Electronic Instrumentation Applied to the Indirect Measurement of 230 kV Overhead Transmission Lines Ampacity

Ampacity is defined as the maximum current carrying capacity of an electrical conductor without compromising its physical integrity. A possible methodology for the monitoring of this parameter in transmission lines consists in the distribution of punctual temperature sensors along the line. This paper presents the development of electronic instrumentation for a current and temperature monitoring equipment to be applied in 230 kV power transmission lines. The chosen current transducer is the Rogowski Coil because of its linear response and decoupling between the measurement and power circuits, while the chosen temperature transducer is the NTC (Negative Temperature Coefficient) thermistor because of its low cost and high sensitivity. The developed prototype dos not use batteries or solar panels as power supply, as it is energized by the voltage induced in a secondary coil coupled to the transmission line. In order to increase the signal-to-noise ratio (SNR) and ensure electromagnetic compatibility (EMC), the hardware was developed and validated through numeric simulations and experimental measurements. Furthermore, digital noise reduction techniques such as oversampling and waveform averaging algorithms were implemented in the system. The developed equipment is theoretically able to measure electrical currents up to 1650 A, and was validated for currents up to 500 A and temperatures up to 90 °C. All collected data is transmitted to a computer for further analysis via wireless communication.