The Difference between Transient & Permanent Faults

Transient Fault

• Transient faults are those that disappear when power is interrupted and then restored.
• Often caused by occurrences like lightning, momentary tree contact, or contact with animals.
• In such cases, the line can be successfully re-closed after it's been tripped.

Source: A.A.Z. Zin, S.P.A. Karim, The application of fault signature analysis in Tenaga Nasional Berhad Malaysia

Permanent Fault

• Permanent faults persist even when power is restored.
• These faults stem from prolonged issues such as tree or crane encroachment, insulation breakdown, tower collapse, or cable damage.
• Reclosing the line fails because the fault persists during the attempt to restore it.

Source: A.A.Z. Zin, S.P.A. Karim, The application of fault signature analysis in Tenaga Nasional Berhad Malaysia

From the statistic of transmission overhead line trippings from Tenaga Nasional Berhad (TNB) for years 2001 until 2006, transient faults were higher than the permanent faults for each year. 

Source: A.A.Z. Zin, S.P.A. Karim, The application of fault signature analysis in Tenaga Nasional Berhad Malaysia