Common Types of Power Cable Faults
Power cables can fail in numerous ways. Understanding the fault type is the first step to selecting the right testing approach.
Short Circuit Faults
Phase-to-phase or phase-to-ground short circuits present low resistance paths. These are the easiest faults to locate using basic TDR methods. The reflection coefficient at the fault point provides a clear, sharp pulse return.
Open Circuit Faults
When a conductor breaks completely, the TDR pulse reflects with maximum amplitude. Open circuits are common in areas with ground movement or at connection points subject to thermal cycling.
High-Resistance Faults
Partial insulation breakdown creates high-resistance faults that standard TDR cannot detect. These require impulse current or multi-pulse methods with high-voltage discharge to temporarily lower the fault resistance for measurement.
Water Tree Degradation
Common in older XLPE cables, water treeing creates microscopic channels that degrade insulation over time. Multi-pulse and bridge methods are most effective for locating water-damaged sections before catastrophic failure occurs.
Sheath Faults
Outer sheath damage allows moisture ingress, accelerating main insulation degradation. The HP Portable Extended system includes dedicated sheath fault location using step voltage and bridge methods.