These findings establish an experimental foundation for conducting voltage and current combined boost tests in the field.

Comparison of accelerated and non-accelerated post-LOCA simulation

Cables important to safety used in nuclear power plants are required to withstand environmental, operational and system conditions to which they are exposed during their design life. This may include harsh conditions resulting from a design basis event (DBE), such as a Loss-of-Coolant Accident (LOCA). The testing procedure includes accelerated thermal and ionizing radiation ageing which brings the tested samples to their end-of-life condition. Accelerated pre-ageing is then followed by accident simulation (LOCA test). The latter part of accident simulation (post-LOCA), which may take up to 1 year, is commonly accelerated based on the Arrhenius approach, however the adequacy of this approach remains a topic of ongoing discussion, lacking a clear scientific or engineering consensus. While numerous works have focused on testing various conditions during accidental and post-accidental conditions in nuclear power plants, there is notable absence of direct assessment of acceleration effects.The aim of this work was to assess the effects of accelerating post-accident conditions on electrical cables using non-destructive electrical measurements. The cables were subjected to thermal and radiation pre-ageing, LOCA test, and then were divided into two groups for post-LOCA tests: one group was tested for one year in non-accelerated post-accident conditions, while the other was accelerated using the Arrhenius approach. Diagnostic methods, including insulation resistance, capacitance, voltage withstand tests, and high-frequency parameters such as attenuation, characteristic impedance, and relative permittivity, were employed for comparing sample conditions. Results from both accelerated and non-accelerated post-LOCA simulations were consistent, indicating that the acceleration was adequate.

Dielectric Failure Analysis of Distribution Transformer

The distribution Transformer acts an important function in the electrical distribution network. Failure of the transformer ends in an outage of power supply to end users. Failure of the distribution transformer usually results in the spare time of some weeks transformer accompanied by commercial misfortunes and the necessity to fix the system at the earliest. The prime reason for the outage of distribution transformers is a short circuit, insulation breakdown, and prolonged overloading. This paper investigates failure analysis of distribution transformers during separate source voltage withstand tests, induced over-voltage withstand tests and short circuit withstand strength tests. In this paper failure cases of three distribution transformers are resolved and the results are analyzed.

Testing and Assessment on the Short-Circuit Withstand Capability of Press-Pack IGBT Considering the Unbalanced Clamping Forces

Press-pack insulated gate bipolar transistors (PP-IGBTs) modules have become the mainstream choice in high-power-density applications such as breakers. Sufficient short-circuit (SC) withstand capacity is the key to the safe operation of power electronic equipment. However, the effect of the unbalanced clamping force, which is experienced frequently in the multichip PP-IGBT, on the SC withstand capacity needs to be studied. First, an SC withstand test platform is established to calibrate the critical energy for different voltage levels. Second, the SC process and the withstand capacity for different clamping forces are investigated experimentally. Combined with the finite-element simulation results, the effect of the clamping force on the SC withstand capability is analyzed, and the weak parts are pointed out. An evaluation method of SC withstand capacity considering the effects of the voltage levels and the clamping force is proposed. Finally, the effect of the unbalanced clamping force is experimentally studied using parallel single-chip modules (PPI), and the SC withstand test of a 3300-V/200-A multichip module with unbalanced clamping force is carried out. The results show that the clamping force has little effect on the critical energy, but the module with greater clamping force has worse SC withstand capacity.

Parallel diode‐clamped linear converter for withstand test and partial discharge measurement of electric equipment

Parallel diode‐clamped linear converter for withstand test and partial discharge measurement of electric equipment

Reconfigurable Large-Current and High-Voltage Test Bench for HVDC Circuit Breaker Verification

This article presents a novel circuit configuration of a high-voltage direct current circuit breaker (HVdcCB) test bench that is based on a modified H-bridge modular multilevel cascaded converter (MMCC). The modified MMCC is composed of fewer H-bridge cells, and it can be reconfigured during operation to allow the proposed test bench to output large current or high voltage for the current breaking and dielectric withstand tests. Although simultaneous output of large current and high voltage is not possible, the maximum transient interrupt voltage (TIV) withstand test can be performed with reduced ratings. The controllable output allows generation of complex waveforms to simulate a wide range of fault conditions. Furthermore, the modified MMCC has some inherent safety features that can reduce the need for additional protective equipment in case of operational failure of the HVdcCB. In contrast, the conventional charged capacitor and inductor-based designs cannot generate arbitrary waveforms, are only suitable for current breaking tests, and require additional circuits to generate initial conditions for the HVdcCB. AC short-circuit generator-based designs offer one degree of freedom for control of the output waveforms and can sustain the maximum TIV withstand test. However, the ac output is unsuitable for the dielectric withstand test, and additional circuits are required to provide initial conditions for the HVdcCB. The proposed test bench circuit configuration is verified using a downscaled experimental test bench that consists of a total of nine H-bridge cells with an equivalent switching frequency of 92.5 kHz.

Partial discharges detection in 1 MV power supplies in MITICA experiment, the ITER heating neutral beam injector prototype

MITICA (Megavolt ITER Injector & Concept Advancement), the full scale prototype of ITER Heating Neutral Beam, is under realization at the Neutral Beam Test Facility (Padova, Italy). It is designed to deliver 16.5 MW to ITER plasma, obtained by accelerating negative Deuterium ions up to 1 MeV for a total ion current of 40 A and then neutralized.MITICA Acceleration Power Supply is composed of several non-standard equipment, beyond industrial standard for insulation voltage level (-1 MVdc) and dimensions.Voltage withstand tests (up to 1.265 MVdc) have been performed in five subsequent steps (from 2018 to 2019), according to the installation progress, after connecting equipment belonging to different procurements.During integrated commissioning, started in 2021, two breakdowns occurred in a position of the HV plant not still identified, so they could be occurred either in air or in SF6. To identify the locations of possible weak insulation points, the existing diagnostics for partial discharge detection (the precursor of breakdowns) as a first step have been improved on air-insulated parts by consisting in a set of instrumentation, like capacitive probes and off-the-shelf instruments for AC application (acoustic and electromagnetic sensors).The paper deals with the instruments qualification to assess their suitability for DC usage and then with the investigation performed in MITICA, in particular:1) sensitivity assessment campaign, with artificially produced corona effect to identify the minimum threshold of each diagnostics2) voltage application to MITICA plant, moving the instrumentation around equipment and increasing progressively the voltage looking for corona phenomena to identify possible weak insulation points.

Understanding of XLPE Cable System Commissioning using Partial Discharge Measurements during AC HV Tests

This paper is based on the work done by Altanova Group, India, and describes the process and procedures used in a Partial Discharge (PD) investigation on a cable circuit during the AC withstand test. The paper focuses on the two most common approaches employed, namely, soak tests and resonant tests. In the latter case, the paper describes two approaches to performing the measurements and the relative benefits of each. De-noising the acquired data using T-F map analysis is also described, and real-world examples are given in the two case studies. These detail EHV resonant tests, one performed where all the accessories were monitored simultaneously and another where each accessory was tested in turn before relocating the PD monitoring equipment to the next location. In both cases, the application of T-F maps shows how different PD sources, such as external corona, can be identified and hence segregated.

Research and application of high voltage measurement technology in DC UHV preventive test

With the state’s high attention to clean energy and the requirement to reduce the loss of power grid transmission lines, DC UHV has developed rapidly in recent years. It refers to DC transmission and related technologies with voltage levels of ±800 kV (±750 kV) and above. In the power system, DC high-voltage transmission is inseparable from power equipment, but the higher the transmission voltage level, the higher the voltage of DC withstand voltage preventive test. Before the transmission of UHV DC transmission lines, if the DC voltage withstand device is 800 kV or above, the voltage withstand test shall not be carried out for the high-voltage line. The traditional direct comparison method using voltage divider cannot be used to measure the DC output voltage of DC UHV withstand voltage device on site. This paper analyzes the method of full coverage of DC UHV system in limited voltage range and the method of out of range calibration using scale factor. In order to solve the problem of voltage traceability in the DC high voltage generator, especially the voltage traceability of the field DC UHV device, when the voltage output range of the calibrated DC high voltage generator exceeds the measurement range of the standard, the standard value of the voltage calibration point beyond the range can be determined by comparison and obtained through the linearity test. The comparison with the standard shall be conducted at a voltage not lower than 20% of the rated voltage of the calibrated DC high voltage generator, and compared to the maximum voltage of the standard voltage divider. The comparison is carried out at a (a ≥ 2) voltage point. When comparing at a point, the highest voltage level is equal to the upper limit of the standard. Under a voltage point, according to the mathematical relationship between the voltage standard value of the tested device and the current flowing through the linear load resistance, the fitting function can be obtained through the linear regression method. For b (b ≥ 4) calibration points beyond the measurement range of DC standard voltage divider, the standard value can be “extrapolated” from the linear load resistance current and the fitting function Yang (2002). Through comparison and verification, the method is feasible, which is of great significance to promote the compilation of calibration specification for DC high voltage generator.

Research on Micro-Water Treatment Technology of High-Voltage SF6 Equipment without Power Failure

With the frequent occurrence of high-voltage SF6 equipment-related problems in recent years, the exceedances of micro-water content and decomposition products of SF6 and other problems are getting increasingly worse. The routine solution involves multiple processes, including powering off the equipment, recovering the SF6 gas in the equipment, flushing, injecting new SF6 gas, and conducting the voltage withstand test, which requires a huge number of manpower and material resources. Besides, the operating process is risky, and power cutting and re-supplying increase the operational risk and impair the reliability of the grid in the power supply. This paper mainly explores an efficient, safe, and intelligent online SF6 purification technology, which can achieve the online detection and purification of SF6 micro-water and impurity gases when the high-voltage SF6 equipment is powered on and make the purification units’ renewable. Applying this technology can prevent the power cut of high-voltage power supply equipment, thereby making sure that the grids are safe. It is also environmentally friendly as it can reduce the usage of SF6 gas.

Dual-Circuit-Based Test Bench Design for HVDC Circuit Breaker Verification

High-voltage direct current (HVDC) circuit breaker development and deployment strongly depend on the testing process, which ensures that the HVDC circuit breakers will satisfy design requirements. This article presents an HVDC circuit breaker test bench circuit configuration that can provide controllable large output currents to simulate different fault conditions for the current breaking test and high output voltage for the dielectric withstand test. The current breaking test circuit is based on multiple cascaded power converters connected in parallel to provide the necessary output current capability. Each cascaded power converter is composed of multiple cells that are operated by a phase-shifted pulsewidth-modulated signal for greater controllability and higher quality of the output waveform. The dielectric withstand test circuit is a simple high-voltage source with a low power rating that can also be used to charge the test bench and the internal circuitry of the circuit breaker that is to be tested. The proposed test bench ensures that fault conditions can be replicated accurately and offers greater flexibility by being able to test mechanical, semiconductor-based, or hybrid HVDC circuit breakers with different current and voltage ratings on the same hardware without any changes. The idea and the operating principle of the proposed test bench are verified experimentally on a downscaled system that consists of three cascaded power converters connected in parallel with three cells per cascaded power converter and with a total equivalent switching frequency of 92.5 kHz.

AC Voltage Withstand Test Method and Risk Suppression Measures of Energized GIS Based on Phase-frequency Control

It is essential to carry out an AC voltage withstand test after GIS extension and maintenance. At present, the common methods of GIS AC withstand test include double isolation gap, reduce the test voltage, and narrow test range. These methods generally have some defects, such as complex test processes, all bus de-energized, some devices failed to test, unreliable test results, and so on. This paper presents a distinctive GIS AC voltage withstand test method. The method controls the phase-frequency (PFC) parameters of the test voltage so that it maintains the same phase-frequency relationships as the in-service bus voltage during the process of testing. At this moment, the GIS can carry out an energized AC voltage withstand test. The article introduces the process of the PFC AC withstand voltage test method in detail and demonstrates the feasibility of the method. The phase difference margin of the PFC method is optimized through simulation and numerical calculation, and a variety of protection measures are proposed to ensure the safety of the test process. The proposed PFC AC voltage withstand test method will not affect the in-service bus and has great practical application value for the field GIS AC voltage withstand test.

Испытания, проверки и диагностическое обеспечение судовых силовых трансформаторов среднего напряжения

Object and purpose of research. The study deals with the diagnostic Issues of ship MV transformers from factory acceptance tests to harbor trials. The purpose is to analyse the requirements and advanced diagnostic tools for status monitoring of ship power transformers, as well as to overview the Issues of electrodynamic withstand checks on transformers. Materials and methods. Stages (operations) are considered that ship power transformers undergo from the stage of factory acceptance tests to harbor trials. Requirements of ship transformers are analyzed. Foreign and Russian tools to check and measure power transformer parameters in industry as well as requirements for electrodynamic withstand testing are compared. Main results. It is shown that in view of high operational risks associated with accidents and failures of onboard transformers it is not enough to check transformer characteristics after transportation or storage (prior to onboard installation) for ensuring their high reliability. Functional analysis of foreign and Russian diagnostic instruments is presented, and vectors for improvement of the Russian tools are defined for the interest of shipbuilding industry. It is shown that the electric withstand tests are particularly important when new designs and technologies are used where reliable verification is impossible neither through calculations nor through modeling, while large safety margins are economically not viable. Conclusion. If some power units in the electric propulsion system (EPS) fail, extra costs would be spent on docking the vessel, dismounting of good equipment and hull structures to remove out-of-order equipment. Regulatory documenttation does not specify the scope of EPS components’ checkup after transportation or storage. Technical measures to ensure reliability of EPS elements include diagnostics of EPS elements prior to their installation on board the ship and during commissioning trials. Diagnostic tools of foreign make have more functional capabilities as compared to Russian instruments. Choice of specific devices and decisions to go for extra costs to further develop the Russian instruments should be based on feasibility studies. New regulations are required for testing rectifier transformers for electrodynamic withstand at short-circuit fault, as well as development and modernization of regional inter-industry shock test facilities.

Calculation and Structure Optimization of Electric Field Distribution of The 10kV Solid-sealed Polar Pole

As one of the core modules of the ring - net switch cabinet, the solid-sealed polar pole was used to seal the three-station isolation ground switch and vacuum arcing chamber together. The electric equipment was concentrated, which was prone to electric field distortion. In this paper, a three-dimensional simulation model was established based on the drawings of the solid-sealed polar pole. The electric field distribution under the initial structure was calculated based on the finite element method, and it was optimized by adjusting the thickness of the moving contact and epoxy layer, changing the radius of the metal pull rod in the control mechanism and adding the equalizing ring on the shell surface. The results showed that when the inner diameter of the moving contact was 20mm, the outer diameter of the air layer was 43mm, and the radius of the metal tie rod in the control mechanism was 18mm, the field intensity in the solid-sealed polar pole was relatively reasonable, but the maximum E-field intensity in the arc-extinguishing chamber gap between the contacts was up to 5041V/mm. It was necessary to carry out pressure withstand test to ensure insulation safety. The results of this paper could provide reference for the optimal design of the solid-sealed polar pole.

Research on the discharge characteristics of XLPE insulated DC cables

This paper focuses on the discharge of cross-linked polyethylene (XLPE) insulated DC cables, which has become a concern of power utilities when carrying out a voltage withstand test or an outage maintenance. Based on the electrical tree initiation test of XLPE block samples under grounded DC voltages, the main cause and key factors for damages of DC insulation resulted by grounding discharge were investigated, and the allowable voltage level to start the accelerated discharge operation was estimated. By the laboratory tests of two XLPE cable samples discharged under different conditions, the basic discharge rules were observed, the equivalent circuit was set up, and the equipment parameters were determined. In addition, a method to estimate the discharge time for cable lines with different lengths was proposed. Finally, the on-site measured data of decay voltage and leakage current were presented for a 200 kV DC XLPE cable line which had been discharged steppedly through a resistance grounding device after the DC voltage withstand test, and the experimental results were found to be in good agreement with the theoretical data.

Investigation Of Enclosure Burn-Through In Hv Gis Circuit-Breakers Due To Internal Arcing

Abstract Modelling of internal arc faults in GIS is a complex and challenging task due to a large number of mutually dependent and highly variable factors, which influence the whole process. This is especially the case in GIS circuit-breakers with high rated short circuit currents, where the risk of internal arcing is much higher due to the presence of the switching arc and contamination of SF6 gas caused by the arc and by the products of material evaporation. Severe conditions resulting from internal arcing ultimately determine its design limits and must therefore be carefully investigated. This paper focuses on one of the main effects of internal arcing, the enclosure burn-through, and presents a novel analytical approach to the estimation of the enclosure burn-through time, as a result of the combined thermal impact of the arc root, arc motion and mechanical stress due to pressure rise, establishing a relation between the thermodynamic and transport gas characteristics in the arcing chamber, and the time to enclosure burn-through. In order to achieve this, this model was implemented within an enhanced internal arc simulation model, derived from the work of the CIGRÉ working group A3.24. Validation of calculation results of the implemented model was conducted using internal arc withstand tests and available measurements of time to enclosure burn-through.

Mycelium brick preparation using cultivated oyster mushroom, Pleurotus ostreatus - A boon for sustainable environment

Nowadays, the cost for housing construction has reached due to increase in the cost of raw materials of which bricks constitute of 5–10% of total cost. As an alternative, Oyster mushroom, Pleurotus ostreatus cultivated using paddy straw can be utilized for the preparation of mycelium bricks. Mycelium bricks are organic bricks synthesized from organic wastes and fungal mycelia including cultivated mushrooms and/or mushroom spawn. Mycelia are thin root like fibers from fungi which run underneath the ground. The compatibility of the synthesized mycelium bricks was determined by carrying out tests such as compressive strength test, water absorption test and drop test. It was observed that, when dried mycelium bricks can be used as a super strong (withstand drop test upto 3 feet above the ground level), water, mould and fire-resistant building material grown into specific forms thereby reducing the process requirements. Therefore, it can be considered as a novel construct which alleviates the problems arising during construction such as poor-quality raw materials, reduced strength, low water absorption capacity and decreased shelf life due to increase in the internal as well as external cracking and so can serve as a suitable next generation alternative for construction.