Photonic Voltage Transducer with Lightning Impulse Protection for Distributed Monitoring of MV Networks

Abstract

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.

Conceptual design and evaluation of an optical sensor for wide-area high-voltage metering and protection applications

“…In addition to the electrical performance of PZTs, their mechanical performance needs to be considered carefully to ensure that the compressive and tensile stress limits for the materials are not exceeded [10], [12], [14]. Both excessive electric field and stress in the material may lead to its depolarization or permanent damage.…”

“…The direct use of a hard-piezo stack for measuring high voltage, a scaled-up version of the previous MV PVT design [10], [12], does not seem to be feasible for the HV PVT construction due to the requirements for the maximum permissible electric field in the PZT components and the stack dimensions. Since the PZT stack cannot be readily protected against overvoltage conditions, it must be designed to withstand power frequency and the lightning impulse voltages.…”

“…To avoid the piezoelectric component depolarization and permanent damage its nominal voltage was chosen to be 1 kV as mentioned earlier. The compressive and tensile stress limits for the material are 100 MPa and 10 MPa, respectively while the permissible electric field limit is 2.5 kV/mm [10], [12], [14].…”

“…A range of photonic voltage and current sensors utilizing fibre Bragg grating (FBG) sensors and piezoelectric transducers was previously proposed by the authors to enable multiple, remote, distributed, passive current and voltage measurements over long distances that can be applicable to a wide range of metering and protection applications [8]- [12]. This included variants of the core technology from using low-voltage "soft" piezoelectric transducers to measure the output of a conventional CT or Rogowski coil for current measurement, through to using the same approach for sensing the secondary voltage of a capacitor divider to achieve voltage measurement at 132 kV [11] to direct voltage measurement at medium voltage by using larger "hard" piezoelectric (PZT) transducers that are capable of being exposed to multi-kV-level voltages [10], [12].…”

Optical Voltage Transformer Based on FBG-PZT for Power Quality Measurement

“…Finally, the work of Fusiek and Niewczas [13] seems to be the first effort to test a photonic voltage transducer under an official and generally accepted IEC standard.…”