Key Technical Specifications
- Part Number: MCGG22D1CB0753C
- Manufacturer: GEC ALSTHOM (France)
- Product Type: Non-Directional Overcurrent & Earth-Fault Relay
- HS Code: 8536.49.00
- Auxiliary Power: 110–250 V DC
- CT Inputs: Phase and Earth (1 A / 5 A Selectable)
- Protection Elements: IDMT + Definite-Time + Instantaneous High-Set
- Curve Standards: IEC / IEEE Style IDMT Curves
- Operating Temperature: -10 °C to +55 °C
- Mounting Style: Compact Draw-Out Case
- Outputs: Trip and Alarm Relay Contacts
Product Introduction
ALSTOM MCGG22D1CB0753C is a non-directional overcurrent and earth-fault protection relay designed for medium and low voltage switchgear panels. It utilizes both IDMT and definite-time elements to coordinate seamlessly with upstream and downstream protection devices in electrical distribution networks.This specific variant supports flexible 1 A and 5 A current transformer inputs, simplifying retrofits on existing switchgear. Field technicians will note the front-access draw-out case, which allows for rapid module swapping without rewiring the panel. Always verify the exact curve selection and high-set stage parameters against the original panel schematics before energizing.
Installation & Configuration Guide
Preparation (10 min)
- Obtain a complete lockout/tagout (LOTO) permit and verify zero energy state on the switchgear.
- Review the original panel schedule for the exact CT ratio and IDMT curve settings.
- Inspect the new MCGG22D1CB0753C for shipping damage and verify the option code matches.
- Gather insulated tools, a calibrated multi-meter, and ESD protection.
Removal (5–10 min)
- Disconnect the auxiliary DC control power to the relay.
- Loosen the front retaining screws and pull the ejector mechanism to unseat the relay.
- Slide the relay completely out of the draw-out housing.
- Inspect the backplane contacts for pitting, oxidation, or debris.
Installation (10 min)
- Align the MCGG22D1CB0753C with the draw-out housing guide rails.
- Push firmly until the relay seats fully against the backplane.
- Engage the front locking mechanism and secure the retaining screws.
- Verify the relay is flush and the mechanical interlock is engaged.
Power-On & Test (10 min)
- Apply the 110–250 V DC auxiliary supply and check for normal power indication.
- Navigate the front panel interface to verify the stored settings match your documentation.
- Perform a primary or secondary injection test using a relay test kit to verify trip times.
- Reset alarms and confirm the breaker trip circuit is intact.
Troubleshooting Quick Reference
| Symptom | Probable Cause | Corrective Action |
|---|---|---|
| Relay is completely dead | Auxiliary DC supply failure | Measure 110-250V DC at the backplane terminals |
| Unwanted Trip Event | CT wiring polarity reversed | Verify P1/P2 and S1/S2 CT orientation and phase rotation |
| Setting Mismatch | DIP switch / Jumper error | Compare physical jumper positions against panel schematic |
| Comm / Test Port Dead | Firmware or option code mismatch | Verify RS-485 option code; base MCGG22 lacks standard comms |
| Intermittent Faults | Backplane contact oxidation | Clean backplane pins with electronic contact cleaner |
Dimensions, Mounting & Wiring Notes
- Form Factor: Compact Draw-Out Case (Front Access)
- Mounting Method: Panel Cut-Out with Rear Backplane Mating
- CT Wiring: Ensure proper burden rating; verify 1 A / 5 A jumper matches CT secondary
- Auxiliary Power: Strictly 110–250 V DC (Verify specific variant voltage range)
- Clearance: Maintain adequate space behind the draw-out housing for wiring bend radius
FAQ
Can I just drop this MCGG22D1CB0753C into my existing panel?
Mechanically, yes, the draw-out case is designed for like-for-like replacement. Electrically, no. You must verify the CT ratio jumper, IDMT curve selection, and auxiliary voltage match your existing setup.I noticed there are no communication ports. Is this normal?
Yes. The base MCGG22 model does not include standard communication. RS-485 is strictly an option-dependent feature. If you need SCADA integration, check the specific option code on the unit’s rating plate.How do I know if the relay was actually tested before shipping?
A reputable supplier will perform live functional testing on a dedicated test rack, including power-on self-tests and secondary injection simulations. Always request the test report and QC signature to ensure it was verified under test conditions.What is the biggest risk when replacing this relay?
CT circuit misconfiguration. Opening a CT secondary circuit while energized can be fatal or destroy equipment. Always short the CT secondaries before removing the old relay, and double-check polarity before removing the shorts.I have a GEC ALSTHOM relay but the suffix letters are different. Will it work?
Not necessarily. In the MCGG22 family, the suffix letters dictate the exact protection elements, voltage ratings, and curve options. A mismatched suffix could result in a failure to trip during a fault. Always cross-reference the complete part number.What happens if the auxiliary power dips during a fault?
This relay is designed for substation environments and operates stably over a wide temperature range, but a severe voltage dip below the minimum threshold can cause a dropout. Ensure your station battery charger and DC system have adequate capacity margin.
