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Collaborative Optimization Solution for Industrial Earthing Transformers and Arc Suppression Coils
1. Background and Pain Points
In industrial power grids (especially underground coal mines, rail transit traction power supply systems, and metallurgical plants), distribution networks mostly adopt neutral point ungrounded or arc suppression coil grounded modes. When a single-phase earth fault occurs, the following problems arise:
- Excessive zero-sequence capacitive current: Electric arcs are difficult to extinguish spontaneously and may easily develop into phase-to-phase short circuits.
- Response lag of traditional arc suppression coils: Compensation is delayed, leading to prolonged fault duration and further insulation degradation.
- Separate design of earthing transformers and arc suppression coils: Difficult parameter matching, low tuning accuracy, and heavy operation and maintenance workload.
- High-risk environments such as coal mines: Electric arcs may trigger gas explosions or equipment damage, and ultra-high power supply continuity is required (annual power outage time < several minutes).
International cases (Germany's Ruhr mining area, Japan's Shinkansen substations) show that if single-phase earth fault compensation and arc extinction can be completed within 200ms, the accident escalation rate can be reduced by over 90%.
2. Solution Architecture
Integrated + Collaborative Control Dual-Core Architecture:
2.1 Hardware Integrated Design
- Integrate the earthing transformer and tunable arc suppression coil into the same oil tank, sharing the iron core and cooling system. This reduces the floor area by 40% and avoids matching errors caused by independent parameters of the two sets of equipment.
- Adopt a graded tap + continuous fine-tuning composite winding structure to realize stepless adjustment of the arc suppression coil inductance within the rated range (e.g., zero-sequence current compensation of 10~200A).
2.2 Intelligent Collaborative Control System
- Real-time capacitive current measurement: Use high-precision zero-sequence current transformers + transient signal extraction algorithms to calculate the system zero-sequence capacitive current within 20ms after a fault occurs.
- Automatic tuning algorithm: Based on fuzzy PID and adaptive resonance control, dynamically match the optimal inductance value to ensure residual current ≤ 5A (recommended value in IEC 60364-4-41) and arc extinction time ≤ 100ms.
- Multi-criterion fault confirmation: Integrate zero-sequence voltage mutation, harmonic characteristics, and waveform symmetry to avoid false triggering caused by transient disturbances.
Hierarchical Protection and Linkage:
- After local rapid arc extinction, upload fault phase information to the substation integrated automation system, and link with the line selection device to lock the fault line, reducing manual troubleshooting time by 80%.
3. Core Technology Highlights
- Integrated magnetic circuit optimization: The earthing transformer and arc suppression coil share the main magnetic flux path, reducing no-load loss by 15% and improving dynamic response consistency.
- Wide-range automatic tuning: Supports 10%~120% system capacitance changes (adapting to grid expansion or line switching) with tuning accuracy of ±1%.
- Edge intelligence prediction: Embed lightweight AI chips, and train models based on historical fault waveforms to realize early warning of earthing hazards (prompting insulation weak sections 1~3 days in advance).
- High-reliability explosion-proof design (suitable for coal mines): The enclosure holds Ex d I Mb explosion-proof certification, and key internal components are encapsulated with arc-resistant resin, enabling safe operation in environments with methane concentration ≤ 1%.
4. Functional Implementation Indicators
| Indicator | Traditional Separate Solution | This Solution | Improvement Effect |
|---|---|---|---|
| Arc Extinction Time | 300~500ms | ≤ 100ms | 3~5 times faster |
| Zero-Sequence Residual Current | 10~30A | ≤ 5A | Reduction rate ≥ 60% |
| Fault Location Accuracy | Section-level | Line-level (≤1km) | 80% accuracy improvement |
| Floor Area | Baseline value | ↓40% | Space saving |
| Annual Power Outage Time (Coal Mines) | 30~60min | ≤ 5min | Improved power supply continuity |
5. Application Scenarios and Cases
Case 1: 10kV Distribution System in Underground Coal Mines
- Pain Points: The original independent arc suppression coil had tuning lag, with single-phase earth faults lasting 400ms on average, which once triggered a gas alarm and shutdown.
- Retrofit Measures: Deploy integrated earthing transformer + arc suppression coil with explosion-proof and automatic tuning functions.
- Results: Shortened fault arc extinction time to 80ms; no production shutdown caused by earthing faults for 18 consecutive months; zero gas alarm incidents.
Case 2: 35kV Traction Power Supply Network of Urban Rail Transit
- Pain Points: Long cable lines and large capacitive current (>150A); traditional solutions cannot suppress arcs quickly, affecting train operation intervals.
- Retrofit Measures: Apply this solution in hub substations combined with line selection linkage.
- Results: Controlled residual current within 4A; reduced train operation delay rate by 75%; saved approximately 2 million yuan in annual operation losses.
6. Benefit Analysis
- Improved Safety: Significantly shortened arc burning time, greatly reducing risks of fire, explosion, and equipment breakdown.
- Enhanced Power Supply Continuity: Compressed annual power outage time to single-digit minutes in scenarios such as coal mines and rail transit, meeting high reliability requirements.
- Reduced O&M Costs: The integrated design reduces the number of equipment and types of spare parts, cuts O&M workload by 50%, and lowers comprehensive O&M costs by about 35%.
- Good Scalability: Supports automatic retuning after grid expansion or line renovation without manual parameter resetting.
7. Standards and Certifications
- Complies with IEC 60364-4-41 (Earthing of Low-Voltage Electrical Installations) and IEC 62271 (High-Voltage Switchgear and Controlgear Standards).
- Obtains Ex d I Mb explosion-proof certification for coal mine applications; meets EN 50121 (Railway Electromagnetic Compatibility) requirements for rail transit scenarios.
Conclusion
Through integrated magnetic circuit design, wide-range automatic tuning and edge intelligence prediction of earthing transformers and arc suppression coils, this solution builds a closed-loop system covering rapid fault detection → precise compensation and arc extinction → line selection and location. It minimizes the hazards of single-phase earth faults, and is particularly suitable for industrial scenarios with high requirements for power supply continuity and safety such as coal mines and rail transit, providing a replicable arc suppression optimization paradigm for high-risk power grids worldwide.
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