latest company case about Xi'an Xu&Hui Electromechanical Technology Co., Ltd. Certifications

110kV Cable Outer Sheath Fault Detection — Xi'an Yanliang Precision Location Case Study

Project Background

On November 25, 2023, a 110kV high-voltage power cable at Xi'an Yanliang experienced an outer sheath insulation fault. The cable, with a total length of 1,000 meters, was installed in a trefoil formation within a cable trench, with the outer sheath lead-out wire at one end on a transmission tower and the other end inside a cross-bonding box at the 1,000-meter mark. A straight-through joint was located at approximately the 500-meter point. The cable route was clearly identifiable within the trench, but the outer sheath fault position remained unknown.

Fault Detection Challenges

• Outer Sheath Fault Specificity: Unlike conductor faults, outer sheath faults involve non-metallic insulation layers. Detection signals are significantly weaker, requiring specialized bridge and high-voltage test equipment.
• Multiple Method Attempt Required: Initial testing with the 523L cable sheath fault locator using both current method and step voltage method failed to locate the fault point, demonstrating the challenge of outer sheath fault detection in complex field conditions.
• Cross-Bonding Interference: The cable system included a cross-bonding box at the far end, introducing additional complexity to the measurement circuit.

Solution

XZH TEST deployed a comprehensive cable outer sheath fault detection system combining multiple complementary technologies:

Implementation Process

Step 1 — Insulation Resistance Testing

Using the XHMR-10kV digital insulation tester at the 2.5kV range, the three-phase armored lead-out wires were measured individually. The C-phase armored-to-ground resistance measured only 0.02MΩ, clearly identifying the faulted phase with severe outer sheath insulation degradation.

Step 2 — Route Confirmation

The cable route was clearly visible within the trench, laid in trefoil formation. No additional route tracing was required.

Step 3 — Initial Fault Location Attempt

The XHHD523L cable sheath fault locator was first deployed using both the current injection method and the step voltage method. However, neither method successfully identified the fault position due to the specific characteristics of the outer sheath fault and site conditions.

Step 4 — High-Voltage Fault Location

The XHHV515-8 high voltage surge generator was then deployed. By applying controlled high-voltage pulses to the outer sheath, the fault point was successfully broken down, generating detectable discharge signals. The fault was located approximately 350 meters from the cable starting point.

Step 5 — Bridge Pre-Location Verification

The XHHG521B cable fault bridge locator was used for cross-verification. Measurement from the starting end indicated approximately 940 meters, while the far-end measurement indicated approximately 160 meters. This cross-confirmed the fault zone consistency. [Note: test personnel observed that bridge measurements on lead-out wire extensions can introduce significant errors.]

Step 6 — Repair and Withstand Test

After fault point repair, the XHHD523L was used to perform a DC withstand voltage test on the outer sheath. The test passed successfully, confirming the integrity of the repair.

Application Results

• Fault Location Confirmed: The outer sheath fault was precisely located at approximately 350 meters from the starting end on a 1,000-meter 110kV cable.
• Multi-Method Approach Success: When the 523L's current method and step voltage method proved ineffective, the 515-8 high-voltage approach successfully located the fault, demonstrating the value of a multi-instrument diagnostic toolkit.
• Cross-Verification Accuracy: The 521B bridge measurements from both ends provided consistent fault zone confirmation.
• Successful Repair Validation: Post-repair withstand testing with the 523L confirmed the outer sheath insulation was fully restored.

Customer Value

This 110kV cable outer sheath fault detection case at Xi'an Yanliang demonstrates the critical importance of a comprehensive, multi-method cable testing equipment portfolio:

• Redundant Diagnostic Capability: When one method encounters limitations in the field, alternative approaches within the same toolkit can successfully resolve the fault — eliminating the need for external equipment sourcing and minimizing outage duration.
• Complete Outer Sheath Testing Solution: From insulation diagnosis (XHMR-10kV) through fault location (XHHV515-8, XHHD523L) to bridge verification (XHHG521B) and final withstand testing, XZH TEST equipment covers the entire outer sheath fault detection workflow.
• Field-Proven Reliability: All instruments performed reliably under real-world 110kV cable testing conditions, confirming their suitability for demanding utility applications.

This case study is based on field test data recorded on November 25, 2023, at Xi'an Yanliang. All detection equipment was provided by Xi'an Xuhui Power Technology Co., Ltd.