Schweitzer Engineering Laboratories SEL-387E - SECTION 3: PROTECTION FUNCTIONS; Differential Element

Date Code 20080110 Protection Functions i
SEL-387E Instruction Manual
TABLE OF CONTENTS
SECTION 3: PROTECTION FUNCTIONS............................................3-1
Introduction...................................................................................................................................3-1
Differential Element......................................................................................................................3-1
Application Description ............................................................................................................3-1
Operating Characteristic .........................................................................................................3-1
Harmonic Restraint .......................................................................................................3-5
Blocking................................................................................................................................3-6
Common (Cross) or Independent Blocking...................................................................3-6
Harmonic Blocking .......................................................................................................3-6
DC Ratio Blocking........................................................................................................3-7
Setting Descriptions ..............................................................................................................3-8
Differential Element Enable (E87W1 through E87W3) ...............................................3-8
CT Connection (W1CT through W3CT).......................................................................3-8
CT Ratio (CTR1 through CTR3) ..................................................................................3-9
Maximum Transformer Capacity, Three-Phase MVA (MVA).....................................3-9
Internal Winding/CT Connection Compensation (ICOM)............................................3-9
Connection Compensation (W1CTC through W3CTC) ...............................................3-9
Line-to-Line Voltage, kV (VWDG1 through VWDG3) ...............................................3-9
Current TAP (TAP1 through TAP3).............................................................................3-9
Restrained Element Operating Current Pickup (O87P)...............................................3-10
Restraint Slope Percentage (SLP1, SLP2) ..................................................................3-10
Restraint Current Slope 1 Limit (IRS1) ......................................................................3-10
Unrestrained Element Current Pickup (U87P)............................................................3-10
Second-Harmonic Blocking Percentage of Fundamental (PCT2)...............................3-10
Fourth-Harmonic Blocking Percentage of Fundamental (PCT4)................................3-11
Fifth-Harmonic Blocking Percentage of Fundamental (PCT5)...................................3-11
Fifth-Harmonic Alarm Threshold (TH5P) ..................................................................3-11
Fifth-Harmonic Alarm Time Delay Pickup (TH5D)...................................................3-12
DC Ratio Blocking (DCRB) .......................................................................................3-12
Harmonic Restraint (HRSTR).....................................................................................3-12
Independent Harmonic Blocking (IHBL)....................................................................3-12
Setting Calculation..............................................................................................................3-13
General Discussion of Connection Compensation......................................................3-13
The Complete List of Compensation Matrices (m = 1 to 12) .....................................3-15
Selecting the Correct Values of WnCTC for Each Winding.......................................3-16
Winding Connection Review ..............................................................................3-16
Five-Step Compensation Process ........................................................................3-18
Example 1 for WnCTC Selection........................................................................3-18
Example 2 for WnCTC Selection........................................................................3-20
Winding Line-to-Line Voltages ..................................................................................3-22
Current TAP................................................................................................................3-22
Restrained Element Operating Current Pickup ...........................................................3-22
Restraint Slope Percentage..........................................................................................3-23
Unrestrained Element Current Pickup.........................................................................3-23
Second-Harmonic Blocking ........................................................................................3-24
Fourth-Harmonic Blocking .........................................................................................3-24
Fifth-Harmonic Blocking ............................................................................................3-24