Component Snapshot At-a-Glance

• Model: MCGG22L1CB0753E
• Alt. P/N: MCGG22B1CB0753E (medium-burden coil variant, higher DC draw); MCGG52 (2-phase + earth fault); MCGG62 (3-phase full set)
• Product Series: MCGG Midos static overcurrent protection relay family, shared rack base with MVAJ/MVAX/MVTT relays
• Hardware Type: Full withdrawable plug-in static single-phase overcurrent relay, blue aluminum industrial chassis, front DIP switch calibration bank
• Key Feature: L-series low-burden 110/125VDC auxiliary coil, single 1A CT input, independent IDMT delayed overcurrent + instantaneous high-set fault element, no earth fault input
• Primary Field Use: Single CT overload and short-circuit backup protection for small MV motors, transformer secondary single-phase legs and distribution branch feeders.

Hard-Numbers: Technical Specifications

• Protocol Support: Static analog sampling hardware, optional rear RS485 IEC 60870-5-103; dry volt-free delayed/instant trip changeover contacts
• Port Count: Single 1A CT secondary input terminals, DC auxiliary coil supply terminals, separate delayed trip and instantaneous fault contact terminal blocks
• Baud/Data Rate: RS485 max 9600bps; core protection logic operates independent of communication link
• Operating Temperature: -10°C to +55°C cabinet operational; -40°C to +85°C storage
• Isolation Rating: 2000Vrms dielectric withstand between CT measurement circuits and trip contact wiring
• Power Draw: Low-burden L coil, minimal DC battery load on densely packed multi-relay panels
• CT Secondary Rating: 1A nominal CT input (suffix C = 1A CT grade)
• Auxiliary DC Supply: 48–125 VDC station control battery wide operating range
• Pickup Current Adjustment: 0.05×In ~ 2.4×In, 0.05×In fine DIP switch steps
• Time Multiplier TMS: 0.05 ~ 1.0 continuous adjustable for IDMT coordination delay
• Instantaneous High-Set Range: 2.5 ~ 20×In, zero intentional delay for bolted short circuits
• Curve Library: 4 standard BS/IEC inverse time curves (SI/VI/EI/LTI) + 3 definite time modes
• Contact Continuous Rating: 5A @300VDC resistive load; 40W DC inductive breaking capacity for breaker trip coils
• Reset Characteristic: High reset ratio, fast auto-reset after fault current drops below pickup threshold
• Physical Weight: 4.1kg fully assembled draw-out unit

The Real-World Problem It Solves

Two/three-phase MCGG52/62 relays waste rack width on single-leg monitoring jobs. Stacking multiple single-phase relays inflates spare inventory and adds redundant CT wiring splices that vibrate open over years of plant cycling.High-burden MCGG22B coils draw heavy DC load during simultaneous multi-feeder faults; station battery voltage sags severely, instantaneous trip logic fails to energize breakers during bolted short circuits.Standard fuses only offer thermal overload protection, cannot deliver coordinated IDMT time grading with upstream/downstream feeder protection.This unit excludes residual earth fault measurement to cut cost and rack width for single CT circuits with separate dedicated earth fault relays.Where you’ll typically find it:

• Fossil power plant small auxiliary fan, pump single-phase backup protection panels
• Refinery MV small process motor MCC overload & short-circuit trip schemes
• Urban distribution substation single-branch low-load feeder coordination cabinetsThis compact single draw-out relay eliminates multi-phase relay over-specification, delivers coordinated single-phase fault coverage and minimizes DC panel loading during mass fault events.

Hardware Architecture & Under-the-Hood Logic

This unit uses one isolated phase analog sampling front-end paired with fixed-function static measurement logic, no user programmable microprocessor code. It shares standardized Midos rack mechanical design with all ALSTOM Midos protection hardware for unified cabinet layout.

1. Single-phase 1A CT secondary current feeds filtered isolated sampling circuitry to block substation VFD and breaker switching EMI noise from field wiring.
2. Dedicated RMS comparator continuously samples CT current magnitude, compares readings against front DIP switch set IDMT pickup threshold.
3. Internal curve algorithm calculates coordinated trip delay proportional to overcurrent magnitude for IDMT protection; independent instantaneous comparator bypasses all delay for severe short-circuit currents above high-set threshold.
4. Low-wattage L-series coil winding limits total DC load draw on station battery, preventing uneven voltage sag across multi-relay panels during concurrent multi-circuit fault events.
5. Front panel dedicated LED indicators: healthy auxiliary supply, time-delayed overload trip active, instantaneous short-circuit fault latched status for quick on-site visual diagnostics without workstation access.
6. Rear Midos rack terminal base integrates factory CT short-circuit jumpers; full chassis withdrawal possible without disconnecting CT secondary wiring to eliminate lethal open CT kilovolt surge hazards.

Field Service Pitfalls: What Rookies Get Wrong

Swapping MCGG22B Medium-Burden Coil Variant For MCGG22L Low-Burden Unit

New technicians pull MCGG22B spare stock without matching model suffix. During multi-feeder simultaneous short-circuit faults, total DC load spikes and bus voltage collapses; medium-burden coils dropout prematurely, breakers fail instantaneous tripping and equipment sustains winding burnout.Field Rule: MCGG22L low-burden variant mandatory for dense multi-relay protection panels; segregate L and B coil MCGG22 spares in clearly labeled locked storage bins.

Deploying MCGG22 On Circuits Requiring Residual Earth Fault Detection

Apprentices install MCGG22L1CB0753E on transformer neutral earth fault protection schemes. This model has no residual CT input terminal; winding ground faults cannot be detected, creating unprotected single-point failure risk.Field Rule: Use MCGG82 series for all circuits requiring overcurrent + earth fault protection; MCGG22 only for phase-fault-only single CT feeder/motor schemes with separate EF relays.

Skipping CT Short Jumper Installation Before Withdrawing Draw-out Relay

Maintenance crews pull relay chassis straight out without shorting CT terminals on the rack base. Open CT secondary windings generate kilovolt surge that damages upstream protection relay sampling boards and creates cabinet electric shock hazard.Quick Fix: Always install factory CT short-circuit jumpers on the Midos base terminal strip before removing any draw-out MCGG protection relay unit.

Misadjusting DIP Switch Pickup & TMS Without Cross-Checking Coordination Drawings

Techs randomly tweak front DIP switches during spare replacement without referencing site protection coordination logic sheets. Mismatched pickup or time multiplier values break protection selectivity; upstream and downstream breakers trip simultaneously during single feeder faults, causing localized plant outages.Field Rule: Record single-phase pickup current, TMS multiplier and instantaneous high-set value on the relay door label after every setting change; cross-verify against substation coordination curve sheet before returning the relay online.

Commercial Availability & Pricing Note

Please note: The listed price is for reference only and is not binding. Final pricing and terms are subject to negotiation based on current market conditions and availability.