Showing papers in "IEEE Transactions on Power Delivery in 1996"
TL;DR: In this article, the authors propose definitions for power terms in alternating current systems that are practical and effective when voltage and/or currents are distorted or unbalanced, and also suggest definitions for measurable values that may be used to indicate the level of distortion and unbalance.
Abstract: Existing definitions for power terms in alternating current systems work well for single-phase and three-phase systems where both voltages and currents are sinusoidal with respect to time. This paper clarifies and proposes definitions for power terms that are practical and effective when voltage and/or currents are distorted and/or unbalanced. It also suggests definitions for measurable values that may be used to indicate the level of distortion and unbalance.
342 citations
TL;DR: In this article, the Simplex two-phase method was used to determine coordinated relay settings for protecting a distribution network. But, the relay settings were not considered in this paper.
Abstract: An adaptive system for protecting a distribution network should determine and implement relay settings that are most appropriate for the prevailing state of the power system. This paper presents a technique for determining coordinated relay settings. The technique uses the Simplex two-phase method; Phase I determines whether the constraints selected for illustrating the conditionality between primary and back up relays are feasible, and Phase II finds the optimal relay settings. A looped distribution system, protected by directional overcurrent relays, was used for testing the technique. The tests were conducted in a laboratory environment; some results from those tests are reported in the paper.
324 citations
TL;DR: In this paper, a new formulation for power system sectionalizing device placement taking into consideration outage, maintenance and investments costs is presented, where a solution methodology based on the optimization technique of simulated annealing is proposed to determine: (i) the number of switches; and (ii) the locations of the switches.
Abstract: This paper presents a new formulation for power system sectionalizing device placement taking into consideration outage, maintenance and investments costs. The formulation of sectionalizing switches is a combinatorial constrained optimization problem with a nonlinear, nondifferentiable objective function. A solution methodology based on the optimization technique of simulated annealing, is proposed to determine: (i) the number of sectionalizing switches; and (ii) the locations of the switches. The proposed solution methodology can offer a global optimal solution for the sectionalizing device placement problem which includes the reliability, investment and maintenance costs.
300 citations
TL;DR: In this article, a technique for power system fault location estimation which uses data from both ends of a transmission line and which does not require the data to be synchronized is described, which can be easily applied for offline analysis.
Abstract: A technique for power system fault location estimation which uses data from both ends of a transmission line and which does not require the data to be synchronized is described. The technique fully utilizes the advantages of digital technology and numerical relaying which are available today and can easily be applied for offline analysis. This technique allows for accurate estimation of the fault location irrespective of the fault type, fault resistance, load currents, and source impedances. Use of two-terminal data allows the algorithm to eliminate previous assumptions in fault location estimation, thus increasing the accuracy of the estimate. The described scheme does not require real-time communications, only offline post-fault analysis. The paper also presents fault analysis techniques utilizing the additional communicated information.
280 citations
TL;DR: The wavelet transform of a signal consists in measuring the "similarity" between the signal and a set of translated and scaled versions of a "mother wavelet" as discussed by the authors.
Abstract: This paper introduces wavelets and shows that they may be efficient and useful for power distribution relaying. The wavelet transform of a signal consists in measuring the "similarity"between the signal and a set of translated and scaled versions of a "mother wavelet". The "mother wavelet" is a chosen fast decaying oscillation function. Wavelets are used to analyse transient earth faults in a 20 kV resonant grounded network as generated by EMTP. It is shown that wavelets may be employed for analysing records to study efficiently the faulted network. Moreover, this new technique can actually be implemented in real time for protection devices. Thus, it is suitable for application to protective relays.
273 citations
Journal Article•
TL;DR: In this article, the authors summarized the works of an IEEE Task Force focused on development of modeling guidelines for fast front transients (i.e., frequency range from 10 kHz up to 1 MHz).
Abstract: This paper summarizes the works of an IEEE Task Force focused on development of modeling guidelines for fast front transients (i.e., frequency range from 10 kHz up to 1 MHz). These guidelines are intended to be used by engineers involved in digital simulations of electro-magnetic transients, with particular emphasis on lightning surge analysis of overhead lines and substations. Modeling philosophies, simplified mathematical relationships, typical data, and examples are given for various power system components. To illustrate the overall modeling procedure, a case study has been presented.
246 citations
TL;DR: A successive linear programming methodology is presented to treat more effectively those applications where a local structure change is performed to a power system already in operation, and where the modification of the settings of already existent relays is not desirable.
Abstract: A successive linear programming methodology is presented to treat more effectively those applications where a local structure change is performed to a power system already in operation, and where the modification of the settings of already existent relays is not desirable. The dimension of the optimization problems to be solved is substantially reduced, and a sequence of small linear programming problems is stated and solved in terms of the time dial settings, until a feasible solution is reached. With the proposed technique, the number of relays of the original system to be reset is reduced substantially. It is found that there is a trade-off between the number of relays to be reset and the optimality of the settings of the relays.
244 citations
TL;DR: In this paper, a complete protection system was designed for the New England 39-bus system and the hidden failure modes were used to develop regions of vulnerability and a vulnerability index, which would help alleviate the problems posed by hidden failures.
Abstract: Major blackouts of electric power systems in which many customers are left without power are rare events. However, the effects of blackouts, for instance, can be catastrophic. It has been observed that protective system failures are a contributing factor in a large proportion of these blackouts. The most troublesome protection system failures are hidden failures, which remain dormant during normal system conditions, and are exposed during system disturbances. A study of hidden failures of the protective systems is undertaken to uncover their modes of failures, and to determine means of supervising their actions in times of highly stressed power system operations. The main contribution of this paper is to develop and document a method of quantitative analysis of the significance of hidden failures of protection systems. A complete protection system was designed for the New England 39-bus system and the hidden failure modes were used to develop regions of vulnerability and a vulnerability index. Through this analysis, critical protection systems, whose hidden failures would have a major impact on cascading failures or blackouts of the power system, can be identified These protection systems are candidates for increased monitoring and control, which would help alleviate the problems posed by hidden failures.
209 citations
TL;DR: In this paper, the authors demonstrate a near shot noise limited in-line Sagnac interferometer current sensor, which is shown to have a number of advantages over the optical current sensors based on polarimetric Faraday and Faraday/Sagnac loop topologies, including lower sensitivity to environmental disturbances, less demanding optical components and easy installation.
Abstract: The authors demonstrate for the first time a near shot noise limited in-line Sagnac interferometer current sensor. It is shown to have a number of advantages over the optical current sensors based on polarimetric Faraday and Faraday/Sagnac loop interferometer topologies, including lower sensitivity to environmental disturbances, less demanding optical components, and easy installation. Its application to power system measurements is also detailed.
206 citations
TL;DR: In this paper, a project undertaken by the Electric Power Research Institute (RP 3022-7) as part of its research on Flexible AC Transmission is described, which avoids dependence on temperature measurement, instead, calculating critical equipment component temperatures based solely on real-time weather and electrical current.
Abstract: ANSI standards for power equipment, and a vast store of technical literature, describe various methods by which thermal ratings may be adjusted if actual weather conditions are known or if the "overload" is to be applied for a limited period of time. These methods have been given various names including dynamic thermal rating, on-line rating, and dynamic ratings to describe the process of adjusting thermal ratings of power equipment for actual weather conditions and actual electrical load patterns. This paper discusses in detail a project undertaken by the Electric Power Research Institute (RP 3022-7) as part of its research on Flexible AC Transmission. This project avoids dependence on temperature measurement, instead, calculating critical equipment component temperatures based solely on real-time weather and electrical current. Inexpensive, commercially available weather stations, digital data loggers, and IBM-compatible PC computers are combined with sophisticated thermal algorithms to yield a portable, flexible, instrumentation method which can rate several transmission circuits simultaneously, including underground cable, overhead lines, power transformers, current transformers, switches, bus, line traps, and circuit breakers. Useable increases of 5% to 15% in the thermal capacity of transmission equipment circuits result.
196 citations
TL;DR: In this paper, the effect of a unified power flow controller (UPFC) on transient stability margin enhancement of a longitudinal power system is analyzed, and three controllable UPFC parameters are determined during the digital simulation process performed by the NETOMAC simulation program.
Abstract: The aim of the paper is to analyze the effect of a unified power flow controller (UPFC) on transient stability margin enhancement of a longitudinal power system. To utilize the UPFC possibilities fully, the three controllable UPFC parameters were determined during the digital simulation process performed by the NETOMAC simulation program. The basis for determination of the suitable damping strategy and for determination of the optimal UPFC parameters is a mathematical model, which describes the interdependence between longitudinal transmission system parameters, operating conditions and UPFC parameters in the form of analytical equations. On the basis of the mathematical model, the theoretical UPFC limits were also detected, and their appearance explained.
TL;DR: In this article, the instantaneous active-reactive power and current on /spl alpha/-/spl beta/ orthogonal coordinates have been defined by the so-called p-q theory.
Abstract: This paper proposes a new definition of the instantaneous active-reactive current and power based directly on instantaneous space vectors on polar coordinates, and presents its application. The definition is applicable in three-phase three-wire systems. The instantaneous active-reactive power and current on /spl alpha/-/spl beta/ orthogonal coordinates have been defined by the so-called p-q theory. In comparison with the p-q theory, our new definition offers a lucid physical concept for the active-reactive current and power in three-phase circuits. The new method, thus, can decompose current into the instantaneous active and reactive currents without calculating the instantaneous active and reactive powers. An application example is presented to confirm the validity and practicability of the new definition using digital simulation.
TL;DR: In this paper, the optimal locations of a limited number of harmonic meters and the optimal dynamic estimates of harmonic source locations and their injections in unbalanced three-phase power systems are solved using Kalman filtering.
Abstract: In this paper, two problems have been addressed on harmonic sources identification: the optimal locations of a limited number of harmonic meters and the optimal dynamic estimates of harmonic source locations and their injections in unbalanced three-phase power systems. Kalman filtering is used to solve these problems. System error covariance analysis by the Kalman filter associated with a harmonic injection estimate determines the optimal arrangement of limited harmonic meters. Based on the optimally-arranged harmonic metering locations, the Kalman filter then yields the optimal dynamic estimates of harmonic injections with a few noisy harmonic measurements. The method is dynamic and has the capability of identifying, analyzing and tracking each harmonic injection at all buses in unbalanced three-phase power systems. Actual recorded harmonic measurements and simulated data in a power distribution system are provided to prove the efficiency of this approach.
TL;DR: In this paper, the authors present a method for time-domain transient calculation in which frequency-dependent transmission lines and cables are modeled in the phase domain rather than in the modal domain.
Abstract: This paper presents a method for time-domain transient calculation in which frequency-dependent transmission lines and cables are modeled in the phase domain rather than in the modal domain. This avoids convolution due to the modal transformation, and possible numerical instability due to mode crossing. In the new approach, time domain convolutions are replaced by an ARMA (auto-regressive moving average) model that minimizes computation and is EMTP-compatible. A fast and stable method to produce the ARMA model is developed, and results are shown to agree well with both rigorous frequency-domain simulations and also field tests.
TL;DR: In this paper, a new time domain controlled voltage source (CVS) model for an arc furnace using the Electro Magnetic Transients Program (EMTP) is presented, which is based on a piecewise linear approximation of the V-I characteristic of the arc furnace load.
Abstract: This paper presents a new time domain controlled voltage source (CVS) model for an arc furnace using the Electro Magnetic Transients Program (EMTP). The developed model is based on a piecewise linear approximation of the V-I characteristic of the arc furnace load. In addition to this, the novelty of this simulation technique lies in the fact that the active power consumed by the load is also considered in the proposed load model, thus making the proposed load model dependent on the operating conditions of the load. Dynamic variation of the arc is incorporated through sinusoidal and band limited white noise variation of the arc resistance in the V-I characteristic of the arc furnace load. Depending on the variation of the arc resistance, the developed load model accurately represents both static (deterministic) and dynamic (random) arc characteristics. While static arc models are useful for harmonic studies, dynamic models are useful for power quality studies and in particular, the study of voltage flicker. The results are compared with actual voltage measurements taken from a local utility to prove the validity of the proposed load model.
TL;DR: A real-time load modeling technique which incorporates the use of customer class curves and provides a measure of the uncertainty (statistics) in the estimates, which also incorporates the possibility of multiple line flow measurements and makesUse of customer billing information.
Abstract: Due to the limited availability of telemetered data on distribution circuits, an integral part of any practical distribution circuit state estimator is a load modeling procedure that provides estimates of load demands at all circuit nodes. Traditional load modeling techniques used for distribution power flows are designed for power system peak studies, and are not suitable for providing real-time statistical load estimates. This paper presents a real-time load modeling technique which incorporates the use of customer class curves and provides a measure of the uncertainty (statistics) in the estimates. It also incorporates the possibility of multiple line flow measurements and makes use of customer billing information. The load modeling technique is combined with a probabilistic distribution circuit state estimation algorithm. Results of the combined load modeling and state estimation algorithm are provided on an actual 934-bus distribution circuit illustrating its feasibility.
TL;DR: In this paper, the authors provide a quantitative measurement of the benefit that a unified power flow controller (UPFC) can provide to increase power transfer between two large power systems, including a complete model for a UPFC control system that contains bus voltage control by the shunt inverter, real power transfer and reactive power control for the transmission line into which the series inverter is inserted.
Abstract: This paper provides a quantitative measurement of the benefit that a unified power flow controller (UPFC) can provide to increase firm power transfer between two large power systems Included is a complete model for a UPFC control system that contains bus voltage control by the shunt inverter, real power transfer between the shunt and series inverters, and real and reactive power control for the transmission line into which the series inverter is inserted A significant part of the model is representation of dynamic limits that coordinate injected current limits for the shunt inverter, power transfer limits between inverters, voltage injection limits for the series inverter, current limits for the series inverter and line voltage limits for the transmission line This paper contains a simple power system simulation to demonstrate the coordinated dynamic control and illustrate issues that power system planning engineers consider in defining applications for a UPFC
TL;DR: In this article, a load survey system is proposed to determine the load characteristics of various customer classes in an electric utility company, where questionnaires are adopted to find the power consumption of key electric appliances.
Abstract: This paper proposes a load survey system to determine the load characteristics of various customer classes in an electric utility company. The questionnaires are adopted to find the power consumption of key electric appliances. The actual power consumption of hundreds of customers are collected by intelligent meters. Sampling theory has been applied to find the proper sample size of both questionnaires and field tests so that the customer load characteristics will be derived with sufficient confidence level. Statistical analysis is then performed to find the power consumption model of each customer class based on the power measurement of field tests. The temperature effect on the power consumption of each customer class is also investigated by differentiating the proposed power consumption model with respect to the ambient temperature. The proposed method has been adopted by the Taipower company to better understand the customer load characteristics to support various functions of power system planning and operation in a more effective manner.
TL;DR: In this paper, the authors investigated a scheme to improve the reach measurement of distance relays and fault locators for series compensated power lines, where a deterministic method and a feed forward neural network method have been implemented for online calculation of the voltage across a nonlinear capacitor installation.
Abstract: This paper investigates a scheme to improve the reach measurement of distance relays and fault locators for series compensated power lines. A deterministic method and a feedforward neural network method have been implemented for online calculation of the voltage across a nonlinear capacitor installation. These techniques are compared and incorporated into a new relaying scheme which is independent of the series capacitor installation, operation of the capacitor protection, and the surrounding power system elements. The proposed scheme is simple and accurate and requires only local voltage and current at the bus. Detailed testing using EMTP has been done to show the benefits of the new adaptive scheme. The results demonstrate the suitability of the techniques for real world applications.
TL;DR: In this article, the effects of various factors, including wind velocity, ice thickness, dry arcing distance of insulators, and conductivity of freezing water, on the flashover performance of a short string of IEEE standard insulators were investigated.
Abstract: This paper first presents two methods for testing insulators under icing conditions. These methods were based on and developed from those described in the standard of IEC 507, which gives instructions for testing insulators under pollution. Then, the effects of various factors, including wind velocity, ice thickness, dry arcing distance of insulators, and conductivity of freezing water, on the flashover performance of a short string of IEEE standard insulators, were investigated. The experiments were carried out in a cold room. Moreover, the repercussions of ice on actual insulators were evaluated by examining the maximum withstand stress of the insulators employed on Hydro-Quebec networks and, by comparison, the effects of ice with salt contamination.
TL;DR: In this paper, the authors discuss technical and non-technical issues associated with applying high impedance fault detectors, and recognize all the issues that are important to the effective implementation of these new fault detecting techniques.
Abstract: Faults on distribution circuits are normally detected by simple overcurrent relays. Faults through a high impedance such as dry earth or asphalt do not have sufficient current to operate overcurrent relays and must be cleared manually. Such high impedance faults may pose a hazard to the public. Equipment is now commercially available to detect a high percentage of high impedance faults, but use of this equipment introduces operational issues which affect applications. This paper discusses technical as well as nontechnical issues associated with applying high impedance fault detectors. Recognizing all the issues is important to the effective implementation of these new fault detecting techniques.
TL;DR: In this article, a fault location system based on the travelling wave principle and capable of locating faults on power lines to within /spl plusmn/one tower span (300 m) has been successfully developed and applied to BC Hydro's extensive 500 kV network.
Abstract: A new fault location system based on the travelling wave principle and capable of locating faults on power lines to within /spl plusmn/one tower span (300 m) has been successfully developed and applied to BC Hydro's extensive 500 kV network. Unlike earlier schemes which are based on impedance measurements, its accuracy is not affected by load conditions, high grounding resistance and most notably series capacitor banks. This system measures the time of arrival of a fault-generated travelling wave at the line terminals using the precise timing signals from the Global Positioning System (GPS). Operating experience with the fault locator on lightning related faults indicated highly accurate results were obtained for the majority of the cases. In a few of the lightning-caused disturbances, the system gave anomalous measurements. This paper describes the operation of the system, summarizes the operating experience and explains the observed anomalous measurements.
TL;DR: In this article, an advanced static VAr compensator (ASVC) employing a three-level inverter has been investigated for three-phase applications and the operating principles of the ASVC using an elementary single phase ASVC circuit.
Abstract: An advanced static VAr compensator (ASVC) employing a three-level inverter has been investigated for three-phase applications. The paper describes the operating principles of the ASVC using an elementary single phase ASVC circuit. The construction of a hardware model of the three-phase, three-level ASVC is then presented. The performance of the ASVC is obtained from an experimental study carried out on this laboratory model. The use of the selective harmonic elimination modulation (SHEM) technique to minimize harmonics is explored. Experimental studies have been carried out to determine the speed of response of the scheme by controlling it in a closed loop.
TL;DR: In this article, an exact solution and an approximation are proposed for modeling magnetic fields produced by the sagged conductors of power lines, by taking advantage of the fact that the equation of the catenary exactly describes the line sag.
Abstract: Traditional extremely low frequency (ELF) magnetic field computation techniques assume that the current carrying power line conductors are straight horizontal wires. This assumption results in a model whose magnetic fields are distorted from those produced in reality. An exact solution and an approximation are proposed for modeling magnetic fields produced by the sagged conductors of power lines, by taking advantage of the fact that the equation of the catenary exactly describes the line sag. The proposed approaches differ in the required computational burden and in the precision of the results. A field mapping measurement example illustrates the applicability and the need for this analysis. The relative importance of the catenary effect is discussed.
TL;DR: In this article, a simplified closed-form approximation for the self and mutual impedances of underground cables is presented, which is related to Pollaczek's and Wedephol's equations.
Abstract: Calculation of the ground return impedance generally requires the evaluation of a complex infinite integral. Converging infinite series that usually converge to the exact value have been known for many years, and most handbook formulas were derived from these series, with only the first one or two terms retained. Several approximations with closed-form solutions have been proposed for overhead lines, but nothing seems to have been done in the case of underground cables. This paper describes a complete, simplified closed-form approximation for the self and mutual impedances of underground cables. The simplified equations are first presented and then related to Pollaczek's and Wedephol's equations. Finally, the errors, which in most cases are very satisfactory, are numerically evaluated.
TL;DR: In this article, a simplified method to evaluate lightning-induced voltages on a multiconductor line from the values obtained for the single conductor case is presented, and a simple formula which gives the magnitude reduction of the induced voltages due to the presence of other conductors is derived.
Abstract: The calculation of voltages induced by indirect lightning on multiconductor overhead power lines has been the subject of several studies. The reported conclusions are not always in agreement with each other. In this paper, using a modeling procedure presented in a previous work, the authors study the shielding effect due to mutual coupling among the conductors of a three-phase power line and between the ground wires and the line conductors. The results are compared with those published by other authors, and explanations of the disagreements are given. Additionally, a simplified method to evaluate lightning-induced voltages on a multiconductor line from the values obtained for the single conductor case is presented, and a simple formula which gives the magnitude reduction of the induced voltages due to the presence of other conductors is derived. It is shown that, for the examined case, the derived simple formula gives practically the same results as those obtained using the rigorous procedure. The authors have also compared results obtained using the simplified formula proposed by Rusck to evaluate the protective ratio of a ground wire with their results, and they have found that the values predicted by the Rusck formula are about 6% lower than their own.
TL;DR: In this article, it was shown that these two disadvantages of the tariff in single-phase systems could be eliminated if the energy account based on the value of the integral of the active power of only fundamental harmonic, P/sub I//, rather than on the whole active power P was used.
Abstract: Pricing of electric energy is based on the value of the integral of the load active power P measured by energy meters. At such a pricing, the electric power utilities waste some revenue for the energy delivered to current harmonic generating customers and/or customers causing current asymmetry. This is because the load generated current harmonics and unbalanced currents cause an increase in the active power loss in the distribution system. At the same time, the customers that do not generate harmonics but are supplied with distorted and/or asymmetrical voltage are billed not only for the useful energy but also for the energy which may cause only harmful effects on their equipment. It is shown in the paper that these two disadvantages of the tariff in single-phase systems could be eliminated if the energy account based on the value of the integral of the active power of only fundamental harmonic, P/sub I/, rather than on the integral of the whole active power P was used. These disadvantages could be eliminated in three-phase systems if the energy account is based on the integral of the active power of the positive sequence component of the fundamental harmonic.
TL;DR: The sag generator enables the user to systematically determine the sensitivity of the components of an installed process line to determine cost-effective ride-through enhancement strategies or to test the effectiveness of currently installed equipment.
Abstract: A diesel powered three-phase standby 480 V, 15 kW, 60 Hz synchronous generator has been modified to give controlled three-phase voltage sags. These sags can be controlled in both depth and duration. A 486-based computer with a data acquisition system controls the generator and monitors the system under test. The custom software interface allows the user to select the depth and duration of the each sag. Typically, the user will select a series of sags in selectable increments down to a certain depth. The data acquisition system has both digital and analog inputs, so that data lines, AC and DC voltages and currents, contactors and relays, etc. can be monitored during the tests. The software interface enables the user to select allowable tolerance bands for the monitored signals. If one or more of the signals falls outside the allowable range, the test is suspended. The sag depth and duration that caused the equipment to "fail" the test is then recorded, After testing over a range of sag durations, a CBEMA-type curve is available for the system under test. The sag generator enables the user to systematically determine the sensitivity of the components of an installed process line. This will enable the user to determine cost-effective ride-through enhancement strategies or to test the effectiveness of currently installed equipment. Although this test generator is small, the basic concept can be scaled up to the 2 MVA range.
TL;DR: In this paper, the authors discuss the process of magnetic field mitigation achieved by use of an additional auxiliary loop placed near load carrying conductors of an existing power line, and the interaction between the original field of the transmission line and that caused by current in the auxiliary loop is followed in detail and thereby an insight into the mitigating process is provided.
Abstract: The paper discusses in a tutorial manner the process of magnetic field mitigation achieved by use of an additional auxiliary loop placed near load carrying conductors of an existing power line. As an example mitigation of a 750 kV class transmission line is presented. The auxiliary circuit is located (i) underneath two outer phases, (ii) above two outer phases, (iii) on ground, or (iv) two shield wires are used for mitigation. The interaction between the original field of the transmission line and that caused by current in the auxiliary loop is followed in detail and thereby an insight into the mitigating process is provided. The approach is best suited for situations where local reduction of the power line field is desired. Reduction of the existing field is possible not only at ground level, such as in the right-of-way, but also at elevated locations, such as at the wall of a building.
TL;DR: In this paper, a transverse differential protection relaying (TDP) scheme was proposed for parallel transmission lines connected to common buses, which relies on current incremental signals in corresponding phases instead of current magnitude.
Abstract: Recently, several papers have discussed the protection of parallel transmission lines connected to common buses. The main purpose of this paper is to discuss problems associated with parallel line relaying schemes, which depend upon the theory of transverse differential protection relaying, and to present a new advanced technique to overcome these problems. The suggested technique relies on current incremental signals in corresponding phases instead of current magnitude. This method eliminates many of the associated problems typically encountered in this area. The possibility of applying the suggested technique on parallel three-terminal power transmission lines was investigated and satisfactory results were recorded. The voltage signal and the communication channel have been excluded from this study.