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This paper introduces a new model for transient moisture equilibrium in oil-paper insulation, easily applicable even in a continuous way, based on Fick's second law. According to the model, the moisture concentration in paper follows step response function, but the equilibration time constant changes with time since it depends on temperature, paper thickness, equilibration moisture in oil-paper insulation, and number of oil-paper interfaces. The model is validated against experimental data. Index Terms--Moisture equilibrium, oil insulation, paper insulation, transient model.

Electrical equipment supplying and distributing energy is used in every pulp and paper industrial process. Many components made of various metallic and dielectric materials are vulnerable to corrosive atmospheres often present in the pulp and paper industrial facilities. Corrosion of electrical conductors may result in fast and irreversible deterioration, causing production loss and safety hazards. The paper reviews the most severe corrosion problems effecting conductivity of electrical contacts that result in overheating of electrical equipment used in this industry. A number of various protecting means are suggested to slow down corrosion of silver and copper and other metals most often used in electrical equipment. The paper discusses implementations and the value of various condition-monitoring techniques to provide timely maintenance of electrical equipment exposed to corrosive environments in the pulp and paper facilities. Index Terms--Corrosion, electrical conductors, monitoring, resistance, silver.

This paper presents and verifies a new mathematical model to explain the dynamic behavior of characteristic gases in the oil-cellulose insulation of high voltage devices like power transformers. The model is based on the diffusion process. Parameters of the model are already quantified from experiments and presented in previous publications. The mathematical model and assumptions are presented here. The model solution is obtained analytically and gas concentration change inside the paper insulation as a function of time is simulated. The results are converted to the concentration change in the oil using the principle of conservation of mass and validated with experimental measurements. The presented model can be used to reduce the error of Dissolved Gas Analysis due to the migration of characteristic gases inside a healthy power transformer. Index Terms--Transformers, diffusion, oil-paper system, Dissolved Gas Analysis.

The use of paper in electrical insulation, especially in power transformers, remains a topical subject. The interest for the insulating paper, despite the emergence of many synthetic materials is ascribed to its low cost price and its ability to an oil impregnation. However its strong hydrophilic character remains the main difficulty for its implementation in electrical insulation. This affinity to water absorption and/or adsorption shows that a good understanding of the moisture effect becomes imperative. Several studies were carried out on the subject but a systematic study of the moisture effect on overall behavior of paper has not been achieved. This work is meant to be a contribution for this systematic investigation. The first step of this study, which is the object of the present article, concerns an examination of time variation of the electrical currents, under dc stress, for different moisture levels. A particular attention is given to the polarization and depolarization currents. These currents are examined during alternate charges and discharges sequences. An increase of the current, during the application of continuous voltage was noticed. This unexpected phenomenon would be related to an electro-dissociation and/or polarization processes. Index Terms--Paper insulation, dielectric materials, moisture effect, dielectric polarization, electrolytic dissociation, electric field effects.

The development of high gradient magnetic separation (HGMS) system for purification of wastewater from paper factory is discussed. Findings reveal that the system is capable of treating more than 2000 t/day.

The purpose of this paper is to present a state variable model for the drying section of a paper-making machine. This model is based on the mass and energy balance relationships written for steam, paper, cylindrical heater wall, and moisture. These relationships give a set of six nonlinear partial derivative equations. The form of these equations changes somewhat from one cylindrical heater to another. The solution for this model yields the operating parameters needed to achieve the desired steam temperature while obtaining good paper drying. Boundary conditions are specified by a stochastic generator, and initial conditions are obtained by solving the static model. The dynamic model is presented in [1]. In this paper, we present only the state variable model for the paper drying, as well as comparing the obtained results with dynamic model results. Solving the set of differential equations with respect to the boundary conditions, we obtain the standard form of the state representation, which represents the dynamic version of the model used for process control. In conclusion, it can be said that the consistency of the model with experimental results seems to be reasonably good and can be used for process control. Index Terms - Drying paper, linearization, state equations, steam dryer.

This paper reviews the motor temperature operating consideration for Totally Enclosed Fan Cooled (TEFC), Open Dripproof, and Weather Protected II type of motor through 500 hp, both low voltage (LV) and medium voltage (MV). The IEEE Standard 841 has been revised as IEEE Std 841-2001 and is expected to be in use for at least five years. The TEFC motors covered in this standard have found wide acceptance in the pulp and paper industry. Much of the material also applies to large motors sizes. The thermal impact on the stator winding rotor core, bearings, and lubrications as specified in standards and applied in mills are considered. Index Terms--AC squirrel-cage induction motors, insulation series factor, thermal life, winding temperature.

The manufacturing imperative of improving uptime presents a number of unique challenges for the plant engineer or industrial facilities manager. The first challenge is to debunk the myths and misconceptions surrounding power conditioning and environmental protection in industrial settings. Like their office system counterparts, control systems are running more mission-critical applications than ever before. Uptime demands are increasing. This, in turn, increases the need for systems availability and reliability 24 hours a day, seven days a week. Pulp and paper mills are continually striving to obtain data center reliability through the use of dual corded loads fed from separate substations. Building in high degrees of redundancy increases the standards for reliable power and provides the ability to perform consistent maintenance for all power and environmental equipment--continuous availability is dependent upon it. This paper covers how to identify the most common challenges--from power conditioning to site monitoring issues to precision air conditioning and other environmental factors--and then configures the best solution for your specific environment. Index Terms--Circuit-breaker trips, distributed generation, dual-corded loads, N + x parallel redundancy, ultracritical loads.

This paper is a basic primer for defining and applying active harmonic filters (AHFs). AHFs are sophisticated electronic devices that offer significant advantages over traditional harmonic mitigation and displacement power-factor-correction methods. This paper will introduce the AHF and discuss when and where these advantages apply. Additionally discussed is the simplicity in selection of the AHF. The author will present specific examples for the various applications to which AHFs have been applied. Index Terms--Active harmonic filter, harmonic filter, harmonics, power-factor correction, var compensation.

Kraft paper is used extensively in the electricity supply industry for the insulation of HV apparatus, such as transformers, capacitors and cables. Because of the fibrous nature of the paper, many layers are stacked or rolled to obtain the required electric strength. The insulation is thus a combination of cellulose and an impregnating fluid, which may be a liquid, a gas or vacuum. The dielectric properties of such a system depend on the dryness, temperature, frequency and the degree of mechanical compression. Although the effects of moisture, temperature and frequency on the dielectric properties of kraft paper have been studied, very little work has been done on the effect of compressive stress, particularly long-term effects. Results are presented of measurements, in the frequency range 50 Hz to 20 kHz, of the effects of compressive stress and temperature on the real and imaginary parts of the complex relative permittivity of a multilayer stack of dry kraft paper under vacuum. The variations of the dc resistance with compressive stress and temperature also are reported. Results are given of the variation of the dielectric properties of a stack of paper following a step change in either the temperature or the air pressure. The long-term variations are attributed to the slow diffusion of ions through the stack, particularly those held at the interfaces between layers.

Reliability and power quality are two of the most discussed topics in the utility industry today. Many groups have performed power quality studies with varying results. One large industrial customer in northern New York State which experienced numerous process interruptions due to power system disturbances was the focus of this study. Monitoring methods, results, inadequacies of standards, and unique mitigation techniques used to conquer their problems are discussed in this paper.

Paper is made by a continuous high-speed filtration drainage of an aqueous suspension of fibers. This paper presents a new approach to the controllable simulation of paper forming, using artificial neural network methods. The model incorporates dynamics of the forming process, like turbulence, drainage speed, and preferential drainage through earlier less-dense regions and fiber properties, like propensity to clump, or 'flocculate,' fiber flexibility, and concentration of fibers in the suspension. Results for monofiber layer structures are described, showing effects of turbulence and its decay during drainage in causing clumping, or 'flocculation.' The commercial process has, as one of its main goals, the reduction to tolerable levels of the nonuniformity in mass distribution resulting from flocculation. The new model yields data corresponding to that obtainable along arbitrary scanning lines in planar stochastic fibrous structures, providing profiles, variances, histograms of local areal density, and histograms of local free-fiber lengths. These results closely resemble experimental data from commercial paper samples obtained from radiographic or optical transmission images subjected to image analysis. Index Terms - Drainage, fabric, flocculation, formation, forming, neural networks, simulation, turbulence.

Motor failures are very costly in a typical paper mill. Typical motor failure cost upwards of $20 000 per hour. Motor repair costs for the North American mills of Champion International total over $10 000 000 per year. Lost production associated with these failures can reach a staggering $1 000 000 per day. Considering these facts, Champion International embarked on a program to use intelligent motor control and protection equipment in all new installations, where applicable, and to replace outdated motor protection equipment. The combination of advanced motor protection, flexible control, and communication provided Champion with the opportunity to directly control and monitor their processes. The advanced features of the new equipment provide warning of impending problems, minimize downtime, and improve process results. This paper provides case histories where the new equipment replaced dated electromechanical protection and control equipment. In addition, we also discuss the present generation of motor protection technologies and the need for a new generation of motor protection equipment that truly provides total motor protection against all known motor failure modes. Index Terms - Case histories, failure cost, monitoring, motor, thermal protection.

Oil impregnated paper or polymer film is the main insulating system for many kinds of power apparatus. The oil impregnated materials, especially oil impregnated kraft paper, include a significant amount of water, and this water disturbs the insulating performance of the devices. The amount of water in the materials usually is represented by the difference in weight between the normal material and the same material after drying. However it is difficult to measure the absolute value of the water content and to determine the state in which the water exists in the materials. In this study, we examined the IR spectra of water in oil impregnated kraft paper, because the IR spectrum of the water indicates not only the amount of water but also its state. It was found that most of the water behaves as liquid water, and some as hydrogen bonded water, interacting with the paper fiber. The dc conductivity of the kraft paper depends only on the amount and state of the water associated with it whether or not the paper is impregnated with the oil.

A utility capacity increase from 50 to 100 MVA was implemented in a large Kraft paper mill. All existing plant 15-kV switchgear and controls were replaced and a new tie line constructed during a nine-month period prior to the utility increase. Electrical and process control rooms were built to house new switchgear and computer control equipment. All installation work was done during outages scheduled for other plant objectives. New switchgear installed consists of 42 cells of 1000-MVA class equipment. The control system includes operator workstations, supervisory PLC, and remote I/O racks. Breaker control, metering, and loadshedding functions are performed by the control system.

The subject of energy-efficient lighting and lighting practices for the pulp and paper industry offers an opportunity to discuss energy-efficient lighting technologies, commencing with new current lighting products, the advantages and disadvantages of these new lighting products, coping with the disadvantages, their performance and design, and ways to apply these new products in an effective retrofit or in new construction applications. We will also review current recommended lighting practices for indoor and outdoor applications, and we will establish guidelines for improved techniques and economics with recommended illuminance values as applied to new projects or in the modernization of existing pulp and paper facilities.

In this paper, the feasibility of inkjet printing of circuit and microwave structures on paper-based substrates is investigated for the first time in the implementation of a complete low-cost wireless platform for sensors. First, the system-level design of the module including the amplifier characterization were carried out to ensure optimum performance of the sensor modules in the UHF bands used in RF identification communication. These results were then used to design two different antenna structures, which are printed on paper along with their respective circuit layouts using inket-printing technology. Different techniques were investigated for the assembly of circuit components on the silver printed layouts. Finally, wireless link measurements on the assembled prototypes verified the good performance on the wireless and sensing sides. Index Terms--Antenna, assembly, dipole, inkjet printing, micro-controller, monopole, paper, power amplifier (PA), RF identification (RFID), sensor, temperature, transmitter, ultra high frequency (UHF), wireless.

This paper presents a comprehensive three-stage computer-based methodology for the initial setting of the speed and torque controllers for the drives of a paper machine. First, the controller gains are selected based on the figures-of-merit for the frequency- and time-domain responses of each drive to commands and disturbances. After that, the effect of the elastic shafts is considered evaluating the resonant frequencies and two-mass system responses. Finally, the responses of each group of drives to the process commands and/or disturbances of interest are evaluated. The use of the proposed methodology will assure fast and well-behaved responses of each group of drives of the different sections of a paper machine, with minimal field adjustments. Index Terms--Controller setting, disturbance rejection, paper machine drive, speed and torque controllers, torsional oscillations.

Effects of oil brand, temperature and atmosphere conditions on copper sulfide deposition on insulating paper were investigated by thermal aging test. Copper sulfide deposition occurred in a certain oil brand and dibenzyi disulfide (DBDS) was found in the oil. There was an incubation period observed before copper sulfide deposition occurred. Copper sulfide deposition was accelerated by temperature. The deposition rate after the incubation period became twice when the heating temperature was increased by approximately 10 [degrees]C. The incubation period and the deposition rate were the same at 140 [degrees]C whether the thermal aging test was done in air or nitrogen atmosphere. On the other hand, the incubation period in air was shorter than that in nitrogen at 120 [degrees]C. The deposition rate was not affected by atmosphere condition at 120 [degrees]C. Intermediate substances due to copper dissolution into oil are introduced to explain the incubation period and the atmosphere dependence of incubation period observed at 120 [degrees]C. Index Terms--Copper, copper compounds, oil insulation, paper insulation, sulfur, sulfur compounds, transformers.

The suppressive effect of triazole-based passivators such as 1,2,3-benzotriazole (BTA) and Irgamet 39[TM] (CIBA Specialty, Basel, Switzerland) on the deposition of copper sulfide on insulating paper in transformers and reactors was investigated by heating test with bare and paper-wrapped copper plates. Commercially available mineral oil meeting the specification of IEC 60296 was used. This oil contained 136 ppm wt./wt, of dibenzyl disulfide (DBDS). The deposition of copper sulfide occurred after 144 h of heating at 140 [degrees]C without these passivators. However, little deposition of copper sulfide occurred even after 432 h of heating when either of these passivators was added to the oil. The concentration of dissolved copper significantly decreased when either of these passivators was added to the oil, which reflects the formation of complex layers on the copper surface caused by the reaction between these passivators and copper. The complex layers were confirmed by time-of-flight secondary ion mass spectrometer (TOF-SIMS). The suppressive effect was derived from retarding copper from dissolving into the oil due to the reaction inhibition between DBDS and copper by the complex layers. The duration of these passivators can be determined by the durability of the complex layers. Index Terms--Copper, copper compounds, oil insulation, paper insulation, sulfur, sulfur compounds, transformers, transformer oil.

For reliable operation of power transformers, the condition of the insulation system is essential. This paper reports on a detailed study of the effect of ageing, temperature and moisture on frequency and time domain spectroscopic measurements carried out on oil-impregnated pressboard samples as well as on a distribution transformer under controlled laboratory conditions. Because field measurements are generally performed after de-energizing the transformer, extreme care is required in interpreting the results due to inherent temperature instabilities. To avoid large thermal variations that may affect the results, a customized adiabatic room was built around the transformer for measurements above the ambient. Capacitance ratio and direct current conductivity deduced from the spectroscopic measurements, helped to interpret the data. Because, low frequency measurements techniques are time consuming, alternative to a transfer of time domain data into frequency domain data was investigated. Index Terms--Dielectric spectroscopy, time domain, frequency domain, conductivity, Aging, moisture, temperature, oil-paper insulation.

Non-destructive diagnosis of power transformer condition is an increasingly important area of research. Power transformer coils are typically insulated with Kraft paper and immersed in mineral oil. There is a clear need to be able to estimate the aged condition of the coil insulation non-destructively. A portable fibre-optic spectroscopic probe system has been developed which can achieve this quickly by determining the degree of polymerization (DP), an indicator of degradation, to an accuracy of 30 DP units. The system can also determine water content to an accuracy of 0.1% w/w, and oil content and condition, very rapidly from the same measurements. The system uses a broadband spectroscopic diffuse reflectance probe operating in the visible and near infrared (NIR) range and interfaced to dedicated multivariate analysis software. Following calibration and measurement trials in the laboratory, the instrument has recently been adapted for use in the field, in which DP predictions have been made from in-situ measurements on the exposed windings of de-tanked transformers. These values have been validated when checked against DP measurements of the same paper taken in parallel using conventional viscometric methods. The system is now being further optimized and is being developed for other applications in the power industry and other industrial areas such as the paper industry and the plastics recycling industry. The system is modular and different probe types can be attached allowing the measurement of a wide variety of solid material surfaces and liquid media. Index Terms--Power transformers, transformer windings, paper insulation, aging, oil insulation, nondestructive testing, spectroscopy, multivariate statistical analysis

Few studies have been carried out on the failure processes of low voltage distribution cables. This is mainly due to their excellent track record of high reliability, and their use of traditional technologies. Growing quantities of aged cable within the network now make management of these assets an important issue. This paper describes measurements of leakage current, partial discharges and arc formation within 400 V oil-impregnated paper insulated cable structures which have been artificially wetted by immersion in bulk water. A generic picture is produced to show the gradual evolution from a leakage current through discharge growth to final catastrophic failure. Rapid changes to the core temperature of a wet cable are shown to produce transient, high levels of leakage current. It is also shown that by increasing the core temperature more slowly these high levels can be reduced. It is suggested that the characteristics of individual arcs within successive half cycles may provide a basis for predicting whether an incipient fault will lead to failure in the short term. Index Terms--Cable insulation, underground power distribution lines, dielectric breakdown, paper insulation, moisture, aging, partial discharges, arc discharges.

Multiwalled carbon nanotubes (MWNTs) are characterized at X., Ku-, Ka-, and Q-bands by rectangular waveguide measurements. The scattering parameters (S-parameters) of thin MWNT papers containing a large ensemble of randomly oriented nanotubes are measured by a vector network analyzer from 8 to 50 GHz. A rigorous extraction algorithm has been developed to compute the effective complex permittivity ([epsilon] = [epsilon]' - [epsilon]') and permeability ([mu] = [mu]' - j[mu]') of the nanotube papers from the measured S-parameters. The extracted effective medium parameters are verified by finite-element simulations using Ansoft's High Frequency Structure Simulator (HFSS). The uncertainties for this characterization method are analyzed. The systematic uncertainties are found larger at lower frequencies than at higher frequencies. The extracted conductivity of the nanotube papers is in the range of 810-1500 S/m and the dielectric constant is from 250 to 700. The extracted complex permittivity can be fitted with the Drude-Lorentz model for the 8-50-GHz frequency range. The effective medium theory is then applied to remove the impact of air in the nanotube paper. Index Terms--Conductivity, Drude-Lorentz model, Drude model, effective medium theory, multiwalled carbon nanotube (MWNT), permeability, permittivity, waveguide.

Dielectric testing techniques, in both time and frequency domains, are currently widely used by power utilities for assessment of the condition of transformer oil-paper insulation systems. However, it has been reported that results of these tests are highly influenced by the operating temperature during measurements. The distribution, migration and equilibrium of moisture between oil and paper in a complicated insulation system is highly temperature dependent. It requires adequate experience and proper understanding to interpret the dielectric response results in the presence of temperature variations and thermal instability. Proper analysis of the dielectric test result is only possible with an understanding of the physical behavior of the insulation system in response to temperature. A circuit model, which describes the dielectric behavior of the transformers main insulation system, has been investigated in this paper. The values of the parameters of the model have been identified from the dielectric tests. A correlation has been observed between the operating temperature and the equivalent model parameters that can be used as additional information for better interpretation of the dielectric test results. This paper thus reports a detailed study on the effects of temperature on dielectric measurements of a transformer under controlled laboratory conditions. Some results of practical on-site testing are also presented to demonstrate the possibility of errors that may be introduced in dielectric test results analysis unless temperature effects are taken into consideration. Index Terms--Conductivity, depolarization current, dielectric response, dissipation factor, equivalent model, polarization current, recovery voltage, temperature, transformer insulation.

In this paper, inkjet-printed UHF and microwave circuits fabricated on paper substrates are investigated for the first time as an approach that aims for a system-level solution for fast and ultra-low-cost mass production. First, the RF characteristics of the paper substrate are studied by using the microstrip ring resonator in order to characterize the relative permittivity ([[epsilon].sub.T]) and loss tangent (tan [delta]) of the substrate at the UHF band for the first time reported. A UHF RFID tag module is then developed with the inkjet-printing technology, proving this approach could function as an enabling technology for much simpler and faster fabrication on/in paper. Simulation and well-agreed measurement results, which show very good agreement, verify a good performance of the tag module. In addition, the possibility of multilayer RF structures on a paper substrate is explored, and a multilayer patch resonator bandpass filter demonstrates the feasibility of ultra-iow-cust 3-D paper-on-paper RF/wireless structures. Index Terms--Cavity resonator, dielectric characterization, inkjet printing, loss tangent, low-cost RF modules, multilayer, paper, printable electronics, relative permittivity, resonator bandpass filter (BPF), RF identification (RFID), ring resonator, UHF, wireless local area network (WLAN).

Special measures may be needed to select line insulators for transmission and distribution lines in locations exposed to freezing conditions. This first part of the paper describes the environmental and electrical stresses encountered in service that influence the risk of flashover on line insulators. Part II of the paper describes the strength of typical line insulation in these conditions and deals with selection and mitigation methods. Index Terms--Climate, contamination, flashover, fog, high voltage, ice, insulation coordination, line insulators, snow.

In this paper, the influence of the stiffness and damping of real elastic shafts on the behavior of a multidrive system driving a tissue paper machine is investigated. The drive system consists of four dc motors, where two of them drive the Yankee drying cylinder and the other two drive the presses section. Six-pulse thyristor bridge power converters that are connected to the same power transformer supply the motors. The inertias of the motors and the driven machines, in conjunction with the shaft stiffness, form mechanical resonators. Thus, resonance phenomena may occur, which may lead to undesirable results. This particular case results to two three-mass and one five-mass systems. This paper presents an analysis of the resonance frequencies of two sections of the machine during startup and machine production, considering the shaft stiffness (shaft diameter, length, and thickness). The elastic shafts eliminate the ripple of the motor electromagnetic torque, which is transferred to the driven machine. The behavior of elastic shafts with different stiffness in the transmission system is studied. Moreover, the steady state and dynamic behavior of the system considering the influence of the elastic shafts and vibration analysis were investigated using simulation. A model algorithm for system simulation was developed using the MATLAB/SIMULINK software. Characteristic simulation results are presented and are expressed in terms of speed and torque response. Considering the resonance frequency analysis and simulation results, mechanical design guidelines can be given for the most significant drive components in order to avoid torsional oscillation resonance phenomena and minimize torsional oscillations of the drive system. Index Terms--Current and torque control, dc motor drives, modeling, pulp and paper industry, resonance, simulation, vibrations.

Critical sections of a paper machine such as the wet end presses, size press, on-machine coater, and reel may be required to undergo large and fast load changes in normal operation. These changes must result in minimum disturbance to the ingoing sheet tension or nip roll speed in order to avoid sheet breaks or wrinkling. This paper evaluates two disturbance-rejection control techniques, one using disturbance feedforward (or disturbance input decoupling) based on a nip-pressure disturbance observer and the other using a two-degrees-of-freedom controller. Evaluations were done in both a press section and a size press section of a lightweight paper machine, and the results showed that both methods are very effective in reducing the maximum speed deviation to about 10% of the values without compensation and can operate combined with torsional oscillation compensation without interference between them. Index Terms--Disturbance observer, disturbance rejection, paper-machine drive, torsional oscillations, two-degrees-of-freedom (2-DOF) controller.

Knowledge about moisture content in oil impregnated paper insulation is essential when estimating remaining lifetime of power transformers. Direct evaluation of moisture content is rarely possible due to inaccessibility of the internal insulation system in transformers. Therefore, various indirect estimation techniques are utilized. Frequency domain spectroscopy (FDS) measurements of transformer insulation belong to this group. To perform high quality interpretation of results of FDS measurements a good knowledge on dielectric responses in oil impregnated pressboard and paper is required, especially as it refers to their variation with water content and temperature. The aim of this paper is to provide an open access to the frequency domain spectra of oil impregnated paper and pressboard samples, which can then be used in modeling of the results of diagnostic measurements in power transformers. Index Terms--Conductivity, dielectric frequency response, modeling, moisture content, oil-paper insulation.

Partial discharge (PD) inception and breakdown (BD) characteristics of liquid nitrogen (L[N.sub.2]) / polypropylene (PP) laminated paper composite insulation system for high temperature superconducting (HTS) cables are presented. In this paper, we measured PD inception characteristics under lightning impulse and ac voltage applications by electrical, optical and acoustic methods. The impulse PD inception characteristics were compared with those under ac voltage application, and the PD generation mechanisms are discussed. Experimental results reveal that PD detection sensitivity under lightning impulse voltage application is as small as 6 pC. PD inception at the lower stress was verified to be generated not only in the butt gaps but also in micro gaps between PP laminated paper layers under both lightning impulse and ac voltage applications. Alter PD inception, PD activity could be developed in the butt gaps at the higher stress, finally leading to BD. Index Terms--High temperature superconducting cable, liquid nitrogen, polypropylene laminated paper, partial discharge, breakdown.

Knowledge of the condition of power transformer winding insulation paper is fundamental to making optimum asset replacement decisions in the power industry. The ability to assess the aged condition of Kraft paper quickly and non-destructively using portable instrumentation would significantly increase the opportunities for gaining this knowledge. Insulation paper degrades over time in-service and its degree of polymerization (DP) reduces, eventually affecting its mechanical strength. At low DP levels the insulation may start to disintegrate and the risk of electrical breakdown increases. Currently-used methods of estimating DP are either approximate or destructive. The use of spectroscopy together with multivariate statistical analysis (MVSA) provides a powerful non-destructive evaluation of the condition of paper. From initial feasibility studies, we have developed a simple, portable system (TRANSPEC) using fiber-optics and broad-band spectroscopy that can measure the degree of polymerization of various aged transformer papers to a precision of approximately 30 DP units with a spatial resolution of 14 mm. The system can also measure the chemical composition and condition of the insulating mineral oil. MVSA regression models were constructed from library spectral data, and these models are used to predict the DP of other papers with parameters that fall within the range spanned by the set of calibration samples. Separating oil and moisture information from wetted paper is possible and will be reported in a separate publication. With a single TRANSPEC system, non-destructive in-situ analysis of the DP of insulating paper is possible, providing a rapid cost-effective method for transformer insulation condition assessment and monitoring, which correlates well with current destructive methods. Index Terms--Cellulose degradation, multivariate statistical analysis, nondestructive testing, paper insulation, power industry, power transformers, spectroscopy, transformer windings

A portable fiber-optic spectroscopic system (TRANSPEC) has been developed for nondestructive measurement of aged transformer insulating paper. Following successful measurement of degree of polymerization (DP) of a range of transformer-aged paper samples, the system has now been shown to separate the oil and paper information for measurement of DP in oil-wetted paper samples. In addition, the system has been shown to be capable of the prediction of both oil and water content of paper to a high accuracy, and is also capable of identifying and quantifying different water species. Spectroscopic measurements have been used together with gravimetric water adsorption measurements to investigate the kinetics of uptake of water vapour into paper from air in the case of nominally dry and oil-impregnated samples. Relationships between water adsorption parameters and properties of the paper insulation have also been investigated using measurements under controlled conditions. Index Terms--Humidity control, multivariate statistical analysis, oil insulation, paper insulation, power transformers, spectroscopy, weight measurement, water content

A capacitor formed of fluid-impregnated paper metalized on one side and a polymer film results in a relaxation peak caused by the much more rapid polarization of the dielectric fluid impregnated paper relative to the polymer film. This results in the capacitance being a function of frequency, with a substantial increase in capacitance at very low frequencies. A theory for such a capacitor is developed and compared with measurements on actual capacitors with relatively good agreement. The implications of the theory for discharge current and discharge efficiency are discussed. Index Terms--Soggy foil capacitor, paper capacitor, dielectric relaxation, metalized paper capacitor.

Torsional oscillations bound the velocity loop bandwidth (BW) of industrial drives and servo systems, deteriorating the transient response to commands and disturbances. This is especially harmful in multidrive systems like paper machines that need to run synchronized. This paper presents two methods to dynamically compensate the torsional oscillations produced by the compliant components between the motor and the load: either a notch filter or an acceleration feedback based on the rigid-body Luenberger observer. The evaluation includes the effect of reducer backlash, whereby both time and frequency domain responses are used to compare the benefits of each technique in a typical paper machine section. Results show that both methods, if properly tuned, are effective techniques to reduce torsional oscillations and are robust to parameter variations. Index Terms--Backlash, frequency response analysis, resonance, torsional oscillations, torsional stiffness, two mass modeling.

Torsional oscillations greatly affect performance and determine the bandwidth (BW) and damping of speed loops. Backlash due to gear reducers can also contribute to the triggering of oscillations, especially when the drive runs at very low load torque. This paper presents a detailed evaluation of these effects in typical electromechanical drive trains applied to paper machine sections. The cases evaluated consider torsional oscillations in two-mass and three-mass systems, and the effect of shaft diameter and length on the resonant frequencies of three typical paper machine sections. Time-domain response plots are evaluated to show the effect of speed response overshoot, reducer backlash, and step or ramp speed commands. Based on these results, mechanical design guidelines are given for the most significant drive train components in order to minimize torsional oscillations of the speed-controlled drive system. Index Terms--Backlash, frequency-response analysis, jackshaft and reducer torsional stiffness, two- and three-mass modeling, resonance, torsional oscillations.