PowerWatcher - Low Hanging Power-Line Safety System

Electricity Distribution Network Operators (DNOs) manage overhead lines supported by wooden poles, which are typically five to ten meters above ground.

In some instances where the overhead line’s conductor support fails, due to a car hitting the wooden pole or adverse weather, a conductor can fall. DNOs are reliant on their protection systems to trip the circuit in the event a conductor contacts the ground.

However, there have been occasions where the conductor has not reached the ground and remains energized and hanging at a hazardous height. Low hanging conductors like these pose a serious potential safety risk to the public and livestock.

For a powerline conductor to become “low hanging” there must be a spatial movement that the PowerWatcher measures with an acceleration sensor which provides two types of data:

• Acceleration vector orientation: This allows determining the direction into which PowerWatcher is either accelerated (moved) or permanently oriented (positioned relative to the earth gravity vector).
• Acceleration vector change:  This allows determining if PowerWatcher is moved or shaken
  

The second case (acceleration vector change) can be used to determine the presence or absence of small vibrations (acceleration vector changes).

If such change in acceleration is above a certain threshold, then this will be reported as part of the regular data telegram. If the acceleration exceeds this threshold for the first time, then this will be reported immediately (wake-on-acceleration).

PowerWatcher integrates high performance sensors to measure temperature, current and acceleration. It will periodically report the status of these sensors using radio telegrams according to LoRaWAN radio specification.

The energy-harvesting sensor module PowerWatcher provides wireless sensing functionality without batteries - it operates fully self-powered when sufficient current is flowing through the monitored conductor is available. The required energy for operation is harvested by an integrated split core current transformer. PowerWatcher operates fully maintenance-free.

Radio telegrams transmitted by PowerWatcher are authenticated and encrypted using AES-128 security based on a device-unique private key and a sequence counter in accordance to the security specifications.

The user interface of PowerWatcher consists of one LED to provide user feedback. Configuration of PowerWatcher parameters is possible via LoRaWAN radio communication protocol for OTA configuration.

During standard (normal) operation, PowerWatcher wakes up periodically and reports the current sensor status using data telegrams. The PowerWatcher wake-up timer is by default configured to wake-up PowerWatcher approximately every 60 seconds.