Presentation is loading. Please wait.

Presentation is loading. Please wait.

IEEE Rural Electric 2009 Testing Numerical Transformer Differential Relays Steve Turner Beckwith Electric Co., Inc.

Similar presentations


Presentation on theme: "IEEE Rural Electric 2009 Testing Numerical Transformer Differential Relays Steve Turner Beckwith Electric Co., Inc."— Presentation transcript:

1 IEEE Rural Electric 2009 Testing Numerical Transformer Differential Relays Steve Turner Beckwith Electric Co., Inc.

2 Testing Numerical Transformer Differential Relays Commissioning versus Maintenance Testing Types of Transformer Differential Protection: Restrained Phase Differential High Set Phase Differential Ground Differential INTRODUCTION

3 Testing Numerical Transformer Differential Relays Topics: Transformer Differential Boundary Test (Commissioning) Ground Differential Sensitivity Test (Commissioning/Maintenance) Harmonic Restraint for Transformer Inrush (Maintenance) INTRODUCTION

4 Testing Numerical Transformer Differential Relays Commissioning Common Practice: Test all numerical relay settings – verify settings properly entered Easily facilitated using computer – automate test set & store results Hundreds of tests are possible – numerical relays have many settings

5 Testing Numerical Transformer Differential Relays Commissioning Final Goal Ensure the transformer is properly protected for the particular application

6 Testing Numerical Transformer Differential Relays RGRG 46 Typical Distribution Transformer 46: Negative-Sequence Overcurrent Element (sees ground faults through bank) R G : Grounding Resistor (Industrial Load)

7 Testing Numerical Transformer Differential Relays RGRG 46 E + ZTZT ZTZT ZTZT 3R G 46 I2I2 Sensitive setting for ground fault - overreach for phase-to-phase fault

8 Testing Numerical Transformer Differential Relays Transformer Differential Characteristic Boundary Test I2I2 I1I1 87 Y Y Y Y I 1 = Winding 1 per unit current (A, B or C-phase) I 2 = Winding 2 per unit current (A, B or C-phase) 3 elements per function (A, B & C-phase) * Simulate Through Current

9 Testing Numerical Transformer Differential Relays Differential Characteristic Operating Equations I d = |I 1 – I 2 |, Differential Current I r = |I 1 | + |I 2 |, Restraint Current 2

10 Testing Numerical Transformer Differential Relays Differential Characteristic IdId IrIr Minimum Pickup (per unit) Percent ( % ) Slope X Y % = Y X *100%

11 Testing Numerical Transformer Differential Relays Differential Characteristic IdId IrIr Minimum Pickup Percent Slope Trip Region Block Region

12 Testing Numerical Transformer Differential Relays Matrix IdIrIdIr [] = 1 -1 ½ [ ] * I1I2I1I2 []

13 Testing Numerical Transformer Differential Relays Inverted Matrix I1I2I1I2 [] = ½ 1 -½ 1 [ ] * IdIrIdIr []

14 Testing Numerical Transformer Differential Relays Differential Characteristic Test Current Equations I 1 = 0.5*I d + I r, Winding 1 Test Current (per unit) I 2 = -0.5*I d + I r, Winding 2 Test Current (per unit)

15 Testing Numerical Transformer Differential Relays Differential Characteristic Test Points IdId IrIr Minimum Pickup Percent Slope Minimum Pickup = 0.2 per unit Slope = 28.6%

16 Testing Numerical Transformer Differential Relays Differential Characteristic Test Points (Per Unit) IdIrI1I2IdIrI1I TABLE 1

17 Testing Numerical Transformer Differential Relays Delta-Wye Differential Characteristic I2I2 I1I1 87 Y Y Y I 1 = Winding 1 per unit current (A, B or C-phase) I 2 = Winding 2 per unit current (A, B or C-phase) 3 elements per relay (A, B & C-phase) * Simulate Through Current DAB

18 Testing Numerical Transformer Differential Relays Delta-Wye Differential Characteristic (Relay Internally Compensates Test Currents) I A1 relay = I A1 /TAP1 DAB WINDING I B1 relay = I B1 /TAP1 I C1 relay = I B1 /TAP1 I A2 relay = (I A2 - I B2 )/(TAP2*SQRT(3)) WYE WINDING I B2 relay = (I B2 - I C2 )/(TAP2*SQRT(3)) I C2 relay = (I C2 - I A2 )/(TAP2*SQRT(3)) TAP# = MVA# kV# LL *CTR#*SQRT(3)

19 Testing Numerical Transformer Differential Relays Delta-Wye Differential Characteristic Single-Phase (Single-Phase Test for A-Phase Element) IdIrI1I2IdIrI1I From TABLE 1: I A1 = I 1 *TAP1 I A2 = I 2 *TAP2*SQRT(3) I A1 test = 0.8*TAP1 I A2 test = 0.6*TAP2*SQRT(3)

20 Testing Numerical Transformer Differential Relays Ground Differential Element Sensitivity Test Directionality (I 0 vs. I G ) Ground Fault Location along Windings

21 Testing Numerical Transformer Differential Relays Ground Differential Element Directional Element Directional Element +90 o -90 o IGIG I0I0 Disabled if |3I 0 | less than 140 mA (Improves Security for CT saturation during external faults) InternalExternal

22 Testing Numerical Transformer Differential Relays Ground Differential Element Pickup Pickup Operate When: |3I 0 – I G | > Pickup

23 Testing Numerical Transformer Differential Relays Ground Differential Element Sensitivity Test Power System Parameters: Source Impedance (Varies) X T = 10% R F (Varies) Ground Fault Location (5% from Transformer Neutral)

24 Testing Numerical Transformer Differential Relays Ground Differential Element R F Coverage vs. Source Strength

25 Testing Numerical Transformer Differential Relays Ground Differential Element Pickup Setting Cold Load Pickup Reclosing into Single-Phase Load Pickup > Unbalance Directional Element Disabled if 3I 0 Low IGIG R

26 Testing Numerical Transformer Differential Relays I G2 = o Threshold = 0.14 Amps 3I 0 (2) = o (Threshold = 0.14 Amps) |CTCF*3I 0 (2) – I G2 | = 0.75 Amps Original Pickup = 0.3 Amps

27 Testing Numerical Transformer Differential Relays I G2 CTCF*3I 0 (2) INTERNAL EXTERNAL I OP New Pickup = 1.0 Amps Directional Element

28 Testing Numerical Transformer Differential Relays Even Harmonic Restraint during Inrush COMTRADE PLAYBACK COMTRADE PLAYBACK Waveform Sources: Events from Numerical Relays Events from Digital Fault Recorders Simulate using Transient Software

29 Testing Numerical Transformer Differential Relays Even Harmonic Restraint during Inrush Traditional Approach Traditional Approach 2 nd Harmonic Restraint Cross Phase Blocking

30 Testing Numerical Transformer Differential Relays Even Harmonic Restraint during Inrush Auto-Transformer Model Auto-Transformer Model wye delta 13.2 kV 345 kV230 kV W1W1 W2W2 W3W3 600 MVA Auto-Transformer (Tertiary Winding DAC)

31 Testing Numerical Transformer Differential Relays Auto-transformer Characteristics Z HM = per unit Z HL = per unit Z ML = per unit = per unit = per unit CTR W1 = 1200:5 (wye connected) CTR W2 = 2000:5 (wye connected) Even Harmonic Restraint during Inrush Auto-Transformer Model Auto-Transformer Model Z H = Z M = Z L = = per unit

32 Testing Numerical Transformer Differential Relays Even Harmonic Restraint during Inrush Auto-Transformer Model Auto-Transformer Model TAP1 = 600 MVA 345 kV * 240 * SQRT(3) TAP2 = 600 MVA 230 kV * 400 * SQRT(3) = 4.18 = 3.77 Minimum Pickup* = 0.5 per unit Slope = 25% Original Pickup = 0.45 per unit *Original Pickup = 0.45 per unit

33 Testing Numerical Transformer Differential Relays Even Harmonic Restraint during Inrush Energize Bank with Heavy A-Phase Residual Flux Energize Bank with Heavy A-Phase Residual Flux Total Phase Current

34 Testing Numerical Transformer Differential Relays Even Harmonic Restraint during Inrush Energize Bank with Heavy A-Phase Residual Flux Energize Bank with Heavy A-Phase Residual Flux 2 nd Harmonic Phase Current

35 Testing Numerical Transformer Differential Relays Even Harmonic Restraint I even = (I I 4 2 ) 1/2

36 Testing Numerical Transformer Differential Relays Even Harmonic Restraint during Inrush Energize Bank with Heavy A-Phase Residual Flux Energize Bank with Heavy A-Phase Residual Flux 4 th Harmonic Phase Current

37 Testing Numerical Transformer Differential Relays Even Harmonic Restraint during Inrush A-Phase Current (Winding 2) A-Phase Current (Winding 2)

38 Testing Numerical Transformer Differential RelaysCONCLUSIONS

39 Transformer Differential Boundary Test (Commissioning) Ground Differential Sensitivity Test (Commissioning/Maintenance) Harmonic Restraint for Transformer Inrush (Maintenance) CONCLUSIONS

40 Testing Numerical Transformer Differential RelaysQUESTIONS


Download ppt "IEEE Rural Electric 2009 Testing Numerical Transformer Differential Relays Steve Turner Beckwith Electric Co., Inc."

Similar presentations


Ads by Google