Analysis and Selection of Current Transformer Installation Positions in Switchgear
2025-06-19 14:13Analysis and Selection of Current Transformer Installation Positions in Switchgear
I. Common Installation Positions
Horizontal Suspension Behind Arc Chamber
Temperature Rise Risk: CT blocks heat dissipation paths, amplifying heat buildup at contact joints.
Airflow Obstruction: Mounting plate impedes ventilation in busbar compartment, hindering cooling.
Pressure Relief Blockage: May obstruct cable compartment pressure relief channels, compromising internal arc fault handling (critical for ≥40kA ratings).
Advantages: Minimal copper busbar usage; simple structure; ample cable connection space.
Applicability: Switchgear with low current and low short-time withstand current ratings.
Issues:
Vertical Installation at Rear Panel
Optimized Heat Dissipation: Improves contact and overall temperature rise, especially for high-current applications (facilitates temperature rise tests).
Efficient Pressure Relief: Enlarges vent channel cross-section, reducing blow-off cover activation time (≈6-7 ms) and minimizing explosion damage.
Maintenance Convenience: Easy replacement and installation.
Advantages (Recommended per State Grid standardization):
Applicability: Medium/high-current switchgear; high internal arc classification.
Horizontal Mounting on Baseplate
Advantages: Facilitates front-access maintenance (wiring checks, testing, secondary connections).
Applicability: Switchgear installed against walls (requires front maintenance clearance).
Design Requirement: Grounding switch contacts and interlocking mechanisms must be front-accessible.
Vertical Installation Below Arc Chamber (Modular Design)
Short Busbar Length: Simplifies assembly (integrated functional module installation).
Integrated Interlocking: Combines with grounding switch for "active protection" (mechanical blocking of racking/grounding ports via compartment door).
Ease of Maintenance: Supports front-access module replacement.
Advantages:
Constraints: Requires compact circuit breakers and customized cabinet height (ideal for space-constrained designs).
II. Comprehensive Selection Criteria
| Factor | Behind Arc Chamber | Rear Vertical | Baseplate Horizontal | Below Arc Chamber |
|---|---|---|---|---|
| Copper Busbar Consumption | ★★★☆☆ (Lowest) | ★★☆☆☆ | ★☆☆☆☆ | ★★☆☆☆ |
| Temperature Control | ★☆☆☆☆ (Poor) | ★★★★☆ | ★★★☆☆ | ★★★☆☆ |
| Internal Arc Relief | ★☆☆☆☆ (High Risk) | ★★★★☆ | ★★★☆☆ | ★★★☆☆ |
| Assembly Simplicity | ★★★☆☆ | ★★★★☆ | ★★★☆☆ | ★★★★★ (Optimal) |
| Front Maintenance Support | ★★☆☆☆ | ★★☆☆☆ | ★★★★☆ | ★★★★☆ |
| Recommended Current Level | Low Current | Med./High Current | Universal | Compact Designs |
Key Conclusion:
Cost Priority: Horizontal suspension viable for low-current cabinets, but requires thorough thermal/arc risk assessment.
Safety Priority: Rear vertical installation is optimal for medium/high-current or high-arc cabinets (State Grid standard).
Compactness & Maintenance: Below-chamber modular design excels for space-efficient applications.
III. Innovation: Modularization & Active Protection
The HZMNX SFA550 Switchgear adopts the Integrated Below-Chamber Module:
Assembly Revolution: Combines CTs + grounding switch; drastically reduces cabinet build time (drop-in module installation).
Zero Misoperation: Mechanical door interlocks physically block racking/grounding ports (inherent safety).
Maintenance Optimized: Enables front-access replacement for confined spaces.
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