Selection Of Breakers Research Articles

Reliability of SF6 Circuit Breaker Cells and Selection of Switchgear Circuits for 220 kV Substations

Reliability of SF6 Circuit Breaker Cells and Selection of Switchgear Circuits for 220 kV Substations

The consequence of ignoring load modeling on the circuit breaker selection in densely-meshed sub-transmission systems

In this paper, the selection of circuit breakers for a densely-meshed sub-transmission system with relatively short transmission lines is investigated. The results highlight the significance of modeling the load at the end of lines for accurately calculating the transient recovery voltage (TRV) following the short-circuit current interruption. According to IEEE standards, assuming load modeling at the end of the transmission lines can result in a maximum discrepancy of 20 % in the calculated TRV. Supposing that the load modeling leads to a moderating effect on the calculated TRV, the difference is considered as a safety margin, and load modeling is ignored. Nevertheless, the results presented here illustrate that this assumption strongly depends on characteristics of the studied network and the load type. In a network possessing the characteristics outlined in this paper, even a passive load as small as 15 % of the nominal capacity can significantly moderate the calculated TRV, with impacts reaching up to 38 %. Conversely, modeling an active load may result in a more severe TRV than if it were disregarded. The simulation results indicate that for networks with transmission lines longer than 70 km, neglecting to model passive loads on the transmission lines still yields sufficiently accurate calculations of TRV.

Maximizing well productivity by using filter cake breaker for synthetic-based mud drill-in fluid (SBMDIF) system

• Formation damage has a significant impact on the overall performance. • An effective filter cake breaker selection is critical to minimize formation damage. • The straightforward reaction of meso‑surfactant and nano-surfactant filter cake breakers with barite. • Surfactant-based filter cake breaker was more efficient in removing synthetic-based drilling mud. Formation damage has a significant impact on the overall performance of the well productivity. Removal of filter cake which is deemed to be the main strategy of formation damage remediation is crucial in open hole completion with pre-slotted liner or stand-alone screen (SAS) as a mean of sand control. Without proper planning, inefficient filter cake removal can lead to tremendous consequences since filter cake can plug the sand control component. Making the condition worse, sand control component is susceptible to plugging. This highlights the importance of selecting an effective filter cake breaker that can successfully remove the filter cake through dissolution of the main solids that constitute the major portions of the filter cake which could be the weighting material, barite, or calcium carbonate. Besides that, a proper understanding of the mechanism of the filter cake breaker chemical would be very beneficial to comprehend the filter cake breaker efficiency. The laboratory study attempted to emulate the reservoir condition. Regained permeability testing using High Pressure High Temperature (HPHT) Filter Press aimed to test the ability of several commercial filter cake breakers in removing synthetic-based-mud drill-in-fluids (SBMDIF). Chelating-based filter cake breaker, meso‑surfactant-based filter cake breaker and nano-surfactant-based filter cake breaker were the samples to be tested in the laboratory work. The condition of the filter cake after being soaked statically was visually interpreted and the regain permeability was recorded. The mechanism of each filter cake breaker to remove the SBMDIF filter cake was also examined. Based on the experimental study, meso‑surfactant-based filter cake breaker was found to be more effective to remove SBMDIF filter cake compared to chelating-based filter cake breaker and nano-surfactant-based filter cake breaker.

A Symmetrical-Asymmetrical Fault Characteristics Analysis within Cogeneration Power Plant in Izmir, Turkey: An Experimental Assessment

The analysis of the short circuit should be understood very well in order to make correct designs in the power systems such as the safety of the personnel and the equipment, the selection of the safety relays, the circuit breaker selection and the selection of the appropriate conductor section. In this study, the parameters about the short circuit and the techniques of calculating the faults in system and the necessary theoretical knowledge for the short circuit fault to be understood better have been given. The effect on the distributed generation and the grid which is caused by the possible short circuit faults have been simulated by being modeled in PSS/Sincal and by using the real grid parameters with cogeneration power plant in Izmir, Turkey. The real short circuit fault results measured from the power plant and the grid and the results obtained from the software program have been compared and it has been determined that there is not a significant difference between them. Thus, it has been emphasized that it is correct to simulate before investing in a power system in for the purpose of restrain the faults during the designing and working before the application. It allows the designer to design new power plant as good as plan expansion of existing power plants with higher degree of precision. Considering the prices of protection equipment, which has a large part in system design, this way would allow designer to reduce the cost of the protective equipment and remaining stability.

Chasing genetic correlation breakers to stimulate population resilience to climate change

Global climate change introduces new combinations of environmental conditions, which is expected to increase stress on plants. This could affect many traits in multiple ways that are as yet unknown but will likely require the modification of existing genetic relationships among functional traits potentially involved in local adaptation. Theoretical evolutionary studies have determined that it is an advantage to have an excess of recombination events under heterogeneous environmental conditions. Our study, conducted on a population of radiata pine (Pinus radiata D. Don), was able to identify individuals that show high genetic recombination at genomic regions, which potentially include pleiotropic or collocating QTLs responsible for the studied traits, reaching a prediction accuracy of 0.80 in random cross-validation and 0.72 when whole family was removed from the training population and predicted. To identify these highly recombined individuals, a training population was constructed from correlation breakers, created through tandem selection of parents in the previous generation and their consequent mating. Although the correlation breakers showed lower observed heterogeneity possibly due to direct selection in both studied traits, the genomic regions with statistically significant differences in the linkage disequilibrium pattern showed higher level of heretozygosity, which has the effect of decomposing unfavourable genetic correlation. We propose undertaking selection of correlation breakers under current environmental conditions and using genomic predictions to increase the frequency of these ’recombined’ individuals in future plantations, ensuring the resilience of planted forests to changing climates. The increased frequency of such individuals will decrease the strength of the population-level genetic correlations among traits, increasing the opportunity for new trait combinations to be developed in the future.

The Influence of Novel Power System Characteristics on 330kV Power Grid Short-circuit Current

Under the development goal of “Carbon Peak, Carbon Neutralization”, the concept of novel power system is proposed. Its representative features include AC/DC interconnection of power grid and large-scale access of new energy power stations. Under these characteristics, higher requirements are put forward for the short-circuit current breaking capacity of the circuit breaker. The DC component of short-circuit current and the injection of new energy into the system short-circuit current cannot be ignored. Based on the 330kV local power grid in Northwest China, this paper studies the power grid operation mode, DC component of short-circuit current and the influence of photovoltaic power station on short-circuit current. The influence law of DC component of short-circuit current on the actual breaking capacity of circuit breaker and access of photovoltaic power station on the short-circuit current are summarized. It can provide a theoretical basis for the selection of circuit breaker in novel power system.

STUDY ON SHORT CIRCUIT ELECTRICAL SYSTEM PT. PLN (Persero) SULSELBAR

In the electric power system, the short-circuit study is essential for planning, designing and extending the electrical system. The data obtained from this calculation will be used to determine busbar tuning and power breaker capacity. The circuit breaker selection for the electrical power system depends not only on the current flowing in the circuit breaker in a normal working state but also on the maximum current that may flow over time and on the current which may have to be decided at the channel voltage where the breaker is located. Disturbance to the electrical system causes the operation of relays and power breakers to decide which parts are experiencing interference. The three phase short circuit is considered to be the interference with the largest disturbance current compared to other interference. While the one-phase short circuit to the ground is a common disorder, especially in the airways. The objective of this research is to analyze the short circuit current of power system of South and West Sulawesi with the condition of the system working at peak load and condition when all the system generator operate. The rail impedance matrix method is used in the calculation of the noise current with the matlab computation tool. Compared with the three-phase interference, the larger one-phase current to the ground is 1.065 times three phase short circuit for maximum peak load state, and 1,233 times three phase short circuit for all active generators.

Optimization of breaker schedules for stimulation of tight gas reservoirs

Breakers are a small portion of the total fracture fluids, but could be very critical in determining the fracture treatment effectiveness. Wrong selection of breaker may result in extended fracture cleanup in weeks or months. An optimized selection and design of breaker schedules help maximize fracture conductivity by cleaning up the proppant pack after a treatment. However, breaker selection and design still remains as a challenge.We conducted an extensive and complete investigation of breakers through a systematic and critical review of relevant publications in this area. We first presented the major breaker types and their own breaking mechanisms, then built guidelines in a flow chart for selection of breakers based on formation temperature, pressure, PH, salinity, and mineral compositions. We then developed a step-by-step procedure for optimizing breaker schedules and finally demonstrated with field case studies of two tight gas wells in Louisiana. The new knowledge helps one optimize breaker design and improve fracture treatments in tight gas wells.

System Analysis with the MVA Method for Symmetrical Three-Phase Faults

Electric energy is one of the fundamental resources of modern industrial society. Electric power is available to the user instantly, at the correct voltage and frequency, and exactly in the amount that is needed. This remarkable performance is achieved through careful planning, design, installation and operation of a very complex network of generators, transformers, and transmission and distribution lines. We must examine all possible types of fault or abnormal conditions which may occur in the power system. The analysis of power systems under faulted condition provides information regarding circuit breaker selection, relay setting, and the stability of the systems operation. In this study, a balanced three phase fault current at a given bus of the system is calculated by using different methods. Especially emphasis on the MVA method and compared other conventional methods.

Aplication of Multi-Criteriaanalysis for Circuit Breaker Selection on Nigerian National Grid

Power System Fault Analysis of The Nigerian 330kV Transmission Grid is a study of the determination of the appropriate circuit breaker. Relevant data were sourced from NCC, Osogbo and a digital computer fault analysis program was applied. The circuit breakers considered are SF6, Air, Oil and Vacuum and the designed criteria employed in the use of multi-criteria analysis are Cost, reliability, Flexibility and Environmental Impact. The Multi-Criteria Analysis (MCA) approach is an improvement over the traditional approach for calculating the symmetrical fault current at a system location and then selects a circuit breaker with a symmetrical interrupting capability equal to or above the calculated current. In the MCA approach, user preferences which take into account the design criteria were not ignored, as a result, a logical and rational approach has been developed for the Nigerian 330kV power system network which meets the input specifications and responds to user preference and concerns of power system operators.

Breaking Loops in Large Complex Pedigrees

For pedigrees with multiple loops, exact likelihoods could not be computed in an acceptable time frame and thus, approximate methods are used. Some of these methods are based on breaking loops and approximations of complex pedigree likelihoods using the exact likelihood of the corresponding zero-loop pedigree. Due to ignoring loops, this method results in a loss of genetic information and a decrease in the power to detect linkage. To minimize this loss, an optimal set of loop breakers has to be selected. In this paper, we present a graph theory based algorithm for automatic selection of an optimal set of loop breakers. We propose using a total relationship between measured pedigree members as a proxy to power. To minimize the loss of genetic information, we suggest selection of such breakers whose duplication in a pedigree would be accompanied by a minimal loss of total relationship between measured pedigree members. We show that our algorithm compares favorably with other existing loop-breaker selection algorithms in terms of conservation of genetic information, statistical power and CPU time of subsequent linkage analysis. We implemented our method in a software package LOOP_EDGE, which is available at http://mga.bionet.nsc.ru/nlru/.

Computer-aided selection and verification of circuit breakers

Procedures governing medium- and high-voltage breaker application, although conceptually tractable, tend to be repetitive for large systems. Hand calculations can become quite laborious when assessing safety margins of installed switchgear on systems that have experienced sudden growth. This article describes how a computer can be used as an efficient tool to address these concerns. The discussion focuses on how the computer can be used to interface the short circuit study results to the breaker modules, on how breaker adequacy evaluation can be computerized, and finally how these calculations can be extended to yield automated breaker selection according to user-defined criteria and breaker rating structures. The discussion is confined to the North American breaker application procedures and rating structures as tabulated in the ANSI Standards, and addresses only short circuit current interrupting requirements.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A Study on the phenomenon of chip breaking by computer analysis

Chip breaker selection analysis, possible only through an experimental process, was obtained by a generalized equation that used an orthogonal cutting model and basic chip deformation.

Estimation of synchronous machine parameters from performance relations

The parameters of synchronous machines are required in system analysis, fault calculations, sizing of cables, circuit breaker selection, power factor correction, and voltage drop calculations. One of the major stumbling blocks is the general lack of design and application data. The design information is generally restricted and not commonly available to all users. Furthermore, the parameters are difficult to obtain through field measurements. In this paper, a mathematical model is presented to estimate the parameters of a synchronous machine from name-plate details. The data used in the estimation include output kVA, voltage, current, speed, rated power factor, field voltage, field current, and short-circuit ratio. The equations are derived from a well-known performance model and solved using a spreadsheet program available on any personal computer. Two case studies are presented in this paper. There is reasonable agreement between the estimated and available parameter values. Finally, the usefulness of this procedure and some of the limitations are outlined.