Electrical Unbalance Research Articles

Evaluation and Mitigation of Voltage and Current Unbalance at MSTP Undip Jepara

Marine Science Techno Park (MSTP) Diponegoro University is a central for the application of technology and research in the fisheries and marine sector under the auspices of Diponegoro University. After measuring the electrical power quality parameters, a voltage and current unbalance problem was found on each SDP and MDP at MSTP Undip Jepara Building. The final project is designed to mitigate current and voltage unbalance with a load equalization method in each phase using ETAP 12.6 software. According to the ANSI C84.1-1995 standard, the maximum current unbalance value is 5% and according to the IEEE 45-2002 standard, the maximum voltage unbalance value is 3%. The equalization results show that the load can decrease the value of current unbalance, voltage unbalance, and neutral current that already meets the standards. Based on the evaluation of existing conditions, the current unbalance value on the MDP decreased from 21.522% to 0.419%, the MDP bus voltage unbalance value decreased from 0.280% to 0.015%, and the neutral current decreased from 35.5 ampere to 1 ampere.

Single-Channel Control for Hemispherical Resonator Gyro Based on Time Division Multiplexing and Demultiplexing

With the feature of high precision, strong reliability, and long life, hemispherical resonator gyro (HRG) has a broader prospect in the field of inertial navigation. However, the electrical gain (EG) and electrical phase (EP) between the two control channels in whole angle mode operation are usually unbalanced, which inevitably lead to drift error in the output angle of gyro. In this paper, the analysis of angle drift error in circumferential range from 0 degree to 90 degree caused by EG unbalance and EP unbalance is conducted theoretically and verified by experiments. To deal with the problem of electrical unbalance, a single-channel control strategy based on time division multiplexing and demultiplexing is proposed. Compared with the traditional dual-channel control, the single-channel control can fundamentally eliminate the angle drift error caused by both EG unbalance and EP unbalance and suppress the peak-to-peak value of angle drift error by 5x. What’s more, the proposed single-channel control strategy can also achieve reducing the cost, size, weight, and power (CSWaP) of gyro control system, which is beneficial to HRG miniaturization.

Studying and Measuring System for Motor Base Unbalance

This paper presents the importance of motor base vibration measurements; different faults which can appear during motor running and how the motor base unbalance and vibration influence the whole system vibration. The electrical and mechanical faults influence the normal functioning of the motor, increase the power consumption, the current, more heat is generated and vibrations are growing too. Balancing is important requirement for motors and all rotating components. An electrical and/or mechanical unbalance affects other parts of the motor or system. A weak motor base is one of the vibration sources which can be detected with vibration transducers. A 3-axis accelerometer was used to detect motor vibration for a small DC motor fixed on different types of base in different manner. A virtual instrument was developed to acquire and analyze the vibration. Analyzing the frequency spectra of the vibration the weak motor base and improper fixing of the motor was highlighted which appear in horizontal direction. Knowing the rotating frequency the measured and analyzed data was compared with the reference data. It is shown that sideband frequencies appear around the fundamental frequency which means an anomaly due to improper motor base.

Specific Features of Application of Current and Voltage Transducers When Calculating Eletrical Network Unbalance

Purpose of research. The purpose of this article is to consider the main features of the application of current and voltage transducers determining the electrical network unbalance factor. Also, an important issue is the value of measuring instruments inaccuracy, at which there is no impact on the unbalance factor determining. Methods. The article describes classifications of main current and voltage transducers. An example of the implementation of one of the voltage transducer and analog-to-digital converter variants is shown. The essence of the process of balancing is explained, various unbalance factors are considered, explanatory formulae are provided. The main requirements for current and voltage measurement circuits and for computational signal processing are mentioned. In particular, such important points as determining the phase angle, determining the network parameters and consideration of the influence of measurement errors on the determination of the unbalance factor are studied. The issur of determining the phase angle is considered and the need for its determination is indicated. It is explained that when determining the network parameters, high precision of measurement is required. Results. The impact of the instrumental error of measurements on the determination of the unbalance factor is considered, and instruments rating below which an error may occur while finding the unbalance factor is determined. When determining the instrument rating at which an unacceptable error occurs, a probabilistic model of power distribution of a three-phase network is mentioned; a graphical description of this model is given. Determining the sets of unbalance factors before balancing, after balancing and after balancing taking into account the error, is provided. It is mentioned that in determining these sets, weights are used as increasing and decreasing factors for the terms included in the set. The factor showing the percentage of the decrease of unbalance changes due to the effect of the error is introduced. The dependence of this factor on the measurement error is considered. Conclusion. A conclusion on the value of the error which does not impact the determination of the unbalance factor is provided.

A Study of Fault Diagnosis Based on Electrical Signature Analysis for Synchronous Generators Predictive Maintenance in Bulk Electric Systems

The condition of synchronous generators (SGs) is a matter of great attention, because they can be seen as equipment and also as fundamental elements of power systems. Thus, there is a growing interest in new technologies to improve SG protection and maintenance schemes. In this context, electrical signature analysis (ESA) is a non-invasive technique that has been increasingly applied to the predictive maintenance of rotating electrical machines. However, in general, the works applying ESA to SGs are focused on isolated machines. Thus, this paper presents a study on the condition monitoring of SGs in bulk electric systems by using ESA. The main contribution of this work is the practical results of ESA for fault detection in in-service SGs interconnected to a power system. Two types of faults were detected in an SG at a Brazilian hydroelectric power plant by using ESA, including stator electrical unbalance and mechanical misalignment. This paper also addresses peculiarities in the ESA of wound rotor SGs, including recommendations for signal analysis, how to discriminate rotor faults on fault patterns, and the particularities of two-pole SGs.

Analysis of energy saving potentials in intelligent manufacturing: A case study of bakery plants

To address the global challenge of the climate change, more strict legislations worldwide on carbon emission reductions have put energy intensive industries under immense pressure to improve the energy efficiency. Due to the lack of technical support and financial incentives, a range of technical and economic barriers still exist for small-medium enterprises (SMEs). This paper first introduces a point energy technology, which is developed for SMEs to improve the insight of the energy usage in the manufacturing processes and installed in a local bakery. Statistical analysis of electricity consumption data over a seven-day period is conducted, including the identification of operational modes for individual processing units using an enhanced clustering method and the voltage unbalance conditions associated with these identified modes. Two technical strategies, namely electrical load allotment and voltage unbalance minimisation, are then proposed, which could attain more than 800 kwh energy saving during this period and the current unbalance could be reduced to less than 10%. In addition, the genetic algorithm is deployed to solve the job shop scheduling problem based upon the commercial electrical tariffs, and this reduces the electricity bill by £80 per day in the case study. Implementation of the recommendations based on the above analysis therefore may potentially yield significant financial and environmental benefits.

Control Techniques With System Efficiency Comparison for Microwind Turbines

This paper presents the implementation of a sensorless speed controller and active rectification in a microwind turbine intended for battery charging. The controller was tested in a wind turbine emulator test rig using real wind data available from British bases in Antarctica. The control algorithm was successfully tested up to 14 m/s wind speed. Beyond this point, the electrical unbalance in the turbine generator compromised the stability and performance of the system. Also, a system efficiency comparison of different control algorithms is given to demonstrate the advantages of using active rectification instead of passive diode rectifiers in microwind turbines. This comparison was done between the sensorless control plus active rectifier, a dc–dc converter regulator, and the direct connection between the turbine and battery by means of a diode rectifier. The turbine with an active rectifier and sensorless control achieved the highest power coefficient over the range of wind speeds showing that this technique is an attractive and relatively low-cost solution for maintaining good performance of microwind turbines at low and moderate wind speeds.

Fuzzy self-tuning PID control algorithm for belt conveyor driven by multi-motor

Aiming at the problems of low efficiency when long distance and high-inclination belt conveyor driven by multi-motor is in light or idle run as well as electrical power unbalance. Control strategy for belt conveyor driven by four-motor via fuzzy self-tuning PID control algorithm was proposed. The Speed setting algorithm of belt conveyor and fuzzy self-tuning PID algorithm for speed control and power balance control are introduced. The application shows that, according to the coal flow changes of the belt conveyor in real-time, the speed can be automatically adjusted through this algorithm, making the power of the four motors convergence both speed control error and the power control error of which are lower than 2.6%.

Current signature analysis to monitor DFIG wind turbine generators: A case study

Abstract As wind energy continues to develop with increasing wind turbine power capacities often deployed offshore, reducing operation and maintenance costs have become a critical aspect. Condition monitoring has been found to be the key to achieve this goal. Under this framework, the induction generator of a wind turbine is a major contributor to failure rates and downtime where doubly-fed induction generators are the dominant technology employed. This paper presents a spectral analysis of a real doubly-fed induction generator of an in-service wind turbine. A one-year measurement campaign on an operating wind turbine has been used to perform the study. Three test cases representing different wind turbine operating conditions are presented to illustrate the results. All the peaks found in the spectra have been identified, and the frequency components related to electrical rotor unbalance have been found. The results show which components are more suitable for effective condition monitoring.

Detection and modelling of incipient failures in internal combustion engine driven generators using Electrical Signature Analysis

Condition-based maintenance of electric generators have been gaining increasing importance due to the electricity demand and the criticality that this equipment represents to electrical power systems. In this context, this paper proposes a methodology and a system for detection and modeling of incipient failures in the components of internal combustion engine-driven generators based on Electrical Signature Analysis (ESA). The proposed methodology enables the detection of incipient faults both in the prime mover and in the coupled synchronous generator, only relying on measurements of the generator stator voltages and currents. The proposed ESA failure patterns are based on defined frequencies and the structural features of the machine, so they can be reproduced in a wide range of engine-generators sets. The main advantages of the proposed system are its low intrusiveness, feasible installation and cost efficiency. A scale model laboratory has been designed to simulate faults in a small diesel generator and apply the ESA methodology to detect these faults and obtain the failure patterns. Experimental results are presented to prove the effectiveness of the proposed methodology. The main results include the findings that exciter generator unbalance induces electrical unbalance components, exciter diode short circuit induces even harmonics, intake valve failure and piston ring failure induce multiples of rotation frequency components, and mechanical misalignment of the engine generator set induces multiples of half order speed frequency components on ESA. Moreover, the proposed prototype is installed at two large in-service internal combustion engine-driven generators and examples of signal analysis are provided.

Online condition monitoring of wind turbines through three-phase electrical signature analysis

In the context of the KAStrion European project, a complete solution was proposed in order to monitor wind turbines. The developed solution comprises both hardware and software parts of the condition monitoring system. In terms of software, modules for vibration analysis and electrical signal analysis have been developed. The current paper presents the electrical analysis solution proposed in the context of this project. The electrical module is able to detect both mechanical and electrical faults in a wind turbine system. The goal of the mechanical fault detection using electrical signals is to confirm the faults also detected by vibration analysis, while the main focus of the module remains the detection of electrical faults. Results showing the performance of mechanical fault detection are presented using electrical signals acquired on the test-bench developed for testing the KAStrion system. Moreover, results regarding the electrical unbalance are presented using signals acquired on a three-phase transformer. The final solution has been implemented on two onshore wind turbines since the end of 2014, and online condition monitoring results are presented at the end of the paper.

Fault Detection of the Electrical Motors Based on Vibration Analysis

Abstract Detection and diagnosis of faults while the system is running can help to reduce all kind of losses. Mechanical faults, usages, slackness's, cause different noises and vibrations with different amplitude and frequency against the normal sound and movement of the equipment. Induction motors are present in any processes and systems and for this it is important to known the types of faults which can occur during its working. This paper presents briefly some electrical and mechanical faults in induction motors and how these faults influence the motor vibration. Each type of fault, electrical faults or mechanical faults, produces a vibration whit a specific frequency. Through monitoring and analyzing the vibration spectrum these specific frequencies can be detect and through these we can detect usages, slackness and forces which act and produce the fault. It is an undestroyed method to find out the functioning problems. If the amplitude of these vibrations reach to a certain level the fault can be detect and identify. The paper presents a possible two degree of freedom model for electrical motors. Motion equations and transfer function are deduced and through simulation can be followed how the vibration spectrum is changing for some important faults, like electrical imbalance, mechanical unbalance, looseness, bearings, external effects, base structure or resonance, which can be reduce to mass or spring variation in the system model. To obtain the behaviour of the system, the equations of the motion and Matlab simulations was used.

Investigation of wound rotor induction machine vibration signal under stator electrical fault conditions

This paper investigates wound rotor induction machine torque and vibration signals spectra for operation with and without a stator short-circuit or open-circuit winding fault. Analytical expressions that enable the healthy and faulty machine pulsating electromagnetic torque frequencies to be related to shaft speed are derived and validated for operating conditions of interest. A coupled-circuit machine model is used to investigate the healthy and faulty electromagnetic torque signal. Shaft torque and stator frame vibration are measured on a laboratory test rig comprising a 30 kW wound rotor induction machine. It is shown that the existence of a stator winding inherent electrical unbalance or that arising from fault gives rise to a range of pulsating torque frequencies that are transmitted to the machine frame and can be detected in the measured vibration signal. The magnitudes of the resulting vibration components are demonstrated to be largely determined by the unbalance severity and the mechanical system response. The presented experimental results clearly validate the analytical and simulation analysis for the operating range of the investigated industrial machine design.

Equitable Multi-Objective Optimization Applied to the Design of a Hybrid Electric Vehicle Battery

This work considers the impact of thermal behavior in battery design. The cell performance worsens when the operating temperature falls outside of the ideal range, and evenness of cell temperatures is sought to prevent cell electrical unbalance which may lead to performance fading and premature failure. The heat transfer between the cells and the coolant depends on the cell packaging and layout. A multi-objective optimization model is posed whose Pareto efficient designs minimize cell temperature deviations while maintaining evenness of temperature distribution. The special characteristics of the battery design problem (comparable objectives, anonymity and Pigou–Dalton principle of transfers) make it suitable for the application of the equitability preference, which is a refinement of the Pareto optimality that has not been used in engineering design. The proposed approach based on equitability is applied to compute the spacing of the cylindrical cells in a battery module that yields an optimal thermal behavior.

A study of producing an LCL probe for residential power lines

Although power-line communications are expected as a promising method to realize an in-home network, one of their difficulties is an unnecessary radiation due to the electrical unbalance of power-line channels. To solve the problem, the statistical data of electrical unbalance based on measurements in the practical fields, that is, many and various Japanese residential power lines, must be collected as the first step. In this paper, a method to produce a longitudinal-conversion-loss (LCL) probe that can be used for the practical measurement is studied. The LCL is a measure of the electrical unbalance, and is often used to determine the impairment of EMC performance of a system by the cabling. To improve the dynamic range of the probe, an adjustment method of the transformers' parameters is proposed. According to our scenario, the obtained dynamic range was better than that of the conventional probe with the frequency band higher than 2 MHz. The achieved improvement was 6 dB at 6 MHz, and 14 dB at 30 MHz, for example. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(3): 38–44, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20166

A Study of Producing an LCL Probe for Residential Power-lines

Although power-line communications are expected as a promising method to realize an in-home network, one of their difficulties is an unnecessary radiation due to the electrical unbalance of power-line channels. To solve the problem, the statistical data of electrical unbalance based on the measurement at the practical fields, i.e., many and various Japanese residential power-lines, must be collected as the first step. In this paper, a method to produce a longitudinal-conversion-loss˜(LCL) probe that can be used for the practical measurement is studied. The LCL is a measure of the electrical unbalance, and is often used to determine the impairment of EMC performance of a system by the cabling. To improve the dynamic range of the probe, an adjustment method of transformers’ parameters is proposed. According to our scenario, the obtained dynamic range was better than that of the conventional probe with the frequency band higher than 2MHz. The achieved improvement was 6dB at 6MHz, and 14dB at 30MHz, for example.

Transient Analysis and Reduction Method of Sheath Circulating Current in Underground Power Cable Systems

Sheath circulating current is increased by the electrical unbalance in underground power cable systems. Such unbalance is caused by the mixed burying formation and length unbalance between cross bonding minor sections. If the sheath circulating current rises in power cable systems, the loss caused by the current will be increased and the permissible current of cable will be reduced. The high sheath current may also cause the danger on person and cause the fault by the breakdown of insulation. Therefore, in this paper, the authors analyse the sheath circulating current in transient state and propose the current reduction device using reactor. Reduction effect is proved by the measurement of current and simulation using EMTP. In order to protect the reduction device in case of transient state, the authors propose the protection methods for the reduction device.

Modification of Surface Charge Properties during Kaolinite to Halloysite-7Å Transformation

The surface charge properties of well and poorly ordered kaolinite and halloysite-7Å, representing three different stages of kaolinite to halloysite-7Å transformation identified in the kaolin deposit of São Vicente de Pereira (Portugal), were studied. Mineralogical (X-ray diffraction, Fourier transformation-infrared) and chemical data (analytic electron microscopy) showed that the gradual transformation from kaolinite to halloysite-7Å minerals was accompanied by an increase in hydration and a decrease in Si/Al ratio. In particular, the replacement of Si(IV) by Al(III) in the tetrahedral layer caused an electrical charge unbalance and a modification of surface charge properties during the kaolinite to halloysite transformation. Accordingly, the cation exchange capacity (CEC) gradually increases when passing from well-ordered kaolinite to halloysite-7Å, attesting the direct correspondence existing among the structural order of the samples, number of tetrahedral substitutions, and CEC. Electrophoretic experiments provided further evidences of the origin of surface charge properties and the variation encountered during kaolinite to halloysite-7Å transformation. The curves of ζ-potential versus pH show the same pH dependency for the three minerals, but a gradual increase of ζ-potential when passing from well ordered kaolinite to halloysite-7Å through the poorly ordered kaolinite. The results can unambiguously be attributed to the increase of permanent charge due to the higher degree of isomorphic substitution, more than to the increase of structural and ionizable water.

A probe for the measurement of electrical unbalance of networks and devices

A probe has been developed to measure residual electrical unbalance of nominally balanced networks and devices. In the form described, it makes convenient the use of single-ended 50 /spl Omega/ instruments to measure electrical unbalance of wire pair networks and two-terminal devices. For electromagnetic compatibility (EMC) planning purposes, a knowledge of the electrical unbalance at signal interfaces in wire pair networks generally allows quantitative prediction of the conversion of wanted differential mode signals into unwanted radiated disturbances which can interfere with reception of radiocommunication services. The probe was first described to the CISPR in 1988. Since then, several other groups have also found it useful for measuring the electrical unbalance of telecommunication networks and devices. It has also been used to measure the differential mode signals and common mode disturbances at signal interfaces on balanced data signaling networks.

Demonstration of AC machine behavior through interactive color graphics

A microcomputer program that graphically illustrates steady-state polyphase machine behavior under a variety of balanced and unbalanced operating conditions is described. Implemented in the C language, the interactive program employs sophisticated screen color graphics to show the slow-motion progression of the appropriate voltage or current waves, the loci of the resulting magnetic fields, and the movement of the machine rotor. It can be used to illustrate dynamically revolving-field concepts, the use of symmetrical components, and the operation of synchronous and induction machines under conditions of sustained electrical unbalance. The motivation for such a program, its operation, and its capabilities are described. >