|
Name |
Saro Esmaeili |
|
University |
University of Liverpool |
|
Title |
Radiation transfer calculation in three-dimensional switching arcs |
|
Abstract |
The most commonly used insulating medium in high-voltage circuit breakers (HVCB) in the power industry is SF6. Despite being an excellent insulator, SF6 causes severe environmental concerns. Its GWP is 23900 times higher than CO2, and its life span is 3400 years. Each year around 8000 tonnes of SF6 is released into the atmosphere, equivalent to the carbon emission of 100 million cars, and 80% of this pollution comes from the power industry. Finding a proper substitute for SF6 in HVCBs requires a thorough understanding of the materials’ performance during the arc as the most extreme and crucial phenomenon in the operation of the circuit breaker. Arc studies rely on computational simulations, currently hindered by the radiation transfer calculation due to its computational costs. The 3-D calculation of the radiation transfer in actual switching arcs enables us to extract quantitative information regarding this phenomenon and establish solid conclusions with direct impacts on the arc simulations in commercial applications. The flexibility of the radiation model allows investigating potential substitutes like C4F7N+CO2 and O2+CO2 mixtures to obtain knowledge, expand our horizons and take steps toward the Net-Zero target. The presentation contains the introduction of the problem and the role of SF6 in the power industry, then the 3-D model for the radiation transfer calculation in actual switching arcs, developed by the presenter, is introduced, plus some of the significant results that can influence the design of the circuit breaker and the material study procedures. |
|
Name |
Neil Wands |
|
University |
University of Exeter |
|
Title |
Preparing for a Netzero future – A National Grid perspective |
|
Abstract |
The challenge for the UK National Grid in preparing for a Net Zero future is significant and will require adaptation to accommodate renewable energy sources while also maintaining a reliable and affordable energy supply for consumers. Renewable energy sources such as solar, wind, hydropower, and geothermal are gaining attention globally and domestically, offering a clearer path to reaching challenging Net-zero environmental targets. Each of these technologies is fundamentally different in profile and output capacity requiring distinct infrastructure/ technology to harness their potential. The immaturity of these technologies and their variability means integrating these renewable sources into existing power grids can pose several challenges. This presentation will briefly review the potential of these sources to meet future demand in the UK, whilst addressing some of the critical challenges around their integration into the existing grid infrastructure |
|
Name |
Ruichang Zhang |
|
University |
University of Manchester |
|
Title |
Privacy-Cost Trade-off Strategies with Smart Meter Management based on Reinforcement Learning |
|
Abstract |
This research delves into the increasingly relevant and critical domain of privacy preservation in the context of Smart Meter Management (SMM). With the escalating adoption of smart meters, consumers’ power usage data has become an attractive target for potential privacy breaches, raising legitimate concerns over privacy protection. The primary objective of this study is to introduce a novel approach to manage the privacy-cost trade-off using Reinforcement Learning (RL) algorithms. The RL framework, by learning the optimal policy, aims to enhance the privacy of consumers without imposing a significant cost burden. The proposed RL-based strategy employs a dynamic approach to adjust the release of energy usage data in a manner that maximizes privacy and minimizes cost, without undermining the overall functionality of the system. Through multiple simulations, the RL algorithm’s performance is tested against conventional methods and demonstrates superior performance, striking an improved balance between the conflicting goals of cost efficiency and privacy preservation. |
|
Name |
Xubin Li |
|
University |
University of Liverpool |
|
Title |
The Application of PIC-MCC in Post-Arc Dielectric Recovery Process Simulation in Vacuum Circuit Breakers |
|
Abstract |
Vacuum circuit breakers(VCBs) have been considered as a strong candidate to replace SF6 circuit breakers. Post-arc dielectric recovery of VCBs determines their interruption capability. To improve the VCBs to a higher voltage level, a clear understanding of the physical processes taking place after the current zero is of great significance. A PIC-MCC model with important collisions considered is developed and applied to the dielectric recovery process of a vacuum gap. The evolution of concerned parameters, such as the sheath thickness in a contact gap and the spatial distribution of particle number density and velocity, are obtained and analyzed. Combined with the current equation which is part of the well-known continuous transition model (CTM), the post-arc current waveform is simulated and compared with available experimental results. Results show that the model is able to predict the peak value, duration time and total charge of the post-arc current. The limitations of the PIC model are also discussed and some proposals for improving the model are then given. |
|
Name |
Christian Pößniker |
|
University |
University of Exeter |
|
Title |
Bubble Formation in Power Transformers – a Potential Risk for the Future Network Reliability |
|
Abstract |
The risk of bubble formation is one of the main loading constraints for transformers and understanding the fundamentals behind bubble formation mechanisms will help utilise short-term overloading capabilities, if necessary, with minimum risks. This paper discusses about an experimental study to evaluate the bubble formation temperature from insulation systems and the results obtained for different oil-paper insulation systems |
|
Name |
Haichuan Yu |
|
University |
University of Manchester |
|
Title |
Streamer and Breakdown Characteristics of Transformer Liquids in Moderately-Uniform Fields under Negative Lightning Impulse |
|
Abstract |
As one of the most important power equipment, the safe and reliable operation of power transformers is vital for the power network. Streamer and breakdown characteristics of transformer liquids under lightning impulse have been widely studied in terms of varying field uniformity. Based on the comparison between streamer initiation voltage and breakdown voltage, the breakdown phenomenon can be classified into streamer initiation dominated breakdown and streamer propagation dominated breakdown. The identification of transition field factor boundary between streamer initiation dominated breakdown and streamer propagation dominated breakdown is important for understanding the breakdown mechanisms of transformer liquids and for the transformer insulation design in practice. The field factor boundary between two breakdown mechanisms have been investigated under positive lightning impulse, which is 53.0 for a mineral oil and 79.0 for a synthetic ester. However, there is no such transition field factor boundary results under negative lightning impulse. This paper proposes a new method to deduce the transition field factor boundary, which is only based on the breakdown voltage measurements under different gap distances. The breakdown voltages of three transformer liquids were measured under negative lightning impulse with rod (tip radius of 0.5 mm) to plane electrode geometry at the increasing gap distances from 2 mm to 40 mm. The results show that the transition field factor boundary between streamer initiation dominated breakdown and streamer propagation dominated breakdown under negative lightning impulse is liquid dependent. It is 9.6 for a mineral oil, 7.3 for a GTL oil, and 42.0 for a synthetic ester. The difference of the transition field factor boundary helps explain the observed breakdown voltage distinctions among the three transformer liquids. In addition, the characteristics of negative streamers leading to breakdown were also investigated in the moderately uniform fields. Streamer mode transitions with gap distance were observed and clarified as shown in Figure 1, which is from 1st mode streamer led breakdown to 2nd mode streamer led breakdown in both the mineral oil and GTL oil, while it is the 2nd mode streamer to fast streamer in the synthetic ester. The streamer morphologies captured at 10 mm gap distance as shown in Figure 2 also support the streamer mode transition phenomena in moderately-uniform field under negative lightning impulse. |
|
Name |
Kaiyuan Zhang |
|
University |
University of Liverpool |
|
Title |
Application of Parallel Computing in Switching Arc Simulation |
|
Abstract |
The performance of modern high voltage circuit breakers as protective equipment involves Multiphysics processes that are coupled with high nonlinearity. Computer simulation has become an essential tool to aid the design of high voltage circuit breakers, especially in the global effort to eliminate the use of SF6 in high voltage systems. Realistic computer simulation needs to include all important components in a high voltage circuit breaker, such as pressure regulating valves (relief, refill, and check valves), moving voltage shield (a special moving structure to minimize the electrical stress) and the contacts. Modelling of switching arcs based on a single computing thread is extremely time-consuming and provides little benefit from upgraded computing power. Liverpool’s arc model has been enhanced to make use of parallel computing. It is implemented in ANSYS Fluent. Compared with serial computing, parallel computing has significantly reduced the calculation time. For the same computational task representative of normal arc simulation, the parallel computation time of 27.1 seconds per time step represents a speedup of approximately 5.3 times compared to the serial computation time of 144 seconds per time step, giving a time saving of approximately 80%. Some typical examples will be presented. |
|
Name |
Gechen Bian |
|
University |
University of Manchester |
|
Title |
Development of a Test Platform for DGA Studies of Transformer Liquids under Electrical Faults |
|
Abstract |
For liquid-immersed power transformers, dissolved gas analysis (DGA) is considered to be one of the most effective techniques for indicating incipient thermal and electrical faults. Electrical faults are classified into partial discharge (PD), D1 (discharge of low energy) and D2 (discharge of high energy). As is well known, the key gases for electrical faults are hydrogen (H2) and acetylene (C2H2), however hydrogen (H2) is escapes easily during a long duration laboratory experiment under electrical faults like PD. This is because of the low solubility of hydrogen in transformer liquids and its small molecular size. Therefore, inconsistent H2 results from DGA-electrical faults are often found in the literature. This paper aims to develop a test platform with a gas-tight test cell that is suitable for studying gas generation in transformer liquids under long duration discharge faults. The test platform includes a high voltage supply system, a gas-tight test vessel with a circulation system, DGA sampling loop and measurement units for voltage, current and PD detection. The voltage source is a step-up transformer capable of 70 kV, supplied on the primary side from a signal generator and power amplifier. The gastight test vessel is made of stainless-steel and has a volume of 1L. A circulation path is added to the test vessel to circulate liquids after fault gas generation, helping to make the fault gas distribution in the liquid more uniform. A gas-tight syringe system is used to take liquid samples from the top of the test vessel. Headspace-gas chromatography (HS-GC) is used to measure the gas in liquid concentrations. Additionally, a commercial PD detector (MPD 600) is used to make PD measurements in accordance with the IEC 60270 standard. A detailed procedure for liquid filling, gas generation and liquid sampling has been developed. Experiments determining fault gas generation in a mineral oil under different durations of PD activity have been conducted and the total PD energy calculated from the recorded PD apparent charge and the instantaneous voltage. This enables a correlation to be made, between fault gas concentration and PD parameters. The results show that the gas generation per unit energy (μL/J) for each fault gas is constant with increasing time duration, up to 5 days, indicating that the experiment is performing well in terms of fault gas capture and retention. |
|
Name |
Yannan Zhou |
|
University |
University of Liverpool |
|
Title |
Surface Average Temperature Measurement of Cu-W Contact Material Burning in CO2: Preliminary Study |
|
Abstract |
During short-circuit current interrupting operations in high-voltage circuit breaker, a considerable part of energy released by the switching arc is transferred to the arcing contacts and nozzles. The surface average temperature and the electrode temperature distribution are key parameters and indictors to predict the electrode erosion. The experimental research on the arc erosion has been carried out at the arcing test platform, in which CO2 was filled in the chamber and Cu-W (40/60 wt%) was used as the contact material. The surface average temperatures of Cu-W plug contact exposed to electric arc with sinusoidal currents of 5 kA were determined by a high-speed pyroscope. The anode surface average temperature, power and electric conductance are plotted for four consecutive arcing tests. The energy flux injected from the electric arc heats up and melt the electrode material. In order to establish a relationship between the average temperature of contact surface and current squared, the data statistics and fitting curves in the current-rising and current-falling stages have been given. It is found that there are two different types of arc erosion processes by comaring the temperature-current squared curves. In other words, the structure of contact surface and the electrode material change obviously after repeated arc erosions. |
|
Name |
Jialin Chen |
|
University |
University of Manchester |
|
Title |
Ageing Assessment of Liquid-Solid Insulation Systems Used in Power Transformers |
|
Abstract |
Over the past century, the combination of mineral oil and Kraft paper insulation materials has been widely used as the main insulation system in power transformers. In the last decades, ester liquids have gradually become one of the alternative insulating liquids used in transformer insulation systems due to their better fire resistance behaviour and biodegradability [1]. In addition, Gas-to-Liquid (GTL) and biodegradable hydrocarbon liquids have also emerged in the market and gradually gain popularity [2]. In terms of solid insulation, there is variety of thermally upgraded Kraft papers due to the different nitrogen contents. Adoption of new insulation materials in transformers requires understanding the long-term ageing performance of the liquid-solid insulation systems [3]. This PhD work focuses on ageing assessment of transformer liquid-solid insulation systems including experimental methodology, material characterisation and identification of new ageing markers. Both non-thermally and thermally upgraded Kraft papers (with different nitrogen contents) are considered. Four types of insulating liquids, including mineral and biodegradable hydrocarbon oils, natural and synthetic esters, are used. In the first set of experiment, cyclic ageing of mineral and biodegradable hydrocarbon oils are conducted at 150 ℃. After each cycle of 7-day ageing, the closed vessels are taken out of the oven to cool down for 47 h then open to air environment for 1 h. This is done deliberately to accelerate the ageing process. Parameters including DP, tensile strength, moisture and acidity are measured during the ageing process. The ageing experiments are stopped when the degree of polymerisation reaches about 250. |
|
Name |
Kamil Erdayandi |
|
University |
University of Manchester |
|
Title |
A Privacy-Preserving and Accountable Billing Protocol for Peer-to-Peer Energy Trading Markets |
|
Abstract |
In this work, we propose a privacy-preserving and Accountable Billing (PA- Bill) protocol for trading in peer-to-peer energy markets. The proposed payment and settlement protocol addresses situations where there may be discrepancies between the volume of energy committed and delivered. PA-Bill is designed to maintain privacy and accountability, with homomorphic encryption utilised to encrypt sensitive user data and blockchain technology employed to ensure accountability. A dispute resolution mechanism is pro- posed to minimise the occurrence of erroneous bill calculations while ensuring accountability and non-repudiation throughout the settlement and billing process. By evaluating the system’s requirements and performance, our study demonstrates that PA- Bill offers an effective billing mechanism that maintains privacy and accountability in peer-to-peer energy markets utilising a semi-decentralised approach. |
|
Name |
Xin Wang |
|
University |
University of Exeter |
|
Title |
High-Voltage Equipment Design – Harnessing the power of Molecular Dynamic Simulation as a Potential Material Selection Tool |
|
Abstract |
Recent advancements in molecular dynamic simulations have made it a popular tool to carry out mechanisms studies in different areas of science and engineering. This paper focuses on the utilisation of molecular dynamic simulation in the material development of high-voltage circuit breaker contacts. MD simulation was used to study the impact of adding Graphene into the traditional Cu-W contact materials |