Cable Testing and Maintenance: Ensuring Network Reliability

Cable Testing Phase Continuity and Order

Checking Cable Continuity

To ensure cable continuity, form a loop bridging two phases at one end. Connect the other end to an isolation and tension meter. Test the continuity of the three possible loops, including one to neutral.

A high impedance reading indicates a discontinuity in the cable.

Verifying Phase Identification

To identify phases, ground one phase at one end of the wire. At the other end, connect an isolation meter between each conductor and ground, applying 500V successively. The lowest of the four measurements corresponds to the same conductor on both ends.

Dielectric Strength Test: Low Voltage Cable Insulation

The risk of damaging a new cable depends on the discharge time constant. Never discharge a cable that has been tested under short-circuit voltage.

Use a constant voltage generator. Connect the generator output to one of the phases and the other output to a ground connection. Increase the voltage slowly to 2.4 kV, controlling the load current to avoid sudden increases.

Maintain the test voltage for 5 minutes, observing the voltage and leakage current levels. The test passes if there is no breakdown.

Maintenance of Distribution Networks

Maintenance involves monitoring the status and functioning of distribution networks to prevent breakdowns.

For effective maintenance, prepare an inspection schedule and identify key components for monitoring.

Air Assembly Distribution Networks

Inspection of air assembly components is typically performed visually and includes:

• Supports (foundation, general support, vertical alignment, cracks, rust, etc.)
• Conductors (insulation, anchors, staples, etc.)
• Clearance of cross-wires in streets, roads, etc.
• General safety boxes (insulation, anchors, exterior condition, etc.)

Underground Lines

Although underground lines are protected from the weather, inspect conductor connections at:

• Low-voltage boxes in the CT (Control Transformer)
• Switching boxes
• Overall protection crates

Monitor loads using a network analyzer in the CT to track consumption and parameters over time. This data reveals the load level of each line and identifies overloaded conductors.

Use a thermographic camera to check the tightness of screws at connection points, measuring the temperature of each element (screws, turret staples, cables, etc.).