Electrical Substation Equipment Research Articles

Response evaluation of interconnected electrical substation equipment using real‐time hybrid simulation on multiple shaking tables

SummaryIn an attempt to quantify the conductor cable effect on substation electrical equipment, real‐time hybrid simulation (RTHS) is conducted on interconnected equipment using two shaking tables. For this purpose, the existing RTHS system with advanced control capabilities at the Pacific Earthquake Engineering Research Center structural laboratory is enhanced to accommodate the simultaneous use of two shaking tables. An experimental parametric study is conducted to investigate the conductor cable effect using this system with a two‐table RTHS setup. Post insulators of disconnect switches, important components of substations that are usually tested with conventional methods for evaluating their seismic performance, are utilized as experimental substructures for realistic representation of the electrical equipment. Various global and local response parameters, including accelerations, forces, displacements, and strains, are considered to evaluate the effect of the tested conductor cable configuration for a wide range of support structure configurations, which are modeled in the computer as analytical substructures. The experimental parametric study results indicate that the conductor cable has a significant effect on the response of the interconnected equipment over the whole range of investigated support structures and needs to be explicitly considered for seismic testing of electrical equipment. Copyright © 2016 John Wiley & Sons, Ltd.

Estimate of small first passage probabilities of nonlinear random vibration systems by using tail approximation of extreme distributions

Efficient estimate of the small first passage probabilities of nonlinear structures under random excitations is of great importance in structural reliability analysis. Some methods, such as the subset simulation method, tail equivalent linearization method, asymptotic sampling method, Monte Carlo simulation method based on the extreme value theory, etc., have been developed for estimating the probabilities, however, the efficiency of the estimate is still a challenging task. In the present study, a new method is developed to overcome the challenge. The method approximates the tails of the univariate extreme distributions of the responses by using the shifted generalized lognormal distributions, in which the model parameters are estimated by an efficient method called the extrapolation method. Based on the approximate tail distributions and covariances of the extreme responses, the tails of the multivariate extreme distributions of the nonlinear response are determined by using the Nataf model. Finally, from the relationship between the first passage probabilities and the extreme value distributions, the small first passage probabilities of interest can be estimated. The efficiency of the developed method is illustrated by the small first passage probability analyses of a single-degree-of-freedom system subjected to a stationary Gaussian process and two connected electric substation equipment items subjected to earthquake base motion.

Substructured Dynamic Testing of Substation Disconnect Switches

The paper demonstrates the substructuring concept in seismic qualification testing of 550 kV electrical substation disconnect switches. In this study, the full and substructured (i.e., without support structure) switches are tested on a six degrees of freedom (DOFs) shaking table. Different combinations of translational and rotational excitations are obtained from full switch tests and used in the substructured ones. The behavior of the post insulators of the switches are compared to demonstrate validity and identify limitations of the substructuring concept applied to electrical substation equipment. From this comparison, critical DOFs for the response of post insulators in switches supported on flexible structures are identified. It is concluded that the in-plane and out-of-plane behavior of the investigated post insulators are uncoupled. The substructured tests driven by combined translational and rotational signals showed the best match with the full switch tests because the out-of-plane rotations contribute significantly to the response of the post insulators.

Structural Performance of Porcelain and Polymer Post Insulators in High Voltage Electrical Switches

AbstractPost insulators are key components of most electrical substation equipment, but they are vulnerable during earthquakes. To better understand the seismic response of post insulators, this paper presents an experimental program that involved two types of 230-kV disconnect switches post insulators. Several solid ceramic (porcelain) and hollow-core composite (polymer) insulators were tested. The experiments consisted of static loading and dynamic shaking table tests. The static cyclic-loading, resonance-search, and pull tests—including material characterization—allowed the determination of the insulators lateral stiffness, fundamental frequency, and mode of failure. Moreover, failure loads and corresponding displacements and strains were determined. Additionally, the shaking table tests involved substructured dynamic tests of single porcelain and polymer post insulators. The main objective of the static and dynamic tests was to compare the behavior of porcelain and polymer post insulators under latera...

A Wireless System for Monitoring Leakage Current in Electrical Substation Equipment

In this paper, the design and the development of a remote system for continuous monitoring of leakage currents and ground currents in high voltage electrical substations are proposed. Based on wireless local area network technology, the system can be used to monitor continuously a variety of plants within the substation and has low power consumption with inbuilt overvoltage protection. It consists of a transmitter module equipped with a data acquisition (DAQ) system connected to leakage current and voltage sensors, and a receiver module connected to a remote controller for data processing and storage. The principle of operation and the characteristics of the various components of the system are described. Validation tests have been used to verify its performance in three different test situations: A) laboratory monitoring of the leakage current and voltage of a distribution surge arrester; B) laboratory measurement of the leakage current of an outdoor insulator; and C) field monitoring of the earth current and potential rise of high-voltage tower. The measured results are in close agreement with those recorded directly through a DAQ card with fiber-optic and coaxial cable connected systems. Data processing is carried out at the receiving end so that the monitored parameter is displayed continuously or at specified time intervals. The operation of the system has been tested and proved resilient under high-frequency interference signals such as those generated by corona and surface discharges.

Shake Table Testing and Numerical Analysis of Transformer Substations Including Main Plant and Electrical Equipment Interaction

Transformer substations are among the most significant components of an electric power distribution system. These critical elements must remain operational during and after any extreme event, especially a severe earthquake. In past studies, the interaction between the main plant and the electrical equipment (EE) in a transformer substation was usually ignored. While a few considered this interaction through numerical simulations, there were no experimental studies to validate the findings. The aim of the present paper is to analyze the seismic reaction of a substation with explicit consideration of the dynamic interaction between the main plant and the EE mounted inside—achieved through a shaking table test and numerical simulations. A 1:8 scale model of a transformer substation plant with EE on its second floor is built and tested on a shaking table. Dynamic response data are gathered during seismic excitations of the substation, with and without the EE. These measurements and the corresponding validated numerical simulations clearly showed that there is obvious interaction between the plant and the EE. The stronger ground motions lead to a higher amplification of the seismic responses of the plant and the EE; and the observed acceleration amplification factors of the EE on the main plant are significantly greater than the factors recommended in the codes. In addition, the study shows that achieving the common performance objective of “ strong columns and weak beams,” may not be possible without explicitly considering the EE-main plant interaction effects, which cause the higher demands to migrate towards the column-ends. As such, those areas should be strengthened when designing substations against earthquakes.

Substation Electromagnetic Environment of Electric Power Communication Equipment and Characteristic Parameters

Ma, H.; Zhang, W.; Cui, X.; An, B.; Jin, Y., and Cheng, K., 2015. Substation electromagnetic environment of electric power communication equipment and characteristic parameters.The steady and transient electromagnetic environment near electrical equipment in substations and converter stations is measured in different voltage levels and different positions. After analyzing and counting a large number of measurement samples, mathematics character parameters of steady electromagnetic disturbance in substations are gained, which provide the theoretical basis for protective measures.

Experimental and Numerical Analysis of Vibration of the Test Stand

Sound effect derives a pair of highly loaded machinery parts-motion screw and nut. Loaded pair is used in non-standard environments of high voltage electrical equipment in electrical substations. The non-standard environment is seen in the movement of this pair immersed in transformer oil deeply below the surface. Transformer oil has no good mechanical lubricating properties because it does not contain sulfur. Loaded pair cannot be lubricated, because there would be oil contamination and deterioration of its electro-insulating properties. The causes were sought in the structure of the machine, frame stiffness, mechanical strength machine and used materials. The aim of the research with help experimental and numerical study was to define the cause and eliminate sound effect coming from the device.

Metrological Estimation of Measurement Error with the Determination of the Technical State of Substation Electrical Equipment

This paper presents an application's experience of estimation of the technical condition state of electrical equipment. Federal Grid Company of United Energy System is the biggest Russian Company for the electrical energy transport. The diagnostics of the basic oil-filled equipment of substations is a very complex problem for the personal of electrical networks and stations .At present there are more than 20-30 electrical and other parameters, which must be measured for the inspection of the state of the electrical equipment. Quality and the authenticity of the results of diagnostic measurements are the guarantee of the trouble-free operation of electrical equipment, the absence of damage from the interruptions of the power supply of the users of electric power. Basic errors, which appear with the measurements of the diagnostic parameters of electrical equipment, are the instrument, systematic and subjective of errors. The errors enumerated above can be considerably decreased with the use of information tools, i.e., software and of specialized automated working place (further SAWP).

Reliability of Latvian Power System’S 330 KV Substations

Abstract Substation reliability is always a topical problem. The authors consider the techniques for reliability calculation based on logical-probabilistic approach to the evaluation of electrical substation switchgear schemes and equipment at emergency situations with disconnections of individual elements of the substation equipment or false operation of relay protection and automation devices. Based on the reliability analysis made for the 330kV substations of Latvian Electric Power System, recommendations are given concerning the reconstruction of switchgear schemes for some substations

Enabling Predictive Maintenance using Semi-supervised Learning with Reg-D Transformer Data

Predictive maintenance has now become a possible avenue within the electricity distribution sector of Eskom. A recent roll-out of large-scale substation data acquisition projects have allowed this sector to use a predictive based maintenance scheduling plan instead of a previously used frequency based maintenance plan. This paper describes the design and implementation of a low-complexity anomaly detection algorithm, which is able to detect discrepancies, indicative of small electrical grid changes or substation equipment deterioration. The algorithm is based on projecting parametric multivariate Gaussian functions on to spatially distributed pre-selected substation data points. This method enables the utility to monitor critical variables, and their relationships, in an effort to foresee equipment or network distresses from high-value assets, particularly in the transmission and distribution sector. The results demonstrate an early positive detection of anomalous load behaviour from a live substation. The presented Semi-supervised learning methodology can form the underpinnings of an integrated approach, to aid with operational decision-making, and seems eminently suitable to reduce unscheduled asset downtime.

Dynamic properties of substation support structures

Substation electrical equipment is usually mounted on different kinds of structures, which can have a very significant effect on the motion that the supported equipment will experience during an earthquake. In this paper, a parametric study is implemented in order to assess dynamic properties of substation support structures.In the first phase of this study, a simplified Four Degrees-of-Freedom (4-DOF) system is proposed in order to model different support-equipment systems and is verified through finite element method (FEM). Based on the proposed model, a practical equation is proposed to calculate the fundamental natural frequency of support-equipment systems and compared to the one proposed by ASCE (substation structure design guide, 2008). Furthermore, dynamic amplification factor (DAF) of substation support structures is calculated, and effect of different parameters (e.g. support mass, height and stiffness) is discussed. Finally, a new criterion is developed to restrict maximum acceleration at support-equipment intersection.Results of this paper can be utilized in order to design more proper support structures to preserve substation electrical equipment from seismic induced damages.

Estimation of Required Slack for Conductors Connecting Substation Equipment Subjected to Earthquake

Typical electrical substation equipment items are usually connected to each other through flexible conductors. If the connections are not flexible enough, they may cause intense dynamic interaction between the equipment during an earthquake. This research is to analytically study the performance of different flexible conductor configurations used mostly in the interconnected substation items, as well as the effects of parameters. A set of three synthetic ground motions, which are matched with IEEE Standard 693 design spectrum, was created as the design input motions and two sample cases of interconnected equipment were considered to put the proposed method into practice. In order to evaluate the reliability of the proposed approach, two sets of real ground motions recorded on stiff soil were used to assess designed conductor configurations. The capability of the OpenSees model in simulating static and dynamic behavior of conductors is studied as well.

The Application of Communication for Inspection System in 500kV Transformer Substation

The monitoring of equipment capability has been strengthened by personnel to meet the inspection standard and intelligent in order to improve the reliability of substation electrical equipment and safety of operating. The system based on Bluetooth wireless communication technology has been pointed out to realize intelligent inspection substation. The system include monitoring terminals, transfer stations, control stations, and has the advantages of inspecting intelligent objectives, high data transmission speed, status inquiries and analysis of inspection equipment running etc.

Measuring Specificities of Dissipation Factor of Electrical Equipment in Substations

Measuring Specificities of Dissipation Factor of Electrical Equipment in SubstationsMeasuring techniques of dielectric losses tanδ of high voltage equipment are discussed and compared in this paper. There are several methods for determining tanδ and capacitance values in high voltage substation on site.Simple measuring methods like GST and UST can be put into practice without result corrections in ideal conditions. However electrical field in substation originates negative affect on measuring results, therefore different connection schemes of measuring methods have to be used.

Analysis Method and Abatement Measure of Magnetic Fields Emitted from Electrified Railway Substations

Recently, electromagnetic environments and electromagnetic compatibility (EMC) in relation to electrical equipment have become important issues. In 2008, the European Union established the EN 50500 standard, which provides measurement and calculation methods for determining magnetic fields emitted from electrical equipment on railways. The major frequency components of the electric and magnetic fields generated from such equipment are in the low range, such as D.C., 16.7 Hz, 50 Hz, 60 Hz and their low-order harmonics. According to the EN 50500 standard, magnetic fields are dominant around this kind of equipment. This paper describes the physical characteristics and analytical methods of low-frequency magnetic fields emitted from electrical equipment in railway substations, and proposes abatement measures and model substation designs based on the above results.

Improved seismic fragility modeling from empirical data

The improved empirical fragility model addresses statistical dependence among observations of seismic performances, which arises from common but unknown factors influencing the observations. The proposed model accounts for this dependence by explicitly including common variables in the formulation of the limit state for individual components. Additionally, the fact that observations of the same component during successive earthquakes are correlated is considered in the estimation of the model parameters. As demonstrated by numerical examples considering the fragility of electrical substation equipment, the improved formulation can lead to significantly different fragility estimates than those obtained with the conventional assumption of statistical independence among the empirical observations. Furthermore, the conventional approach underestimates the statistical uncertainty associated with the resulting fragility estimates. The paper concludes with an investigation of the effects of statistical uncertainty and component statistical dependence on the system fragility. Numerical examples demonstrate that these effects are significant and must be addressed in the analysis of redundant systems.

Seismic interaction in electrical substation equipment connected by non‐linear rigid bus conductors

AbstractAn important element within the power transmission lifeline is the electrical substation that typically consists of a complex set of equipment items interconnected through conductor buses or cables. If the connections are not sufficiently flexible, significant dynamic interaction may occur between the connected equipment items during a seismic event, which may result in damage and loss of the equipment. This paper investigates the interaction effect between electrical substation equipment items connected by non‐linear rigid bus conductors. The equipment items are modelled as single‐degree‐of‐freedom oscillators by use of appropriate shape functions. The hysteretic behaviours of rigid bus connectors are described by differential equation models fitted to experimental data. An efficient non‐linear random vibration method is used to quantify the seismic interaction effect of the connected equipment items. Based on the developed analytical models and method, the effect of interaction in the connected equipment system is investigated through extensive parametric studies. The results lead to practical charts and guidelines for the seismic design of interconnected electrical substation equipment. Copyright © 2006 John Wiley & Sons, Ltd.

Seismic Retrofit Using Spring Damper Devices on High-Voltage Equipment Stands

The Bonneville Power Administration (BPA) operates a significant portion of the electrical high-voltage transmission grid in the Pacific Northwest. As part of a long-term seismic mitigation program, BPA sponsors research into ways to minimize the vulnerability of existing electrical substation equipment. Passive energy dissipation devices add supplemental damping to improve the dynamic response of structures to earthquakes. One such mechanism, a friction spring damping device, utilizes a primary and secondary set of self-centering ring springs installed around a single end-mount load shaft to reduce peak accelerations. The adaptation of this technology to seismically retrofit existing high-voltage substation equipment single-pedestal support stand is the subject of this paper. Dynamic properties were determined from force-displacement and vibration tests. Full-scale earthquake transient tests conducted on a support stand equipped with friction spring devices resulted in substantial reductions of the in-plane peak accelerations in comparison to tests performed without the friction spring devices.

Generalized Bouc–Wen Model for Highly Asymmetric Hysteresis

Bouc–Wen class models have been widely used to efficiently describe smooth hysteretic behavior in time history and random vibration analyses. This paper proposes a generalized Bouc–Wen model with sufficient flexibility in shape control to describe highly asymmetric hysteresis loops. Also introduced is a mathematical relation between the shape-control parameters and the slopes of the hysteresis loops, so that the model parameters can be identified systematically in conjunction with available parameter identification methods. For use in nonlinear random vibration analysis by the equivalent linearization method, closed-form expressions are derived for the coefficients of the equivalent linear system in terms of the second moments of the response quantities. As an example application, the proposed model is successfully fitted to the highly asymmetric hysteresis loops obtained in laboratory experiments for flexible connectors used in electrical substations. The model is then employed to investigate the effect of dynamic interaction between interconnected electrical substation equipment by nonlinear time-history and random vibration analyses.