Air-insulated Switchgear Research Articles

Study on Pd-MoTe2 monolayer for adsorption and sensing of air decomposition products in air-insulated switchgear

Detecting characteristic decomposition components has become a popular method for assessing the operational stability of air-insulated switchgear. This paper investigates the adsorption and sensing properties of a Pd-modified MoTe2 (Pd-MoTe2) for two common defective gases, namely, NO2 and CO, in air-insulated switchgear and employs the first-principles density functional theory (DFT) to conduct the analysis. According to the findings, Pd has a preference for doping in the TMo site on the MoTe2 monolayer, with a binding energy (Eb) of −2.240 eV. The Pd-MoTe2 monolayer exhibits effective adsorption of NO2 and CO, with both molecules chemisorbed. The adsorption energies (Ead) for NO2 and CO are −1.307 eV and −1.550 eV, respectively. Furthermore, there is an evident reduction of the band gap for the Pd-MoTe2 upon adsorbing NO2, decreasing the resistance value. In short, the Pd-MoTe2 monolayer has shown great promise as a gas sensor, laying the groundwork for improving power system stability.

Carbon Emission Evaluation Method and Comparison Study of Transformer Substations Using Different Data Sources

The construction of transformer substations in transmission lines is a systematic, technical, and complex project with the need for numerous materials and resources. Under the development of the green economy, the requirements for energy conservation and carbon reduction have improved; hence, an assessment of carbon emissions in transformer substations is urgently needed. A calculation method was proposed in the present study to analyze the carbon emissions of transformer substations with different kinds of data sources, which were collected from several practical projects in the west-to-east power transmission project. In this study, a detailed comparison and discussion regarding the differences in carbon emissions of 750 kV transformer substations caused by hydrology, geology, engineering quantity, and other factors were conducted. The mean value, standard deviation, and 90% confidence interval of carbon emissions were obtained by Monte Carlo simulation through MATLAB. Results show that the total carbon emissions of the selected 750 kV transformer substations are between [56,000, 68,000] t CO2 eq. Construction engineering accounts for more than 50% of carbon emissions, followed by installation engineering and additional services. In terms of input items, electricity distribution buildings contribute more than 39% of total carbon emissions, followed by cable/earthing systems, which account for 14% of total carbon emissions. Gas insulated switchgear (GIS) and air insulated switchgear (AIS) could adopt different types of equipment foundations, and GIS equipment foundations would generate fewer carbon emissions due to the smaller land area and input materials. This study can provide experience and reference for similar projects and further guide the substation carbon emission reduction work.

Comparative Analysis of Transients in AIS and GIS With Vacuum Interrupters

Gas-insulated switchgear (GIS), at the medium voltage (MV) level, uses vacuum interrupters for current interruption. They are as compact as GIS while retaining the superior performance of vacuum interrupters. The presence of SF6 influences the transient behavior of the system. As the use of GIS with vacuum interrupters becomes rampant, the knowledge of differential transient behavior is critical for proper application. This article presents a comparative study of the transients in GIS and air-insulated switchgear (AIS) with vacuum interrupters, through simulation and observations during testing of switchgear.

First-principles investigation of Pt-doped MoTe2 for detecting characteristic air decomposition components in air insulation switchgear

Air-insulated switchgear plays a significant role in electrical engineering; the running stability of this equipment is required higher. In this work, the Pt-doped MoTe2 (Pt-MoTe2) monolayer is proposed as a novel sensing material for the detection of air decomposition components: NO2 and O3, to evaluate the operation status of air insulation switchgear. The Pt dopant is stably anchored on the MoTe2 surface with the binding force (Eb) of −3.02 eV, and the band gap decreases after Pt-doping on the pure MoTe2 monolayer. Besides, the Pt-MoTe2 monolayer behaves as chemisorption upon NO2 and O3 molecules adsorption with adsorption energy (Ead) of −1.750 eV, −2.045 eV, respectively. Furthermore, the NO2 and O3 molecules behave as electron-acceptor withdrawing charges from the Pt-MoTe2 monolayer, based on the Hirshfeld analysis. Comparing two gas systems, it is found that band gap decreases in both gas systems, and the degree of decrease varies significantly, which makes it possible to develop resistance-type gas sensor to detect NO2 and O3 molecules. Our calculations give an insight into the physicochemical property of Pt-MoTe2 monolayer, and elucidate their promising potential as novel gas sensors for air insulating switchgear.

Diagnosis of Partial Discharge Based on the Air Components for the 10 kV Air-Insulated Switchgear.

Partial discharge (PD) is a common phenomenon of insulation aging in air-insulated switchgear and will change the gas composition in the equipment. However, it is still a challenge to diagnose and identify the defect types of PD. This paper conducts enclosed experiments based on gas sensors to obtain the concentration data of the characteristic gases CO, NO2, and O3 under four typical defects. The random forest algorithm with grid search optimization is used for fault identification to explore a method of identifying defect types through gas concentration. The results show that the gases concentration variations do have statistical characteristics, and the RF algorithm can achieve high accuracy in prediction. The combination of a sensor and a machine learning algorithm provides the gas component analysis method a way to diagnose PD in an air-insulated switchgear.

Redesign Gas Insulated Switchgear to Semi Air Insulated Switchgear 500 kV side and 150 kV side in EHVS Kembangan

The main role of 500 kV extra high voltage Gas Insulated Substation in transmission system is serves connection between the electrical generation and transmission system. To improve equipment performance and the quality and reliability of electricity distribution need time to maintain gas insulated line compartment but preparation to maintenance requires a long time, limited maintenance duration and long implementation of gas evacuation. This paper is object to redesign Gas Insulated Switchgear (GIS) to Semi Air Insulated Switchgear (AIS) on 500 kV side and 150 kV side with new design of Gas Insulated Line compartment in order to accelerate maintenance and gas evacuation job. with surveys, observations, analyses and Root Cause Problem Solving (RCPS), it can be seen the initiation of improvement to accelerate the maintenance of IBT and accelerate the repair of anomalies in the gas insulated line. After redesign Gas Insulated Switchgear to Semi Air Insulated Switchgear, this results show maintenance IBT after redesign is 25 hours faster and duration anomaly on GIL after redesign 24 hours faster.

Hybrid Sensing of Internal and Surface Partial Discharges in Air-Insulated Medium Voltage Switchgear

Partial discharge (PD) measurements have proved their reliability for health monitoring of insulation systems in power system components including synchronous generators, power transformers, switchgear and cables etc. Online condition monitoring and pro-active detection of PD faults have been highly demanded over the last two decades. This paper provides results from a research project to develop advanced non-intrusive sensing technologies that are cost effective, reliable and efficient for early detection of PD faults in medium voltage (MV) and high voltage (HV) air-insulated switchgear. Three sensors (high frequency E-field (D-dot) sensor, Rogowski coil and loop antenna) have been developed and tested under various PD faults and their performance were evaluated in comparison with high frequency current transformer (HFCT) which is being used commercially for PD testing and measurement. Among these three sensors, it is shown that D-dot sensor and Rogowski coil are more dependable when it comes to the PD measurements due to their high signal to noise ratio and hence high accuracy. These sensors can be customized according to a specific application and can be connected together with one data acquisition device while developing an online condition monitoring system.

Environmentally Friendly Compact Air-Insulated High-Voltage Substations

This paper investigates the possible options for achieving a substantial reduction in a substation footprint using air-insulated switchgear as a more environmentally-friendly alternative to gas-insulated substations that use SF6 gas. Adopting a new approach to surge arrester location and numbers, International Electrotechnical Commission (IEC) minimum clearances can be successfully selected instead of the maximum clearances as currently adopted by many utilities, as is the case in the UK. In addition, innovative alternative compact busbar arrangements using vertical and delta configurations have been proposed by the authors. A further opportunity for compaction is offered by the application of compact and integrated technology offered from several manufacturers. The full overvoltage control within the entire substation under any surge condition is a key aspect of the feasibility of this type of substation. This work demonstrates that the new design option can be an attractive alternative for future substation configuration with minimum footprint.

Detection of Ozone and Nitric Oxide in Decomposition Products of Air-Insulated Switchgear Using Ultraviolet Differential Optical Absorption Spectroscopy (UV-DOAS).

Air-insulated switchgear cabinets play a role in the protection and control of the modern power grid, and partial discharge (PD) switchgear is a long-term process in the non-normal operation of one of the situations; thus, condition monitoring of the switchgear is important. The air-insulated switchgear during PD enables the decomposition of air components, namely, O3 and NO. A set of experimental platforms was designed on the basis of the principle of ultraviolet differential optical absorption spectroscopy (UV-DOAS) to detect O3 and NO concentrations in air-insulated switchgear. Differential absorption algorithm and wavelet transform were used to extract effective absorption spectra; a linear relationship between O3 and NO concentrations and absorption spectrum data were established. O3 detection linearity was up to 0.9992 and the detection limit was at 3.76 ppm. NO detection linearity was up to 0.9990 and the detection limit was at 0.64 ppm. Results indicate that detection platform is suitable for detecting trace O3 and NO gases produced by PD of the air-insulated switchgear.

Environmental and safety aspects of AirPlus insulated GIS

New insulation gases as alternatives to SF6 have been presented in the last years. The main focus has been on technical performance and reduced global warming potential compared with SF6 gas-insulated switchgear (GIS). Another very important aspect for customers is the environmental impact and safety in all operational situations, as well as during leaks or even internal arc failures. This study introduces a solution using AirPlus™ as an insulation gas mixture, with results of comparison tests to SF6 GIS and air-insulated switchgear.

Evaluation of lifetime of air-insulated switchgear versus service conditions in MV substations

Evaluation of lifetime of air-insulated switchgear versus service conditions in MV substations

Предотвращение повреждений трансформаторов на электростанциях с укрупненными энергоблоками, подключенными к комплектному распределительному устройству через высоковольтные кабели

Many hydro power plants (HPP) in various countries are being operated with double generating units (DGU) where each unit generator-transformer has its own generator circuit breaker (CB) and both units are connected to a high voltage (HV) network via two common CBs installed in an air-insulated switchgear (AIS). Such circuitry was designed to halve the number of rather expensive HV CBs and to save on the space necessary for their installation. The necessary flexibility of HPP is continued as DGUs allow keeping one unit transformer in idle mode and putting into operation a unit generator via generator CB very rapidly if necessary. Long-term experience has demonstrated the high reliability of operation of HPPs with such circuitries, nevertheless due many reasons the AISs in HPPs are replacing now with more compact and convenient in operation gas-insulated switchgears (GIS). This replacement is taking place in many countries, and everywhere, the existing DGUs are connected to GISs via HV cables. It shall also be noted that each GIS circuitry is generally designed identically to previous AIS circuitry. But cases of damage of some unit transformers working in idle mode have been observed in a number of countries after such replacement. This paper reports the results of investigating one of these cases of damage, discusses the possible causes of this incident and elaborates some measures to prevent such damages in the future.

On-site standard lightning impulse test for 1,100-kV gas-insulated switchgear with large capacitance

Gas-insulated metal-enclosed switchgear (GIS) was developed in the mid-1960s [1]–[5]. Compared with traditional air-insulated switchgear, the GIS concentrates the bus, isolating switch, circuit breaker, lightning arrester, transformer, and many other devices in an enclosed grounding metal case. It has many advantages such as reliability, compactness, long maintenance cycle, and low environmental impact, which have led to it being widely used in electrical power systems [6]–[16]. However, increased operating voltages and more extensive power grids have given rise to increased GIS failure rates [17], [18].

Influence of humidity and voltage on characteristic decomposition components under needle-plate discharge model

Detecting the decomposition components in air-insulated switchgear is an effective method to evaluate the discharge severity of air-insulated switchgear. Experimental and theoretical studies are conducted to investigate the types of decomposition components and generation mechanism under the partial and disruptive discharge conditions. The discharge experiments use a needle–plate discharge tank, and the effect of relative humidity (50, 70 and 90%) and voltage (6, 6.5, 7 and 7.5 kV) are studied in detail. Considering the partial discharge process, the concentrations of CO and NO2 increase with the applied voltage and partial discharge time. The CO concentration increases with the increase of humidity, while NO2 concentration shows the reverse change trend. During the disruptive discharge process, the decomposition component NO increases with humidity. The dissipation of these decomposition components is also investigated using experiment. The small part of CO dissipation is from the adsorption with H2O molecules and onto the surface of discharge tank. The reaction between NO and O free radical, O2 and O3 consumes the concentration of NO and produces NO2. And the reaction between NO2 and H2O consumes most of the generated NO2 in the discharge tank. In the theoretical research, the reaction energy of CO, NO and NO2 generation is computed to analyze the generation and dissipation mechanism of decomposition components using Materials Studio.

친환경 고압배전반 개발을 위한 dry air의 압력별 절연내력특성 분석에 관한 연구

The environmental pollution caused by green-house gases such as CO₂ and SF6 has been becoming the main issue of industrial society. Many developed countries are making efforts to minimize the amount of CO₂ emission come from the operation of high voltage electrical apparatuses. As a part of these efforts, 180 countries signed the Kyoto Protocol in 1997 to cut back on their green-house gas emissions. Nowadays, the study on the development of dry air insulated switchgear (DAIS) which is known as an eco-friendly electrical apparatus is in progress. A DAIS is advantageous for minimizing the effect of impurities and enhancing the dielectric characteristics over an air insulated switchgear (AIS) by applying constant pressure to an enclosed cubicle. Therefore, a study on the electrical insulation performance of dry air as a gaseous insulation medium is conducted in this paper to substitute a gas insulated switchgear (GIS) for DAIS. As results, it is verified that the AC dielectric characteristics of dry air are similar to those of air and the lightning impulse dielectric characteristics of dry air are superior to those of air at 1bar pressure condition. However, dry air is of inferior dielectric characteristics to SF6 at 4bar pressure condition. Finally, it is suggested that the internal pressure of DAIS should be over 4bar pressure to develop a high voltage switchgear which has similar electrical performance to a conventional GIS. Also, the empirical formulae on calculating the maximum electric field intensity at sparkover of dry air are deduced by experiments according to pressures. It is expected that these results are helpful to design and develop a high voltage electrical apparatus.

Overvoltages in secondary circuits of medium-voltage switchgear generated by multiple reignitions of circuit breakers

During switching operations in the high-voltage system, transient voltages and currents occur that can generate overvoltages in the secondary circuits of switchgear. The investigations reported in this article are focused on medium-voltage air-insulated switchgear. The introduced model is able to identify the coupling mechanisms. The coupling via the instrument transformers and the secondary wiring to the electronic equipment is described. At first, the frequency-dependent coupling is explained for each secondary component. These are instrument transformers, the secondary wiring, and the electronic equipment. Then it is shown how to combine these components in order to get a complete description of the interfering mechanisms.

Partial discharge. XIV. Acoustic partial discharge detection-practical application

For pt.XIII see ibid., vol.8, no.4 (July/August 1992). The finer points of acoustic partial discharge (PD) detection systems and their common applications are treated. The PD source, propagation path of the waves, the acoustic sensor, and system noise are described. The design of acoustic PD instrumentation, the location of discharges, and the detection and evaluation of signals are discussed. Applications to outdoor insulation, medium-voltage air-insulated switchgear, capacitors, transformers, and cables are covered. >

Contribution on the Specification of an Aging Test for the Insulation of Enclosed, Air-Insulated Switchgear

Because of high humidity and condensation, layers of moisture are formed on the surface of insulating materials in indoor switchgear installations which, as a result of contamination, are conductive electrolytic boundary layers. When this happens, electrochemical interactions can produce aging of the insulating material surfaces that may even lead to failure of the insulation. Basic investigations were carried out on a rod-shaped model insulator with simul taneous subjection to an electric field, moisture, and polution. Electrical, chemical, and optical diagnostic methods make it possible to determine aging related surface changes. Based on these results and taking into account the results of work done by the International Working Group IEC-SC17/WGIO Aging Tests, proposals are discussed for an aging test for enclosed indoor switchgear. In particular, procedures are discussed for simulating the aging phenomena with time compression. The suitability or nonsuitability of individual parameters are discussed.