Single Ended Location of Faults

SELF (Single-Ended Location of Faults) is an impedance-based method applied to Low Voltage power system cables.

What is SELF?

  • Allows pre-location of fault even without customer interruptions
  • Easy to use – simply select the circuit cable details

The term “Single-ended” refers to the fact that the impedance estimation is based on the measurement of current and voltage at one point on the faulted phase. Unlike TDR it does not care about the number of joints on the network.

Single Phase SELF only measures one point at the substation using a REZAP FAULTMASTER

3 Phase SELF measures all 3 phases voltage and current simultaneously using a combination of auto-reclosing Devices from KELVATEK.

How SELF works

  • Based on voltage and current recordings
  • Identify fault half-cycles
  • Input Network cable details
  • SELF outputs pre-location distance in meters.

Fault Modes

  • Fault can change mode - PP, PN, PPN, 3P, 3PN
  • Often changes mode within a half-cycle

Typical Setup

Typical Setup

SELF Key Benefits

  • Results are displayed as a distance in metres
  • The network is being constantly measured so every fault event no matter the size will be recorded and used to automatically calculate the distance, providing all three phases have devices fitted.
  • Can identify Welded or Arcing Fault
    • Welded fault tends to be permanent
    • Arcing fault has variable arc voltage

SELF Devices

SELF Devices


  • Fault waveforms are typically non-sinusoidal
  • Fault can be welded or arcing
  • Fault can be intermittent
  • LV networks not often single phase (!)

Inrush Detection

Inrush can look like fault current

Inrush can look like fault current - Inrush Current ~1700 Â