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Showing papers on "Electrical network published in 1986"


Journal ArticleDOI
TL;DR: In this paper, a fast algorithm was developed for automatic selection and ranking all possible circuits for corrective control by network switching to relieve system overloads, where the non-iterative DC approximate model for a power system was used to generate linear sensitivity factors.
Abstract: A fast algorithm is developed for automatic selection and ranking all possible circuits for corrective control by network switching to relieve system overloads. The non-iterative DC approximate model for a power system is used to generate linear sensitivity factors. These factors are calculated using relevant elements of the sparse bus impedance matrix and branch reactances. Special treatment of substation circuit breakers makes it possible to use bus-bar splitting for corrective action. The method was tested on two systems. Test results show the reliability and effectiveness of the method in selecting lines and circuit breakers for corrective overload control.

191 citations


Journal ArticleDOI
TL;DR: The penalty function - linear programming technique method is used in a complete reactive power dispatch solution algorithm, the performance of which is discussed by solving a 256-node, 58 control-variable test system.
Abstract: This work presents a linear programming based algorithm to solve reactive power dispatch problems. A mixed set of variables (generated voltages and reactive power injections) and the reactive power model of the fast decoupled load flow algorithm are used to derive linear sensitivities. A suitable criterion is suggested to form a sparse reactive power sensitivity matrix. The sparse sensitivity matrix is in turn modeled as a bipartite graph which is used to define an efficient constraint relaxation strategy to solve linearized reactive power dispatch problems. The penalty function - linear programming technique method is used in a complete reactive power dispatch solution algorithm, the performance of which is discussed by solving a 256-node, 58 control-variable test system.

129 citations


Journal ArticleDOI
TL;DR: In this article, the authors used the telegraph equations as a line model, voltage and current samples taken at one end of a line within the first 5 ms of fault inception are used to generate instantaneous voltage and currents profiles for the rest of the transmission line.
Abstract: The high frequency components in fault waveforms present undesirable effects to most fault location algorithms and as a consequence filtering of postfault signals, to remove the high frequency transients, is essential for accurate fault location. A fault location algorithm that derives from travelling wave principles can cope with high frequency transients since these basically depend on travelling wave phenomena. The development of such an algorithm is the objective of this paper. Using the telegraph equations as a line model, voltage and current samples taken at one end of a line within the first 5 ms of fault inception are used to generate instantaneous voltage and current profiles for the rest of the transmission line. The voltage and current estimation is based on the solution of the equations of the line model by the method of characteristics. Criteria functions involving any of the square of the voltage, the square of the current, or the product of the two are applied for determination of the fault position. Fault position is given by the peak variation in tangent to the above basic functions. The algorithm finds application in fault location on two and three-terminal networks at both transmission and distribution levels.

101 citations


Journal ArticleDOI
TL;DR: In this paper, an electronic compensator that can compensate the reactive current drawn by an arc furnace is presented, consisting of three independent single-phase pulsewidth modulated (PWM) inverters.
Abstract: This paper presents the design of an electronic compensator that can compensate the reactive current drawn by an arc furnace. Consisting of three independent single-phase pulse-width modulated (PWM) inverters, the proposed compensator responds quickly to any sudden load changes and compensates both the fundamental displacement current and the harmonic distortion current drawn by the load. Unlike conventional static var compensators, the electronic compensator can also supply the active current demanded by the load if an energy source independent of the utility is available. Simulations are conducted, including the modelling of the furnace current and voltage waveforms during the early stage of scrap melting, in order to determine the effectiveness of several suggested detection methods that can be used to separate the active and reactive components of the furnace current. Actual waveforms observed on a local furnace are included that corroborate the computer modelling. Experimental results indicate that the electronic compensator equipped with a suitable detection circuit can accurately compensate an arc furnace.

61 citations


Journal ArticleDOI
TL;DR: In this paper, the authors developed a new formulation of distribution factors which is suitable for the analysis of the reactive power problem, which is based on the S-E (complex power - complex bus voltage) representation of a power network instead of the usual I-E(complex current-complex bus voltage).
Abstract: During recent years, problems associated with reactive power flow and bus voltages have acquired greater importance. The transmission capacity may sometimes be limited by reactive power considerations. In a few instances collapse of transmission network has been attributed to abnormal reactive power flow patterns. Some recent papers have addressed the question of improving the contingency study techniques for the reactive power flow problem. A commonly used method for contingency analysis is based upon the use of distribution factors. The distribution factor method of contingency analysis is very fast in its execution time, and for this reason is widely used in real time applications as well as planning studies. This technique is known to be particularly suited to the study of real power redistribution following an outage. It is not as accurate in dealing with problems of reactive power flow redistribution and accompanying effects on bus voltages. The inaccuracies are particularly significant when voltage controlled buses are present in the power system. The distribution factors are based on approximating active power injections by current injections under the assumption that voltage magnitudes throughout the system are kept constant. This is an unacceptable assumption for reactive power. This paper develops a new formulation of distribution factors which is suitable for the analysis of the reactive power problem. The new formulation is based on the S-E (complex power - complex bus voltage) representation of a power network instead of the usual I-E (complex current - complex bus voltage) formulation.

53 citations


Journal ArticleDOI
TL;DR: In this article, a new operations research model of optimal load flow solved by nonlinear programming methods (the generalized reduced gradient algorithm) is presented, which incorporates network performance variables such as scheduled bus voltages as well as topological and elemental constraints.

48 citations


Patent
02 May 1986
TL;DR: In this article, a power-conserving apparatus for recording information in a well bore includes a plurality of independently energizable electrical circuits for receiving electrical signals from a transducer which senses an environmental condition, for processing the electrical signals, and for storing information related to the detected environmental condition.
Abstract: A power-conserving apparatus for recording information in a well bore includes a plurality of independently energizable electrical circuits for receiving electrical signals from a transducer which senses an environmental condition, for processing the electrical signals, and for storing information related to the detected environmental condition. A power control circuit is provided for continuously providing electrical power to at least one of the electrical circuits and for independently switchably providing electrical power to selectable ones of at least two others of the separately energizable circuits.

44 citations


Journal ArticleDOI
TL;DR: In this paper, an electrical power generation system for two nearby oilrigs is discussed, where the amounts of power that may possibly be supplied to the two oil-rigs are considered as system states.
Abstract: Fortunately traditional reliability theory, where the system and the components are always described simply as functioning or failed, is on the way to being replaced by a theory for multistate systems of multistate components. However, there is a need for several convincing case studies demonstrating the practicability of the generalizations introduced. In this paper an electrical power generation system for two nearby oilrigs will be discussed. The amounts of power that may possibly be supplied to the two oilrigs are considered as system states.

42 citations


Journal ArticleDOI
TL;DR: In this paper, the direct stability analysis of a power system in which both active and reactive power flows are considered is considered, and flux decay action is included in the generator model, and the load is modelled with complex load power as a function of both bus voltage magnitude and frequency.

29 citations


Journal ArticleDOI
TL;DR: The typical design of a power circuit now used to interface a dc system to the electric utility is such that a heavily distorted current is drawn from the utility as discussed by the authors, since this distortion has the potential to interfere with the normal operation of the utility and its load, efforts are underway to develop power-conditioning interfaces that draw a nearly harmonic free ac current waveform.
Abstract: The typical design of a power circuit now used to interface a dc system to the electric utility is such that a heavily distorted current is drawn from the utility. Since this distortion has the potential to interfere with the normal operation of the utility and its load, efforts are underway to develop power-conditioning interfaces that draw a nearly harmonic-free ac current waveform. The design of these interfaces is discussed. The salient issues of the power circuit's topology and its control are presented.

29 citations


Journal ArticleDOI
TL;DR: The development of a new three-port model of the thickness-mode piezoelectric transducer, employing linear systems theory, is presented, where a discrete bidirectional lattice is used to describe mechanical wave propagation and continuous transfer functions to represent the electrical parameters.
Abstract: Abstmct-The development of a new three-port model of the thickness-mode piezoelectric transducer, employing linear systems theory, is presented. A discrete bidirectional lattice is used to describe mechanical wave propagation and continuous transfer functions to represent the electrical parameters. When presented in block-diagram format, an extremely valuable insight is gained into the nature of piezoelectric interaction. The lattice concept is extended to the analysis of multilayered structures and, when implemented in the discrete time domain, close agreement with experimental data is obtained. A number of experimental and simulation results are included for comparison. I. INTRODUCTION ONVENTIONAL models of the thickness-mode piezoelectric transducer invariably utilize transmissionline analogs in which the electromechanical properties of the system are evaluated by means of electrical network concepts. Examples of this include the equivalent circuits of Mason [l] and the more recent KLM [2] model, which uses a center-tapped transmission line to model acoustic wave propagation. In this form both models are also readily adapted for the analysis of multilayered transducer structures. However, electrical analogs possess some disadvantages which limit their flexibility when applied to piezoelectric transducer modelling [3]. Physical insight into the nature of the transduction process is often masked, and as a'result the influence of external electrical and mechanical load conditions on transducer behaviour is difficult to determine. To overcome this, an alternative strategy has been proposed by Hayward [3] who adopted a systems feedback approach to

Patent
19 Mar 1986
TL;DR: In this article, a peak demand limiter is used to monitor a plurality of electrical circuits and selectively switch the circuit in a predetermined pattern based on priority selection, where a load detection circuit coupled to a logic processor generates and sends output data to control switches on preselected non-priority circuits.
Abstract: A peak demand limiter to monitor a plurality of electrical circuits and to selectively switch the circuit in a predetermined pattern based on priority selection comprises a load detection circuit coupled to a logic processor that generates and sends output data to control switches on preselected non-priority circuits.

Journal ArticleDOI
TL;DR: In this article, the amplitude and phase noise spectra of the internal and external fields of a negative resistance oscillator were derived using electrical circuit theory, and it was shown that the difference between external and internal fluctuations becomes important in the quantum domain where external noise sources are not negligible as they often are in the classical domain.
Abstract: The amplitude and phase noise spectra of the internal and external fields of a negative resistance oscillator are derived using electrical circuit theory. It is shown that the difference between internal and external fluctuations becomes important in the quantum domain ( h\omega > kT ) where external noise sources are not negligible as they often are in the classical domain ( h\omega ). Using established methods to describe quantum fluctuations in electrical circuits, we obtain results in full agreement with the more exact but less general direct quantum mechanical analysis of a Fabry-Perot laser in Part I.

Journal ArticleDOI
TL;DR: In this paper, a simple method for the determination of traction power substation spacings is developed for ac railroad electrification systems, which can be extended to include autotransformer systems and can also be used for calculation of substation spacings for dc light rail and heavy rail systems.
Abstract: A simple method for the determination of traction power substation spacings is developed for ac railroad electrification systems. Single-end-feed, center-feed, and double-end-feed systems with or without booster transformers can be represented, being the most common supply configurations. The method is extended to include autotransformer systems and can also be used for calculation of substation spacings for dc light rail and heavy rail systems. The entire power system is represented, including the electric utility system, the traction substations, the catenary system or third rail, the return current system, and the trains. Multitrack systems can be approximated, and effects of currents at harmonic frequencies produced by the electrical locomotives are evaluated. The mathematical description results in a number of equations suitable for microcomputer solution. The use of the method is demonstrated a sample case, and a convenient way of presenting the substation spacings for a given set of conditions is illustrated by the use of nomographs.

Journal ArticleDOI
TL;DR: In this paper, the output of a conventional transient stability program is analyzed using transient energy functions for individual generators, and the analyst is provided with a quantitative index of the degree of stability or instability for each generator.
Abstract: The output of a conventional transient stability program is analyzed using transient energy functions for individual machines. The analyst is provided with a quantitative index of the degree of stability or instability for each generator. This index is useful for guiding the selection of subsequent case studies. The transient energy consists of two components: kinetic and potential energy. In the post-disturbance period, profiles of the kinetic energy (VKE), the potential energy (VPE), and the time derivative of the potential energy (V?PE) are obtained. These are used to develop a criterion for the degree of stress on a disturbed but stable machine, and to assess the extent of instability for an unstable machine. The method of analysis has been tested on two power networks representing the system of the state of Iowa, and validated by studies on a Philadelphia Electric Co. network.

Journal ArticleDOI
TL;DR: In this paper, a method of analysis based on rigid water column theory for slow transients and steady-state flows in pipe networks is described, and a graph theoretic formulation yields a system of ordinary differential equations of the first order that describes the dynamic behavior of the network.
Abstract: A method of analysis based on rigid water column theory for slow transients and steady-state flows in pipe networks is described. A graph theoretic formulation yields a system of ordinary differential equations of the first order that describes the dynamic behavior of the network. A definite Liapunov function of quadratic form to prove asymptotical stability of the network at the steady state is derived from Tellegen’s Theorem in electrical circuit theory; this function gives a unique and precise criterion for the attainment of the steady state by the system. The time integration can be performed directly by using, for example, the Runge-Kutta method without involving any iterative procedure. Simulations of slow transients and dynamic relaxation processes to solve the steady-state flow problem are shown in terms of small networks.

DOI
01 Jul 1986
TL;DR: In this paper, the authors proposed a new and simple planning approach for transmission, sub-transmission and distribution networks, which considers all possible routes with the maximum allowable number of parallel circuits for each route.
Abstract: The capital investment required for transmission, subtransmission and distribution networks amounts to roughly over 50% of the total investment for the whole power system. Hence, the problem of planning these networks has received increased attention. The present paper proposes a new and simple planning approach. The process is initialised by considering all possible routes with the maximum allowable number of parallel circuits for each route. As loads and generation schedules are predetermined, system model equations are solved using matrix inversion to obtain line flows. A criterion is established to determine the least effective circuit or route to be chosen for removal in the next step. The line flow and removal procedure is repeated to achieve a planned network which will serve the load, without overloading the lines. Finally, an iterative procedure has been developed to realise the reliability level constraint.

Journal ArticleDOI
TL;DR: In this article, a large-scale simulation/optimization model provides schedules for operation of water and power for the California State Water Project (SWP), which consists of a series of reservoirs linked by rivers, pumping plants, canals, tunnels, and generating plants.
Abstract: A large-scale simulation/optimization model provides schedules for operation of water and power for the California State Water Project (SWP). The SWP consists of a series of reservoirs linked by rivers, pumping plants, canals, tunnels, and generating plants and is operated by the California Department of Water Resources. The Department provides water to municipal and agricultural users, and manages its electrical loads and resources. The model, therefore, performs hydraulic and electrical computations leading to optimal operation of the entire system. It consists of hydraulic network programming components to meet the storage objectives at all the reservoirs, a linear programming component to determine the schedules at pumping and generating plants, an electrical network programming component to balance electrical loads and resources, and a number of other simulation components. It operates on yearly, weekly, and daily bases. It is primarily used for real-time operation of the SWP and can provide hourly detail schedules which are implemented by the SWP staff via a computerized system.

Journal ArticleDOI
TL;DR: In this article, an automated on-line harmonic measurement system used by the authors is described along with the advantages of using such a system along with two specific examples showing the application of an automated ON-LINE HAR measurement system.
Abstract: Any industrial plant that has a considerable amount of rectification may experience harmonic-related problems (e.g., solid-state control circuit malfunctioning, communication noise, etc.). The application of power-factor correction capacitor banks to such a system will generally increase the likelihood of such problems occurring. To properly identify the cause of such problems and, in some cases, recommend solutions, an on-line analysis of the system may be necessary. This usually involves a harmonic analysis of the current or voltage waveforms observed in the electrical system. A description of an automated on-line harmonic measurement system used by the authors will be presented along with the advantages of using such a system. In addition, two specific examples showing the application of an automated on-line harmonic measurement system will also be presented.

Patent
01 Oct 1986
TL;DR: In this article, an electrical connector for selectively connecting various electrical circuits of a first vehicle to corresponding electrical circuit of a second vehicle is presented. But the connector includes variably positionable switches whereby no rewiring of either vehicle is necessary.
Abstract: An electrical connector for selectively connecting various electrical circuits of a first vehicle to corresponding electrical circuits of a second vehicle. The connector includes variably positionable switches whereby no rewiring of either vehicle is necessary. The housing for the connector is parallelepipedonal in form and the switches project from a major surface of the housing.

Journal ArticleDOI
TL;DR: The paper describes the computerized algorithm as well as numerical results for the IEEE 118-bus power system to demonstrate the applicability of the algorithm to actual systems.
Abstract: This paper presents a combined optimization/reliability technique to evaluate the reliability of large power systems. It uses Monte Carlo simulation for the individual operation/failure random performance of elements of a power network. This simulation overcomes the difficulty in constructing the many possible states for large power systems of complex topology. A simplified power-flow representation of the power network is used and a network reduction is implemented to reduce the size of the power-flow problem, such that only the effective part of the network (for a given contingency) is retained. The control parameters are optimized in order to simulate practical contingency situations in which suitable controls are invoked to preserve, as much as possible, the continuity of supply. The optimization problem is solved by linear programming in which the generator powers are manipulated as optimization variables to maximize the load power supplied and subject to the power flow equations as well as upper and lower bounds on the optimization variables. The outputs of the performance simulation and the optimization problem are subsequently used to compute the system reliability indices. The paper describes the computerized algorithm as well as numerical results for the IEEE 118-bus power system to demonstrate the applicability of the algorithm to actual systems.

Patent
19 Aug 1986
TL;DR: In this article, a residual current circuit breaker for insulation monitoring of electrical circuits has a total current transformer (8), the primary circuit of which consists of the outgoing and return lines (3, 4) of the circuit to be monitored and whose secondary winding (15) acts on an electronic limit value circuit (17) that operates an electromagnetic one controls holding device (32) with switch contacts (5, 6) for switching off the circuit when a certain fault current is exceeded.
Abstract: A residual current circuit breaker for insulation monitoring of electrical circuits has a total current transformer (8), the primary circuit of which consists of the outgoing and return lines (3, 4) of the circuit to be monitored and whose secondary winding (15) acts on an electronic limit value circuit (17) that operates an electromagnetic one Controls holding device (32) with switch contacts (5, 6) for switching off the circuit to be monitored when a certain fault current is exceeded. In order to achieve self-monitoring, according to the invention, a current which briefly simulates a fault current is periodically fed into an additional winding (24) of the summation current transformer (8), and the pulse voltage thus generated at the output of the electronic limit value circuit (17) is sent to an evaluation circuit (18 to 40) supplied, which causes the switching contacts (5, 6) to open when the periodic impulses fail via the electromagnetic holding device (32).

Journal ArticleDOI
TL;DR: In this paper, a simple algorithm for the real-time measurement of power system frequency is proposed, using simple microprocessor hardware results of acceptable accuracy can be obtained in the presence of substantial DC and harmonic components.

Journal ArticleDOI
01 May 1986
TL;DR: In this paper, the effect of paralleling electric circuits has been long understood by the electrical engineer and proper engineering has led to solutions to most of these problems, however, a problem has developed with the addition of pipelines to the electrical corridors or, conversely, electrical lines to the pipeline corridors.
Abstract: In recent years, a trend has developed toward building energy corridors which better utilize land resources. Due to the adverse environmental impacts of building electrical power lines by utility companies and the installation of pipelines by the petrochemical industry, many governmental entities are requiring that electric power lines and underground pipelines use the same transmission (energy) corridor. The energy corridor, by design, is used to minimize the land requirements for transmitting energy?whether by electrical transmission lines or through pipelines. The energy corridor does not necessarily minimize the lengths of transmission lines but, conversely, may require longer lines to utilize the land resources better by paralleling transmission systems. The electric power companies have utilized this practice in the past with electrical corridors and are being pressured to make every effort to parallel electric lines in the future on these same corridors. The effect of paralleling electric circuits has been long understood by the electrical engineer. Induced currents and voltages occur between the electrical circuits and may cause relaying, communications, and safety problems. Proper engineering has led to solutions to most of these problems. A problem has developed with the addition of pipelines to the electrical corridors or, conversely, electrical lines to the pipeline corridors. The problem is that the pipeline has become part of the electrical circuit due to electrostatic and electromagnetic coupling. This coupling may cause induced currents and voltages to exist on the pipeline. The pipeline is addressed as an electrical circuit.

Journal ArticleDOI
TL;DR: In this paper, the problem of designing co-ordinated stabilizers in a multi-machine environment is addressed by using linear state space methods to design coordinating stabilizing inputs for the exciter and governor loops.
Abstract: This paper describes the application of multi-variable control design methods to the problem of designing co-ordinated stabilizers in a multi-machine environment. Linear state space methods are used to design co-ordinating stabilizing inputs for the exciter and governor loops, based on a number of local outputs. The dynamics of the multi-machine power system are taken into account by determining a dynamic equivalent model of the power system as seen from the transformer bus of the design generator. This is accomplished using identification techniques as described in a previous paper[2]. The generator equations are linearized and combined with this dynamic equivalent of the remainder of the power system, resulting in a reduced order representation of the combined system. Linear optimal control methods are then used to determine the co-ordinated controller. The effects of nonlinearities are taken into account by experimenting with different cost function weightings. The method is demonstrated by applying it to a generating station in an example 63 bus power system with a total of 59 generators represented.

Patent
07 Feb 1986
TL;DR: In this article, a remotely controlled assembly for controlling the electrical power to an electrical load having an electrical circuit was presented, in response to a predetermined female threadable radio signal which was supported by a housing (16) which had a receptacle contact (38) for receiving the electrical load and a male threadable contact (42) for securing the housing in an electrical receptacle for receiving power.
Abstract: A remotely controlled assembly (10) for controlling the electrical power to an electrical load having an electrical circuit (14) for controlling the electrical power supply to the electrical load in response to a predetermined female threadable radio signal which is supported by a housing (16) which has a receptacle contact (38) for receiving the electrical load and a male threadable contact (42) for securing the housing (16) in an electrical receptacle for receiving power.

Patent
31 Jan 1986
TL;DR: In this paper, the authors describe a building electrical network including a power circuit constituted by several loops connected to sockets, lamps, lamps 35, 36, 37 and/or other electrically-operated apparatus, and a low-voltage circuit comprising of several loops controlled to control means or sensors 38, 39, 40, 41 for controlling the loops of the power circuit.
Abstract: In a building electrical network including a power circuit constituted by several loops connected to sockets, lamps 35, 36, 37 and/or other electrically-operated apparatus, and a low-voltage circuit constituted by several loops connected to control means or sensors 38, 39, 40, 41 for controlling the loops of the power circuit, each loop of the low-voltage circuit and the corresponding loop of the power circuit are interconnected through a removable switching module 16 located in a centralized switching block 5. The low-voltage loops are not directly connected to terminals 12, 14 of the switching block, but are connected to terminals 45, 47 of a terminal strip 6, jumpers 46 establishing the connection between the terminals of the terminal strip(s) 6 and the terminals 12, 14 of the switching block 5. The plug-in switching modules 16 include an electronic relay member 21 (e.g. an optocoupler) and a power circuit switching component 23 which may perform various functions (remote ON/OFF, remote dimming, timing, etc.).

Journal ArticleDOI
TL;DR: A new model generator implementation in which a microprocessor solves the discretized generator dynamic equations is described, implemented using digital hardware.
Abstract: A major shortcoming of real-time analog power system simulators has been the lack of an inexpensive and flexible dynamic generator model. This paper describes such a model, implemented using digital hardware. Issues which are addressed in the design include model-to-network interfacing, stability, accuracy, and processor architecture. Simulation results of the resulting model generator are presented. Real-time power system simulation is typically carried out on a scale model of the power system known as a Transient Network Analyzer (TNA), which consists primarily of passive component models of power system elements such as transmission lines and transformers. Several dynamic generator models have been constructed for use with TNA's with varying degrees of success. [1,2] The primary shortcomings of these implementations have been high cost and lack of flexibility. This paper describes a new model generator implementation in which a microprocessor solves the discretized generator dynamic equations. Interface to the TNA is via analog-to-digital and digital-to-analog converters. A few of the advantages to this approach are: the parameter values are easy to change, the mathematical model itself is easily modified, and the hardware is inexpensive.

Patent
29 Oct 1986
TL;DR: In this article, an electrical time constant that approximates a thermal time constant of a semiconductor device is used to compensate for temperature dependent operating characteristics of the semiconductor devices, and a control voltage is applied to the device with a sense for substantially negating temperature dependent deviations of the operating characteristic of the device.
Abstract: Apparatus for compensating a temperature dependent operating characteristic of a semiconductor device includes a compensation circuit which exhibits an electrical time constant closely approximating a thermal time constant of the semiconductor device. A control voltage exhibiting the electrical time constant is applied to the semiconductor device with a sense for substantially negating temperature dependent deviations of the operating characteristic of the semiconductor device.

Journal ArticleDOI
TL;DR: In this paper, three pole assignment methods using output feedback have been employed to design a suitable controller in order to improve the dynamic stability characteristics of a two input-output time-invariant linear model of an unregulated turbogenerator (supplying power to an infinite grid through a transformer and a highvoltage transmission line).