ii
Line Current Differential, Distance, Out-of-Step, Overcurrent,
Date Code 20011112
Voltage, Synchronism Check, and Frequency Elements
SEL-311L Instruction Manual
TABLES
Table 3.1: Three Possible Combinations of Remote and Local Currents at Relay R. Relays S and
Table 3.3: Relay Word Bits Representing Actual Trip/Restrain Decision of Three-Terminal
FIGURES
Alpha Plane Represents Complex Ratio of Remote-to-Local Currents................................3-2
Figure 3.4:
Alpha Plane Angel Setting 87LANG Is Based on Maximum Alpha Plane Angle for
Figure 3.6:
Phase 87L Element Trip Speeds for Symmetrical Fault Currents With 87LANG =
Figure 3.7:
87LG and 87L2 Element Trip Speeds for Symmetrical Fault Currents With
87LANG = 195 and 87LR = 6 Using a Direct Fiber Connection. .................................3-9
Figure 3.8:
Ground Fault Sensitivity of 87L2 and 87LG Elements With 87L2P = 0.5 or 87LGP
Figure 3.9:
SEL-5601 Screen Capture of the Alpha Plane Plot for an External Fault With CT
Figure 3.10:
SEL-5601 Screen Capture of the Alpha Plane Plot for an Internal Fault With CT
Figure 3.11:
SEL-5601 Screen Capture of the Alpha Plane Plot for an External Fault With No CT
Internal Fault on Three-Terminal Line May Produce Outfeed at One Terminal................3-19
External Fault on Three-Terminal Line With Equal Infeed from Two Terminals .............3-20
Figure 3.16:
SEL-311L Relay Protects Three-Terminal Line Using Only Two Communications
Figure 3.17:
Phase Differential Element 87LA Processing for Channel X. B and C Phases and
Figure 3.18:
Negative-Sequence Differential Element 87L2 Processing for Channel X. Channel
Figure 3.19:
Ground Differential Element 87L2 Processing for Channel X. Channel Y
Summary of Contents for SEL-311L
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