XZH TEST Engineers Locate 10kV Cable Fault in 42 Minutes in Chengdu, Power Restored in 3 Hours

On-Scene Report

At 2:25 PM on July 21, alarms blared inside the power distribution room of Tianfu Software Park Phase III in Chengdu Hi-Tech Zone. A 10kV XLPE main feeder cable supplying power to Buildings D, E, and F had suffered a ground fault, leaving over 60 tech companies and approximately 4,000 employees without power. The Chengdu Hi-Tech Power Supply Company's operations dispatch center immediately activated its emergency repair protocol and called XZH TEST (Xi'an Xuzhihui Electric Power Technology Co., Ltd.) for technical support.

1. Emergency Response: On-Site in 25 Minutes

At 2:28 PM, XZH TEST's Southwest Regional Technical Service Department received the call. Technical supervisor Zhang Jianguo quickly retrieved the line's maintenance history and found that the cable section was installed in 2017, spanning approximately 2.8 km, with roughly 1.9 km routed through underground cable trenches beneath the Tianfu Avenue South Extension municipal conduit — an environment known for high humidity and standing water in certain sections.

At 2:32 PM, Zhang assembled a three-person emergency team with engineers Li Siyuan and Wang Hao, deploying with the following core diagnostic equipment:

At 2:50 PM, the emergency team arrived at the Tianfu Software Park Phase III distribution room — just 25 minutes from dispatch.

2. Precision Diagnosis: Three Steps to Identify the Fault

Upon arrival, Zhang's team immediately initiated standard operating procedures for power cable fault detection:

Step 1: Safety Isolation and Insulation Testing

At 3:00 PM, after confirming both ends of the cable were reliably disconnected and properly grounded, Li Siyuan used the XHMR-10kV Insulation Resistance Tester to apply DC high voltage to each of the three phases. Results: Phase A — 2.8 GΩ (normal), Phase B — 3.1 GΩ (normal), Phase C to ground — only 0.05 MΩ (critically abnormal). The fault was identified as a Phase C metallic ground fault.

Step 2: TDR Pulse Reflection for Rough Distance Measurement

At 3:12 PM, Wang Hao connected the XHGG501A2 Cable Fault Pre-Locator between Phase C and ground. After configuring test parameters on the 12.1-inch industrial touch display, a 400V low-voltage pulse was transmitted into the cable. The pulse propagated through the cable and reflected at the high-impedance fault point. With the instrument's 400MHz high-speed sampling engine, a clear reflection waveform with polarity reversal was observed at a distance of 1,865 meters. The instrument's blind zone of ≤10m ensured reliable near-end signal clarity without terminal interference.

Step 3: ARC Multi-Pulse Method for Precise Verification

At 3:18 PM, for further verification, Zhang switched to ARC multi-pulse mode. The XHHV535-4Z Portable High Voltage Surge Generator was used to apply impulse high voltage (16kV setting) to Phase C, causing the fault point to momentarily break down and form an arc channel. The XHGG501A2 simultaneously captured the measurement waveform and compared it against a reference waveform taken without high voltage. With multiple waveform groups overlaid, the fault point divergence was clearly resolved — the corrected distance was 1,872 meters. With a measurement error of ≤±(0.5%×L+1m), the theoretical error at 1,872m was no more than 10.4m, providing an excellent window for acoustic-magnetic pinpointing.

Referencing the park's GIS cable route drawings, the 1,872m mark corresponded to a cable manhole near the southeast corner of the Tianfu Avenue South Extension and Jitai Road intersection. Zhang determined the fault was most likely within or adjacent to that manhole.

3. Precision Pinpointing: Acoustic-Magnetic Synchronization Locks the Fault

At 3:30 PM, the team deployed the XHDD503C Cable Fault Pinpointer and the XHHV535-4Z Portable High Voltage Surge Generator to the target area.

Li Siyuan connected the XHHV535-4Z high-voltage output to Phase C, setting output voltage to 16kV with a 7-second cyclic discharge interval. Wang Hao walked along the cable route surface with the XHDD503C acoustic probe, monitoring point by point. Thanks to the XHDD503C's IP65 waterproof probe design, it performed reliably even in the post-rain standing water conditions on the road surface. As the probe approached the manhole at the 1,872m mark, the acoustic-magnetic time difference signal on the 5-inch touch LCD began to converge. Clear, powerful "thump-thump" sounds synchronized with the discharge interval came through the headphones, and the acoustic intensity reading peaked at 98 dB.

At 3:42 PM, Wang Hao reported: "Acoustic-magnetic synchronization confirmed — the fault point is in this manhole!" The team opened the manhole cover to find approximately 40 cm of standing water with the cable joint completely submerged. After dewatering and inspection, it was determined that the intermediate joint installed during 2017 construction had suffered insulation breakdown due to prolonged water immersion, with clear arc burn marks on the joint body.

From arrival at the target manhole to confirmed fault location, the XHDD503C acoustic-magnetic pinpointing process took only 12 minutes. The entire detection and location workflow — from equipment connection to fault point lock — totaled just 42 minutes.

4. Efficient Repair: Power Restored in 3 Hours

At 4:00 PM, with the fault point confirmed, Zhang Jianguo submitted a detailed fault detection report to the on-site supervisor from Chengdu Hi-Tech Power Supply Company, recommending complete replacement of the intermediate joint and resealing of the manhole waterproofing.

The power company repair crew, guided by the precision coordinates, excavated only approximately 2 square meters of work area around the manhole (compared to dozens or even hundreds of square meters required by traditional blind excavation along the cable trench). The damaged joint was cut out, a new intermediate joint was fabricated on-site, and a waterproof sealing enclosure was installed. Wang Hao used the XHMR-10kV to retest the repaired cable insulation: Phase A — 2.9 GΩ, Phase B — 3.0 GΩ, Phase C — 2.7 GΩ. All three phases had returned to normal.

At 5:25 PM, the line was successfully re-energized on the first attempt, and full power was restored to Buildings D, E, and F of Tianfu Software Park Phase III. The total time from fault report to power restoration: just 3 hours.

5. Customer Feedback and Performance Summary

Chen Gang, Director of Operations and Maintenance at Chengdu Hi-Tech Power Supply Company, stated at the post-repair review meeting: "The efficiency of this fault resolution far exceeded expectations. For similar underground cable testing and fault localization in the past, the process from line patrol to fault pinpointing typically required 8–12 hours or longer, often accompanied by widespread power outages. XZH TEST's cable fault locator and XHDD503C acoustic-magnetic pinpointing technology enabled us to complete the entire workflow — from fault location to repair — in just 3 hours, minimizing production losses for the businesses in the park."

Key performance comparison of this operation:

The property management of Tianfu Software Park estimated that the rapid power restoration prevented approximately 2.8 million RMB in potential production downtime losses for park-based enterprises.

6. Engineer's Notes: Zhang Jianguo's Field Reflections

At the post-operation review session, XZH TEST Technical Supervisor Zhang Jianguo shared his thoughts:

"The core of cable fault detection lies in two words: speed and accuracy. The reason we could complete precise location within 42 minutes this time comes down to the XHGG501A2 pre-locator's 400MHz high-speed sampling and ARC multi-pulse comparison capability — with 0.1m reading resolution and three selectable pulse widths (0.25μs / 2μs / 4μs), we could flexibly switch between high-resolution near-end measurement and high-energy long-distance scanning. The XHDD503C's IP65 protection rating and precise acoustic-magnetic synchronization algorithm allowed us to clearly capture discharge acoustic signals even in the challenging flooded-manhole environment, and its 0.1m pinpointing accuracy meant our excavation hit the fault joint directly. The XHHV535-4Z's portable design (≤35kg total weight) enabled single-person transport to the site, while its 32kV three-level adjustable output provided flexible energy selection for different fault types.

For power system maintenance, equipment precision determines repair efficiency, and efficiency directly impacts urban electrical safety and the normal power supply to thousands of households and businesses. This is the driving force behind our continuous pursuit of technical breakthroughs."

Chengdu Hi-Tech Power Supply Company has decided to incorporate this fault detection case into its annual O&M training curriculum and plans to expand the deployment of XZH TEST's cable fault location technology across its key distribution lines to improve overall power supply reliability.

About XZH TEST

XZH TEST (Xi'an Xuzhihui Electric Power Technology Co., Ltd.) is a high-tech enterprise integrating R&D, manufacturing, sales, and technical services for power testing equipment, headquartered in the Xi'an High-Tech Industries Development Zone, Shaanxi Province, China. Since its establishment in 2013, the company has focused on innovation in power cable fault detection and location technology. Its core product portfolio includes cable fault pre-locators (XHGG series), acoustic-magnetic synchronous pinpointers (XHDD series), portable high-voltage surge generators (XHHV series), insulation resistance testers (XHMR series), cable identifiers, and partial discharge detection systems — covering the full spectrum of power O&M testing equipment.

The company operates an R&D center led by multiple Ph.D.-level power system automation experts, supported by a high-voltage laboratory, environmental adaptability testing center, and EMC laboratory. XZH TEST holds ISO 9001 quality management certification, CE certification, and multiple national invention patents. Its products are widely deployed across State Grid, China Southern Power Grid, the five major power generation groups, Sinopec, PetroChina, rail transit systems, large industrial parks, and data centers. With an export ratio of 80%–90%, XZH TEST products are distributed across more than 40 countries and regions in Southeast Asia, the Middle East, Africa, South America, and the CIS.

XZH TEST operates eight regional technical service centers nationwide, equipped with 24/7 emergency response teams, delivering a complete service cycle from equipment selection and on-site training to routine inspection and emergency repair technical support. The company's mission: To safeguard every meter of cable with advanced detection technology, leaving no power fault undetected.