Equipment Tripping Research Articles

A Low-Data-Dependence Assessment Method of Industrial Process Interruption Probability Due to Voltage Sag

Information about the interruption probability of sensitive industrial processes is important for devising mitigation strategies against voltage sags. However, the existing method for assessing interruption probability is less practical, owing to the difficulty in collecting technical information and data from industrial users. This study proposes a low-data-dependence assessment method for the interruption probability of an industrial process. First, it establishes a general assessment model for the tripping probability of sensitive equipment. Second, it proposes a parameter estimation method to determine the probability density function of the voltage tolerance curve of sensitive equipment in the uncertainty region, according to the equipment trip information recorded by the user. This improves the accuracy of the assessment. Third, this study establishes the logic function expression form of the industrial process structure to describe the relationship between the process interruption probability and the equipment tripping probability. Finally, it proposes a solution method for the process interruption probability based on a heuristic search algorithm, which overcomes the problem of technological process information acquisition, such as the logical relationship among various equipment in the industrial process. The rationality and applicability of the proposed method are verified through a case study.

Design of a Hybrid Fault-Tolerant Control System for Air–Fuel Ratio Control of Internal Combustion Engines Using Genetic Algorithm and Higher-Order Sliding Mode Control

Fault-tolerant control systems (FTCS) are used in safety and critical applications to improve reliability and availability for sustained operation in fault situations. These systems may be used in process facilities to reduce significant production losses caused by irregular and unplanned equipment tripping. Internal combustion (IC) engines are widely used in the process sector, and efficient air–fuel ratio (AFR) regulation in the fuel system of these engines is critical for increasing engine efficiency, conserving fuel energy, and protecting the environment. In this paper, a hybrid fault-tolerant control system has been proposed, being a combination of two parts which are known as an active fault-tolerant control system and a passive fault-tolerant control system. The active part has been designed by using the genetic algorithm-based fault detection and isolation unit. This genetic algorithm provides estimated values to an engine control unit in case of a fault in any sensor. The passive system is designed by using the higher-order sliding mode control with an extra fuel actuator in the fuel supply line. The performance of the system was tested experimentally in MATLAB/Simulink environment. Based on the simulation results, the designed system can sustain the AFR despite sensor failures. A new method of managing the AFR of an IC engine has been demonstrated in this study, and it is highly capable, robust, reliable, and highly effective. A comparison with the existing works found in the literature also proves its superior performance. By inserting the fault in each sensor, it was clearly observed that proposed HFTCS was much better than the existing model as it was more fault-tolerant due to its ability to work in both online and offline modes. It also provided an exact value of 14.6 of AFR without any degradation.

Numerical investigation and prediction of phase separation in diverging T-junction

Purpose In plethora of petroleum, chemical and heat transfer applications, T-junction is often used to partially separate gas from other fluids, to reduce work burden on other separating equipment. The abundance of liquid carryovers from the T-junction side arm is the cause of production downtime in terms of frequent tripping of downstream equipment train. Literature review revealed that regular and reduced T-junctions either have high peak liquid carryovers (PLCs) or the liquid appears early in the side arm [liquid carryover threshold (LCT)]. The purpose of this study is to harvest the useful features of regular and reduced T-junction and analyze diverging T-junction having upstream and downstream pipes. Design/methodology/approach Volume of fluid as a multiphase model, available in ANSYS Fluent, was used to simulate air–water slug flow in five diverging T-junctions for eight distinct velocity ratios. PLCs and LCT were chosen as key performance indices. Findings The results indicated that T (0.5–1) and (0.8–1) performed better as low liquid carryovers and high LCT were achieved having separation efficiencies of 96% and 94.5%, respectively. These two diverging T-junctions had significantly lower PLCs and high LCT when compared to other three T-junctions. Results showed that the sudden reduction in the side arm diameter results in high liquid carryovers and lower LCT. Low water and air superficial velocities tend to have low PLC and high LCT. Research limitations/implications This study involved working fluids air and water but applies to other types of fluids as well. Practical implications The novel T-junction design introduced in this study has significantly higher LCT and lower PLC. This is an indication of higher phase separation performance as compared to other types of T-junctions. Because of lower liquid take-offs, there will be less frequent downstream equipment tripping resulting in lower maintenance costs. Empirical correlations presented in this study can predict fraction of gas and liquid in the side arm without having to repeat the experiment. Social implications Maintenance costs and production downtime can be significantly reduced with the implication of diverging T-junction design. Originality/value The presented study revealed that the diameter ratio has a significant impact on PLC and LCT. It can be concluded that novel T-junction designs, T2 and T3, achieved high phase separation; therefore, it is favorable to use in the industry. Furthermore, a few limitations in terms of diameter ratio are also discussed in detail.

Wyznaczenie najlepszego miejsca montażu urządzeń technologicznych na podwoziu pojazdów naprawczych na polach naftowych

Currently, it is impossible to imagine the repair and drilling of any well without the use of modern mobile equipment. With technological progress, not only new development technologies in the branch of field exploitation appear, but also new equipment with which oil and gas wells are repaired and reconstructed. Today, oil production is mainly carried out by the operation of wells without a pumping derrick, which makes it possible to sharply reduce the cost of metal and funds. Operations of downhole equipment lifting and tripping in a well are carried out using self-propelled mobile units representing tracked or wheeled transport vehicles on which a derrick (mast) with a winch, transmission and hoisting system is mounted. Lifting units are equipped with a mechanism for raising the mast to the working position and lowering it to the transport position. Installations with a lifting capacity of up to 32 tons inclusive are designed for lifting operations during routine underground repair of wells, whereas over 32 tons minimal lift capacity are required during major repairs and well development. The mobile unit is subjected to oscillatory movements both during transportation along unpaved, semi - destroyed, muddy and snow-covered roads to the well (for development, repair), and during well drilling. The frequency of the oscillating movement depends on the state of the uneven road. The unevenness of the road is expressed by spectral functions. In this case, both the chassis and the body of the mobile unit, as well as the technological equipment located on it, are subjected to oscillatory movements. As a result, technological equipment, as well as devices and equipment located on it, lose their accuracy, which leads to accidents both during drilling and during operation. Therefore, in order to minimize the influence of oscillatory movements on the operability of technological equipment, a technique was developed for technological equipment positioning on the chassis of a mobile unit at an optimal scheme according to the proposed method.

Investigation of Impact of Contingencies on Power Plant and Transmission Lines

Contingency analysis are widely applied to predict the effect of outages in power systems, like tripping of equipment in power plants and transmission lines. Using off line analysis to predict the effect of individual contingency is a tedious task on power system containing large number of components. Practically, only selected contingencies will lead to severe conditions in power system, like violation of voltage and active power flow limits. Simultaneously, the value of active power flow before and after severe transmission and power plant contingencies was analysed using Genetic Eigenvalue Analysis Technique. This was achieved by simulating the Simulink of Nigerian 330KV 48 bus power system using m-file programme in MATLAB environment.The result of the simulation for the power flow solution for transmission line outage contingencies shows that the voltage trajectory at bus 11 stood at 0.3934 p.u, at bus 15 is0.4986 p.u, and bus of 23 is 0.4647 p.u while for the contingencies on power plant, there voltage trajectories stood at 0.2342 p.u for bus 11, 0.3987 p.u for bus 23. The result shows that the impact on power plant is higher than that of transmission line by 40%, 20%, 14%for sampled buses 11, 15, and 23 respectively. Keywords: Power Stability- Genetic Eigenvalue, Load flow DOI: 10.7176/JETP/11-1-04 Publication date: January 31 st 2021

Practical test method for the sensitivity of programmable logic controller to voltage sags and short interruptions

Voltage sag and short interruption lead to the tripping of sensitive equipment and cause the economic loss of the industry users. A programmable logic controller (PLC) is essential equipment used in the industrial process. However, there is no detailed understanding of the sensitivity of PLC under voltage sag and short interruption. The response characteristic of PLC under voltage sag is studied. This study proposes a new testing method, called the dichotomy test method (DTM) to do the test. This study builds the testing platform and tests the sensitivity of six PLCs from five famous PLC manufacturers. The testing considers the characteristics of voltage sag, including magnitude, duration, point-on-wave, phase-angle-jump, different supply voltage, slow recovery voltage sag, multiple voltage sags and so on. The tests prove that DTM has the advantage of accuracy, robustness and workload, compared with the traditional test method. The quantitative and qualitative response characteristics of PLC under voltage sag are obtained.

A probabilistic approach for assessment of financial loss due to equipment outage caused by voltage sag using cost matrix

In the industrial sector, poor power quality (PQ) can malfunction or shut down the processes or equipment, which leads to excessive loss in revenue. During a visit to a chemical industry, it has been observed that equipment ceases operation frequently due to PQ issues, which hinders the completion of consignment within the stipulated time. It has made the industrial authority to feel the need for quantifying the loss of economy due to frequent equipment trip to provide proper immunity to the system against PQ issues. This paper deals with the assessment of financial losses in industrial loads due to voltage sag. Analytical methods considering Monte Carlo simulation technique is implemented for the evaluation of voltage sag due to the occurrence of symmetrical and unsymmetrical faults. Depending on the characteristics of sensitive equipment towards voltage sag, the process trips were evaluated using probabilistic methods for a chemical industry's distribution system. In this paper, a concept of sag score is used to find out the most sensitive buses for the evaluation of the cost of the equipment trip. An energy index is given for the industrial system to find out how much energy is being unused during a voltage sag event. Factors like variable cost, restart cost and hidden cost are influenced by the tripping of sensitive equipment due to voltage sag. The data are collected from the industrial personnel for the evaluation of the proposed methodology.

Study on identifying the vulnerability of the data center power network

With the wide application of the internet and rapid development of the information technology, the scale of the internet data center power network is growing larger and larger. Some of the troubles in the internet data center (IDC) power network may cause extensive service out of service or even collapse. However, without considering the characteristics of the IDC power network, the important node identification methods for the IDC power network based on graph mainly focus on the graph structure itself. Since a large number of automatic switching equipment such as ATS, STS and loop switch have been used in IDC, when the electrical fault occurs, the load will be automatically migrated to the adjacent electrical equipment, which may lead to overloading or even tripping. So the failure is extended. So how can we efficiently and effectively capture the fault evolution mechanism of the IDC power network? How do we go about identifying the vulnerable nodes causing the collapse of the IDC power network.In this article, we propose DCPNFEM, a novel fault evolution model for the IDC power networks, as well as a fitting algorithm, BCBL, which can solve the proposed problems. Our algorithms have the following properties: (a) Intuitively: it detects fault evolution mechanism, such as power load migration, electrical equipment tripping, and so on; (b) Timely: our method is based on the real-time power loads; (c) General: our algorithms are general and practical, which can be used in various power network topologies, including data center infrastructures from tier1 to tier4.Extensive experiments on a real IDC power network demonstrate that some particular nodes’ failure can lead to the power network crash under DCPNFEM. And BCBL algorithm outperforms better accuracy and speed than many other algorithms.

Experimental determination of partial discharges in a model of a digital instrument transformer by differential method

Power facilities are now implementing the concept of smart grid and its essential elements – high-voltage digital current and voltage transformers. However, the implementation of digital technologies is slowed down by the lack of operation experience and reliability indicators. One of the main causes of high-voltage equipment failures is insulation damage. The most informative parameters determined by insulation evaluation are partial discharge characteristics. There are rated values of these characteristics for rotating electrical machines and power transformers measured by external equipment. But the existing method of partial discharge analysis cannot be applied to digital current and voltage transformers as there are no criteria for tripping of the innovative equipment with comprehensive insulation. All this urges us to study the possibility to determine experimentally the characteristics of partial discharges in the insulation of digital current and voltage transformers by using embedded inductive sensors in order to develop a method for condition monitoring of digital current and voltage transformers and improving of their reliability. In this work, we have used a model of digital current and voltage transformers, a high-voltage test unit, a digital multi-input oscciloscope and inductive sensors. The experiment includes: detecting partial discharges in the model of digital current and voltage transformers by the external bridge connection, recording the voltage at which partial discharges occur in the simulated fault area, measuring the corresponding value of the apparent charge of the partial discharge, detecting partial discharges in the model of digital current and voltage transformers by a differential method with the help of embedded inductive sensors. The characteristics of partial discharges in the simulated fault area have been experimentally determined on a model of digital current and voltage transformers. The pulse voltage on the embedded inductive sensor corresponding to the apparent charge of 80 pC was equal to 600 mV at the test voltage of 2,7 kV. Embedded inductive sensors allow implementing the method of insulation condition monitoring for digital current and voltage transformers in accordance with the partial discharge characteristics both at the stages of production and operation extending the potential of the electronic (microprocessor) module and increasing the reliability of digital current and voltage transformers.

A Learning Framework for Size and Type Independent Transient Stability Prediction of Power System Using Twin Convolutional Support Vector Machine

Real-time transient stability assessment (TSA) of power systems is an important real world problem in electrical energy engineering and pattern recognition scope. The definition of most discriminative trajectory features and proper supervised trajectory-based classifier has remained a motivational challenge for scholars vis-a-vis real-time TSA. In addition, increase in the consumption of electrical energy along with constraints such as amortization of network equipment induces electric power system inadequacy risk. The retrieval of power system adequacy involves network expansion planning such as installing new power plants for the network. This policy affects the structure and electrical specification of the network significantly. Furthermore, due to sudden or the scheduled tripping of network equipment stemming from action of protection devices or maintenance procedures, the network must undergo shallow structural changes. The different level of changes in network specification is becoming a potential barrier for network analysis tools like real-time TSA platform. In fact, the lack of consideration of the incompatibility of TSA tool with expansion planning affects the performance of TSA learning model that is trained using the pre-expansion network. However, this paradoxical problem can be solved by generalized learning for power system size & type independent (PSs&tInd) real-time TSA. For this purpose, first, we used a set of PSs&tInd trajectory features. Next, we presented a trajectory-based deep neuro classifier to eliminate kernel functions weaknesses plugged into the hyperplane-based classifier. Finally, experimental comparisons were conducted to assess the efficacy of the proposed framework. The results showed that the proposed technique offered high-generalization capacity on real-time TSA during network expansion.

Analytical Expressions for Multiobjective Optimization of Converter-Based DG Operation Under Unbalanced Grid Conditions

Recently, riding through grid faults and supporting the grid voltage by using grid-connected converters (GCCs) have become major requirements reflected in the grid codes. This paper presents a novel reference current generation scheme with the ability to support the grid voltage by injecting a proper set of positive/negative active/reactive currents by using four controlling parameters. Analytical expressions are proposed to obtain the optimal values of these parameters under any grid voltage condition. The optimal performances can be obtained by achieving the following objectives: first, compliance with the phase voltage limits, second, maximized active and reactive power delivery, third, minimized fault currents, and fourth reduced oscillations on the active and reactive powers. These optimal behaviors bring significant advantages to emerging GCCs, such as increasing the efficiency, lowering the dc-link ripples, improving ac system stability, and avoiding equipment tripping. Simulation and experimental results verify the analytical results and the proposed expressions.

Minimisation of voltage sags-induced financial losses in an Indian distribution system using a static VAR compensator

A voltage sag can cause tripping of sensitive electronic equipment and cause production stops in many industries. Therefore, it can have significant economic consequences for different types of industries. Flexible AC Transmission System (FACTS) devices were originally developed for transmission networks but similar ideas are now starting to be applied in distribution systems. FACTS devices have become popular as a cost-effective solution for the protection of sensitive loads from a voltage sag. This paper, therefore, presents the modelling of the FACTS device Static VAR Compensator (SVC) to minimise voltage sag-induced financial losses. The overall system financial losses due to a voltage sag could significantly be reduced depending on the type of FACTS devices used. The short circuit analysis approach is used to incorporate the effect of these devices on financial losses. Voltage sags produced by balanced and unbalanced short circuits are analysed by means of a new analytical approach using the system impedance matrix (ZBus), which incorporates SVC. Case studies based on a real Indian distribution system are used to illustrate the modelling method and the effectiveness of these devices in voltage sag mitigation.

Oil/Water Separation Experience From a Large Oil Field

Summary This paper discusses challenges related to emulsions that have been encountered in a large Saudi Arabian field. The field produces from several different reservoirs with a range of fluid properties. These properties provide an interesting case of operational challenges in oil/water separation, including increased incidents of shorting in the separator, tripping of equipment, and increased demulsifier consumption. This paper presents the results of a comprehensive study that was initiated to understand the main causes of emulsion formation in the field and ways to optimize oil/water separation. The effects of several recommendations that were implemented by operations engineering in the field were evaluated. These include the conversion of a two-phase separator into a three-phase separator, splitting of the demulsifier injection between offshore producing platforms and onshore wet-crude handling facilities, and field trials with promising chemicals. The demulsifier costs have been reduced by more than 50% by the implementation of retrofitting and proper demulsifier-injection strategies. The results presented in the paper provide invaluable operational experience, and many lessons learned are applicable to any crude-oil-treating facility.

Oil/Water-Separation Experience From a Large Oil Field

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 93386, “Oil-Water Separation Experience From a Large Oil Field,” by S. Kokal, SPE, and A. Al-Ghamdi, Saudi Aramco, prepared for the 2005 14th SPE Middle East Oil & Gas Show and Conference, Bahrain, 12–16 March. The full-length paper discusses challenges related to emulsions in a large Saudi Arabian field. The field produces from several different reservoirs with a range of fluid properties. These properties provide an interesting case of operational challenges in oil/water separation including increased incidents of shorting in the separator and tripping of equipment and increased demulsifier consumption. The paper presents the results of a comprehensive study to understand the main causes of emulsion formation and ways to optimize oil/water separation. Introduction Crude oil has to be separated from produced water at wet-crude handling facilities or gas/oil-separation plants (GOSPs). The GOSP produces dry crude, gas, and water. The incoming oil and water can form an emulsion and may be difficult to separate. When emulsions are tight, they can create a number of operational challenges such as tripping of equipment in a GOSP, plant instability, increased demulsifier consumption, production of off-specification crude, and high pressure drops in flowlines. These emulsions have to be treated to meet crude specifications for transportation, storage, and export and to reduce corrosion and catalyst poisoning in downstream processing. This field produces from seven different reservoirs including the more-viscous crude from the Arab reservoirs. Viscosities of these oils range from 2 to more than 10 cp, and gravities range from 28 to 40°API. The n-pentane asphaltene content varies from 0.2 to more than 7%, and water cut for producing wells ranges from dry wells to more than 70%. Most of the wells are offshore, and the crude is delivered to onshore GOSPs by undersea trunklines. The onshore GOSP includes a high-pressure production trap (HPPT) or separator, an intermediate-pressure production trap (IPPT), and a two-stage dehydrator/desalter train. The dry oil from the desalter has to contain less than 0.2% water and less than 10 lbm/1,000 bbl of salt. The separated water is processed further in a water/oil separator (WOS) and injected back into the reservoir through disposal wells. The water from the WOS generally has to meet a specification of less than 100 ppm oil. The GOSP was designed to handle approximately 30% water cut. The water cuts in the field have been increasing steadily over the years and are expected to increase further in the coming years. Soon the water cuts will be higher than the design capacity of the GOSP. To handle the extra volume of water, and to avoid overloading the dehydrator/desalter vessels, one option was to convert the two-phase HPPTs into three-phase separators. A comprehensive study was undertaken earlier to understand the main causes of emulsion formation in the field. The factors investigated were water cut, temperature, shear, asphaltene content, demulsifier dosage, and crude mixtures. These factors were quantified with an emulsion separation index developed to measure emulsion stability. The results showed a strong correlation of asphaltene content in the crude oil with emulsion tightness. Several recommendations were made and implemented for optimizing oil/water separation and reducing demulsifier usage in the field.