High-Voltage Insulation Inspection

Abstract

Recently, the full set of partial discharge free power frequency withstand voltage test system independently developed by DEMIKS has completed installation and commissioning at the assembly workshop of CRRC Changke Chengdu Rail Vehicle Co., Ltd. & Chengdu Changke Xinzhu Rail Transit Equipment Co., Ltd. The complete test solution, equipped with partial discharge free test transformer, dual-screen intelligent control cabinet and 100kV high voltage RC voltage divider, is dedicated to mandatory factory high-voltage insulation inspection for new panda-themed modern trams and urban metro vehicles. This integrated testing equipment fills the gap of simultaneous withstand voltage & partial discharge precise detection for whole rail vehicles in the factory, fully complying with domestic rail transit standards and international EN electrical safety testing specifications for rolling stock.

1. Project Background: Mandatory High-Voltage Testing Demand for Rail Vehicles

As a core urban rail vehicle manufacturing hub in Southwest China, CRRC Chengdu Changke specializes in R&D and production of modern trams and municipal metro trains. Every rail vehicle must pass full high-voltage circuit insulation verification before delivery. Traditional split withstand voltage testing equipment suffers high background partial discharge, low boost control precision, incapability of synchronous data acquisition and poor mobility, failing to meet refined insulation defect screening requirements for new lightweight trams and large-capacity metro trains. To satisfy CRCC factory certification and international ANSI testing standards for exported rail vehicles, the factory introduced DEMIKS integrated partial discharge free power frequency withstand voltage test system, building a mobile whole-vehicle high-voltage testing station to realize cyclic high-efficiency inspection for multi-marshalling trains.

2. Core Components & Technical Advantages of the Complete Test System

The DEMIKS partial discharge free power frequency withstand voltage test system delivered to the site consists of three integrated core units:

1. YDW Series Partial Discharge Free Test Transformer (High Voltage Generation Core) The core component adopts special low-partial-discharge insulating oil and multi-layer shielding winding structure. Model YDW-50/100 partial discharge free test transformer provides a maximum test voltage of 100kV with ultra-low inherent partial discharge. It can capture invisible internal insulation defects including tiny air bubbles, insulation cracks and assembly damage on high-voltage cables, traction transformers and pantograph insulators during power frequency withstand voltage loading. The heavy-duty mobile trolley design enables flexible transportation among multiple rail test bays without fixed civil test platforms.
2. Dual-Touch-Screen Intelligent Program Control Cabinet (System Operation Core) The integrated industrial control console is equipped with dual touch screens, embedding automatic voltage boosting logic, instant breakdown cut-off protection, real-time leakage current monitoring and synchronous partial discharge waveform display modules. Operators can set test voltage, voltage holding duration and over-current protection threshold with one click. The equipment automatically completes full procedures of boost, voltage stabilization and depressurization, while storing test data and partial discharge curves to generate standardized inspection reports, effectively eliminating manual operation errors. On-site electrical engineers finished equipment operation training and joint commissioning with rail vehicles as shown in photos.
3. 100kV High-Voltage RC Voltage Divider (Voltage Sampling Unit) The matched high voltage divider works in linkage with the partial discharge free test transformer to feed back actual high-side voltage with high precision, forming a closed-loop program control circuit. It isolates high voltage circuits from low-voltage control systems to eliminate electric shock risks caused by high voltage leakage into the operation console, ensuring full safety of operators and rail vehicles during whole-vehicle testing.

3. On-Site Test Application in Rail Transit Workshop

The test targets cover full high-voltage systems of panda-themed modern trams and standard metro trains in the factory, including pantograph assemblies, on-board traction transformers, high-voltage cable busbars, high-voltage switch cabinets, traction inverters and all on-board insulators. Two core inspection items are performed by the complete partial discharge free power frequency withstand voltage test system:

1. Whole-Vehicle Power Frequency Withstand Voltage Test: Simulate extreme working conditions such as power grid surge and lightning overvoltage, apply 2~3 times rated test voltage on full high-voltage circuits with fixed holding duration to verify insulation withstand capacity. In case of insulation damage, water ingress or assembly defects, the equipment will instantly cut off high voltage and record fault positions, fundamentally avoiding safety hazards including short circuit, fire and electric leakage during vehicle operation.
2. Synchronous Partial Discharge Detection: Relying on the ultra-low background partial discharge characteristic of the partial discharge free test transformer, the system detects tiny internal insulation defects undetectable by conventional withstand voltage test, predicting long-term insulation aging risks of rail vehicles in advance to meet refined factory inspection standards for high-end urban rolling stock.
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4. Industrial Value & Future Cooperation Outlook

The deployment of DEMIKS partial discharge free power frequency withstand voltage test system at CRRC Changke production base marks the deep matching of domestic integrated high-voltage insulation testing equipment with leading domestic rail transit vehicle manufacturers, breaking the monopoly of imported high voltage test equipment. The complete system complies with both domestic GB/T 25122 urban rail standards and EU EN50155 rolling stock electrical standards, supporting dual inspection demands for domestically delivered and exported trams & metro vehicles. DEMIKS will continuously upgrade partial discharge free test transformers and mobile withstand voltage test integrated systems, providing all-in-one high-voltage insulation testing solutions for rail transit, power transformers, cable manufacturing and new energy energy storage industries, and boosting domestic high-end electrical testing equipment to global markets.