Temperature characterisation of an optically-interrogated Rogowski coil

An investigation into the performance of an optically-interrogated Rogowski coil over temperatures up to 80 °C is presented. Preliminary thermal tests reveal that the sensor response is temperature-dependent and the measurement errors are increased at higher temperatures. Compensation of temperature effects is, therefore, necessary in order for the sensors to meet the requirements of protection and metering classes specified by relevant IEC standards over the considered operating temperature range. This can, however, only be achieved when the utilised sensor interrogator is adapted to ensure sufficient resolution and accuracy from a generally low-output transducer. As such, the design of a new multiplexing, interferometric interrogation platform is also proposed in this paper

Solid-state interferometric interrogator and multiplexer for high-speed dynamic and absolute FBG wavelength measurement

We present a solid-state FBG array interrogator and multiplexer capable of determining absolute FBG wavelengths and of providing high-speed, high-resolution static and dynamic measurements. Using a described procedure, deployable on multiplexing passive-interferometric schemes, the system is able to determine initial sensor wavelengths and thereafter track wavelength changes with interferometric resolution. The scheme allows high-resolution interrogation of FBG sensor arrays to be applied to many industrial applications, where previously the lack of combined absolute and quasi-static wavelength measurement precluded the use of interferometric techniques. Using a preliminary laboratory embodiment, we demonstrate a wavelength determination accuracy of <0.3 nm and a measurement resolution of 10 fm/√Hz, and propose pathways to improved performance and miniaturisation

Laboratory investigation of an intensiometric dual FBG-based hybrid voltage sensor

In this paper, we investigate experimentally the performance of a prototype optical voltage sensor utilizing a piezoelectric component and a dual FBG sensor combined with an intesiometric detection scheme. The sensor construction allows for the sensor interrogation using a single photodetector, and by eliminating spectral scanning devices, the measurement system benefits from a significant cost reduction and potentially improved speed of operation. Preliminary voltage characterization reveals that the proposed sensor is capable of reliable ac voltage measurement

All-optical differential current detection technique for unit protection applications

In this paper we demonstrate a novel, all-optical differential current protection scheme. By monitoring the optical power reflected from two matched hybrid fiber Bragg grating current sensors and using a simple optoelectronic threshold detector, an immediate response to an increase in differential current is achieved. A preliminary laboratory embodiment is constructed in order to characterize the performance of the scheme. The proposed technique does not require a complex sensor interrogation scheme, usually characterized by a limited sampling frequency, and thus will be capable of facilitating inexpensive and fast-acting differential protection over long distances

Photonic voltage transducer with lightning impulse protection for distributed monitoring of MV networks

The design, construction and characterization of a photonic voltage transducer with a lightning impulse protection for distributed measurements on medium voltage (MV) networks (11 kV) was presented in this paper. The sensor prototype, comprising a combination of a piezoelectric transducer and a fibre Bragg grating (FBG) as a core optical sensing element, and a dedicated lightning protection device comprising a set of reactive components, was evaluated through laboratory testing and its performance was assessed based on the accuracy requirements specified by the relevant industry standards. It was demonstrated that the sensor has the potential to meet the accuracy requirements for the 3P protection and 0.2 metering classes specified by the IEC 60044-7. The device successfully underwent lightning impulse withstand tests, satisfying the safety requirements applicable to 11 kV networks as specified by the standard. The usage of an FBG as a photonic sensing component enables the multiplexing of multiple such sensors to provide the distributed measurement of voltage along a power network

Temperature-independent high-speed distributed voltage measurement using intensiometric FBG interrogation

In this paper, we demonstrate through simulation a low - cost, high - speed optical voltage sensing system with a multiplexing capability. The scheme utilizes transducers based on a hybrid piezoelectric/ optical construction, whereby the optical power reflected from dual - peak fiber Bragg gratings is modulated in response to an excitation voltage and monitored by photodetection while remaining robust to fluctuations in optical power and temperature. A dedic ated solid - state interrogation system incorporating passive wavelength division multiplexing allows for high - speed measurement over the ac/dc voltage sensor array without the use of expensive components, such as tunable filters or lasers

Reliability of an all-optical differential current detection technique during environmental temperature perturbations

The reliability of a novel, all-optical differential current protection scheme over varying environmental conditions is investigated in this paper. By monitoring the optical power reflected from two matched hybrid fiber Bragg grating current sensors and using a simple and low-cost optoelectronic threshold detector, a sub-cycle response to an increase in differential current can be achieved. A preliminary laboratory embodiment is constructed in order to emulate a practical deployment of the sensors and characterize the performance of the scheme when the sensors are at different temperatures. We demonstrate that even at a temperature difference of 20 °C between the sensors the system is capable of robust and fastacting fault detection

Design of an optical sensor with varied sensitivities for overhead line sag, temperature and vibration monitoring

This paper reports on the design of a fiber-optic sag, temperature, and vibration sensor to implement overhead line (OHL) dynamic rating and health monitoring in electrical power networks. The proposed sensor is based on the fiber Bragg grating technology to be compatible with a suite of photonic voltage and current sensors previously developed by the authors. A range of different strain transfer and attachment structures for an FBG-based strain sensor that facilitate varied strain transfer from the conductor to the FBG are considered and the expected sensor performance is theoretically evaluated through software simulations and the finite element analysis. The results suggest that the proposed sensor, when fabricated, should be a valuable tool for the conductor sag, temperature, and vibration monitoring. The choice of a strain transfer and attachment structure to achieve desired sensitivity can be made based on the requirements of a given application

Geopolymeric thermal conductivity sensors for surface-mounting onto concrete structures

In this work, we present a novel, geopolymer temperature-sensing patch which can be heated using induction and used to infer thermal conductivity of the surrounding medium. The sensor patches, applied to concrete specimens, were fabricated by loading a geopolymer binder with 0 - 60 wt% ground magnetite. The magnetite content allowed the patches to be heated using an induction coil, while temperature profiles were monitored via changes in patch electrical impedance. Sensor patches were left uncoated, or were coated in surface-water, soil and sand. Each material provided a unique thermal signature which, with simple signal processing, could be used to reliably detect whether the patch was buried

Wind turbine foundation deburial sensors based on induction-heated ceramic patches

The deburial and scouring of concrete wind turbine and bridge foundations presents a risk to structural stability and safety. In this work, we present a novel, ceramic temperature-sensing patch which can detect whether sections of a foundation are buried or exposed to air. The sensor patches, applied to concrete specimens, were fabricated by loading a geopolymer with 0 - 60 wt% ground magnetite. The magnetite content allowed the patches to be heated using an induction coil, while temperature profiles were monitored via changes in patch electrical impedance. Sensor patches were left uncoated, or were coated in surface-water, soil and sand. Each material provided a unique thermal signature which, with simple signal processing, could be used to reliably detect whether the patch was buried