Electronic Current Transformer (ECT) Solution: Economically Driven Retrofit
I. Pain Points: Challenges in Conventional Substation Retrofit
Traditional electromagnetic current transformers (CTs) present numerous issues in aging substations:
- High Retrofit Cost: Replacing conventional CTs requires large-scale power outages, civil construction, and updates to protection panels, cabling, and grounding systems. Combined costs exceed 50%.
- Poor Compatibility: New devices have interface mismatches with legacy secondary systems (e.g., relays, meters), necessitating additional conversion devices.
- Space Constraints: Aging substations have limited space. Conventional CTs are bulky and heavy, making hoisting difficult and potentially requiring foundation expansion.
- Lengthy Commissioning: Retrofits involve multi-system integration testing. Tight outage windows delay grid restoration.
II. Solution: ECT (Electronic Current Transformer) Economical Retrofit
Achieve an upgrade path of "minimizing retrofit cost, maximizing compatibility with existing systems" through ECT technology:
**▶ Core Economic Advantage: Significant Reduction in Comprehensive Retrofit Cost**
|
Cost Item |
Conventional CT Retrofit |
ECT Retrofit Solution |
Cost Savings |
|
Equipment Installation |
Crane/Civil Works/Foundation Reinforcement |
Direct Stud Mounting |
**↓ 40% construction cost** |
|
Cabling |
Multi-strand Copper Cables + Extensive Wiring |
Fiber Optic / Digital Signal Lines |
**↓ 60% cable cost** |
|
Secondary Equipment Interface Retrofit |
Protection Panels & Meter Replacement Required |
Compatible with Traditional Analog Output |
**↓ 80% secondary retrofit cost** |
|
Outage Duration |
≥7 Days (Full Substation Shutdown) |
≤3 Days (Partial Outage) |
**↓ 50% outage loss** |
**▶ Compatibility Design: Seamless Integration with Existing Infrastructure**
- Hybrid Interface Output:
ECTs feature built-in Analog Output (4-20mA/0-5V) + Digital Output (IEC 61850-9-2), compatible with three scenarios: - Legacy Protection Devices: Connect directly to existing current input terminals.
- Digital Protection Systems: Send GOOSE messages via Merging Units (MUs).
- Metering Systems: Simultaneously output analog signals for meter sampling.
- Plug-and-Play Installation:
- No Crane Required: ECT weight <15kg (vs. ~150kg for conventional CTs), enabling manual installation.
- Compact Size: Diameter ≤200mm, fits original CT mounting brackets.
- Flexible Rogowski Coil: Can be wrapped around existing primary conductors, eliminating busbar disassembly.
- Adaptive Power Supply Scheme:
- Laser Power Supply: Energy delivered via fiber optics embedded in insulators, eliminating separate power supplies.
- Busbar Power Harvesting: Inductive power harvesting uses primary current for self-supply, suitable for passive environments.
III. Value Realization: Rapid Return on Retrofit Investment
|
Retrofit Phase |
Core Value of ECT Solution |
Economic Impact |
|
Pre-construction & Construction |
Shortens Schedule by 70% |
Reduces Outage Loss ≥ ¥2 million |
|
Commissioning |
Plug-and-play, no calibration for legacy protection |
Commissioning Costs **↓60%** |
|
Operation & Maintenance |
No magnetic saturation, wideband measurement (0.1Hz~5kHz) |
Maintenance Frequency Reduced by 90% |
|
Long-term Expansion |
Pre-installed digital interfaces support future smart substation upgrades |
Avoids secondary retrofit investment |
IV. Representative Case Study: 110kV Gudu Substation Retrofit
- Original Configuration: Electromagnetic CTs (Commissioned 1985)
- Retrofit Solution:
Installed 12 ECTs (Class ±0.5S) to replace conventional CTs. Output signals:
→ 4-20mA fed into existing relay protection devices.
→ IEC 61850-9-2LE fed into newly installed smart control cabinets. - Economic Results:
- Total Investment Reduced by 42% (Primarily saved on cabling, civil works, commissioning).
- Outage Time Reduced from originally planned 7 days to 2.5 days.
- Compatibility Verified: Conventional differential protection operating time maintained at 15ms, with no failure to trip / maloperation.
V. Why Choose the ECT Economical Retrofit?
- Controlled Cost: Retrofit budget reduced by 30%-50%, ROI < 3 years.
- Risk Mitigation: Maintains existing protection logic, avoiding system reconfiguration risks.
- Smooth Evolution: Compatible with today's analog systems, supporting tomorrow's digital grid.
- Emergency Replacement: Faulty CT replacement completed in as little as 48 hours.
