Single-phase ground faults demand swift diagnosis and methodical corrective action. Effective handling hinges on accurately identifying the faulted line, locating the precise defect, and restoring service only after full remediation. The following sections outline the complete detection and elimination workflow.

I. Fault Detection — Three-Stage Localization

1. Line Identification

Line discrimination is the first and most decisive step. When a single phase is grounded, the voltage of the faulted phase collapses—often dropping near zero—while non-faulted phases exhibit an abnormal elevation approaching line voltage.
Using insulation monitoring devices such as voltmeters, this asymmetry becomes immediately apparent.
To further pinpoint the faulty feeder, the sectionalized pull-test method is applied: segments of the line are opened one by one while observing voltage restoration. The segment after which voltages normalize is the faulted line.

2. Outdoor Fault Point Investigation

Once the problematic line is identified, the focus shifts to field inspection.
High-risk locations include:

• Insulators with potential fractures, contamination, or flashover traces.

• Conductor joints prone to loosening, overheating, or oxidation.

• Tower grounding systems vulnerable to corrosion, breakage, or accidental disconnection.

Infrared thermography is invaluable at this stage. Abnormal hotspots often correspond to deteriorated components or high-resistance connections, shortening the search radius.

3. Indoor Fault Point Investigation

For faults within substations or indoor wiring, attention must be directed at:

• Cable terminations, particularly where aging or moisture ingress can lead to puncture.

• Switchgear terminals, including circuit breakers and contactors with degraded insulation.

• Internal wiring of equipment, where hidden aging, abrasion, or short-circuiting may occur.

A megohmmeter (insulation tester) is used to measure insulation resistance. Any section showing significantly reduced resistance relative to normal values typically reveals the fault location.

II. Fault Elimination — Four Essential Steps

1. Fault Isolation

Before any repair, the circuit must be completely de-energized.
Open the power switch and all associated isolators on both ends of the faulty feeder.
Post clear signage such as “Do Not Energize” to ensure absolute operational safety.

2. Fault Repair

Corrective actions depend on the defect type:

• Replace damaged or contaminated insulators.

• Recrimp or replace degraded conductor joints.

• Rebuild or reseal cable terminations.

• Replace faulty indoor components or equipment.

Each repair must restore mechanical integrity and dielectric strength.

3. Insulation Verification

After repairs, remeasure the insulation resistance using a megohmmeter.
Values must meet or exceed regulatory requirements—typically ≥0.5 MΩ for low-voltage circuits.
Only after proper insulation values are confirmed can re-energization be considered.

4. Power Restoration

Reconnection follows a strict sequence:
First, close the isolators.
Then, close the power switch.
Monitor phase voltages and equipment status closely.
If all parameters remain stable, normal power supply is officially restored.

A systematic and disciplined approach to single-phase ground faults not only restores service efficiently but also enhances long-term system resilience.