The GEC Alsthom MVTI12C1CD0751G is a high-precision, solid-state inverse time overcurrent and earth fault protection relay from the venerable MVTI series. Originally manufactured under the GEC Alsthom (now Alstom/AREVA/Schneider Electric) brand, this relay is designed to provide essential protection for transformers, motors, and radial feeders in medium-voltage distribution systems. The MVTI series is celebrated for its mechanical robustness and long-term calibration stability, making it a reliable choice for utility and industrial substations worldwide.

 

Technical Description & Parameters

The MVTI12C1CD0751G utilizes a static (electronic) design to mimic the characteristics of traditional induction disc relays while offering faster reset times and better accuracy.

• Model Number: MVTI12C1CD0751G
• Relay Type: Single-phase (or multi-phase depending on the modular housing) Inverse Time Overcurrent.
• Characteristic Curve: Very Inverse (Standard IDMT curve).
• Current Rating: Dual rated for 1A or 5A secondary CT inputs (Jumper/Terminal selectable).
• Setting Range: Typically 50% to 200% for overcurrent or 10% to 40% for earth fault.
• Burden: Extremely low burden on the current transformers (CTs).
• Frequency: 50/60 Hz universal operation.
• Auxiliary Power: Self-powered from the current circuit or requires a DC auxiliary supply (check suffix CD for specific voltage).

 

Product Datasheet Essentials

This relay features a “Very Inverse” time characteristic, which is particularly effective in systems where the fault current drops significantly as the distance from the source increases. The “G” suffix typically denotes a specific case size or mounting arrangement (standard draw-out case). It includes a high-visibility mechanical flag (target) indicator that drops when the relay trips, providing clear local diagnostics for maintenance personnel. The electronics are housed in a dust-proof, plug-in case that allows for testing and replacement without disturbing the factory wiring.

 

Country of Origin

United Kingdom / France (GEC Alsthom Protection & Control)

 

Application Fields

The MVTI series is a fundamental protection component in:

• Utility Distribution: Protecting radial feeders in municipal power grids.
• Industrial Plants: Secondary protection for large oil-filled transformers.
• Mining Operations: Providing reliable earth fault detection in underground power systems.
• Retrofit Projects: Replacing older electromagnetic induction disc relays with a footprint-compatible electronic version.

 

Product Usage Instructions

1. Mounting: Install the draw-out case into the switchgear panel. Ensure the earthing strip at the rear of the case is securely bonded to the panel ground.
2. CT Connection: Wire the CT secondary leads to the appropriate 1A or 5A terminals. Warning: Never open-circuit a CT primary while the secondary is disconnected.
3. Setting: Use the front-panel rotary switches or plugs to set the “Plug Setting Multiplier” (PSM) and the “Time Multiplier” (TM). These define the current threshold and the delay before tripping.
4. Testing: Use a secondary injection test set to verify the trip curve. The relay should be tested at 2x and 5x the set current to ensure it follows the specified IDMT curve.

Common Questions & Answers (Q&A)

Q: Can I replace an old induction disc relay with the MVTI12C1CD0751G? A: Yes, the MVTI series was specifically designed to be a solid-state alternative to legacy induction disc relays, often fitting into similar cutouts and offering much more consistent timing.

Q: What does the “Very Inverse” curve offer over a “Standard Inverse” curve? A: A Very Inverse curve is steeper. This means that for a small increase in fault current, the operating time decreases more rapidly, allowing for better coordination in systems with high source impedance.

Q: How do I reset the trip flag? A: There is a manual reset lever or button on the front faceplate. Once the fault has been cleared and the breaker is ready to be re-energized, simply push the lever to return the flag to its concealed position.

 

Explore More Protection Hardware

For genuine MVTI12C1CD0751G relays and other GEC Alsthom legacy spare parts, visit our online technical inventory.

 

Recommended Similar Models

1. MVTI11 – A single-phase version of the inverse time relay.
2. MCGG22 – A newer generation digital overcurrent relay from the same manufacturer.
3. METI – A definite time overcurrent relay often used in the same lineups.
4. MVTT – A voltage-controlled overcurrent relay for generator protection.
5. KCGG140 – A modern Alstom numerical relay used for feeder management.