Description
Product Name : 12SGC21B1A GE Input module
Product details:
The GE 12SGC21B1A is a solid-state (static) Negative-Phase Sequence Time-Overcurrent Relay belonging to GE’s SGC product family. It is specifically designed to protect AC generators and electrical equipment against overheating and damage caused by unbalanced phase currents and negative-sequence current conditions.
Note: This model has been discontinued by the manufacturer, but it remains widely used in retrofits, industrial maintenance, power distribution systems, and legacy infrastructure setups.
2. Product Parameters & Technical Specifications
| Parameter | Specification Details |
| Manufacturer | General Electric (GE) |
| Model Number | 12SGC21B1A |
| Product Line / Family | SGC Relay Series |
| Relay Type | Static / Solid-State Negative-Sequence Time-Overcurrent Relay |
| Protective Function | Negative Sequence Overcurrent / Phase Unbalance Protection |
| Nominal Current (CT Secondary) | 5 Amps |
| Nominal Frequency | 60 Hz |
| Control / Auxiliary Voltage | 48 / 110 / 125 VDC |
| Approximate Weight | ~21.5 lbs (9.75 kg) |
| Mounting / Case Style | Draw-out case style for panel mounting |
3. Key Product Advantages
- Targeted Generator Protection: Specifically calibrated to match the thermal capability (I_2^2 t) curves of AC generators, preventing localized rotor overheating caused by negative-sequence currents.
- Solid-State Reliability: Static electronic circuitry provides high precision, repeatable trip characteristics, and resistance to physical shock or mechanical wear compared to older electromechanical relays.
- Draw-out Case Design: Allows for easy testing, calibration, and maintenance without disturbing rear terminal connections or panel wiring.
- Stable Thermal Tracking: Accurately models heat buildup in power machinery caused by unbalances such as open phases or asymmetrical line faults.
4. Key Applications
- AC Generator Protection: Primary application in protecting synchronous generators against unbalanced loads, phase loss, or asymmetric system faults.
- Industrial Power Plants & Substations: Employed in utility and heavy-industrial electrical systems where power quality and phase balance are critical.
- Legacy Power Grid Maintenance: Used as direct replacements for older protective schemes in existing medium-to-high voltage power distribution panels.
5. Important Precautions & Considerations
- Discontinued Status: Since GE has discontinued this legacy series, official manufacturer warranties are typically no longer provided; replacement units and spare parts are sourced via certified surplus/refurbished suppliers.
- Auxiliary Power Matching: Verify that the supply control voltage (48, 110, or 125 VDC) matches your station battery voltage before commissioning.
- Proper Calibration Required: Ensure the relay’s trip curves and settings are adjusted by qualified field technicians in alignment with generator thermal withstand ratings (I_2^2 t = K).
- Safe Isolation: Use standard isolation procedures or the draw-out test plugs to safely isolate current transformers (CTs) and avoid open-circuiting CT secondary windings during service or testing.
Advantages: Foxboro, OVATION, TRICONEX, Allen-Bradley, ABB, Motorola, Siemens Moore, Ge Fanuc, Woodward, Bently Nevada and other major import brands!
We have the same series of models in stock. If you don’t find the model you need, please contact us and we will provide you with an official quotation！
Colour：new Warranty: 12 months
Lead Time：3-day working day Country of origin: United States
Price: Please contact us Product weight：0.515kg
Shipping Port: Xiamen, China
Payment: Bank of Chicago, Bank of Singapore
Express cooperation: fedex, DHL, UPS and your express account
Service: Professional Sales provides 24 hours /7 days online service
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