GE L90 Instruction Manual page 18

PRODUCT DESCRIPTION
• Two-terminal and three-terminal line applications
• Zero-sequence removal for application on lines with tapped transformers connected in a grounded wye on the line
side
• GE phaselets approach based on the Discrete Fourier Transform with 64 samples per cycle and transmitting two time-
stamped phaselets per cycle
• Adaptive restraint approach improving sensitivity and accuracy of fault sensing
• Increased security for trip decision using disturbance detector and trip output logic
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• Accommodates in-zone transformer with a magnitude and phase compensation and second harmonic inhibit during
transformer magnetizing inrush
• Continuous clock synchronization via the distributed synchronization technique
• Increased transient stability through DC decaying offset removal
• Accommodates up to five times CT ratio differences
• Peer-to-peer (master-master) architecture changing to master-slave via DTT (if channel fails) at 64 kbps
• Charging current compensation
• Interfaces direct fiber, multiplexed RS422, IEEE C37.94, and G.703 connections with relay ID check
• Per-phase line differential protection direct transfer trip plus eight user-assigned pilot signals via the communications
channel
• Secure 32-bit CRC protection against communications errors
• Channel asymmetry (up to 10 ms) compensation using GPS satellite-controlled clock
2.1.2.2 Backup protection
• DTT provision for pilot schemes
• Five zones of distance protection with pilot schemes, power swing blocking and out-of-step tripping, line pickup, and
load encroachment
• Two-element time overcurrent and two-element instantaneous overcurrent directional phase overcurrent protection
• Two-element time overcurrent and two-element instantaneous overcurrent directional zero-sequence protection
• Two-element time overcurrent and two-element instantaneous overcurrent negative-sequence overcurrent
protection
• Undervoltage and overvoltage protection
2.1.2.3 Additional protection
• Breaker failure protection
• Stub bus protection
• VT and CT supervision
• GE Multilin sources approach allowing grouping of different CTs and VTs from multiple input channels
• Open pole detection
• Breaker trip coil supervision and seal-in of trip command
• FlexLogic allowing creation of user-defined distributed protection and control logic
2.1.2.4 Control
• One and two breaker configuration for breaker-and-a-half and ring bus schemes, pushbutton control from the relay
• Auto-reclosing and synchrochecking
• Breaker arcing current
2.1.2.5 Monitoring
Oscillography of current, voltage, FlexLogic operands, and digital signals (1 × 128 cycles to 31 × 8 cycles configurable)
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• Events recorder: 1024 events
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CHAPTER 2: PRODUCT DESCRIPTION
L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL