T2 conductor consists of two standard stranded conductors twisted about one another with a twist length of approximately 9 feet. Because of its aerodynamic and mechanical properties, the conductor is resistant to both galloping and aeolian vibration. Extensive field tests and laboratory tests were performed to verify the reduction in amplitude and frequency of wind induced motions with T2. As a result of these studies it is possible to string T2 to higher unloaded tensions and thus reduce structure height and/or the number, of structures per mile. An economic analysis is presented wherein the economic benefits of increased tension and decreased phase to phase spacing are measured against the increase in wind and ice loading characteristic of T2. It is concluded that the conductor offers significant advantages in decreased cost and/or increased reliability in common line design situations.
A project was undertaken to test the validity of the electromagnetic transients simulation of dc links using digital computer programs. The Nelson River dc transmission system of both Bipoles One and Two were modeled on the computer using Manitoba Hydro's EMTDC program. The well known Electromagnetic Transients Program EMTP was also used for small reduced system models. Results from actual system tests were used to compare with the computer simulation of the same test. Comparisons are also made between EMTDC and EMTP as simulation tools for studying dc transmission. Computer simulation of dc links is presented as a valid option to the use of real time hard wired simulators.
Field tests on the subject switching of capacitive currents with disconnectors were carried out in a 420 kV Gas Insulated Substation (GIS). The overvoltages and transients occurring were recorded at several points within the GIS while different disconnectors were operated.
American Electric Power's (AEP) Static Var System (SVS) was placed in service at the Beaver Creek Station in eastern Kentucky in November 1980 and has since maintained an excellent record of operation. The purpose of this SVS installation was to provide both steady-state and dynamic voltage control on the 138 kV transmission system. This paper describes the application and operating experience of this unique installation, which is comprised of two thyristor controlled reactors (TCR) and two thyristor switched capacitors (TSC) with an overall dynamic range of ±125 MVAR. These components are connected to the 138 kV transmission system via a 125 MVA, 138/ 8.3 kV transformer. The +125 MVAR upper limit has been extended to +325 MVAR by installing four 50 MVAR, 138 kV capacitor banks which, in effect, function as a steady-state voltage control to optimize the SVS dynamic range.
The Athens Automation and Control Experiment is a hardware/software-oriented research and development project [1]. The basic purpose of the experiment is to automate the distribution system and to develop and test control strategies that improve the efficiency and controllability of the power system. The hardware system will be installed on the Athens Utilities Board distribution system in Athens, Tennessee. The experiments are being designed to develop and test load control, volt/var control, and distribution automation functions [2]. Since this project is sponsored by the Electric Energy Systems Division of the U. S. Department of Energy and by the Electric Power Research Institute, the transference of experimental results to the electric utility industry is a primary objective.
Subsynchronous torsional resonances have interacted with subsynchronous network resonances to cause shaft failures-in synchronous generators. But what of their interactions in the supersynchronous span of the frequency spectra? Are they safe? These questions have become relevant as more network resonances are being added to the power system through the increasing use of static VAR compensators and their smoothing filters. The paper offers a few answers to these questions using the phase modulation theory of the torsional interaction phenomenon.
In this paper (Part I) and two companion papers (Part II and Part III) the problem of volt/var control on general radial distribution systems is formulated, simplified and solved. The objective is to minimize the peak power and energy losses while keeping the voltage within specified limits under varying load conditions. The decision variables to be optimally determined are (i) the locations, sizes and the real-time control of the specified number of ON/OFF switched and fixed capacitors and (ii) the locations and real-time control of the minimum number of voltage regulators. It is shown in this paper (Part I) that the regulator (volt) and the capacitor (var) problem may be treated as two decoupled problems. Part II of this set of three papers, conjoined with part I, provides the analytical tools by which optimal solutions for both problems may be determined. Application of the theory to representative radial systems is shown in Part III which also illustrates the ecomonic benefits and numerical results achievable through both regulation and compensation schemes.
This paper describes a new technique that has been developed to facilitate the preparation of frequency and duration models for large composite systems. These models are required for power system reliability and probabilistic production cost evaluations. The technique is based on the sequential composition and state aggregation of component subsystems and composite partial systems. A significant feature is the fact that state aggregation is performed at the subsystem level rather than the final system level. This has important computational consequences since it greatly reduces the number of states that must be stored and manipulated during the computational process.
Compressed air energy storage (CAES) is a resource being evaluated by Houston Lighting and Power Company (HL&P). There is underground salt formation suitable for CAES development around HL&P's service area. This paper presents the results of a preliminary economic analysis of a 660 MW CAES plant in 1994 in comparison with a coal/lignite plant. Sensitivity analysis was conducted to examine the effect of off-peak charging energy from outside systems and the effect of gas prices. Results indicated that the CAES plant had a benefit to cost ratio of 1.15 which would be raised above 1.5 if off-system charging energy at a reasonable price could be obtained. Decreasing gas price would favor CAES in comparison with coal or lignite. The CAES plant in operation would save 5 to 13 million mcf of gas per year.
A new approach is discussed to the finite element analysis of eddy currents flowing in parallel conductors in transformer windings. Simplified equivalent circuits are introduced in the formulation of the scalar potential, that is indispensable in the analysis of the eddy current problems, thereby clarifying its physical meanings and showing a general formulation procedure. The validity of the approach thus developed is verified through evaluating results of calculations by circuit equations. In addition, the approach was applied to a model transformer and the analysis results were compared with those measured with respect to the circulating currents flowing in the parallel conductors that make up a transformer winding.
This paper presents a new predictive approach to the intertacing of rotating electric machinery for the transient analysis of universal multi-machine systems, i.e., the machines contained in the system may be of different types-such as induction, synchronous, doubly-fed and direct-current machines, Basic considerations and theory underlying the approach are covered. The corresponding interfacing scheme is shown to be crucial to certain machine types. The approach has been successfully implemented to the Universal Machine module of the well-known Electromagnetic Transients Program (EMTP). Application to test cases involving rather severe transient conditions demonstrates the lack of any interfacing-error amplification. Gain in computational efficiency by application of the proposed interfacing, rather than interfacing as based on phase compensation, is significant.
In many situations of power system restoration or emergency control load flow, often dynamic load flow, results are needed at a time scale which makes regular load flow computations impractical. In this paper a low order dynamic model is introduced which retains fully detailed and precise representation of the critical components (such as strong backbone lines like EHV or weak tie lines) where the interest is focused and reduces the detail of representation of other parts of the system gradually with their distance from the spotlighted sections where details are needed. The result is a low order and hence very fast computation with not only detailed but also quite precise results for those parts of the system which are critical. This approach is very flexible, it can be used to compute tie line load and frequency swings on an interconnection of areas or static loads on the tie lines of such a system affecting third parties in a power trading situation. It can be used to compute precisely and fast the EHV system loads or any combinations of such elements. The operator is quite free to choose what should be represented in precise detail.
Some of the torsional modes of oscillation of turbine-generator multimass shaft systems can be destabilized through the control action of high speed electrohydraulic turbine governing systems. This form of destabilization surfaced during the commissioning of one of Ontario Hydro's 665 MVA nuclear units. The causes of the problem were identified by measurements taken during the commissioning process and a detailed study of the control system. Conclusions reached as to the causes were supported by computer modelling. More accurate valve linearization circuits and filtering of shaft torsional components in the governor speed signal resolved the problem. A recommendation is made for direct monitoring of shaft torsional components, at least during the commissioning process.
A wide range of techniques have been proposed for reliability evaluaticn in composite generation and transmission systems. Many of the proposed methods are basically variations on fundamental approaches to the problem. Over the years, however, it has become obvious that there are in general, basic conceptual differences between the techniques used in Europe, particularly Italy and France and those utilized in North America. This paper briefly illustrates some of the fundamental differences between these techniques for composite system reliability evaluation by applicaticn to the IEEE Reliability Test System.
The established principles of multiterminal dc transmission are applied to the planning needs of practical projects. Without further detailed review of operating techniques, possibilities and contraints that are intended to be useful in the assessment of potential projects are discussed. Reference is made to the plans for certain schemes and the status of dc circuit breakers is reviewed.
For years no replacement parts have been available for electromechanical voltage regulators supplied by various manufacturers. The Tennessee Valley Authority (TVA) has developed a solid-state replacement for these obsolete voltage regulators. This regulator has proven to be reliable and inexpensive compared to other systems provided as alternatives.
The texture of the power system which govern, the interplay of reactive power and voltage is emulated by a textured model which assembles local groups of buses into a multi-leaf structure. Groups on the same leaf of the model are not coupled with each other, groups on different leaves overlap partially and are thus coupled. The paths of computational information are organized in an efficient manner and inefficient computation and information paths are eliminated, yet the computation converges to the exact solution, not an approximate one. The resulting model is ideally suited for parallel processing especially since there is no sequential component in the computation no computation overhead and (if the size of the groups and their numbers per leaf are uniform) there is no waiting time. Computation time savings of as much as 100÷1 (i.e. a hundred fold saving) were observed in experiments on steepest descent algorithms with systems of around 100 buses. Computation times also favorably compare with existing speed up techniques such as block pivoting. Computation times for common algorithms (like matrix manipulations, Newton-Raphson, linear and nonlinear programming) increase with the system size at a fast non- linear rate. The computation times remain essentially constant for the textured model in parallel processing. Thus very large computation time savings are implied on larger systems. Consequently this new model should prove to be a valuable tool for on line computations in the course of reactive power control and management.
The paper summarizes the results from Phase I of EPRI Research Project 1782-1 (EPRI Report EL-3501). Fifteen utilities supplied data on failures and operating parameters for more than 34,000 miles of HMWPE- insulated cables and 47,000 miles of XLPE-insulated cables. Data reduction and statistical analyses identified important predictors of high failure rates. For HMWPE, these are age, operating stress, and year of installation. Age and insulation wall thickness are the most important predictors of high failure rates for XLPE cable.
The operation of On Line Tap Changing (O.L.T.C.) transformers is subject to many power system variables and characteristics. These conditions include voltage variations, load fluctuations, transformer configurations and settings of tap changing relays. In this paper a graphical method is presented which simplifies analysis of O.L.T.C. transformer operation for variation in all the power system parameters. The graphical method eliminates the need for tedious repetitive calculations and allows the distribution engineer to readily determine transformer tapping requirements. The tapping range compatability of existing transformers can easily be determined in addition to the optimisation of system voltage float levels.
