SMART CABLE GUARD: THE TECHNOLOGY

Smart Cable Guard is a digital solution for monitoring the health of medium-voltage cables. It is unique in being able to detect both faults and the partial discharges (PDs) that indicate cable weak spots which may develop into faults. Smart Cable Guard can pinpoint both faults and weak spots with an accuracy of 1% of the length of the monitored cable.

Smart Cable Guard: the basics
Each Smart Cable Guard system comprises two Sensor Units and two Control Units. One Sensor Unit and one Control Unit is installed at each end (termination or sealing end) of the cable to be monitored, potentially covering multiple cable sections. The Sensor Units are enhanced High Frequency Current Transformers that detect and measure high-frequency pulses coming from faults and partial discharges. They also inject small pulses into the cable for time synchronization required to accurately pinpoint the weak spot or fault location. The Control Unit handles the measured data and sends it via a wireless connection to one of our Smart Cable Guard control centres for processing.

If a fault occurs, the network operator is notified within minutes with the precise location of the fault. In addition, status updates showing any partial discharge activity are available every hour via a secure web Portal.

Cable fault detection
Uniquely, Smart Cable Guard locates faults by detecting the travelling wave that the fault produces in the power cable. The wave indicates the start of a short-circuit current and is always present. As a result, Smart Cable Guard can be used in any type of power cable network, and can detect faults even when short-circuit currents would be undetectable (for example in high-impedance grounded networks). This novel approach also means that Smart Cable Guard can give you insight into anomalies occurring in unmonitored sections of a cable.

Weak spot detection via partial discharge
Partial discharges are a result of small impurities, voids or damages in a power cable’s insulation and can further degrade the insulation to the point of (full) short circuit. High partial discharge activity is a good indicator of weak spots in an underground cable. However, partial discharge activity can be sporadic, disappearing for days or weeks at a time, making it difficult to pick up. In contrast to offline monitoring approaches which only provide snapshots of cable health, Smart Cable Guard’s pulse injection technology provides 24/7 surveillance of partial discharge activity – so no weak spot is missed. Moreover, its excellent noise reduction eliminates false positives, ensuring results you can trust.

Location pinpointing
Our patented pulse injection technology ensures Smart Cable Guard Sensor Unit’s time synchronization is accurate to within 100 nanoseconds. This enables faults and weak spots to be located to within 1% of the length of the monitored cable.

In addition, this approach is:

• Economical: same Sensor Unit is used for partial discharge, fault detection and time synchronization
• Practical: no additional hardware such as GPS module or antenna required
• Reliable: built-in performance checks for accurate and correct fault / partial discharge detection.