Evaluation of Flexible Rogowski Coil Performances In Power Frequency Applications

This paper investigates the effects of some influence quantities on the measurement of power frequency sinusoidal currents by means of flexible Rogowski coil sensors. The analysis is carried out through a numerical model, which is specifically developed and allows both the prediction of the circuital and coil parameter effects and the improvement of the coil design. The estimate of the measurement uncertainty associated with the on-site use of a flexible and openable Rogowski coil is finally given by assuming relatively controlled operating conditions

Online condition monitoring of MV cable feeders using Rogowski coil sensors for PD measurements

Condition monitoring is a highly effective prognostic tool for incipient insulation degradation to avoid sudden failures of electrical components and to keep the power network in operation. Improved operational performance of the sensors and effective measurement techniques could enable the development of a robust monitoring system. This paper addresses two main aspects of condition monitoring: an enhanced design of an induction sensor that has the capability of measuring partial discharge (PD) signals emerging simultaneously from medium voltage cables and transformers, and an integrated monitoring system that enables the monitoring of a wider part of the cable feeder. Having described the conventional practices along with the authors’ own experiences and research on non-intrusive solutions, this paper proposes an optimum design of a Rogowski coil that can measure the PD signals from medium voltage cables, its accessories, and the distribution transformers. The proposed PD monitoring scheme is implemented using the directional sensitivity capability of Rogowski coils and a suitable sensor installation scheme that leads to the development of an integrated monitoring model for the components of a MV cable feeder. Furthermore, the paper presents forethought regarding huge amount of PD data from various sensors using a simplified and practical approach. In the perspective of today’s changing grid, the presented idea of integrated monitoring practices provide a concept towards automated condition monitoring.fi=vertaisarvioitu|en=peerReviewed

Online condition monitoring of MV cable feeders using Rogowski coil sensors for PD measurements

Condition monitoring is a highly effective prognostic tool for incipient insulation degradation to avoid sudden failures of electrical components and to keep the power network in operation. Improved operational performance of the sensors and effective measurement techniques could enable the development of a robust monitoring system. This paper addresses two main aspects of condition monitoring: an enhanced design of an induction sensor that has the capability of measuring partial discharge (PD) signals emerging simultaneously from medium voltage cables and transformers, and an integrated monitoring system that enables the monitoring of a wider part of the cable feeder. Having described the conventional practices along with the authors' own experiences and research on non-intrusive solutions, this paper proposes an optimum design of a Rogowski coil that can measure the PD signals from medium voltage cables, its accessories, and the distribution transformers. The proposed PD monitoring scheme is implemented using the directional sensitivity capability of Rogowski coils and a suitable sensor installation scheme that leads to the development of an integrated monitoring model for the components of a MV cable feeder. Furthermore, the paper presents forethought regarding huge amount of PD data from various sensors using a simplified and practical approach. In the perspective of today's changing grid, the presented idea of integrated monitoring practices provide a concept towards automated condition monitoring.This work is done under the project Smart Condition Monitoring of Power Grid that is funded by the Academy of Finland (Grant No. 309412)

Current Sensing for Automotive Electronics -- A Survey

Current sensing is widely used in power electronic applications such as dc-dc power converters and adjustable-speed motor drives. Such power converters are the basic building blocks of drivetrains in electric, hybrid, and plug-in hybrid electric vehicles. The performance and control of such vehicles depend on the accuracy, bandwidth, and efficiency of its sensors. Various current-sensing techniques based on different physical effects such as Faraday\u27s induction law, Ohm\u27s law, Lorentz force law, the magnetoresistance effect, and the magnetic saturation effect are described in this paper. Each technique is reviewed and examined. The current measurement methods are compared and analyzed based on their losslessness, simplicity, and ease of implementation

Current measurement in power electronic and motor drive applications - a comprehensive study

Current measurement has many applications in power electronics and motor drives. Current measurement is used for control, protection, monitoring, and power management purposes. Parameters such as low cost, accuracy, high current measurement, isolation needs, broad frequency bandwidth, linearity and stability with temperature variations, high immunity to dv/dt, low realization effort, fast response time, and compatibility with integration process are required to ensure high performance of current sensors. Various current sensing techniques based on different physical effects such as Faraday\u27s induction law, Ohm\u27s law, Lorentz force law, magneto-resistance effect, and magnetic saturation are studied in this thesis. Review and examination of these current measurement methods are presented. The most common current sensing method is to insert a sensing resistor in the path of an unknown current. This method incurs significant power loss in a sense resistor at high output currents. Alternatives for accurate and lossless current measurement are presented in this thesis. Various current sensing techniques with self-tuning and self-calibration for accurate and continuous current measurement are also discussed. Isolation and large bandwidth from dc to several kilo-hertz or mega-hertz are the most difficult, but also most crucial characteristics of current measurement. Electromagnetic-based current sensing techniques, which are used to achieve these characteristics, are analyzed. Many applications require average current information for control purposes. Different average current sensing methods of measuring average current are also reviewed. --Abstract, page iii

Design and operation of a harmonic gyrotron based on a cusp electron gun

Strathclyde theses - ask staff. Thesis no. : T13121This thesis presents the results of successful operation of a 2nd harmonic gyrotron based on a cusp electron gun. The numerical and experimental results agreed well with the gyrotron design parameters. Two gyrotrons based on a cusp electron gun were designed: the first gyrotron operated at the 2nd harmonic and the second gyrotron was studied to look at the scaling of this concept for operation at the 7th harmonic at a frequency of 390 GHz. The cusp electron gun was used to produce the electron beam in the gyrotron which was annular in shape. The electron beam had a voltage of 40 kV, a current of 1.5A and a velocity ratio (perpendicular component to horizontal component) of 1.5. The experimental results from the first cusp electron gun and measurements of the high quality electron beam with ~8% velocity spread and ~10% alpha spread are presented. Analytical, numerical and experimental results of a DC harmonic gyrotron are presented. The 3D PIC code MAGIC was used to simulate the interaction of the harmonic gyrotron such as the TE71 mode at the 7th cyclotron harmonic with the large orbit electron beam with the beam thickness and beam spread introduced into the simulation. The interaction cavity of both gyrotrons was in the form of a smooth cylindrical waveguide. The relationship between the cavity dimensions and cavity Q values has been studied for optimized output at the design mode with the aim of suppressing other competing modes. A linear output taper was designed with low mode conversion at the gyrotron output. A Vector Network Analyzer with high frequency millmetre wave heads was used to measure the millimeter wave properties of the gyrotron cavity. Experiments were conducted using the electron gun for the harmonic gyrotron. The gyrotron and electron gun were built as well as the interlock and safety system, pulsed power supply and magnet, the cooling and vacuum system. Millimetre wave radiation was measured for the 2.6 mm diameter cavity gyrotron operating at the 2nd harmonic at a magnetic field of 2.08 T. Experiments demonstrated that the harmonic gyrotron was sensitive to the magnetic field and electron beam parameters. Millimetre wave radiation from 108GHz to 110GHz was measured with the use of a W-band rectifying crystal detector and high pass cut off filters. The frequency of the measured millimeter wave radiation agreed very well with the design and predictions of theory.This thesis presents the results of successful operation of a 2nd harmonic gyrotron based on a cusp electron gun. The numerical and experimental results agreed well with the gyrotron design parameters. Two gyrotrons based on a cusp electron gun were designed: the first gyrotron operated at the 2nd harmonic and the second gyrotron was studied to look at the scaling of this concept for operation at the 7th harmonic at a frequency of 390 GHz. The cusp electron gun was used to produce the electron beam in the gyrotron which was annular in shape. The electron beam had a voltage of 40 kV, a current of 1.5A and a velocity ratio (perpendicular component to horizontal component) of 1.5. The experimental results from the first cusp electron gun and measurements of the high quality electron beam with ~8% velocity spread and ~10% alpha spread are presented. Analytical, numerical and experimental results of a DC harmonic gyrotron are presented. The 3D PIC code MAGIC was used to simulate the interaction of the harmonic gyrotron such as the TE71 mode at the 7th cyclotron harmonic with the large orbit electron beam with the beam thickness and beam spread introduced into the simulation. The interaction cavity of both gyrotrons was in the form of a smooth cylindrical waveguide. The relationship between the cavity dimensions and cavity Q values has been studied for optimized output at the design mode with the aim of suppressing other competing modes. A linear output taper was designed with low mode conversion at the gyrotron output. A Vector Network Analyzer with high frequency millmetre wave heads was used to measure the millimeter wave properties of the gyrotron cavity. Experiments were conducted using the electron gun for the harmonic gyrotron. The gyrotron and electron gun were built as well as the interlock and safety system, pulsed power supply and magnet, the cooling and vacuum system. Millimetre wave radiation was measured for the 2.6 mm diameter cavity gyrotron operating at the 2nd harmonic at a magnetic field of 2.08 T. Experiments demonstrated that the harmonic gyrotron was sensitive to the magnetic field and electron beam parameters. Millimetre wave radiation from 108GHz to 110GHz was measured with the use of a W-band rectifying crystal detector and high pass cut off filters. The frequency of the measured millimeter wave radiation agreed very well with the design and predictions of theory

Development of non-conventional instrument transformers (NCIT) using smart materials

In this paper is presented a novel approach for current measurement using smart materials, magnetic shape memory (MSM) alloys. Their shape change can be controlled by the application of magnetic field or mechanical stress. This gives the possibility to measure currents by correlating the magnetic field produced by the current, shape change in an MSM- based sensor and the voltage output of a Linear Variable Differential Transducer (LVDT) actuated by this shape change. In the first part of the paper is presented a review of existing current measurement sensors by comparing their properties and highlighting their advantages and disadvantages

Design and Implementation of Partial Discharge Measurement Sensors for On-line Condition Assessment of Power Distribution System Components

Unplanned interruptions of power supply due to failure of critical components of the distribution network have considerable impact on the modern society. Efficient condition assessment can avoid the loss of critical components by early detection of incoming threats. One of the biggest shortcomings of today's progressing maintenance technology is the lack of low cost instrumentation solutions which are simple in implementation and easily applicable to the network. In this work partial discharge (PD) measurements have been considered for insulation condition assessment of distribution system components such as overhead covered conductors (CCs) and cables. A high frequency Rogowski coil induction sensor is designed for this purpose. An accurate electrical model of the sensor is necessary for efficient signal processing of the sensed signal and for reliable interpretation of the measured signal. A new method to determine the electrical parameters of Rogowski coil sensor is presented. In-depth analysis of the design stages of Rogowski coil is presented using experimental and simulated environment. Various geometrical designs of Rogowski coil are investigated to analyze the effects of geometrical parameters on high frequency performance of the coil. The guidelines presented regarding geometrical structure are useful when trading off the benefits for better mechanical and electrical design of such sensors. Location of the detected PD faults is an important task of the diagnostics system in power lines. The conventional techniques of locating PD faults have been known for a single section of a power line. However, these techniques are not suitable for power lines having multi-sections or for branched line networks. In this work, finding the location of PD fault on a power line is recognized as a two stage function; (i) identification of the faulty section, and (ii) location of fault point on the identified section. The direction of arrival (DOA) technique is introduced to identify faulty section whereas fault point location can be determined by conventional techniques. The technique is equally applicable for CC lines or cable networks. The DOA technique is integrated over a cable feeder and an on-line automated condition monitoring and diagnostic scheme is proposed. Low cost, non-intrusive installation and favorable operating features of Rogowski coil sensor make it suitable for development of an enhanced and automated diagnostic system which can easily be integrated into the distribution network