ALSTOM MCGG52H1CB0753C – Industrial Overcurrent & Earth Fault Protection Relay for Feeder and Motor Protection

The ALSTOM MCGG52H1CB0753C is part of the well-known MCGG series of protective relays used on medium-voltage feeders, transformers, and large motors. From my experience, this series is chosen when you want proven IDMT overcurrent and earth fault protection with a straightforward draw-out case and simple wiring. The “H” variant typically includes a high-set instantaneous stage for fast tripping on heavy faults, while the base unit covers time-delayed 50/51 and 50N/51N protection with selectable IDMT curves.

Company’s Order Placement Process and Guarantees

• Warranty: 365 days
• Delivery time: 1 week for in-stock, no more than one month at the latest
• Payment: 50% advance payment, full payment prior to delivery
• Express options: FedEx, UPS, DHL

Key Features

• Three-phase overcurrent + earth fault (IDMT) – Designed to protect feeders, transformers, and motors using IEC inverse-time curves.
• High-set instantaneous trips – The “H” variant typically provides instantaneous 50/50N elements to clear severe faults quickly and reduce stress on equipment.
• Selectable IDMT characteristics – Commonly supports Normal Inverse, Very Inverse, and Extremely Inverse curves for coordination with upstream/downstream devices.
• 1 A / 5 A CT inputs – Usually configurable per element, simplifying retrofit into existing switchgear without CT changes.
• Draw-out case design – You might notice that maintenance is easier thanks to the withdrawable chassis and test-plug access.
• Simple, robust outputs – Form-C (changeover) trip and alarm contacts for reliable interlocking and breaker tripping.
• Clear front-panel settings – In many cases, pickup, time multipliers, and curve selection are set on the front, reducing commissioning time.

Technical Specifications

Application Fields

Typical use cases include medium-voltage distribution feeders in substations, transformer incomers and feeders, motor feeders in oil & gas or mining MCCs, and auxiliary protection in power plants. You’ll often see the MCGG52 protecting radial networks where selective grading with upstream relays is required. It also fits well in refurbishment projects where a reliable, non-communications relay is preferred for simplicity.

Advantages & Value

• Reliability – The MCGG family has a long track record; in many cases, it’s selected for its stability and predictable grading performance.
• Compatibility – 1 A/5 A CT options and a standard draw-out case make retrofits easier with minimal panel rework.
• Cost-effective protection – If you don’t need digital comms, this relay usually delivers the core protection at a lower lifecycle cost.
• Serviceability – One thing I appreciate is how quickly maintenance teams can test or swap units using a test plug—downtime stays low.
• Coordination-friendly – Selectable inverse curves simplify grading with reclosers and upstream transformer protection.

Installation & Maintenance

• Panel and wiring – Install in a clean, ventilated switchboard per typical IEC panel standards. Keep auxiliary supply within the specified range and use correctly rated CT circuits (burden and accuracy class considered).
• Earthing and safety – Ensure protective earth bonding of the case; isolate CT circuits before maintenance. CT secondaries should be shorted when not connected—this is critical.
• Setting and coordination – Verify CT ratios, pickup settings, TMS, and curve selection. From my experience, a quick grading study against upstream transformer relays prevents nuisance trips.
• Routine checks – Annual functional trip tests using a secondary injection kit are typically sufficient. Clean the front panel and terminals; check contact resistance if tripping duty is frequent.
• Firmware – For this series, there’s usually no field firmware to update, which keeps maintenance straightforward.

Quality & Certifications

Units of this class generally comply with CE requirements for EMC and low voltage safety. Depending on the production batch and region, UL or CSA recognition may apply to the case and terminals, and materials are typically RoHS-compliant for replacement supply. Manufacturer’s standard warranty coverage is one year.

Typical Accessories and Supporting Components

• Test plug / test block – For secondary injection and isolation during commissioning.
• Withdrawable case hardware – Replacement bezels, guide rails, and terminal kits for panel refurbishments.
• Auxiliary relays – Trip relays and lockout (86) relays when additional contacts or latching are needed.
• Current transformers – 1 A or 5 A CTs matched to the feeder rating to ensure correct pickup and time grading.

If you want us to confirm the exact auxiliary supply and setting ranges for MCGG52H1CB0753C, share your panel photo or the relay’s rating label. We can cross-check the build code and send a settings template to speed up commissioning.