Page 153 - UKZN Proceedings of the Conference Report

The proposed theft detection and monitoring device for HV transmission towers represents a novel approach to combatting the persistent issue of theft of steel members and tower footing electrodes, since traditional methods have proven to be reactive, costly, and only partially effec- tive. This device introduces a real-time, proactive solution that leverages audio and vibration detection technology, combined with wireless communication capabilities, to provide immediate alerts of theft or tampering activities.
Key features of the device
1. dual-sensor detection system: The device employs a dual-sensor system consisting of a vibration sensor and an audio sensor. This combination ensures that both physical vibrations and specific audio frequencies associated with steel cutting are detected:
• Vibration sensor: The sensor detects vibrations caused by tools such as angle grinders, which are commonly used to cut through steel members. It is calibrated to recognise the unique vibration patterns of such activities while filtering out minor disturbances from environmental factors like wind or small wildlife.
• Audio sensor: The audio sensor identifies the characteristic frequencies (ranging from 839 Hz to 14,319 Hz) produced when steel is cut, such as by an angle grinder. It is set to trigger alarms only for frequencies above 1200 Hz, minimising the likelihood of false-positives from ambient noise.
2. remote monitoring and real-time alerts: The device integrates with an ESP32 microcontroller, chosen for its compact size, processing capabilities, and built-in Wi-Fi communication. It uses the Simple Mail Transfer Protocol (SMTP) to send real-time alerts to control room operators when theft or tampering is detected.
This remote monitoring capability significantly reduces response times, allowing utility operators or law enforcement to act quickly.
3. Self-sustained power system: The device is designed to operate in remote locations without access to external power sources. A 12V, 7Ah rechargeable battery, paired with a 12V, 5W solar panel, powers the device. The inclu- sion of a charge controller ensures the battery is protect- ed from overcharging and reverse current, thereby ex- tending the device’s operational life. The power system is optimised to keep the device running for a minimum of 3 days without sunlight, providing consistent moni- toring even in adverse weather conditions.
4. footing electrode monitoring circuit: In addition to detecting steel member theft, the device also monitors the status of the tower footing electrode, a critical component for grounding the tower. A voltage divider circuit detects changes in resistance across the electrode, enabling the system to distinguish between a healthy, degraded, or stolen electrode. This feature enhances the device’s functionality by not only addressing the theft of steel members but also protecting the integrity of the grounding system.
5. rugged enclosure design: The device is housed in a custom-built, IP66-rated enclosure, making it resistant to dust, water jets, and other environmental factors. The enclosure is designed to be mounted above the tower’s anti-climb device, reducing the risk of tampering. It is built with durable materials and features silicone seals, grommets, and PVC piping to ensure a waterproof and secure installation.
The proposed design components were then designed, calibrated, and simulated to ensure that it will function as designed.
Figure 3: Final circuit design for the HV tower theft detection and monitoring tool
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