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

Area of Science:

• Electrical Engineering
• Optical Sensing Technologies
• Power Systems Instrumentation

Background:

• Photonic current transducers (PCTs) offer advantages for electrical power networks.
• Existing PCTs have limitations in dynamic range, hindering combined metering and protection applications.
• Extending the measurement range of PCTs is crucial for advanced power system monitoring.

Purpose of the Study:

• To develop and evaluate a passive autoranging (AR) method for PCTs.
• To enable PCTs to function as both metering- and protection-class current sensors.
• To demonstrate the feasibility of a single optical fiber for serial interrogation of multiple PCTs.

Main Methods:

• Integration of a current transformer (CT), piezoelectric transducer (PZT), and fiber Bragg grating (FBG) in the PCT.
• Implementation of a passive autoranging circuit using MOSFET switches to short CT burdens.
• Development of a switching algorithm to interpret signal features and reconstruct current measurements.
• Laboratory experiments to validate AR circuit thresholds, reaction time, and sustained operation.

Main Results:

• The AR circuit successfully reacted to thresholds at 130% (metering) and 22 times (protection) the nominal current.
• The circuit reaction time was measured to be below 4 ms, suitable for power system protection.
• The AR circuit operated for burden currents up to 100 A for over 1 second, meeting secondary CT circuit test procedures.
• Accurate reconstruction of burden currents from optical signals was achieved using the proposed algorithm.

Conclusions:

• The passive autoranging method effectively extends the dynamic range of PCTs.
• The developed system has the potential to realize a dual-class optical current sensor for power systems.
• This technology supports the development of advanced, versatile current sensing solutions.