I. Product Description
Full model: REL551
Original factory order part number: 1MRK002480-AE (AE represents the standard hardware configuration version)
Product series: ABB ProtectIT 500 series older digital line differential protection device, belonging to PANORAMA substation automation system, has been discontinued. The replacement model is REL670 (Relion670)
Core purpose: High-voltage overhead line and cable full-line current differential main protection, suitable for 110kV/220kV transmission lines, taking into account backup distance, overcurrent, measurement and control, and waveform recording integration IED
Model code explanation
REL551: Basic model of line differential protection terminal
1MRK002480: Product base code
-AE: Hardware configuration version, including LON bus, basic optical differential communication, standard I/O terminal layout
Core Protection Functions (Main Line Differential)
1. Main Protection: Phase current differential (core)
Phase independent differential algorithm, simultaneously comparing the amplitudes and phases of the currents on both sides
Built-in CT saturation detection, transmission delay dynamic compensation, anti-zone external fault saturation maloperation
Support for fiber optic direct connection, multiplexed channels, switch router networking to transmit differential data
Main / main dual-end peer architecture, no need to distinguish master-slave, single / three-phase tripping selectable
Applicable to series compensation lines, weak feed power side line protection
2. Backup distance protection (quadrilateral impedance characteristic)
Three-stage distance protection Z1/Z2/Z3, load encroachment anti-maloperation
Power oscillation locking, out-of-step detection, weak feed logic
Z1 zone internal fault tripping time < 20ms, high-speed tripping to ensure system transient stability
3. Companion auxiliary protection
Phase-to-phase / Grounding time-limited / Reverse-time overcurrent, zero-sequence grounding protection
Breaker failure protection, CT open circuit / PT open circuit monitoring, tripping circuit monitoring
Automatic reclosing (synchronous check / no pressure check), low frequency / overvoltage protection
4. Measurement and recording
Three-phase voltage, current, power, frequency high-precision measurement
SOE event sequence recording (1ms resolution), complete fault disturbance recording DR
Programmable logic CFC, custom five-prevention, interlock logic
Hardware Structure and Terminal Interfaces
Integrated embedded screen-mounted equipment, divided into front operation panel + rear I/O terminal area
Front HMI
Small LCD display, operation keys, operation / fault / action status indicator lights, local debugging serial port; can view set values, fault recording, real-time measurement
Back panel terminal zones
CT/PT analog input: three-phase current, three-phase voltage connection (1A/5A CT universal)
DI digital input: circuit breaker position, isolator, ground knife, protection action, remote/local switching
DO tripping output: three-phase tripping, alarm, reclosing, failure remote trip contacts
Communication interfaces: LONWORKS in-station bus, optical differential channel, RS485 serial port
Working power supply: DC110/220V operation power supply terminal
Communication Protocol Capability
Differential channel: single-mode fiber (standard kit), supports multiplexed 2M communication channel
In-station monitoring: LONWORKS bus, Modbus RTU, IEC60870-5-103
Remote transmission expansion: optional module supports IEC 60870-5-104; older models do not natively support IEC61850 (difference from 650 series)
Debugging software: PCM600 dedicated setting, recording reading, logic programming tool
Electrical and Environmental Specifications Auxiliary power supply: DC 88~264V wide-range direct current, total machine power consumption ≤ 28W
CT circuit withstand voltage: 2kV AC isolation, resistant to strong electromagnetic interference from power plants
Operating temperature: -25℃ ~ +70℃, storage – 40~+85℃
Protection level: IP20 (only for installation in switch cabinets)
Safety standards: CE, complete set of EMC certification from the power industry IEC6100
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