Selection Of Circuit Breakers Research Articles

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.

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.

Development of A Newton Raphson Symmetrical Component Based Technique for Fault Analysis on Nigerian 330 KV Transmission Lines

Fault analysis is one of the basic problems of power system engineering. It plays a significant role in the power system security for supply of stable and economical operations of power systems. This study carried out fault analysis on Nigerian 330 kV, 28 bus system using Newton-Raphson analysis and symmetrical components method to determine the voltage magnitude and fault magnitude in the system. Newton-Raphson method was used to calculate the short circuit pre-fault voltages and currents on power system. This was used to check the weak buses that are out of acceptable voltage limit of ± 10%. After identifying the buses with problems, a three-phase fault on the power network was then calculated using symmetrical component analysis and was simulated using MATLAB to determine the post-fault voltage magnitudes, angles and fault magnitudes of the power network. The pre-fault result showed that buses 13 (New-Haven), 14 (Onitsha) 19 (Jos), 22 (Kano) and 25 (Markurdi) were the buses that fell out of tolerance range of ± 10% and were termed as weak buses. These buses with low voltage values were examined and post-fault calculations were carried out and the results of voltage magnitude and voltage angle were reduced to zeros.The results of pre-fault current magnitude showed that the selected weak buses namely; Makurdi, New-Haven, Kano, Onitsha and Jos have the current magnitude values of 10.4200 p.u, 9.4350 p.u, 8.4501 p.u, 7.5440 p.u and 5.3320 p.u respectively. The results also showed that Makurdi, had the highest fault magnitudes with a value of 25.1006 p.u followed by New-Haven with value of 23.9455, Kano with value of 22.4917, Jos with value of 21.4686 and Onitsha had the least fault magnitude value of 19.8765 p.u under post-fault condition. More so, it was observed that the voltage on the affected buses was reduced however current magnitudes of these buses when fault occurred were excessively high compared to the pre-fault currents.The result confirmed that symmetrical three phase fault is the most severe kind at the transmission lines. The result also revealed the abnormally high magnitude of current that flows through the Nigerian power network to the point of fault. Therefore, the Nigeria power regulator and policies are required to determine the flow of current regularly during faults occurrences in the power system so as to ensuring improvements in the country power sector. The study therefore recommendations that additional lines should be introduced into the network to assist in the strengthening and reduction of long lines to improve the voltage profile of the network, especially New-Haven, Kano, Onitsha and Markurdi lines. The study will assist the power regulators for selection of circuit breakers and rating of protective switchgears installed in power system to enhance the efficiency of the power supply in Nigeria. Keywords: Fault Analysis, Nigerian Power Network, Newton-Raphson, Symmetrical Components, Three-Phase Fault, Voltage Magnitude, Fault Magnitude. DOI : 10.7176/JNSR/9-16-02 Publication date : August 31 st 2019

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.

Analytic Approximation of Fault Current Contribution From AC Networks to MTDC Networks During Pole-to-Ground Faults

HVDC short-circuit calculation standards will be required to simplify the dimensioning and selection of circuit breakers (CBs) in future HVDC networks. This paper proposes new analytical formulas for the calculation of the ac-side contribution through the blocked half-bridge-based converters during pole-to-ground faults in multiterminal HVDC cable networks. Analytic approximations are derived for the steady-state short-circuit currents and the peak of the transient response for point-to-point HVDC links and extended to multiterminal HVDC cable networks with arbitrary grid topology. The results of the proposed expressions are compared with simulations in PSCAD and provide accurate calculations for the transient peak and steady-state values of the ac-side fault current contribution to the prospective CB current.

Interruption of Inductive Load Currents with High-Voltage Circuit Breakers

The switching of shunt reactor and no-load transformer with high-voltage circuit breakers is discussed. Recommendations are given on the selection of circuit breakers for switching shunt reactors and on the analysis and integration of data on faults caused by switching of no-load transformers.

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.

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.

Low-voltage arcing-fault currents

One method used in the selection of circuit breakers for application to low-voltage a-c circuits is based on the assumption of “bolted” faults. Some engineers, however, believe that these fault currents never are reached in practice. An extensive series of tests shows a distinct need to clarify the situation in so far as the effect of arc drop is concerned.

The authors' reply to the discussion on “Restriking voltage as a factor in the performance, rating and selection of circuit-breakers”

The authors' reply to the discussion on “Restriking voltage as a factor in the performance, rating and selection of circuit-breakers”

Discussion on “Restriking voltage as a factor in the performance, rating and selection of circuit-breakers” and “The influence of resistance switching on the design of high-voltage air-blast circuit-breakers” before the Mersey and North Wales Centre, at Liverpool, 16th October, 1944

Discussion on “Restriking voltage as a factor in the performance, rating and selection of circuit-breakers” and “The influence of resistance switching on the design of high-voltage air-blast circuit-breakers” before the Mersey and North Wales Centre, at Liverpool, 16th October, 1944

Discussion on “Restriking voltage as a factor in the performance, rating and selection of circuit-breakers” before the North-Western Centre, at Manchester, 9th May, 1944

Discussion on “Restriking voltage as a factor in the performance, rating and selection of circuit-breakers” before the North-Western Centre, at Manchester, 9th May, 1944

The authors' replies to the discussions on “Restriking voltage as a factor in the performance, rating and selection of circuit-breakers” and “The influence of resistance switching on the design of high-voltage air-blast circuit-breakers”

The authors' replies to the discussions on “Restriking voltage as a factor in the performance, rating and selection of circuit-breakers” and “The influence of resistance switching on the design of high-voltage air-blast circuit-breakers”

Discussion on “Restriking voltage as a factor in the performance, rating and selection of circuit-breakers” before the North-Eastern Centre, at Newcastle, 11th December, 1944

Discussion on “Restriking voltage as a factor in the performance, rating and selection of circuit-breakers” before the North-Eastern Centre, at Newcastle, 11th December, 1944

Restriking voltage as a factor in the performance, rating and selection of circuit-breakers

Restriking voltage as a factor in the performance, rating and selection of circuit-breakers

Discussion on “Restriking voltage as a factor in the performance, rating and selection of circuit-breakers” and “The influence of resistance switching on the design of high-voltage air-blast circuit-breakers” before the Institution, 30th March, 1944

Discussion on “Restriking voltage as a factor in the performance, rating and selection of circuit-breakers” and “The influence of resistance switching on the design of high-voltage air-blast circuit-breakers” before the Institution, 30th March, 1944

Discussion on “Restriking voltage as a factor in the performance, rating and selection of circuit-breakers” and “The influence of resistance switching on the design of high-voltage air-blast circuit-breakers” before the South Midland Centre, at Birmingham, 3rd April, 1944

Discussion on “Restriking voltage as a factor in the performance, rating and selection of circuit-breakers” and “The influence of resistance switching on the design of high-voltage air-blast circuit-breakers” before the South Midland Centre, at Birmingham, 3rd April, 1944

Restriking voltage as a factor in the performance, rating and selection of circuit-breakers

Experience in service and at short-circuit testing stations has demonstrated that the behaviour of circuit-breakers when breaking shortcircuit currents depends on a number of factors which have been termed conditions of severity. They include circuit power-factor, recovery voltage, earthing conditions, and current asymmetry, and are specified in certain clauses in current testing specifications.The paper deals with a further condition of severity which has been acknowledged but is not specified in specifications, namely the restriking- voltage transient and its important controlling attribute, the ate of rise of restriking voltage. The aim of the paper is to place this severity factor in its correct perspective by stating its effect on the performance of plain-break oil circuit-breakers, oil circuit-breakers fitted with arc-control devices, and air-blast circuit-breakers. Compared with the relatively small effect that rate of rise has on plainbreak and arc-control oil breakers, the importance of the effect of rate of rise on the performance of air-blast breakers is emphasized, and recommendations are made as to the utilization of this important factor in the rating, testing and selection of these breakers.A method is proposed for testing certain types of high-voltage airblast breakers whose breaking capacities are above those for which testing stations are normally equipped.

The authors' replies to the discussions on “Restriking voltage as a factor in the performance, rating and selection of circuit-breakers” and “The influence of resistance switching on the design of high-voltage air-blast circuit-breakers”

The authors' replies to the discussions on “Restriking voltage as a factor in the performance, rating and selection of circuit-breakers” and “The influence of resistance switching on the design of high-voltage air-blast circuit-breakers”