Comprehensive monitoring of electrical machine parameters using an integrated fibre Bragg grating-based sensor system

In this paper a multi-parameter, multi-sensor system for comprehensive electrical machine condition monitoring has been developed and the results of an evaluation reported. The FBG-based system developed allows for the simultaneous monitoring of key parameters including machine vibration, rotor speed and position, torque, spin direction, temperature distribution along the stator windings and on the rotor surface as well as the stator wave frequency. This all-optical sensing solution has been designed to be compatible with being fitted in the tight confines of an electric motor and uses the optical nature of the measurement and the insulating nature of the sensor material to avoid problems of electrical interference. The system reduces the component count over conventional sensor systems, i.e., all sensing elements are contained within the machine and operated by a single sensing interrogation unit, thereby reducing cost and allowing for a convenient interface for the user. The design of the system is presented, as are results on the testing and evaluation of the device the sensing system has been successfully integrated into and tested on a permanent magnet motor prototype

Determination of temperature distribution on windings of oil transformer based on the laws of heat transfer

Object of research: development of a technology for determining the temperature of the winding of a power oil transformer, in particular, the analysis of thermal processes in the winding of a power transformer during short-term overloads, taking into account the influence of the environment. Investigated problem: temperature distribution in the winding of a power oil transformer taking into account short-term load surges in the problem of assessing the residual life of the insulation of the transformer winding by temperature aging. The calculation of the temperature distribution in the winding was carried out using the passport data and characteristics of the power oil transformer, including the winding, transformer oil, load currents. Main scientific results: a mathematical model was calculated, with the help of which the results of temperature distribution in the transformer winding were obtained during short-term load surges or constant work with an increased load. According to the presented model, the analysis of the cooling time of the transformer winding after short-term overloads is carried out. Comparing the results obtained on the simulation model with the known results of experimental studies of the temperature distribution in the winding of a power transformer, the adequacy of the mathematical model is proved. It is shown that the use of the laws of heat transfer in a homogeneous plate to analyze the temperature distribution in the transformer winding is not wrong, but requires clarifications and simplifications. The area of practical use of the research results: enterprises of the machine-building industry and energy companies specializing in the production and operation of transformer equipment. Innovative technological product: simulation model of heat distribution in a transformer winding, which can take into account the load of the transformer, the effect of the environment on the insulation of the transformer windings. An innovative technological product: a method for diagnosing the duration of the non-failure operation of a transformer, which makes it possible to ensure trouble-free operation and save money for the repair of transformer equipment. Scope of application of the innovative technological product: design and development of diagnostic systems for windings of power oil transformer

Condition Monitoring and Fault Detection for Electrical Machines Using Advanced Sensing Techniques Based on Fibre Bragg Gratings

Emerging techniques are being researched to expand the suite of condition monitoring solutions available for electric machines to adapt to a world of net zero carbon emissions. This research investigates the use of fibre bragg gratings (FBG) for condition monitoring and fault detection in three 2.2kW induction motors (IMs) using stray flux in a non-invasive manner. Optical fibre is immune to electromagnetic interference (EMI) which is an advantage but limits its direct use for magnetic field sensing. A magnetostrictive transducer, terfenol-D was bonded to FBG to form a composite sensor - FBG-T. The FBG-T was inserted into an acrylic tube - which is unaffected by magnetic field - and then positioned both axially and transversely relative to the machine’s rotor shaft at the drive end (DE). The transverse position showed better repeatability and sensitivity over different operating frequencies. Temperature and magnetic flux calibrations of the FBG-T sensor gave sensitivities of 20.77 picometre per degree Celsius (pm/°C) and 19.38 picometre per micro-tesla (pm/μT) respectively. Various investigations were carried out at different operating frequencies and under three motor conditions viz: healthy, broken rotor and inter-turn short circuit conditions. Experimental results confirm that the FBG-T sensor reliably distinguished each of the three machine conditions using different orders of magnitudes of braggshifts. The FBG-T sensor accurately detected faults with the short circuit condition reaching braggshifts of hundreds of pm. Healthy and broken rotor conditions reached braggshifts in the low–to-mid-hundred and high-hundred pm range respectively. Fast Fourier Transform (FFT) analysis performed on the measured stray flux showed that not only its amplitude but also the harmonic component of its spectrum, affected the magnetostrictive behaviour of the magnetic dipoles of the terfenol-D transducer. This effect was translated into strain on the FBG. The investigation proved that FBG technology can reliably and accurately monitor the condition of the motors as well as detect faults in a non-intrusive manner

Power system applications of fiber optics

Power system applications of optical systems, primarily using fiber optics, are reviewed. The first section reviews fibers as components of communication systems. The second section deals with fiber sensors for power systems, reviewing the many ways light sources and fibers can be combined to make measurements. Methods of measuring electric field gradient are discussed. Optical data processing is the subject of the third section, which begins by reviewing some widely different examples and concludes by outlining some potential applications in power systems: fault location in transformers, optical switching for light fired thyristors and fault detection based on the inherent symmetry of most power apparatus. The fourth and final section is concerned with using optical fibers to transmit power to electric equipment in a high voltage situation, potentially replacing expensive high voltage low power transformers. JPL has designed small photodiodes specifically for this purpose, and fabricated and tested several samples. This work is described

Fiber-Optic Sensor for Aircraft Lightning Current Measurement

An electric current sensor based on Faraday rotation effect in optical fiber was developed for measuring aircraft lightning current. Compared to traditional sensors, the design has many advantages including the ability to measure total current and to conform to structure geometries. The sensor is also small, light weight, non-conducting, safe from interference, and free of hysteresis and saturation. Potential applications include characterization of lightning current waveforms, parameters and paths, and providing environmental data for aircraft certifications. In an optical fiber as the sensing medium, light polarization rotates when exposed to a magnetic field in the direction of light propagation. By forming closed fiber loops around a conductor and applying Ampere s law, measuring the total light rotation yields the enclosed current. A reflective polarimetric scheme is used, where polarization change is measured after the polarized light travels round-trip through the sensing fiber. The sensor system was evaluated measuring rocket-triggered lightning over the 2011 summer. Early results compared very well against a reference current shunt resistor, demonstrating the sensor's accuracy and feasibility in a lightning environment. While later comparisons show gradually increasing amplitude deviations for an undetermined cause, the overall waveforms still compared very well

Fiber optic acoustic sensor based on SMS structure with thin polymer diaphragm for partial discharge detection

This paper proposes a fiber optic acoustic sensor (FOAS) based on a single-mode fiber - multimode fiber - single-mode fiber (SMS) structure attached to a thin polymer film used as a diaphragm. The diaphragm was specially developed to enhance the sensitivity towards the acoustic pressure-wave resulted from the partial discharge (PD) events. The sensitivity and signal-to-noise ratio (SNR) characterizations of the FOAS without and with a thin polymer film were performed. Both time-resolved and phase-resolved partial discharge (PRPD) patterns measurements were carried out in air and oil media. The experiment was conducted with three-electrodes using FOAS in conjunction with the conventional PD measurement as per IEC 60270 standard. The sensor achieved a sensitivity up to −31.21 dBm and −30.8 (0 dBm is defined as 1V/µBar) using broadband and tunable light source, respectively. The discharge characteristics pattern of FOAS was verified with IEC 60270 standard, and the patterns of FOAS resembled IEC 60270 standard. The proposed FOAS was capable for detecting the PD using both broadband and tunable laser lights. The use of the thin polymer film had a significant impact on the acoustic sensitivity. With the simple, low-cost design structure and free from electromagnetic interference, FOAS is found to be suitable as an in-situ sensor for detecting the acoustic signals of partial discharge and can be utilized inside the transformer