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2 PRODUCT DESCRIPTION
LINE CURRENT DIFFERENTIAL:
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Phase segregated, high-speed digital current differential system
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Overhead and underground AC transmission lines, series compensated lines
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Two-terminal and three-terminal line applications
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Zero-sequence removal for application on lines with tapped transformers connected in a grounded wye on the line side
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GE phaselets approach based on the Discrete Fourier Transform with 64 samples per cycle and transmitting two time-
stamped phaselets per cycle
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Adaptive restraint approach improving sensitivity and accuracy of fault sensing
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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
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Continuous clock synchronization via the distributed synchronization technique
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Increased transient stability through DC decaying offset removal
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Accommodates up to five times CT ratio differences
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Peer-to-peer (master-master) architecture changing to master-slave via DTT (if channel fails) at 64 kbps
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Charging current compensation
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Interfaces direct fiber, multiplexed RS422, IEEE C37.94, and G.703 connections with relay ID check
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Per-phase line differential protection direct transfer trip plus eight user-assigned pilot signals via the communications
channel
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Secure 32-bit CRC protection against communications errors
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Channel asymmetry (up to 10 ms) compensation using GPS satellite-controlled clock
BACKUP PROTECTION:
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DTT provision for pilot schemes
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Five zones of distance protection with six pilot schemes, power swing blocking and out-of-step tripping, line pickup,
and load encroachment
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Two-element time overcurrent and two-element instantaneous overcurrent directional phase overcurrent protection
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Two-element time overcurrent and two-element instantaneous overcurrent directional zero-sequence protection
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Two-element time overcurrent and two-element instantaneous overcurrent negative-sequence overcurrent protection
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Undervoltage and overvoltage protection
ADDITIONAL PROTECTION:
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Breaker failure protection
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Stub bus protection
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VT and CT supervision
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GE Multilin sources approach allowing grouping of different CTs and VTs from multiple input channels
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Open pole detection
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Breaker trip coil supervision and seal-in of trip command
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FlexLogic allowing creation of user-defined distributed protection and control logic
CONTROL:
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One and two breaker configuration for breaker-and-a-half and ring bus schemes, pushbutton control from the relay
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Auto-reclosing and synchrochecking
GE Multilin
L90 Line Current Differential System
2.1 INTRODUCTION
2.1.2 FEATURES
2
2-3
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