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Tongchuan PV Plant Underground Cable Fault Precision Location — Rapid Detection Restores Solar Generation

2026-07-20

Tongchuan PV Plant Underground Cable Fault Precision Location — Rapid Detection Restores Solar Generation

Integrated Cable Fault Detection System Deployed at Utility-Scale Solar Plant — Same-Day Fault Location with 0.1m Accuracy Despite High-Resistance Fault and Railway Noise Interference

0.1m

Pinpointing Accuracy

80–90m

Fault Distance

Same Day

Detection-to-Repair

Instruments Deployed

~900m

Cable Route Length

Project Background

Item	Detail
Project	Tongchuan Photovoltaic Power Plant — Low-Voltage Cable Fault Detection
Location	Tongchuan, Shaanxi Province, China
Date	June 7, 2026
Personnel	Li Cheng, Gao Fei, Du Chaochao
Cable Type	Single-core unarmoured low-voltage cable, bundled in groups of several dozen parallel cables
Cable Length	Approximately 800–900 metres (PV panels to inverter)
Installation	Primarily inside protective conduit, with sections of direct-buried at 0.3–1.0m depth
Site Conditions	Adjacent to Longhai Railway — frequent passing trains generate substantial ambient noise

Fault Challenge

The on-site investigation presented multiple compounding difficulties that tested the limits of conventional cable fault detection methods:

Challenge	Impact on Detection
High-Resistance Fault ~2 MΩ red phase to ground	Weak discharge acoustics during HV impulse testing — traditional acoustic pinpointing unreliable
Inconsistent Pre-Location TDR reading >1,000m vs known ~900m	Wave velocity calibration error produced misleading distance; phase-to-phase measured ~5 kΩ indicating compound fault
Unreliable Waveforms 4–5 attempts per capture	High-resistance fault required repeated HV discharge cycles to produce usable waveform data
Railway Noise Interference Continuous high-decibel train noise	Acoustic-only pinpointing rendered ineffective — operator unable to distinguish fault discharge from environmental noise
Dense Cable Bundle Dozens of parallel cables	Positive identification of faulted cable among adjacent live circuits critical to avoid unnecessary excavation

Solution — Integrated Detection System

XZH TEST deployed a comprehensive five-instrument diagnostic chain covering the complete fault location workflow:

#	Instrument	Model	Role in Detection Chain
1	ARC Multi-Pulse Pre-Locator	XHGG502	High-precision fault distance measurement using 8-pulse ARC technology; converts complex high-resistance fault waveforms into interpretable short-circuit equivalent traces
2	Digital Fault Pinpointer	XHDD503E	Acoustic-magnetic synchronous pinpointing with 0.1m accuracy; immune to ambient noise through dual-signal time-difference analysis
3	Cable Pipe Locator	XHGX507C	Cable route verification and depth measurement along the full 800m+ path
4	Integrated Surge Generator	XHHV515-8L	Controlled high-voltage impulse delivery for reliable fault-point arc discharge
5	Cable Outer Sheath Tester	XHHV523L	Supplementary fault zone narrowing through sheath integrity analysis

Implementation Process

Step	Operation	Instrument	Findings
1	Route Verification	XHGX507C	Re-surveyed full ~800–900m underground cable path from PV panels to inverter; confirmed route despite challenging high-resistance ground conditions
2	Fault Characterization	Insulation Tester, Multimeter	Red phase confirmed open-circuit; insulation: ~2 MΩ (PV end), ~2–3 MΩ (inverter end); phase-to-phase: ~5 kΩ — compound ground leakage + inter-phase fault
3	Fault Pre-Location	XHGG502	Connected at inverter end; red phase HV + black phase grounded → fault distance: 80–90 metres; PV end phases shorted to ground to improve discharge reliability for pinpointing
4	Precision Pinpointing	XHDD503E	Walked cable path with acoustic-magnetic probe; discharge sound detected near fence line despite railway noise; magnetic time-difference confirmed fault location
5	Excavation & Verification	—	Single-point excavation at pinpointed location; root cause: fence post installation hole directly penetrated cable, severing red phase conductor; confirmed within 0.1m accuracy

Application Results

Metric	Result
Fault Location Accuracy	Within 0.1m — excavation directly above fault point, no exploratory digging required
Pre-Location Distance	80–90 metres from inverter end (confirmed at excavation)
Detection Timeline	Same-day completion — from initial testing through final pinpointing
Excavation Efficiency	Single pinpointed location; zero trial trenches; zero collateral damage to adjacent cables
Root Cause	Third-party damage: fence post installation hole penetrated cable conductor
Noise Immunity	Acoustic-magnetic technology maintained reliable operation despite adjacent railway noise

Customer Value

Minimized Generation Downtime: Same-day fault location enabled immediate repair scheduling. The faulted PV string was restored to full generation capacity with minimal revenue loss — critical for a utility-scale solar asset where every hour of downtime translates to measurable financial impact.
Precision Excavation — Zero Waste: 0.1m pinpointing accuracy meant the repair crew excavated exactly at the fault location. No trial trenches, no unnecessary cable exposure, and no collateral damage to adjacent healthy cables in the tightly bundled group of several dozen parallel circuits.
Railway-Proven Noise Immunity: The site's proximity to the Longhai Railway would have rendered a conventional acoustic-only pinpointer unusable. The XHDD503E's acoustic-magnetic synchronous technology continuously delivered reliable time-difference data regardless of passing train noise — validating the technology for high-noise industrial environments.
Complete In-House Diagnostic Capability: The five-instrument suite provided a seamless diagnostic chain from initial fault characterization to centimetre-level excavation. No third-party equipment or external service providers were required — reducing both cost and logistical complexity.
Root Cause Documentation & Accountability: Positive identification of the fence installation as the fault cause provided the plant operator with concrete evidence for contractor accountability and informed future cable protection protocols during on-site construction activities.

Contact XZH TEST for technical consultation, on-site demonstration, or custom cable fault detection solutions tailored to your infrastructure.