FAULT TYPE SELECTION Jeff Roberts April 6 and 9, 2005

Fault-Selection Logic Purpose Ensures Single-Pole Trip Security: - SLG vs LLG Faults Blocks BG CG for BCG Faults Avoids Ground Overreach – SPT & 3PT Relay Targeting Fault Locator Loop Selection FS1

Real-Time Fault Type Selection Methods Overcurrent (Switched Scheme) Fault Selection Zones (Switched Scheme) Distance Element Torque Analysis Angle I 0 - Angle I 2 Comparison: –Single-Ended (Distance and Directional Relays) –Double-Ended (Line Current Differential)

From the V and I Shown … Is The System Is Normal or Faulted? V A = V  -13.9° I A = 1.58 A  ° V B = V  ° I B = 1.32 A  63.90° V C = V  106.1° I C = 1.58 A  -57.6°

Faulted …. Now Can You Determine Which Phase(s) Is(Are) Faulted? V A1 = V  -13.9°I A1 = 1.49 A  ° V A2 = V  °3I A2 = 0.27 A  114.7° V A0 = V  106.1°3I 0 = 0.27 A  °

What Tools Do You Have Available To You? Phase Current Magnitude and Angle Phase Voltage Magnitude and Angle Sequence Current Magnitude and Angle Sequence Voltage Magnitude and Angle Apparent Impedance Distance Element Pickup Status

Example Fault Type Selection System Radial Line

Many “Loops” Detect Close-In Phase A- Ground Faults

Fault Location Also Effects Which Loops Can Detect Ground Faults

Line Angle NO LOAD R CA CG BC AB BG X BCG Remote Terminal CASE # RF CASE # RF

AG Fault Sequence Components and Connections

BCG Fault Sequence Components and Connections

I0 and I2 for AG, BCG Faults 1012PH I2 I0 AG, BCGBG, CAG CG, ABG 0 120° 240° 2 0 2

Increasing BCG Fault R F Effects

FIDS Sectors – Grounded Systems 0° 30° 60° 90° 120° 150° 180° 210° 240° 270° 300° 330° FSB30 FSA30 FSC30 FSA60 FSB60 FSC60 FSB60

Fault Selection Logic Tolerating Resistance and Non-Homogeniety 0 ± 30°: Enable AG, BC Block Others 30° to 60°: Compare Rg with Selected Rpp Select Rpp Using Distance or |I PH-PH | RGRP1

Past Homework ATP Single-Line

COMTRADE File Evaluation of Faults on Homework System (#5) Try1.cfg – Complex Fault(s) (#4) Try2abg.cfg – Simultaneous AG and BG Faults on Differing Lines (#1) Try3ag.cfg – Reverse AG Fault (#2) Try4ca.cfg – Forward CA Fault (#3) Try5cag.cfg – Forward CAG Fault

Double Circuit Simultaneous Faults AG & BG

87L Schemes Use FTS

Total Current FTS Sectors

Fault Selection Conclusions Overcurrent Type Fault Selection Must Be Set Above Load Multiple Distance Element Loops Detect Close-in Ground Faults Increasing RF Can Cause Incorrect Phase Selection for Traditional 21 Element Phase Selection

Fault Selection Conclusions (continued) Difference Angle Between I 0 and I 2 Method: –Correctly Identifies SLG and PPG faults –Can be made very RF tolerant by Rg vs. Rpp comparison –Independent of protection element reach settings. SPT and 3PT Schemes Require Fault Type Selection Logic