Top PDF Software System for Finding the Incipient Faults in Power Transformers

Software System for Finding the Incipient Faults in Power Transformers

Software System for Finding the Incipient Faults in Power Transformers

In order to study the phenomenon of partial discharge, a simple model with insulation between copper conductor and steal tank is made. Partial discharge can be described as an electrical pulse or discharge in a gas-filled void or on a dielectric surface of a solid or liquid insulation system. This pulse or discharge only partially bridges the gap between phase insulation to ground, or phase to phase insulation. These discharges might occur in any void between the copper conductor and the steel of the grounded tank. The voids may be located between the copper conductor and insulation wall, or internal to the insulation itself, between the outer insulation wall and the grounded shield, or along the surface of the insulation. The pulses occur at high frequencies; therefore they attenuate quickly as they pass to ground. The discharges are effectively small arcs occurring within the insulation system, therefore deteriorating the insulation, and can result in eventual complete insulation failure.
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Power transformers winding fault diagnosis by the on-load exciting current extended Park's vector approach

Power transformers winding fault diagnosis by the on-load exciting current extended Park's vector approach

The most difficult transformer winding fault for which to provide protection is the fault that initially involves only one turn [14]. A short-circuit between turns can start with point contact resulting from mechanical forces, from insulation deterioration due to excessive overload, a loose connection or breakdown of transformer insulation by an impulse voltage [15]. Initially, the insulation breakdown leads to internal arcing [16], which results into a low current, high impedance fault [17]. If undetected, this incipient fault will then progress, with random propagation speed, involving additional turns and layers, leading to a high current, low impedance fault [18], [19]. Usually, the incipient interturn insulation defect does not draw sufficient current from the line to operate an ordinary overload circuit-breaker or even more sensitive protection devices, such as differential relays [20], [21]. In fact, the main function of the conventional transformer percentage differential protection is to limit the extent of the damage caused by an internal defect, isolating the fault as rapidly as possible, rather than providing an indication of early stages of the winding deterioration. In addition, differential relay security (i.e., avoiding false trippings) is a major issue, and is obtained at the expense of protection sensitivity. As a consequence, the traditional transformer differential protection is typically not sensitive enough to detect turn-to-turn winding insulation winding defects before they developed into more serious and costly to repair ground-faults [22]. The transformer will, in fact, be disconnected from the line automatically when the fault has extended to such degree as to embrace a considerable portion of the affected winding [20], [23].
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Probabilistic Security Evaluation Software for Bulk Power System Considering Bus Arrangement

Probabilistic Security Evaluation Software for Bulk Power System Considering Bus Arrangement

Abstract—more accurate algorithm based on analytical approach for probabilistic security evaluation is proposed in this paper. New software named PSD-PRE is developed using Visual FORTRAN and Visual C++. It achieves calling of PSD-BPA which is the basis of PSD-PRE for state evaluation. Trait of PSD-PRE is that it can evaluate bulk power system probabilistic security considering bus arrangement. It makes the calculation results more accurate. Accelerating algorithm is adopted to alleviate the calculation burden of PSD-PRE. Not only the single or double faults of line or transformer but also the multi-fault caused by protection failure to operate or rejection can be modeled to get the probabilistic security risk indices. PSD-PRE has been tested by IEEE-RTS79 test system. Simulation results show that PSD-PRE is valid, available and indices can be used as the basis of transmission network planning.
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Incipient turn-to-turn winding fault diagnosis of power transformers by the on-load exciting current Extended Park`s Vector Approach

Incipient turn-to-turn winding fault diagnosis of power transformers by the on-load exciting current Extended Park`s Vector Approach

In the presence of a primary winding fault, the short-circuited turns act as an autotransformer load on the winding, as shown in Fig. 2(a). However, if the fault takes place on the secondary winding, the short-circuited turns act as an ordinary double winding load, Fig. 2(b), [4]. In both cases, the occurrence of winding inter-turn short-circuits leads to an increment in the magnitude of the on-load exciting current in the affected phase, as compared to a healthy situation, which results in an unbalanced system of currents. Under these conditions the on-load exciting current Park's Vector modulus will contain a dominant DC level and an AC level, at twice the supply frequency (2f), whose existence is directly related to the
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Transformers on-load exciting current Park`s vector approach as a tool for winding faults diagnostics

Transformers on-load exciting current Park`s vector approach as a tool for winding faults diagnostics

Under the deregulation policy of electric systems, each utility is trying to cut its costs, and the prevention of acci- dental loss is much more important than before. The capi- tal loss of an accidental power transformer outage is often counted in million dollars for output loss only, not to say the costs associated with repair or replacement. Because of this economic incentive, preventive test and on-line moni- toring are benefit to predict incipient fault conditions, and to schedule outage, maintenance and retirement of the transformers [2].
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J. Microw. Optoelectron. Electromagn. Appl.  vol.16 número1

J. Microw. Optoelectron. Electromagn. Appl. vol.16 número1

Usually, high voltage generators are related to high costs. They are expensive and their energy production is financially very relevant. The detection of an incipient fault at its initial stage helps to avoid serious breakdown including the assets of the company and consequently reduces the deficit. The capability on detecting faults at initial stages provides also an upgrade of the security on the machine operation, increasing the reliability of the electrical system. These are the elements justifying and motivating the study and the development of systems for monitoring the health of the machine. Works about measurements of external fields have been discussed since 1970. Some of them deal with measurements and numeric simulations of the field in the vicinity of low power machines [1]- [4]. Several papers consider fault diagnosis of machines, mainly three-phases induction machines. In 1998, reference [5] used the analysis of the external field to detect faults in induction motors. Such works use non-invasive methodology which consists on analyzing the frequency spectral components of the measured external field. Nevertheless, studies addressing methodologies of sensing external magnetic field on generators, are still are [6]-[8]. Near the generators, there are leakage field originated by the machine. This magnetic field is due to the leakage flux of the end windings and the stator core (the tangential components of the magnetic field are conserved between two media [9]).
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Intermittent turn-to-turn winding faults diagnosis in power transformers by the on-load exciting current Park's Vector Approach

Intermittent turn-to-turn winding faults diagnosis in power transformers by the on-load exciting current Park's Vector Approach

The most difficult transformer winding fault for which to provide protection is the fault that initially involves only one turn [3]. Initially, the insulation breakdown leads to internal arcing, which results into a low current, high impedance fault [4]. Usually, this incipient inter-turn insulation failure does not draw sufficient current from the line to operate an ordinary overload circuit-breaker or even more sensitive balanced pro- tective gear [5]. This turn-to-turn fault will then progress, with random propagation speed, involving additional turns and lay- ers, leading to a high current, low impedance fault, [6]. The transformer will, in fact, be disconnected from the line auto- matically when the fault has extended to such degree as to em-
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Application of Park's power components to the differential protection of three-phase transformers

Application of Park's power components to the differential protection of three-phase transformers

As it is evident from the preceding paragraphs, it is of prime importance the development of protection schemes, which can improve the sensitivity of differential relays to detect incipient winding faults and which can also provide a solution to the second harmonic restrain drawbacks. Not surprisingly, a significant amount of research work has been devoted over the last decades to solve the inrush/fault discrimination dilemma of the transformer differential protection. Several solutions have been proposed in this context, including the refinement of the traditional harmonic restrain methods [14- 17], the development and exploration of new trip and restrain signals [10, 12-13, 18-31], the use of wave-shape recognition methods [32-34], and the application of advanced digital signal processing tools [11, 35-37], fuzzy logic and artificial intelligence
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Power transformers behavior under the occurrence of inrush currents and turn-to-turn winding insulation faults

Power transformers behavior under the occurrence of inrush currents and turn-to-turn winding insulation faults

The most difficult transformer winding fault for which to provide protection is the fault that initially involves only one turn [3]. A short-circuit between turns can start with point contact resulting from mechanical forces, from insulation deterioration due to excessive overload, a loose connection or breakdown of transformer insulation by an impulse vol- tage [4]. Initially, the insulation breakdown leads to internal arcing, which results in a low current, high impedance fault [5]. Usually, this incipient inter-turn insulation failure does not draw sufficient current from the line to operate an ordi- nary overload circuit-breaker or even more sensitive ba- lanced protective gear [6]. This turn-to-turn fault will then progress, with random propagation speed, involving addi- tional turns and layers, leading to a high current, low imped- ance fault, [7], [8]. Failure of the protection devices to detect these faults and quickly isolate the transformer may cause severe damage to the device and seriously affect the power
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Faults Classification of a Scooter Engine Platform Using Wavelet Transform and Artificial Neural Network

Faults Classification of a Scooter Engine Platform Using Wavelet Transform and Artificial Neural Network

In this paper, a scooter fault diagnosis system based on continuous wavelet transform technique and faults classification using artificial neural network for the purpose of the fault detection has been developed. Wavelet analysis, which allows the sound emission signals of frequency content with time to be visualized, can extract key features using time-frequency representation of sound emission signals from a scooter. A feature selection method called “spectrum trend feature method” was proposed. The selected feature vectors are diagnostic trouble codes corresponding to their fault condition. The features are subsequently used for the intelligent classifier to evaluate the performance of proposed fault diagnosis system. The proposed diagnosis system using GRNN method was able to reach a fault recognition rate of about 99%. The experimental results show that the proposed fault diagnosis system with neural network can be effectively used in scooter diagnosis of various faults through measurement of scooter sound emission signal.
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Mat. Res.  vol.15 número5

Mat. Res. vol.15 número5

Therefore, replacement of conventional transformers with cores of cold-rolled-oriented silicon steel (CRGO) by transformers with amorphous alloy core can mean energy conservation and environmental preservation, contributing to the reduction of need for building new power plants and their environmental impacts. In the case of hydroelectric plants, ecological and social impacts, and in case of power plants, lower fuel consumption and emissions. In the latter case, the benefits of conservation can be characterized by significant reduction in emissions of greenhouse gases such as sulfur dioxide (SO 2 ), nitrogen oxides (NO x ) and carbon dioxide (CO 2 ).
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A survey on power grid faults and their origins: A contribution to improving power grid resilience

A survey on power grid faults and their origins: A contribution to improving power grid resilience

A grid connection with communities of net zero energy buildings is a research opportunity concerning the community load flexibility that can improve its resilience in case of a fault occurrence. Considering the cluster of smart grid-based solutions, which represents 33% of the articles considered with EPG resilience improvements, and the net zero energy building (NZEB) concept, a new solution to improve the resilience of a community when an outage occurs can be studied. The NZEB concept is based on the fact that a building produces the same amount of consumed energy during a certain time period (usually one year) [133]. Gathering prediction strategies with the idea mentioned above, the resilience of a community can be improved during an outage. Thus, in order to follow this research, it will be conductive to study the improvement of LV grid resilience, applying the NZEB community together with prediction systems as well as load flexibility. With this, it will be possible to study different scenarios and try to understand how different faults can influence the behavior of a community during an outage.
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Design And Construction Of 300W Audio Power Amplifier For Classroom

Design And Construction Of 300W Audio Power Amplifier For Classroom

FET is controlled by the input gate voltage and BJT is controlled by the input base current. The cost of the BJT is much lower cost than FET. The losses of the BJT are lower than FET. The trans conductance of the BJT is higher than FET. By using BJT, BJT can give low current and low voltage supply. BJT is good in amplification. By using FET, FET can give high current and high voltage supply. FET is not good in amplification. To get the high power, FET can be used. ————————————————
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Model of knowledge representation about materials in the form of a relational database for CAPCAST system

Model of knowledge representation about materials in the form of a relational database for CAPCAST system

This article presents a methodology used in creation of a knowledge base for CAPCAST system, based on different types of input data under the conditions specified by the problem do- main, that is, selection of materials for the designed cast products. The database structure and, as a consequence, also the structure of the knowledge base are strongly determined by the availability of data on this particular subject and by the adopted relational mod- el. Under these circumstances, and bearing in mind future expan- sion of the system in subsequent iterations, which cannot be pre- dicted in advance, the decision tables were chosen as a formalism for recording the conditional knowledge of the toughening processes. It also gives prospects for creation of a universal, from the viewpoint of the reasoning systems, tool to generate rules in a particular language of logic based on rules encoded in an attribute decision-making table.
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Analysis of Photovoltaic Fed Partially Isolated Three-Port Full Bridge Converter with the Centralised Controller

Analysis of Photovoltaic Fed Partially Isolated Three-Port Full Bridge Converter with the Centralised Controller

As the demand for the power generation increases day by day, to meet this energy crisis many researchers were focusing their interest on the generation of power from the renewable energy sources like fuel cell, wind energy conversion system, photovoltaic system etc. The future power system interfaces all these sources with the load along with the energy storage device. In case of the stand-alone system the storage device is required to provide backup power and for the fast dynamic response. To interface the sources which are intermittent in nature a multi-input dc-dc converter is proposed [1]-[3].The conventional multi-input dc-dc converters for interfacing many renewable sources use a common dc link which has the drawbacks like requirement of more number of conversion devices, complex design and it is applicable only for the low power application.
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Design parameter based method of partial discharge detection and location in power transformers

Design parameter based method of partial discharge detection and location in power transformers

In the low frequency range, the signal travels through the equivalent transmission line of the winding with a finite propagation velocity. The time delay between the two terminal signals depends on the position of the PD source relative to the terminals. This time delay can be used for location and such a technique is called the travelling wave method. In the higher frequency range, the capacitive ladder network applies. The ratio of the two terminal signal magnitudes can be used for location. This is called the capacitive ratio method. From the previous works on the PD location using the series resonant frequencies the equation is given as:
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Mobility and market power in the Portuguese financial system

Mobility and market power in the Portuguese financial system

The traditional explanatory variations of market power in a context of differentiated product are concentration and the market share. In Hannan (1991), these two variables are recognised to be positively related to market power, the former through a lower elasticity of demand and the latter, through the reduction of perceived elasticity resulting from the greater dimension of the bank. Also in Pinho (2000, 2001), these variables are used to explain market power. Thus we shall use these two variables in the present study. As a measure of concentration, we shall use the Herfindal index for deposits (HERFD) and credit (HERFL), to estimate rD or rL , respectively. To estimate the parameter , relative to no price competitive instruments, Herfindal’s index for branches (HERFBR) will be the variable representing concentration. As for the variable representing the market share, we chose to consider the control variable LARGE (= 1 for “banks with a market share above 5%”) in the estimation of the parameters rD and rL and the variable branches’ market share s BR in order to estimate the parameter of the competitive no price instruments. It is assumed that, generally speaking, the dominant companies or those with a large market share have significant advantages over their customers, translated in terms of the margins applied to them.
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Half Swing Clocking Scheme at 45nm

Half Swing Clocking Scheme at 45nm

In recent ages major interest of designers were on area, performance, cost, reliability, and power. Power is most crucial factor of the embedded processor technology. Power distribution in embedded processor differs from product to product but due to the large capacitance and high switching activity clock system dissipates enormous portion of power which is about 18-43% of total circuit. One of the main reasons for enormous power consumption in the clock system is that the transition probability of the clock is 100% while in ordinary logic it is about one-third on average.
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Determining the reliability function of the thermal power system in power plant "Nikola Tesla, Block B1"

Determining the reliability function of the thermal power system in power plant "Nikola Tesla, Block B1"

A fundamental element of the reliability analysis of any complex system is the appro- priate characterization, representation, propagation, and interpretation of uncertainty [7]. Un- certainty is an unavoidable component affecting the behavior of systems and more so with re- spect to their limits of operation. With respect to uncertainty, the final objective of reliability analysis and risk assessment is to produce insights in the analysis outcomes which can be mean- ingfully used by the decision makers. With respect to the treatment of uncertainty, in the reliabil- ity analysis and risk assessment practice both types of uncertainties are represented by means of probability distributions [8].
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Criterion for selection the optimal physical and chemical properties of cobalt aluminate powder used in investment casting process

Criterion for selection the optimal physical and chemical properties of cobalt aluminate powder used in investment casting process

The effect of modification of the surface layer of the castings made from superalloys: Inconel 713C, René 77 and MAR-M 509 was investigated on the cross sections of the castings. The reduction of grain size of invested alloys after modification was obtained independently from the kind of used cobalt aluminate (Fig. 6.). The measurements of the average surface area of grain cross section of γ matrix in the cross section of casting revealed the differences in the size of grains up to the type of modifier. From Figure 6 one can see that the most coarse grain structure characterize the nonmodified castings. The finest macrostructure characterizes the samples which were modified by 5% of Mason Color and Remet powders with higher contamination of cobalt: 39.43%, 34.79
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