Gas Distribution System Research Articles

Low Methane Emissions from the Natural Gas Distribution System Indicated by Mobile Measurements in a Chinese Megacity Hangzhou

Low Methane Emissions from the Natural Gas Distribution System Indicated by Mobile Measurements in a Chinese Megacity Hangzhou

Acoustic emission-based leakage detection for gas safety valves: Leveraging a multi-domain encoding learning algorithm

Safety valves in gas distribution systems are crucial for preventing excessive pressure buildups. Leakage in these valves compromises system stability, causing equipment damage and environmental pollution. Acoustic emission signal analysis from the valve body is essential for detecting leakage, but these signals are often weak and easily disrupted by noise, complicating detection. This paper proposes a multi-domain encoding learning algorithm to address these challenges. Unlike conventional single-domain methods, it combines two encoding images, the Gramian angular difference field and the Markov transition field, to enhance the comprehensive expression of leakage features. A lightweight convolutional neural network reduces computing resource dependency, and a convolutional block attention mechanism improves feature identification. Experimental results demonstrate that our method detects gas leakage with an accuracy of at least 96.77%. It maintains superior performance even under intense noise interference, offering a promising solution for detecting weak gas leakages in safety valves amidst high background noise.

Томографический измеритель концентрации метана на приземных трассах

Using a prototype of a remote lidar created in the laboratory for measuring methane concentration, a study of the distribution of methane along a route ~ 2.25 km long was carried out in order to localize gas emissions and control leaks in unfavorable areas. The lidar prototype, operating at a wavelength of 1653 nm, included a powerful Raman amplifier and made it possible to measure the distance to the reflection point with an accuracy of no worse than 50 meters. The lidar scanned the track, starting from short distances and ending with measurements along the entire measured track. The route included a near zone with modern multi-storey buildings without gas infrastructure, a middle zone with multi-storey buildings and gas infrastructure, as well as an extended forest area ending with a busy highway with heavy traffic. That is, it was possible to assess the contribution of each zone to the background methane concentration along the route. Observations were carried out during the winter-spring period and were carried out at different times of the day under weather conditions that were recorded. Processing of the results showed a significantly different contribution of each zone to the average concentration on the route. The contribution of the middle zone with multi-storey buildings equipped with gas infrastructure turned out to be especially large, which suggests a possible gas leak from the gas distribution system in this area. On average, the background concentration of methane on this route repeated the value measured in 2023 during the same seasonal period in 2023.

PROBLEMS OF MANAGING TECHNOLOGICAL REGIMES IN GAS DISTRIBUTION NETWORKS AND MODERN APPROACHES TO THEIR SOLUTION

This article systematically discusses the problems of managing technological regimes in gas distribution networks and modern approaches to their resolution. The scientific-theoretical and practical aspects of managing gas distribution networks (GDN) are analyzed. Based on the obtained results, a scientifically grounded comparative explanation of the existing contradictions in modern and traditional gas distribution networks is provided, and the role of key factors in the emergence of these contradictions is investigated. It is shown that technological backwardness in traditional GDNs increases energy consumption and operational costs, thereby reducing the economic efficiency of the system and increasing the risk of accidents. The research suggests decision-making methods for solving management problems in traditional GDNs by maintaining the technical-structural level and implementing telemetry systems. It is indicated that the widespread use of telemetry and telemechanics tools in the gas distribution industry enhances the safe delivery of gas to end-users and significantly reduces service costs. Another focus of the research is on the issues related to the processing of spatial information for the management of the technical components of gas distribution systems. The article also analyzes scientific research dedicated to the application of modern IT methods and tools in the management of GDNs, investigating management and forecasting models using neural networks and intelligent methods. Keywords: Gas distribution networks, modern GDN networks, traditional GDN networks, GIS systems, digital technologies, technogenic risks, neural networks, forecasting methods

A hybrid gradient climbing algorithm for a swarm robot-based gas leak detector

Methane emissions from leak sources can have a negative climate impact, in addition to contributing to the risk of explosions in urban environments. These risks can be minimized by developing systems that provide for an accurate and timely detection and localization of a gas leakage point. This research used a swarm of robots to detect and locate a leakage point. The localization algorithm derives from further optimization of the gradient climbing algorithm using fireflies acting as opportunistic agents. Firefly agents are characterized by their bioluminescent communication which guides them to dynamically adjust their positions and intensities based on the quality of the gradient information available to them. The proposed research focuses on enhancing gas leak detection through the development of a hybrid gradient climbing algorithm. This algorithm integrates gradient climbing techniques with swarm intelligence, utilizing the strengths of both approaches. This simulation resulted in the hybrid algorithm leading to a reduced convergence time and path lengths when compared to the swarm without opportunistic agents. The suggested approach can be important especially in gas distribution systems or in areas where human intervention is considered to be unsafe.

Optimal planning of integrated electricity-natural gas distribution systems with hydrogen enriched compressed natural gas operation

In future integrated electricity-natural gas distribution systems (IEGDS), hydrogen and methane converted from excessive renewable generation will be mixed with natural gas to form hydrogen enriched compressed natural gas (HCNG) for fewer carbon emissions. Consequently, optimal planning of the HCNG-integrated IEGDS plays an essential role in increasing the economy and technical benefits. However, integrating HCNG operation into the planning of IEGDS still has many challenges, such as unrealistic modeling, nonlinear constraints, and the potential risk of voltage violations. The purpose of this paper is to develop a tractable optimization model for planning and operation of the HCNG-integrated IEGDS, aiming to minimize the investment and operating cost, reduce the voltage violation, and improve the renewable power penetration rate. To achieve this, a bilevel optimization model is developed for optimal planning of wind turbines and soft open points (SOPs) in the IEGDS considering comprehensive HCNG operation, in which both hydrogen and methane injection are considered and optimized for different system operation scenarios. Furthermore, the proposed nonlinear model is reformulated to a tractable bilevel mixed-integer second-order cone model using several reformulation techniques and solved by the reformulation and decomposition algorithm. Case studies, performed using the publicly available datasets, are conducted to demonstrate the economic and technical improvement by implementing the proposed planning model. The annual planning results show that incorporating the coordination between SOPs and methane injection results in a 6.77% reduction in investment cost, a 22.64% reduction in operating cost, a 62.69% decrease in voltage violation, and a 23.58% increase in the wind power penetration rate. Moreover, SOPs are more applicable to the safe operation of the IEGDS under high energy load conditions.

APPLICATION OF THE METHOD OF GROUP ARGUMENTS ACCOUNTING FOR BUILDING MODELS OF SHORT-TERM FORECASTING OF GAS CONSUMPTION BY THE POPULATION

Problem statement. One of the most important tasks in optimizing the operation modes of urban gas distribution systems is to develop a short-term strategy for such modes. Processing of planned and statistical indicators of gas consumption modes is one of the key methods for ensuring the optimal functioning and normal operation of gas supply systems. The most promising modeling method for solving forecasting problems is the method of self-organization of models implemented as the method of group arguments accounting (MGАA). Short-term forecasting of gas consumption is the main source of information for decision-making in the process of planning consumption regimes and operational dispatch control. The MGАA method, also known as the Ivakhnenko method, is a powerful tool for obtaining highly accurate forecasting models and is gaining importance for forecasting in energy resource management and planning their use. The solution to such a problem is relevant, as it makes it possible to analyze the volume of natural gas consumption by the population for the future period. The purpose of the article is to build mathematical models for forecasting gas consumption using the method of group arguments accounting based on input data. Conclusion. To select the best models the following parameters are recommended: tomorrow's gas consumption as a function (main criterion) and arguments (additional criterion) - gas consumption to date, air temperature to date, yesterday's temperature and temperatures for the past 3, 5, 7 days, wind speed and day of the week. The resulting mathematical models of natural gas consumption by the population can be used to analyze the volume of natural gas consumption. The method allows us to find a single optimal mathematical model that best solves the problem.

Improving interdependent urban power and gas distribution systems resilience through optimal scheduling of mobile emergency supply and repair resources

Urban electric power and natural gas systems, serving as the most critical facilities that provide fundamental support to people's daily life, have been increasingly interdependent in their operation over the past decades. This growing interdependency presents great challenges and demands for enhancing the resilience of the interdependent systems, particularly driven by the recent cold weather events. In this paper, we propose a comprehensive strategy for scheduling various types of emergency resources, including mobile and stationary generators, repair crews, and fuel tankers, with the goal of enhancing the resilience of interdependent power and gas distribution systems in the aftermath of disasters. In particular, the strategy incorporates the routing of mobile resources to orchestrate their dynamic moving behaviors. Fuel supply issue for mobile and stationary distributed generators is also addressed through modeling the fuel exchange processes among generators, fuel tankers, and locations. Furthermore, we present a model of repair process to fully capture the real-world repair activities, allowing varying numbers of repair crews to work in a cooperative way. The proposed strategy is formulated into a tractable mixed-integer second-order cone problem. Finally, case studies are carried out to demonstrate the effectiveness of the strategy in enhancing the resilience of the interdependent power and gas distribution systems.

Cross-Temporal Hierarchical Forecast Reconciliation of Natural Gas Demand

Local natural gas distribution companies (LDCs) require accurate demand forecasts across various time periods, geographic regions, and customer class hierarchies. Achieving coherent forecasts across these hierarchies is challenging but crucial for optimal decision making, resource allocation, and operational efficiency. This work introduces a method that structures the gas distribution system into cross-temporal hierarchies to produce accurate and coherent forecasts. We apply our method to a case study involving three operational regions, forecasting at different geographical levels and analyzing both hourly and daily frequencies. Trained on five years of data and tested on one year, our model achieves a 10% reduction in hourly mean absolute scaled error and a 3% reduction in daily mean absolute scaled error.

A novel method for gas mixing and distribution in multi-chamber embryo incubators.

High-quality control of the gas environment in incubators is crucial for in vitro embryo development, which requires high accuracy, fast recovery, and low gas consumption. In this study, we propose a novel gas mixing and distribution system and method as an alternative solution for multi-chamber embryo incubators. The system-based embryo incubator enables a controllable gas circulation process and a quantitative supply of CO2 and N2. To determine the optimal parameters for the mixing time and flow rate of the circulated gases, we conducted contrast experiments on the system-based incubator. To evaluate the performance of the gas system in the incubator, we conducted tests under four different initial conditions, simulating various practical application scenarios. Furthermore, we performed a mouse embryo assay to assess the system's effectiveness. The results show that the system achieved a gas concentration accuracy of ± 0.2% (volume fraction) after stabilization, a minimum recovery time of 5 minutes, an average consumption of 8.9 L/d for N2 and 0.83 L/d for CO2 during routine operation, and a blastocyst rate exceeding 90% observed after 96 hours of culture in the incubator. The system and method demonstrate a significant advantage in terms of low gas consumption compared to existing incubators, while still maintaining high accuracy and fast recovery.

Research on the minimum detection limit for measuring high-purity gases by gas chromatography

Abstract At present, the application fields of high-purity gases (purity reached 99.999% and above) include the semiconductor manufacturing industry, chemical analysis, fuel cells, aerospace, medicine, etc., and the quality and purity requirements of high-purity gases are also getting higher and higher. As the only detector that can detect ppb-level trace impurities, the pulsed discharge helium ionization detector (PDHID) is the most used detector in the field of high-purity gases. The minimum detection limit of existing PDHID-related analysis methods is usually calculated theoretically. In order to verify the actual minimum detection limit of PDHID, a multi-group gas distribution system was used in this paper to dilute the permanent gas components in the high-purity gas, and the gas chromatograph with pulsed discharge helium ionization detector (GC-PDHID) was used to detect the obtained different concentrations of standard gases. The experimental results showed that PDHID possessed high sensitivity, good linearity, and a wide linear range. The actual minimum detection limit for the permanent gas components in the high-purity gas could reach the ng/g (ppb) level, which could realize the detection of ultra-low concentration samples, and further verify the actual minimum detection limit of PDHID. This experiment provides a reference basis for the analysis of trace gases in the gas industry, especially in industries such as high-purity and ultra-high-purity gases and gas for the electronics industry, and is of great significance in actual production work.

Novel high-pressure/high-temperature reactor cell for in situ and operando x-ray absorption spectroscopy studies of heterogeneous catalysts at synchrotron facilities.

This paper presents the development of a novel high-pressure/high-temperature reactor cell dedicated to the characterization of catalysts using synchrotron x-ray absorption spectroscopy under operando conditions. The design of the vitreous carbon reactor allows its use as a plug-flow reactor, monitoring catalyst samples in a powder form with a continuous gas flow at high-temperature (up to 1000 °C) and under high pressure (up to 1000bar) conditions, depending on the gas environment. The high-pressure/high-temperature reactor cell incorporates an automated gas distribution system and offers the capability to operate in both transmission and fluorescence detection modes. The operando x-ray absorption spectroscopy results obtained on a bimetallic InCo catalyst during CO2 hydrogenation reaction at 300 °C and 50bar are presented, replicating the conditions of a conventional microreactor. The complete setup is available for users and permanently installed on the Collaborating Research Groups French Absorption spectroscopy beamline in Material and Environmental (CRG-FAME) sciences and French Absorption spectroscopy beamline in Material and Environmental sciences at ultra-high dilution (FAME-UHD) beamlines (BM30 and BM16) at the European Synchrotron Radiation Facility in Grenoble, France.

ON THE RELIABILITY AND MAINTAINABILITY OF INDIVIDUAL ELEMENTS OF GAS DISTRIBUTION SYSTEM VALVES

At the current stage of the development of society, including in our country, there is an accelerating urbanisation process. The increasing role of cities in the country’s development, on the one hand, contributes to social, scientific, and technical development, and on the other hand, creates new economic, ecological, informational, social, and other challenges. One of the features of urbanisation is the increase in energy use. One of the primary sources of energy is natural gas. Transportation of natural gas from deposits and gas storages and its distribution to consumers occurs with the help of gas transportation systems. One of the components of gas transportation systems is gas distribution systems. They have a broad range of components and elements and a long list of requirements for the conditions of their manufacture, operation, and repair, and they are under the influence of numerous external factors. Such multivariability necessitates the development of specific models, methods, and information technologies for monitoring their state in conditions of uncertainty to solve the problems of forecasting and planning repair work on gas transportation systems. During the study, we determined the main factors affecting the reliability of gas pipelines overall. We also analysed the operational characteristics of the shut-off valves of elements of gas distribution systems, typical malfunctions, and the main features of its diagnosis and repair. During operation, gas distribution system elements are under the influence of many factors that affect their reliability. Considering all the factors arising at different stages of the life cycle of the gas distribution system elements will ensure their operational reliability, indestructibility, and durability. The results of the analysis of individual parameters of shut-off fittings of gas distribution systems are applicable for creating models and methods of monitoring, forecasting, and planning repair work on gas transportation systems under conditions of uncertainty. Keywords: shut-off valves, models and methods of monitoring, reliability, repair, defects.

Development of Company-Specific Emission Factors with Confidence Intervals for Natural Gas Customer Meters in Southern California.

Methane is both a significant and short-lived greenhouse gas compared to CO2, and reducing methane emissions from natural gas distribution systems may offer cost-effective reduction opportunities. We report substantial new direct leak rate measurements from customer meter set assemblies (MSAs) in Southern California. In a novel way, emission factors are defined in terms of aboveground Hazardous and Nonhazardous leak categories, which take direct advantage of readily available industry leak data. We also studied leaks that were not detected as part of normal leak survey procedures. As a result, this yields company-specific emission factors that can be used to track progress in reducing methane emissions. This approach also has the advantage of explicitly accounting for the skewed or fat-tail distribution of leak rates by treating high flow rate MSA leaks separately from low flow rate MSA leaks. The Southern California Gas (SoCalGas) methane emission factors, based on 485 leak rate measurements by direct enclosure, were 4.55 (95% confidence interval: 2.32 to 7.14) kg/day for Hazardous leaks, 0.149 (0.119 to 0.183) kg/day for Nonhazardous leaks, and 0.0039 (0.0003 to 0.0198) kg/day for Non-Detected leaks. The percentage of surveyed meters with nondetected leaks was 29.1% (24.3 to 34.6%). Based on a robust Monte Carlo analysis, total leak emissions from MSAs for the SoCalGas system were reduced by 35% based on data from 2015 to 2022. These reductions were attributed to surveying a larger number of MSAs and accelerated leak repair rates. In traditional population-based emission inventories, an individual emission factor for a given asset category is multiplied by the total population of MSAs within the category. This approach simply cannot capture the reduction in leak numbers and methane emissions resulting from leak mitigation and prevention programs.

The peculiarities of the execution of natural gas supply contracts

The legal basis for the functioning of the natural gas market of Ukraine, based on the principles of free competition, proper protection of consumer rights and security of natural gas supply, has been determined by the Law of Ukraine “On the Natural Gas Market” No. 329-VIII dated 04/09/2015.
 The supply of natural gas to household consumers is carried out on the basis of the standard contract. According to the content of the provisions of the Code of the Gas Transportation System and the Code of the Gas Distribution System, it is understood that, in order to supply natural gas to consumers, its supplier purchases this gas from a wholesaler at a virtual point of sale, and consumers receive it directly from the operator of gas distribution networks at the limit of the balance sheet ownership of their facilities (at destinations). In the context of updating the civil legislation of Ukraine and its harmonization with the law of the European Union, the study of the peculiarities of the execution of the gas supply contract as a type of contract for the supply of energy and the other resources through the connected network is relevant. Taking into account the specifics of the supply object, namely that natural gas is a commercial product that is a mixture of hydrocarbons and non-hydrocarbon components in a gaseous state under standard conditions, the legal nature of the supply contract has certain peculiarities. At the same time, under the contract for the supply of energy and the other resources through the connected network, one party (supplier) undertakes to provide the other party (consumer, subscriber) with energy and the other resources provided for in the contract, and the consumer (subscriber) undertakes to pay the cost of the received resources and to comply with the mode of its use stipulated by the contract, as well as to ensure safe operation of energy and the other equipment.
 The peculiarities of the execution of the contract for the supply of natural gas have been determined by the legal regime of the commercial product, which is natural gas, and the peculiarities of its supply (no other than through the gas transportation and gas distribution systems in which natural gas is received from various economic entities, as a result of which it is mixed and changes in physical chemical parameters).

Iterative convex relaxation of unbalanced power distribution system integrated multi-energy systems

This study describes a multi-period, multi-energy operation of a three-phase unbalanced Electric Distribution System (EDS) that coordinates with a District Heating System (DHS) and a Natural Gas (NG) distribution system. The electrical subsystem problem is formulated as a bi-level programming problem, with levels 1 and 2 solving the subsystem’s linearized and relaxed nonlinear versions, respectively. Second-Order Cone Programming (SOCP) and polyhedral relaxations are availed to circumvent the non-convexities involved in the subsystems. The SOCP relaxation for an unbalanced power distribution network is inexact; also, the subsystems applying polyhedral relaxation may not generate a meaningful solution as the relaxations are not tight. Therefore, a solution recovery algorithm is developed for each subsystem to recover a feasible solution from their relaxed counterparts. The successive bound tightening algorithm employing a solution recovery procedure is proposed for each subsystem, improving solution quality and strengthening the relaxations with the desired computational efficiency. The proposed solution strategy to optimize the Multi-Energy System (MES) operation cost is verified on the three-phase IEEE-13 and IEEE-123 bus systems, each coordinating with a 30-node DHS and a 6-bus NG network. The results analyses demonstrate that the proposed solution strategy efficiently achieves an optimal solution, reducing maximum relaxation error below 0.1% for each subsystem. The proposed strategy delivered a 14.58% reduction in real power losses and a 12.73% decrease in phase voltage unbalance rate for the EDS in MES. Furthermore, a 1.96% decrease in operational cost demonstrates the techno-economic benefits of the proposed strategy.

A Multi-Agent Distributed Operation Solution to Electricity and Natural Gas Distribution Systems for Enhancing Resilience

A Multi-Agent Distributed Operation Solution to Electricity and Natural Gas Distribution Systems for Enhancing Resilience

Ground-Based Mobile Measurements to Track Urban Methane Emissions from Natural Gas in 12 Cities across Eight Countries.

To mitigate methane emission from urban natural gas distribution systems, it is crucial to understand local leak rates and occurrence rates. To explore urban methane emissions in cities outside the U.S., where significant emissions were found previously, mobile measurements were performed in 12 cities across eight countries. The surveyed cities range from medium size, like Groningen, NL, to large size, like Toronto, CA, and London, UK. Furthermore, this survey spanned across European regions from Barcelona, ES, to Bucharest, RO. The joint analysis of all data allows us to focus on general emission behavior for cities with different infrastructure and environmental conditions. We find that all cities have a spectrum of small, medium, and large methane sources in their domain. The emission rates found follow a heavy-tailed distribution, and the top 10% of emitters account for 60-80% of total emissions, which implies that strategic repair planning could help reduce emissions quickly. Furthermore, we compare our findings with inventory estimates for urban natural gas-related methane emissions from this sector in Europe. While cities with larger reported emissions were found to generally also have larger observed emissions, we find clear discrepancies between observation-based and inventory-based emission estimates for our 12 cities.

Ways to improve the reliability of gas supply systems

Background: The concept of reliability of gas distribution systems implies the possibility of reliable transportation of the required amount of gas to the consumer in compliance with the specified parameters in normal operation for a certain period of time.
 Aim: The peculiarity of gas distribution networks is that they are long-term planning systems, with the growth of cities and the connection of consumers, the radius of their impact increases, expands, rebuilds, worn-out nodes and elements are replaced with new ones. The main goal at this stage of operation is the absence of significant reconstruction measures to improve the reliability of the system.
 Materials and methods: Work has been carried out to analyze the probability of triggering, the failure rate and the probability of failures of gas supply systems for single indicators.
 Results: To ensure the reliability and durability of gas boilers during replacement, the following 8 different measures were proposed.
 Conclusion: The article proposes a closed circuit, the introduction of network redundancy in the system by ringing or duplicating elements and considers the social nature of gas distribution systems.

Experimental measurements of the new gas smart meters’ current discharges to suggest improvement solutions for power supply battery life extension

Several reasons justified introducing the smart metering concept in the gas distribution sector and supporting its digitalization. Specifically, among their functionalities, the new smart meters would improve the ability to identify abnormal consumption or malfunctions in the gas grid or at customers’ appliances as soon as possible, improving the gas distribution system’s safety performance. The installation and operation of gas smart meters result in a significant amount of data to be managed. Specifically, gas consumption, the supply pressure, and information about the status of the device, such as the events that occurred, are some of the data communicated daily to the gas Distribution System Operators (DSOs). However, despite the advantages, some drawbacks were first experienced by the DSOs, requiring unplanned intervention and increasing the operative costs. Among these, the discharge of the batteries sooner than expected increases the operative costs. In fact, due to ATEX safety aspects, the smart meters are not directly connected to the electric grid but they are powered by batteries that have to be replaced only by authorized personnel. The present paper reports the preliminary results obtained during an experimental campaign to investigate the impact of data communication on the battery lifetime. Specifically, four communication protocols that differ in the number of data strings and the communication frequency were compared, and preliminary conclusions were given.