Project Overview
I'm building a system to detect when power lines are physically cut (for transformer theft prevention) and automatically send GSM alerts. The main challenge is distinguishing between legitimate power outages (load shedding) and actual wire theft.

What I Have Tried
1. Simple voltage monitoring - Fails because both load shedding and wire cuts show zero voltage
2. Current monitoring with end-of-line resistor - Fails because during load shedding, no voltage = no current through resistor
3. Dual monitoring points - Not feasible, can only access wire endpoints at my location

Hardware Available

• Arduino Nano/Uno
• SIM800L GSM module
• Various sensors (ACS712, voltage dividers, etc.)
• 12V battery power supply
• Access to only TWO wires: Live and Neutral at endpoint

Key Constraint
Cannot run additional monitoring wires alongside the main power cables.

Specific Questions

1. Wire Continuity Testing
Is it safe and legal to inject a small DC voltage (5-12V) through high-value resistors (100kΩ+) into AC power lines to test continuity? Would this interfere with the power grid or violate electrical codes?

2. Resistance Monitoring
Can I safely measure wire loop resistance using very low test currents (1-5mA) to detect if wires are physically intact, regardless of AC power status?

3. Alternative Detection Methods
Are there other approaches I haven't considered that work with just two wires and can differentiate power source issues from physical wire damage?

Code Requirements
* Arduino-compatible
* GSM call/SMS capability (SIM800L)
* Low false-alarm rate (critical - don't want calls during every load shedding)
* Battery-powered operation
* Simple, reliable detection logic

Safety & Legal Considerations

• Must not interfere with power grid
• Should comply with electrical safety standards
• Need to avoid creating fire/shock hazards
• Working with 230V AC single-phase supply

What Would Help

• Circuit diagrams for safe wire monitoring
• Arduino code examples for pattern-based detection
• Experience with similar transformer/utility theft prevention
• Alternative approaches I might have missed

Any help, code examples, or alternative approaches would be greatly appreciated!

Thanks in advance for your help!

 

Connect this thing: when it goes silent- the wires are gone and there is no voltage.

 

Who would need to know if wires have been cut or transformers have been stolen except the distribution company?
The distribution company controls load shedding, so if the power is off but they haven't switched off then someone has stolen it (or the fuse has blown)

 

Looking at your diagram, if they steal the transformer but leave your device connected to the loads being supplied, you can forget continuity checks legal or not, simply because someone's toaster will give you continuity. (or other loads with low resistance)

 

Just get a camera, pointed at the transformer with motion detection.