The GEC Measurements CDG16AF0008A5 is a classic induction disc protection relay from the legendary CDG series. This electromechanical relay is specifically designed for inverse time overcurrent and earth fault protection in electrical power systems. Known for its extreme durability and “fail-safe” mechanical nature, the CDG16 remains a staple in power distribution and industrial substations worldwide for protecting feeders, transformers, and AC machines.

 

Product Technical Description

The CDG16 is a single-pole relay that operates on the induction disc principle. It features an “IDMT” (Inverse Definite Minimum Time) characteristic, meaning the operating time is inversely proportional to the magnitude of the fault current—the higher the current, the faster the relay trips. The “AF0008A5” specification identifies its specific current range, frequency, and time-lag characteristics. The relay is housed in a standard Midos or vertical draw-out case, allowing the internal movement to be removed for testing without disturbing the current transformer (CT) secondary wiring.

 

Product Datasheet & Parameters

• Model Number: CDG16AF0008A5
• Relay Type: Single-Pole IDMT Overcurrent / Earth Fault
• Series: CDG (Induction Disc Type)
• Current Rating (In): Typically 1A or 5A (Standard CT secondary)
• Frequency: 50Hz or 60Hz (Factory calibrated)
• Time Characteristic: Standard Inverse (3.0 seconds at 10x setting)
• Setting Range: 50% – 200% for overcurrent or 10% – 40% for earth fault
• Burden: Low burden design to minimize CT requirements
• Contacts: 1 Normally Open (NO) or 2 NO self-reset/hand-reset options
• Case Size: Size 1 or 1.5 Draw-out vertical case

 

Country of Origin

This protection relay was manufactured by GEC Measurements (later Alstom/Areva) in the United Kingdom (Stafford, UK).

 

Application Fields

• Feeder Protection: Providing primary or backup overcurrent protection for radial and ring mains.
• Transformer Protection: Sensing external phase and earth faults on the HV or LV side.
• Industrial Plants: Reliable motor and cable protection in harsh electrical environments.
• Substations: Used in traditional protection schemes where mechanical reliability is preferred over digital complexity.
• Legacy System Support: Replacement and expansion of existing electromechanical protection panels.

 

Product Usage Instructions

Before installation, ensure the relay is mounted perfectly level; the induction disc relies on precise balance for accurate timing. Adjust the current “Plug Bridge” to the desired pickup level (e.g., 100% of CT rating). Use the “Time Multiplier” dial to shift the inverse curve to coordinate with upstream and downstream breakers. When testing, the module can be withdrawn from the case; the integrated shorting switches will automatically bridge the CT circuit to prevent high-voltage spikes. Regularly inspect the disc and magnets for dust or debris to ensure smooth rotation during a fault.

Common Questions & Answers (Q&A)

Q: How do I read the trip status on a CDG16? A: The relay features a mechanical “Flag” or “Target” indicator (usually bright orange or red) that drops when the relay operates. This flag must be manually reset using the external push-button on the cover.

Q: Is this relay compatible with digital SCADA systems? A: While the CDG16 is purely mechanical, its output contacts can be wired into a digital Remote Terminal Unit (RTU) or PLC to provide trip status to a SCADA system.

Q: What is the difference between a CDG11 and a CDG16? A: Both are IDMT relays, but they differ in their specific time-current characteristic curves. The CDG16 is specifically tuned for a Standard Inverse curve as per BS 142/IEC 60255 standards.

Q: Does this relay require an auxiliary DC power supply? A: No. One of the greatest advantages of the CDG series is that it is self-powered from the current being measured. It does not require a separate battery or power source to function.

 

Similar Model Recommendations

1. GEC Measurements CDG11AF001SA
2. GEC Measurements CDG31AF002SA (3-Pole version)
3. GEC Measurements CDG61 (Extremely Inverse version)
4. Alstom MiCOM P12x (Modern digital equivalent)
5. GEC Measurements METI series