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This papers presents a numerical approach based on computational fluid dynamics (CFD) that was developed to ensure that gravity oil-water separators at Hydro-Québec electrical substations comply with the environmental legislation in place. More precisely, multiphase simulations are performed for two operating conditions of an in service separator, and an experimental setup is used to produce an oil spill and to measure the time-varying oil concentration at the separator outlet. The results show that, for the tested conditions, the oil droplet size at a separator inlet generally follows a log-normal distribution and that the droplet diameter varies between 100 and 1000 µm with a mean value of 475 µm. Furthermore, both the experimental and numerical results show that the time required for the oil droplets to reach the separator outlet is quite shorter than the theoretical mean residence time. Finally, this study demonstrates that the numerical model predicts the separator efficiency within 1% of the measured value, and that it can be a valuable tool to investigate existing separators or to design new ones. [ABSTRACT FROM AUTHOR]

To evaluate the earthquake-resistance capability of an entire substation, which is a complex multi-input-multi-output system (MIMOS) composed of many various types of electrical equipment interconnected by conductors, a flow-based analysis model integrating the merit of the flow block diagram and state tree method was introduced. Two performance indicators of a substation were defined from different stakeholders, one is the expected total power transmission capacity and the other is the power accessibility to the targeted users from the substation. And directed graph logic system analysis models were developed on the Simulink platform based on the original internal logic relationship among distributed components and the power delivery path in the substation with different function types. Afterward, the defined reliability indicators associated with the overall system under a certain seismic intensity level can be obtained by combining the seismic vulnerability curve at the equipment level through the Monte Carlo simulation method. The feasibility and accuracy of the proposed system vulnerability analysis model were verified by comparison with the analytical solution through the illustrative simple MIMOS. Then A case study on a practical 220/110 kV substation was conducted, the analysis results can assist decision-makers in seismic optimization of different retrofitting measures and distribution plans for substations. [ABSTRACT FROM AUTHOR]

This paper presents the possibilities of reducing emergency situations and reducing the time of failure in the power grid. The paper contains a detailed description of the method (algorithm) of operation in emergency situations on the example of a Gas-Insulated Switchgear (GIS) located in one of the system-forming (node) stations in the power grid. The level of detail contained in this paper, which has not been previously encountered in previous publications, favors an in-depth understanding of the possible solutions that result from these emergencies. The above method (algorithm) of activities has been developed based on three levels of research: simulation, theoretical and practical. This means that the simulation analysis that was performed based on theoretical information was experimentally tested as part of an emergency situation in one of the system-forming (nodal) stations in the power system. In order to achieve the result described in this article, one of the most promising types of devices used in power systems was selected - the GIS. This has been confirmed by numerous analyzes of the effectiveness of these devices included in this article. The paper contains a detailed description of the individual steps in the field of corrective actions and aimed at minimizing downtime. In addition, this article provides guidance to monitor possible emergencies that are designed to increase the reliability of the power grid. [ABSTRACT FROM AUTHOR]

Substation bus ampacity calculations perform a steady-state heat transfer analysis on a unit length of bus. In this analysis, the convective heat transfer coefficients for rectangular, universal angle bus (UAB), and integral web bus conductor (IWBC) have historically been calculated by applying flat plane correlations to the individual bus surfaces. The research presented here will show that the Nusselt correlations developed for the specific bus, similar to what is currently used for round bus, increases accuracy in bus ampacity predictions. Additionally, the correlations are easier to use and less likely to result in calculation error. This paper presents natural and forced convection correlations for rectangular, universal angle bus, and integral web bus. [ABSTRACT FROM AUTHOR]

Excessive exposure to high levels of electromagnetic fields can induce adverse health effects. Numerical calculation is often used in the exposure assessments. However, in the traditional methods, the relative variables are all assumed to have fixed values without considering the effect of staff activity. To improve the deficiencies caused by this assumption, a new method for the exposure assessments based on the reliability theory was proposed in this investigation. As an example, the electric-field exposure in the booster station of a power plant with several paths was studied by the new method. The exposure reliability index and the failure probability of each path were first determined. Then, based on the determined reliability indices, the influence of the bus framework on the exposure was discussed by the sensitivity study, and a series system was set up to evaluate the electromagnetic exposure of the entire booster station. The proposed approach could be employed to assess the electric field in the substations by taking into account the staff activity, in order to improve the management of the occupational exposure in the power transmission and distribution projects. [ABSTRACT FROM PUBLISHER]

Secondary or low-voltage (LV) networks are applied in many large cities throughout the U.S., and in some other countries. Various grounding schemes have been employed for the primary systems supplying these secondary networks. In this paper, characteristics of the different grounding schemes for the substation and primary feeders that supply the LV networks are reviewed. The impacts of primary system grounding on the ground fault currents, the unfaulted line-to-ground voltages, as well as the voltage sags in the LV network have been considered for the single line-to-ground fault on the primary. The differences between systems with network transformers having the delta- or grounded-wye-connected primary windings are discussed. The relationships between grounding characteristics and protection settings, including actual examples, have been documented. [ABSTRACT FROM AUTHOR]

The IEC 61850-based substation automation system (SAS) provides opportunities for a new level of substation operation, enhancing operating efficiency and protection reliability with a new environment based on an Ethernet-based communication network and high-performance intelligent electronic devices (IEDs). With these changes, importance and dependence on IEDs are increasing rapidly in IEC 61850-based substations. While consideration of protection device faults has so far been infrequent, IED faults will become increasingly important in the future. Thus, this paper proposes a design of a backup IED for protection IED faults in IEC 61850-based substations. The proposed backup IED can be remotely converted into any type of protection IED without IED exchange, firmware update, or field control. The backup IED was designed through SCL engineering and file transfer functions in IEC 61850 and implemented by Windows programming with a commercially available IEC 61850 library. [ABSTRACT FROM AUTHOR]

The determination of the maximum ground fault current, which has a close relation to the maximum hazardous step-and-touch voltage, is essential for the safety of a substation. Seasonal frozen soil changes the grounding resistances of the substation grounding grids and the tower footing devices, which seasonally influences the maximum grid current. This paper first introduces the method to calculate the fault current-division factor, and then discusses the influence of the seasonal frozen soil layer on it by using the proposed method. Based on the cases of two substations connected by the transmission lines and without neutrals or other connection paths, the influence of several factors on the fault current-division factor, including the thickness of seasonal frozen soil, and the number of transmission lines with overhead ground wire connected to the substation grounding grid, is analyzed. It is reasonable to consider the influence of the seasonal frozen soil on the fault current-division factor in grounding grid design. According to the analysis, adding vertical grounding rods to the grounding grid and the tower footing grounding device can almost eliminate this seasonal influence. [ABSTRACT FROM PUBLISHER]

The industry-standard IEEE C37.99-2000 recommends the use of Peninsula Neutral Ground as the preferred method to ground the neutrals of capacitor banks in high-voltage substations. The basis for this recommendation is a 1972 IEEE paper by Rogers and Gillies that has remained unchallenged until now. Many grounding designs are carried out according to this approach despite the fact that it is the least efficient one. As long as this IEEE standard is not updated to reflect the new findings reported in this paper, designers will continue to be misguided. In this paper, we demonstrate that IEEE standard C37.99-2000 recommendations have no valid scientific basis by comparing the overall performance of a 735/230-kV substation grounding system designed according to the Peninsula Neutral Ground method, the single-point neutral ground and a more conventional design consisting of reasonably dense ground conductors in the 230-kV capacitor banks area and conclude that the conventional design offers superior performance from a safety and electromagnetic-interference perspective based on the fundamental frequency and full frequency spectrum of the back-to-back capacitor switching transient current discharge. [ABSTRACT FROM AUTHOR]

The choice of the right maintenance strategy is an important but also difficult topic for every energy utility. The difficulty consists in the huge number of interacting cost parameters. The present paper shows how from the biology well known process is adapted as an optimization algorithm in order to handle the parameter diversity. Outgoing from the definition of Life Cycle Cost and a method for substation reliability calculation the main idea of genetic algorithm and its application for Life Cycle Cost optimization is presented. Closing a case study shows the suitability of the algorithm. [ABSTRACT FROM AUTHOR]

Recent lightning current observations have suggested that a front duration of 1.7 \mus is more appropriate than the conventional 1.0 \mus for the lightning protection design of ultra-high voltage (UHV) systems in Japan. This study examined overvoltages at gas-insulated subsystems (GIS) and transformers in a UHV (the rated voltage of 1100 kV) substation during backflashovers, with the front duration of lightning stroke current waveforms taken as a parameter. The dependence of overvoltages on the front duration of the lightning stroke current is significant at GIS and relatively small at the transformer. Generally speaking, the shorter the front duration is, the higher the voltage will be. The transformer capacitance, ranging from 0 to 1000 pF, equivalently increases the distance to the surge arrester, and a voltage increase was observed at the transformer terminal. However, the steepness of the intruding surge waveform is reduced and the voltage increase suppressed at 1000 pF and over. The effect of overvoltages on insulation design was also evaluated and the results thereof indicated the possibility of reducing the lighting impulse withstand voltage. [ABSTRACT FROM PUBLISHER]

Capacitive current interruption with air-break disconnectors in a high-voltage network is an interactive event between the circuit and arc with a variety of interruptions and reignitions. In this contribution, first, a theoretical analysis related to this interaction is presented. The effect of capacitances at the source side (Cs) and load side (Cl) is investigated. Three distinct frequencies are identified as contributing to the voltage and current events in the circuit. Besides the power frequency quantities, a medium frequency transient arises related to the excursion of voltage across capacitances to the applied voltage, and a high-frequency transient arises due to charge redistribution between load- and source-side capacitance at reignition. Second, experimental results from an interruption measurement are studied in detail. Typical waveshapes of voltages across the capacitances, disconnector, and currents through the disconnector show that the transients during interrupted are in agreement with the theoretical analysis. Reignition voltage of the air gap and energy input to the arc on reignition are also studied. It is concluded that besides a higher interruption current and a higher power supply level, a lower (Cs/(Cl)ratio leads to more severe interruption and longer arc duration. Finally, the actual status of IEC recommendations on testing, that has taken into account this arc-circuit interaction, is summarized. [ABSTRACT FROM AUTHOR]

Accurate predictions of lightning surge overvoltages are essential to power equipment insulation design. Recent observations of lightning strokes to uiltra-high-voltage designed transmission lines confirmed direct lightning strokes caused by shielding failure and found phenomena unexplainable by conventional shielding theories. However, there are few detailed studies of direct lightning surge overvoltages. This study assumed direct lightning stroke currents based on observational data and performs Electromagnetic Transient Program analysis of the gas-insulated switchgear (GIS) and transformer overvoltages at substations to study the basic characteristics of overvoltages due to direct lightning strokes and evaluate lightning protection design. Consequently, the maximum GIS overvoltages were found during back-flashovers, and the locations of maximum overvoltages from direct lightning strokes and back-flashovers differ. Direct lightning strokes may be more severe than back-flashovers for transformers. This paper also studied the overvoltage generation mechanism and showed the relationship of the maximum voltage to lightning stroke current and transformer capacitance. [ABSTRACT FROM AUTHOR]

The peak current amplitude and front duration of lightning stroke current waveforms have conventionally been evaluated independently, and severe waveform assumptions are usually adopted in the current of lightning insulation designs. If lightning stroke waveform conditions are optimized, lightning insulation specifications of power facilities can be further rationalized. This paper proposes a new statistical technique to better evaluate lightning stroke current waveforms. The characteristics of lightning stroke current waveforms (i.e., that peak amplitudes correlate with front durations) are taken into account in this technique. The proposed technique was validated with various statistical tests. The front duration currently used in the design of the ultra-high-voltage system in Japan is 1.0 μs, but the potentially more accurate value of 1.7 μs was found when waveforms were evaluated with the proposed technique, and overvoltage analyses of gas-insulated switchgear show that overvoltages decrease with longer front duration. [ABSTRACT FROM AUTHOR]

Electromagnetic exposure of the general public due to large substations transforming voltages of 150 and 36 kV to 11 kV is investigated and safety distances for these substations have been determined. In total, 142 field measurements were executed for two substations: 91 measurements of the magnetic field and 51 measurements of the electric field. Measured momentary magnetic field values are within the range of 0.051 to 13.17 μT. The levels of the electric field are within the range of 0.095 to 270.0 V/m. The cumulative distribution function of the measured magnetic-field values has been determined, and it is shown that the fields excellently follow a lognormal distribution. The maximal magnetic and electric-field values for all the investigated substations are below 100 μT (values over a day and year) and 5 kV/m, respectively. When comparing the average exposure with the value of 0.4 μT, safety distances of maximally 8.1 m (average day) and 7.1 m (average year) are obtained. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to search for the optimal connection of power transmission lines with underground power cables for a newly constructed substation to reduce the magnetic flux density around it. The genetic algorithm method is employed for solving the problem of optimization mentioned above to get a best connection. With the optimal connection, the magnetic flux density can be reduced effectively without spending or utilizing extra time, manpower, and equipment. [ABSTRACT FROM AUTHOR]

In the past decade, new communication schemes have been designed and retrofitted into substations by utilities to integrate data from relays and Intelligent Electronic Devices (IEDs) and capitalize on the protection, control, metering, fault recording and communication functions available in digital devices. The introduction of IEC 61850 has made it possible and justifiable to integrate station IEDs on a high-speed peer-to-peer communication network (ethernet) through standardization. However, more advances are needed in order to establish an open and standard working environment allowing for more functions to be developed. In this paper, the authors propose a real-time publisher/subscriber communication model as a means of satisfying the unique behavior and communications needs of the IEC 61850 protocol. The authors provide a detailed design and implementation detail of this model along with interesting performance results. The target audience for this paper includes power system protection and automation engineers and technicians as well as research personnel who have at least a basic understanding of the IEC 61850 international standard and other technology mechanisms addressed in this paper. [ABSTRACT FROM AUTHOR]

This paper presents the observation results of surge waveforms in substations and the frequency components of such waveforms. In the Higashikanazu 77 kV power system, distribution transformers were damaged three times by winter lightning. In particular, almost the same parts were damaged at the No. 3 transformer in Katayamazu substation. To investigate the cause of the transformer failures, observation apparatus were installed at four substations in the Higashikanazu power system. Approximately 490 waveforms of incident surge were measured during the observed period. In 11 cases, simultaneous measurements of the incident surge waveforms at the four substations were achieved. By the analysis of the observed waveforms, the specific frequency components were found. From the investigation of theoretical and analytical approaches, it became clear that these frequency components depended on the power system configuration. By comparing the specific frequency components of the observed waveforms and the natural frequency components of the transformer, it was clearly shown that the overvoltages due to the internal resonance phenomena were the cause of failures. As a result, the internal resonance phenomena should be considered in the design of transformers, and the specific frequency components should be also estimated by the theoretical and analytical approaches. [ABSTRACT FROM AUTHOR]

The design principles and performance characteristics of a prototype high-temperature superconductor saturable magnetic core-type fault current limiter are described. These are based on a distribution network service provider feasibility specification that included the footprint and regulatory requirements for limiting fault currents. Time-domain simulations using PSCAD/EMTDC are given to illustrate specific applications and the transient behavior of the different distribution system configurations are investigated. [ABSTRACT FROM AUTHOR]

In order to measure the grounding impedance of a grounding system more precisely and easily, two key problems of the measurement system: the location of the voltage electrode and the elimination of the noise and interference must be conquered. The new theoretical analysis and measurement system of the grounding impedance based on short-current lead wire and a swept frequency ac source is proposed. The compensating position of the voltage electrode to obtain the real grounding impedance is evaluated by analyzing the soil structure, the grounding system under test, and the position of the current electrode. This new system measures the ground impedance at several frequencies other than power frequency, then interpolates them to acquire the ground impedance at the power frequency. The mutual inductance between the potential and current wires is analyzed and eliminated. The industrial computer-based grounding impedance measurement system is developed and the analysis software is programmed. A field test was performed and compared with the traditional method in the substation and the novel system worked well. [ABSTRACT FROM AUTHOR]

EMTP has been widely used in Japan to analyze switching and lightning overvoltages to design power stations and substations from the viewpoint of insulation coordination. The Japanese standard of high voltage testing, JEC-0102-1994, and the insulation design and the coordination of an 1100-kV line of Tokyo Electric Power Company were mostly based on EMTP simulations. This paper presents a method of a lightning surge analysis using the EMTP recommended in the Japanese standard and related guidelines, and suggests further work to be done based on discussions of applicable limits and problems of the recommended models. [ABSTRACT FROM PUBLISHER]

Grounding system is very important to maintain the safe and reliable operation of power network and ensure the safety of power apparatus and operators. A new technique to decrease grounding resistance of substation is presented in this paper, which makes use of deep ground well to decrease the grounding resistance. The ground well is formed by metal tube with water percolation apertures in the soil with groundwater, which has the ability to gather the groundwater and wet the surrounding soil. The principle of deep ground well to decrease grounding resistance is to decrease the resistivity of the soil region surrounding the grounding well by leading the groundwater moving to the deep ground well under pressure, and consequently decrease the grounding resistance of the deep ground well. This novel method was applied in a substation grounding engineering, and good effect was achieved. [ABSTRACT FROM PUBLISHER]

This paper presents an artificial neural network (ANN) and support vector machine (SVM) approach for locating faults in radial distribution systems. Different from the traditional Fault Section Estimation methods, the proposed approach uses measurements available at the substation, circuit breaker and relay statuses. The data is analyzed using the principal component analysis (PCA) technique and the faults are classified according to the reactances of their path using a combination of support vector classifiers (SVCs) and feedforward neural networks (FFNNs). A practical 52 bus distribution system with loads is considered for studies, and the results presented show that the proposed approach of fault location gives accurate results in terms of the estimated fault location. Practical situations in distribution systems, such as protective devices placed only at the substation, all types of faults, and a wide range of varying short circuit levels, are considered for studies. The results demonstrate the feasibility of applying the proposed method in practical distribution system fault diagnosis. [ABSTRACT FROM PUBLISHER]

Coupling of carrier wave frequencies up to 95 kHz (within the European CENELEC A-band) for online diagnostic data transfer in medium voltage cables is studied. Inductive and capacitive signal coupling is considered not only on basis of technical performance, but also on basis of practical aspects. The effectiveness of coupling schemes depends on the impedances of substation equipment at the cable terminals. The frequency response of a 10-kV, 400-kVA three-phase cast resin distribution transformer is investigated. In the frequency range of interest, the behavior is well described by a capacitance of typically 1 nF. The signal transfer over a 4-km paper cable, terminated by various load impedances to mimic real equipment is studied. From the results it is concluded that for inductive coupling performance within the CENELEC A-band may be sufficient, except for substations at the end of a grid. Transferring signals containing frequencies up to several megahertz, which is already required for synchronization of partial discharge detection and location equipment, is feasible under all conditions. Measurements on life substations indicate that up to these frequencies substation components can still be accurately modeled as lumped circuit impedances. [ABSTRACT FROM PUBLISHER]

The growth in substation data generated by microprocessor-based IEDs has far outstripped our capability for interpretation. In competitive energy markets, the success and survival of power utilities hinge upon their ability to skillfully locate, analyze and make use of the information. Hence, it is now necessary to consider moving beyond data acquisition to knowledge discovery. To accomplish this task, we require a new information processing and data analysis tool that can intelligently process a large volume of data. The paper describes the data explosion problem and illustrates how a new computational intelligence approach can be used within a substation to group objects of interest into classes indiscernible with respect to some or all of their features. This reduces superfluous and irrelevant data, which then improves the performance of the data analysis tools and helps speed up the knowledge acquisition process. It also provides a condensed report summary that can be used by the operator to react to the emergency. [ABSTRACT FROM PUBLISHER]

How to precisely measure the grounding resistance of substations is the fundamental factor to guarantee the safe operation of power systems. The placement rules of test electrodes for the grounding resistance measurement of grounding system in vertical-layered soil were analyzed by the numerical method in this paper. The actual demanded location of the test potential electrode respective to the true grounding resistance of grounding system in different measuring directions changed (in a wide range) when the grounding system was arranged in different soil models. The test error of 0.6 18 method to measure grounding resistance sometimes is very high. The test route that the test circuit is in parallel with the vertical boundary is recommended for measuring the grounding resistance of grounding system in the vertical-layered soil area. The scientific and suitable measuring method of grounding resistance is based on analyzing the actual soil model and the grounding system structure to obtain the suitable test route and choose the correct compensated point location of the potential electrode. [ABSTRACT FROM AUTHOR]

Electric utilities began to operate distribution systems at 35 kV about 20 years ago. Experience soon revealed that some unique conditions existed as the distribution voltage was increased to this level. Customers served by a substation feeder complained of blinking lights and equipment problems when a fault occurred on the adjacent feeder of the same substation. A comparison can be made between the voltage sag that occurs on a 12-kV and 35-kV system using system impedance and symmetrical component calculations. Most of the 35-kV voltage drop, during a fault, occurs in the substation power transformer. The low voltage appears at the substation low side bus. This paper includes field test data that verify the symmetrical component calculations for existing system conditions. It explains how lower impedance power transformers and special considerations for 35-kV system design will make improvements in voltage sag of up to 20%. [ABSTRACT FROM AUTHOR]