GE Multilin L90 Line Current Differential System 5-615 SETTINGS 5.4 SYSTEM SETUP5The phase sequence of the power system is required to properly calculate sequence components and power parameters.The PHASE ROTATION setting matches the power system phase sequence. Note that this setting informs the relay of theactual system phase sequence, either ABC or ACB. CT and VT inputs on the relay, labeled as A, B, and C, must be con-nected to system phases A, B, and C for correct operation.The FREQUENCY AND PHASE REFERENCE setting determines which signal source is used (and hence which AC signal) forphase angle reference. The AC signal used is prioritized based on the AC inputs that are configured for the signal source:phase voltages takes precedence, followed by auxiliary voltage, then phase currents, and finally ground current.For three phase selection, phase A is used for angle referencing ( ), while Clarke transformation of thephase signals is used for frequency metering and tracking ( ) for better performance dur-ing fault, open pole, and VT and CT fail conditions.The phase reference and frequency tracking AC signals are selected based upon the Source configuration, regardless ofwhether or not a particular signal is actually applied to the relay.Phase angle of the reference signal will always display zero degrees and all other phase angles will be relative to this sig-nal. If the pre-selected reference signal is not measurable at a given time, the phase angles are not referenced.The phase angle referencing is done via a phase locked loop, which can synchronize independent UR-series relays if theyhave the same AC signal reference. These results in very precise correlation of time tagging in the event recorder betweendifferent UR-series relays provided the relays have an IRIG-B connection.FREQUENCY TRACKING should only be set to “Disabled” in very unusual circumstances; consult the factory for spe-cial variable-frequency applications.The frequency tracking feature will function only when the L90 is in the “Programmed” mode. If the L90 is “Not Pro-grammed”, then metering values will be available but may exhibit significant errors.The nominal system frequency should be selected as 50 Hz or 60 Hz only. The FREQUENCY AND PHASE REFERENCEsetting, used as a reference for calculating all angles, must be identical for all terminals. Whenever the 87L functionis “Enabled”, the frequency tracking function is disabled, and frequency tracking is driven by the L90 algorithm (seethe Theory of operation chapter). Whenever the 87L function is “Disabled”, the frequency tracking mechanismreverts to the UR-series mechanism which uses the FREQUENCY TRACKING setting to provide frequency tracking forall other elements and functions.5.4.3 SIGNAL SOURCESPATH: SETTINGS ÖØ SYSTEM SETUP ÖØ SIGNAL SOURCES Ö SOURCE 1(4)Identical menus are available for each source. The "SRC 1" text can be replaced by with a user-defined name appropriatefor the associated source.The first letter in the source identifier represents the module slot position. The number directly following this letter repre-sents either the first bank of four channels (1, 2, 3, 4) called “1” or the second bank of four channels (5, 6, 7, 8) called “5” ina particular CT/VT module. Refer to the Introduction to AC sources section at the beginning of this chapter for additionaldetails on this concept. SOURCE 1SOURCE 1 NAME:SRC 1Range: up to six alphanumeric charactersMESSAGE SOURCE 1 PHASE CT:NoneRange: None, F1, F5, F1+F5,... up to a combination ofany 6 CTs. Only Phase CT inputs are displayed.MESSAGE SOURCE 1 GROUND CT:NoneRange: None, F1, F5, F1+F5,... up to a combination ofany 6 CTs. Only Ground CT inputs are displayed.MESSAGE SOURCE 1 PHASE VT:NoneRange: None, F1, F5, L1, L5Only phase voltage inputs will be displayed.MESSAGE SOURCE 1 AUX VT:NoneRange: None, F1, F5, L1, L5Only auxiliary voltage inputs will be displayed.VANGLE REF V A=VFREQUENCY 2V A V B– V C–( ) 3⁄=NOTENOTENOTE
