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

Project Background

On February 27, 2026, the facilities management team at the University of Moratuwa, Sri Lanka — one of South Asia's premier engineering universities — reported a critical 400V power outage affecting a key academic building. The affected circuit was an armored three-phase power cable (YJV 3×120+1×95) connecting the main low-voltage switchgear to a remote distribution panel 370 meters away across a dense campus environment. XZH TEST field engineers were dispatched for emergency fault detection and localization.

Fault Diagnosis

Preliminary testing using a 500V insulation resistance tester established the fault profile:

Multimeter measurement confirmed Phase A exhibited only tens of ohms to ground and healthy phases — a definitive low-resistance short-circuit fault. The armored cable construction introduced the risk of multiple incidental ground paths that could mislead single-method detection.

Dual-Method Fault Localization

Method 1: Low-Voltage TDR

Time-domain reflectometry on Phase A to neutral revealed a characteristic short-circuit reflection at 43 meters. Healthy phases B/C returned full-length traces at 371 meters, confirming continuity and isolating the fault. Inter-phase TDR (A-B, A-C) showed short-circuit waveforms at approximately 37 meters.

Method 2: High-Voltage Arc Reflection

A DC high-voltage source with discharge capacitor was applied to Phase A. The fault broke down at approximately 12 kV, generating a classic near-end flashover waveform. Analysis of adjacent wave peaks yielded a fault distance of 40 meters — tightly corroborating the TDR range of 37–43 meters.

Precise Pinpointing & Repair

With the fault constrained to approximately 40 meters, the step voltage method was employed — well-suited to this sub-100Ω fault. A pulsed surge generator discharged through the fault, creating a detectable surface voltage gradient traced to 40.2 meters from the switchgear end. Excavation confirmed a damaged cable section where prior campus construction had compromised the outer sheath and armor, creating a direct Phase-A-to-armor short. The fault was repaired on-site and power restored the same day.

Key Engineering Insights

1. Route tracing first in built-up environments. Campus, residential, and commercial areas with dense underground utilities demand cable path identification before fault localization to prevent costly routing errors.
2. Low-resistance faults favor step voltage pinpointing. When fault resistance approaches zero, step voltage delivers faster, more reliable pinpointing than acoustic or electromagnetic alternatives — especially for armored cables with incidental ground paths.
3. Armored cables require multi-method verification. Cross-validating TDR, arc reflection, and step voltage eliminates ambiguity from multiple ground points along the metallic armor layer.

Equipment Deployed