Fiber-optic Current Sensor (FOCS): Fully Digital Non-conventional Instrument Transformer

This paper reports on the testing and evaluation of a passive autoranging (AR) method designed to dynamically extend the measurement range of a photonic current transducer (PCT) to pave the way toward a realization of a combined metering- and protection-class current sensor. The PCT utilizes a current transformer (CT), a piezoelectric transducer (PZT), and a fiber Bragg grating (FBG) to enable current measurement at multiple points in an electrical power network whereby multiple sensors are deployed and interrogated serially using a single optical fiber. The autoranging technique relies on incorporating static MOSFET switches to instantaneously short individual serially connected CT burdens in response to a measured current magnitude exceeding pre-set thresholds. The AR circuit switching events produce distinctive signal features that are used by the proposed switching algorithm to apply appropriate scaling factors to reconstruct the measured current from the optical signal. It is shown through laboratory experiments that the AR circuit correctly reacts to pre-set burden current thresholds of 130% of the nominal value and 22 times the nominal value, signifying its “metering” and “protection” range boundaries. The circuit reaction time is below 4 ms, rendering it suitable for standard power system protection purposes. Moreover, the operation of the AR circuit is demonstrated for burden currents of up to 100 A for over 1 s, satisfying a test procedure for the secondary CT circuit, as required by some power system operators. It is demonstrated that the proposed switching algorithm allows for a correct reconstruction of the burden currents from the optical signal acquired by the FBG interrogator, offering the potential to realize a dual-class optical current sensor.

Section: Introductionmentioning

confidence: 99%

The Performance of a Passive Autoranging Method for a Photonic Current Transducer

Fusiek,

Mir,

Niewczas

2024

“…NCITs include low-power voltage and current transformers (LPVTs and LPCTs), electronic voltage and current transformers (EVTs and ECTs) or Rogowski coils, all interfaced with corresponding electronics allowing for digital communication within substations. They provide many benefits in comparison to the traditional CTs and VTs such as reduced weight, lower environmental hazards, reduced insulation requirements, improved operational safety, lower primary circuit losses, increased bandwidth, and increased dynamic range [ 3 , 4 ]. However, they still suffer from the electromagnetic interference, core saturation and, fundamentally, lack passivity, requiring local power supplies [ 1 , 2 ].…”

Section: Introductionmentioning

confidence: 99%

“…They offer several additional benefits such as light weight, small size, wide bandwidth, high accuracy, immunity to electromagnetic interference and galvanic isolation. A single FOCS can be used for DC and AC measurements with high accuracy, down to ±0.1%, covering metering and protection classes [ 3 ]. However, the commercial uptake of this technology has been slow due to the relatively high cost of the optical instrumentation solutions based on polarimetry and their vulnerability to temperature and vibration effects [ 7 ].…”

Section: Introductionmentioning

confidence: 99%

Design and Implementation of a Passive Autoranging Circuit for Hybrid FBG-PZT Photonic Current Transducer

Mir

Niewczas

Fusiek

2023

In this paper, we present a novel technique for passively autoranging a photonic current transducer (PCT) that incorporates a current transformer (CT), piezoelectric transducer (PZT) and fiber Bragg grating (FBG). Due to the usage of single-mode fiber and FBG, multiple PCTs can be interconnected and distributed over a long distance, for example along a power network, greatly reducing the cost of sensor deployment and offering other unique advantages. The autoranging technique relies on the usage of multiple, serially connected CT burden resistors and associated static MOSFET switches to realize instantaneous shortening of the resistors in response to increasing measured current. This functionality is realized passively, utilizing a modular, μW-power comparator circuit that powers itself from the electrical energy supplied by the CT within a small fraction of the 50/60 Hz cycle. The resultant instantaneous changes in sensor gain will be ultimately detected by the central FBG interrogator through real-time analysis of the optical signals and will be used to apply appropriate gain scaling for each sensor. The technique will facilitate the usage of a single PCT to cover an extended dynamic range of the measurement that is required to realize a combined metering- and protection-class current sensor. This paper is limited to the description of the design process, construction, and testing of a prototype passive autoranging circuitry for integration with the PCT. The two-stage circuitry that is based on two burden resistors, 1 Ω and 10 Ω, is used to prove the concept and demonstrate the practically achievable circuit characteristics. It is shown that the circuit correctly reacts to input current threshold breaches of approximately 2 A and 20 A within a 3 ms reaction time. The circuit produces distinct voltage dips across burden resistors that will be used for signal scaling by the FBG interrogator.

“…In [13,17], for example, the authors developed new compensating techniques, while novel procedures have been developed by the authors of [14][15][16]. Even digital output ITs were well tackled by the literature [19,20]. Finally, an onsite calibration system and method were proposed by the authors of [21][22][23] for EITs, respectively, whereas their accuracy vs. harmonics was studied by the authors of [24].…”

Section: Introductionmentioning

confidence: 99%

Toward the Standardization of Limits to Offset and Noise in Electronic Instrument Transformers

Mingotti

Peretto

Tinarelli

2020

The scenario of instrument transformers has radically changed from the introduction of the Low-Power version, both passive and active. The latter type, typically referred to as Electronic Instrument Transformers (EITs), has no dedicated standard within the IEC 61869 series yet. To this purpose, in the authors’ opinion, it is worth understanding how the limits of typical disturbances affecting EITs should be standardized. In particular, after a brief review of the standards, the work presented a mathematical approach to determine the sources of signal disturbances influence, which affect the rms value, on the ratio error. From the results, we discussed that the emergence of disturbances generated within the EIT is a critical aspect to be studied with data of typical off-the-shelf devices. Therefore, to guarantee a correct operation of the devices, a proper standardization of the sources of disturbance should be provided.