Advanced Feeder Protection: ABB 1MRK000844-BB with High-Resolution Metering

The ABB REXPDK21H 1MRK000844-BB is a sophisticated directional time-overcurrent protection relay from ABB’s Relion® product family, designed for selective protection in complex power system networks. It functions as a specialized Intelligent Electronic Device (IED) that not only detects overcurrent conditions but also determines the directionof the fault current, a critical capability for protecting parallel lines, ring main systems, and interconnected networks where fault current can flow in multiple directions. This enables selective tripping, isolating only the faulty section while maintaining power flow elsewhere.

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Description

Application Scenarios:In a medium-voltage (e.g., 33kV) industrial ring main distribution system supplying multiple factory substations, a fault on one feeder cable must be isolated without de-energizing the entire ring. A standard overcurrent relay cannot distinguish between a fault downstream on its own feeder and fault current feeding intoits feeder from the other side of the ring. The ABB REXPDK21H 1MRK000844-BB solves this. Installed at each feeder breaker, it uses both current and voltage inputs to calculate the direction of fault power flow. For a fault on its protected cable section, it detects current flowing awayfrom the bus and into the line. It then issues a trip command. For a fault elsewhere on the ring, it sees current flowing intothe bus and blocks operation. This directional selectivity is the key pain point it addresses, preventing unnecessary blackouts, maintaining supply to healthy sections, and allowing for rapid localization and repair of the actual fault, maximizing network availability.

Parameter:

Main Parameters	Value / Description
Product Model	REXPDK21H (Series), 1MRK000844-BB (Article Code)
Manufacturer	ABB
Product Category	Directional Time-Overcurrent Protection Relay (IED)
Main Protection Functions	Directional Phase Overcurrent (67), Directional Earth Fault (67N/67G), Non-Directional OC (50/51), Auto-reclosing
Voltage Requirements	Requires VT/PT input for directional reference (e.g., 110V or 120V phase-to-phase)
Current Inputs	3 phase currents (IL1, IL2, IL3) + 1 residual/earth current (Ie)
Operating Characteristics	Multiple selectable curves (IEC, IEEE, User-defined) for time-overcurrent
Communication Protocols	IEC 61850 (GOOSE, MMS), IEC 60870-5-103/104, DNP3.0, Modbus
Binary Inputs/Outputs	Multiple programmable BI/BO for interlocking, blocking, and control
HMI	Front-panel graphical or alphanumeric display with navigation keys
Standards	IEC 60255, IEEE C37.90, IEC 61850 Ed.2