The GEC Measurements CDG66FF2010FS is a high-performance, three-phase electromechanical protection relay from the legendary CDG series. This unit is specifically designed for time-graded overcurrent protection in power systems. Known for its “Standard Inverse” characteristic, the CDG66 ensures that the tripping time is inversely proportional to the fault current, providing reliable selectivity. This allows downstream faults to be cleared by local breakers before the main supply is interrupted, minimizing downtime in industrial and utility networks.

 

Product Datasheet & Technical Specifications

The CDG66 series is engineered for durability and consistent timing accuracy:

• Model Type: CDG66 (Three-pole/Three-phase Inverse Time Overcurrent)
• Configuration Code: FF2010FS
• Measurement Elements: Three independent induction disc elements in a single case
• Current Rating: 1A or 5A secondary current compatibility
• Time Characteristic: Standard Inverse (SI) to BS 142 and IEC 60255 standards
• Setting Range: 50% to 200% of rated current (adjustable via plug bridge)
• Time Multiplier: 0 to 1.0 adjustable dial for fine-tuning trip speed
• Case Size: Large modular drawout case (typically Size 3 or 4)
• Flag Indicator: Mechanical hand-reset operation indicators for each phase

 

Country of Origin

This protection relay was manufactured in the United Kingdom (UK) at the Stafford site, a facility renowned for producing the most reliable electromechanical protection devices in the world under the GEC, Alsthom, and English Electric brands.

 

Application Fields

The CDG66FF2010FS is a staple in medium and high-voltage electrical infrastructure:

• Feeder Protection: Providing primary overcurrent protection for radial distribution lines.
• Transformer Protection: Guarding the primary and secondary windings against sustained overloads.
• Backup Protection: Acting as a reliable fail-safe for modern digital relays in critical substations.
• Industrial Plants: Protecting large-scale power distribution boards in steel mills and refineries.
• Marine Power Systems: Ensuring electrical stability on large vessels and offshore platforms.

Product Instructions & Technical Notes

When installing the GEC Measurements CDG66FF2010FS, ensure the relay is mounted perfectly level to prevent friction on the induction disc spindle. The “FF” in the code typically refers to the frequency (50Hz/60Hz) and mounting style; verify your system frequency before commissioning. To adjust the trip threshold, move the captive plug to the desired percentage of the rated current. It is vital to perform a secondary injection test every 2 years to ensure the induction disc rotates freely and the contacts close within the specified time-current curve.

 

Q&A – Frequently Asked Questions

Q1: What is the benefit of a three-phase CDG66 over three single-phase CDG11 relays? A: The CDG66 houses all three phases in a single enclosure, saving significant panel space and simplifying the wiring of the trip circuit.

Q2: Can I adjust the tripping speed without changing the current setting? A: Yes, by adjusting the Time Multiplier (TM) dial on the front of the relay. This shifts the entire inverse curve up or down to coordinate with other relays in the system.

Q3: Does this relay require an auxiliary power supply? A: No. The CDG66 is a “self-powered” electromechanical relay that derives its operating energy directly from the current transformer (CT) secondary circuit.

Q4: How do I reset the fault indicator? A: Once the fault is cleared, you must manually reset the mechanical flag using the push-button or lever located on the front of the relay cover.

 

Similar Model Recommendations

1. GEC Measurements CDG11 (Single-phase version)
2. GEC Measurements CDG31 (Three-phase version with different case style)
3. GEC Measurements MCGG82 (Modern digital equivalent)
4. Alstom/AREVA CDG61 (Legacy variant with different contact logic)
5. GEC Measurements METI (Dedicated Earth Fault relay often used alongside CDG66)