Lightning Insulation Coordination Study

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1 Lightning Insulation Coordination Study Presenter: Nguyen Dong Hai Le Pacific 1 Presentation Outline Introduction Network Components Model Stroke Current Model Case Studies and esults Conclusions 1

2 Introduction Lightning Insulation Coordination Insulation Coordination is required to ensure Equipment s insulation shall withstand voltage stress caused by lightning strike. Efficient discharge of over voltages due to lighting strike. 3 Network Component Models Transmission Line Model Equipment's Stray Capacitance Surge Arrester. Current Dependant Characteristic of Tower Footing esistance Tower Surge Impedance. Time Dependant Characteristic of Insulator Strength. Stroke Current Model. Determination of Critical Stroke Current s Parameters. 4

Network Component Models Transmission Line Individual tower model Separated circuit of Earth Wire(s) Ph-E coupling capacitance due to string insulator 5 Network Component Models Equipment s Stray

3 Network Component Models Transmission Line Individual tower model Separated circuit of Earth Wire(s) Ph-E coupling capacitance due to string insulator 5 Network Component Models Equipment s Stray Capacitance Typical data of equipment's stray capacitance Equipment Capacitive Potential Transformer Magnetic Potential Transformer Current Transformer Disconnector Circuit breaker Bus Support Insulator 70MVA Transformer HV 60MVA Transformer LV 10MVA Transformer TV Between Transformer winding Capacitance to Ground 6000pF 600pF 350pF 10pF 150pF 100pF 700pF 350pF 000pF 30pF 6 3

0 7 Network Component Models String Insulator Model V 1. B = 0.

4 Network Component Models Surge Arrester Model Typical Discharge Current vs esidual Voltage Characteristic of 0kV Surge Arrester. Discharge Current(kA) Max esidual Voltage(kV) Network Component Models String Insulator Model V 1. B = CFO t where V B : the breakdown, flash over, or crest voltage, t : the time to breakdown or flash over CFO : Critical Flash Overvoltage in kv. (CFO implies the voltage level that result in a 50% probability of flash over if applied to the insulation.) 8 4

5 Network Component Models Tower Surge Impedance Conical Tower (SargenetA.M.) Cylindrical tower (SargenetA.M.) Z T = 60ln h sinθ Z = 60ln r 60 T where θ is the sine of the half angle of the cone where h and r are the height and radius of the cylinder, respectively 9 Network Component Models Tower Footing esistance(1) Current to initiate sufficient soil ionization 1 ρe I g = π 0 0 Tower Footing esistance = i I / I g where i : Surge tower footing resistance 0 = 100Ω is assumed to be low current resistance for transmission tower footing resistance and 0 = 10Ω for earth resistance inside substation (worst case). E 0 = 400kV / m : assumed soil ionization gradient I : lightning current through the footing impedance ρ : soil resistivity. 10 5

6 Network Component Models Tower Footing esistance() Current to initiate sufficient soil ionization 1 ρe I g = π 0 0 Tower Footing esistance = i 0 1+ I / I g 11 Stroke Current Model Heidler Function Mathematical Model - Heidler function 1 6

Stroke Current Model Heidler Function 4.00 Mathematical Model - Heidler function -4.00-8.00-1.00-16.00-5.0000 5.999 56.998 87.998 119.

7 Stroke Current Model Heidler Function 4.00 Mathematical Model - Heidler function [us] Direct Stroke: Stroke Current (ka) 15 Lightning Studies Plots Stroke Source Date: /3/011 Annex: /1 13 Stroke Current Model Heidler Function 14 7

8 Stroke Current Model Direct Strokes The maximum shielding failure current Im is calculated by: 1 r b gm Im = A where approximation of rgm is calculated by: ( h + y) r gm = (1 γ sin α ) h: shielding height(m) y: highest conductor height(m) Geometric Model of Tower for Lightning Study sin α = a a + ( h y) where a is the horizontal distance between highest phase conductor and shielding wire(m) γ = 444 /(46 h) for h>18m; γ =1 for h<=18m. (IEEE-1995 Substation Committee, Hileman pp.44, pp.48) 15 Stroke Current Model Back Flashover ate(bf) 1 BF = d MTBS m flashes over per 100km-years where d m is the distance from gantry to the first With any specific MTBS, there exists a critical stroke current I s that the substation insulation may fail under if the first tower suffered from stroke current I>I s 1 P( I > I S ) = 0.6d N MTBS m L 16 8

9 Stroke Current Model Critical Stroke Current CIGE Working Group eport [9] suggests the statistical distribution of all parameters of the flash can be approximated by the lognormal distribution whose probability density function is of the form: 1 1 Z f ( I) = e π βi I ln( ) where Z = M β M :probability distribution median and β is the log standard distribution obtained from Berger s data [1] We have: 1 1 Z 1 P( I > I S ) = 1 e dz π IS 1 P( I > I ) = S 1 π I S e 1 Z dz From table of Cumulative Normal Distribution Function, finding the approximate value of Z. The critical stroke current is then calculated: I = Me c Zβ 17 Stroke Current Model Front Time Median Front Time Median t = f Ic (Conditional Lognormal Distributions from Berger s Data) 18 9

10 Stroke Current Model Tail Time Median Determining the tail time constant is an iterative process, whereby the following formula is applied in the sequence, as suggested by Bewley (Hilemen pp397): e i Z g = Z + g i I = I g = e i 1 π I S E ρ 0 0 Iteration no. i(ω) e(ω) I (ka) i(ω) Calculation Example i = I / I Z g is the surge impedance of earth wire conductor(s). g 19 Stroke Current Model Tail Time Median Tail Time Median τ = Z g TS i Where T s is to be time travel of surge for the first span length. 0 10

11 Case Studies Tower Earth esistance Struck Tower Lightning Stroke Gantry SA1 SA SA3 SA4 T0001 BK 11kV T000 BK 33kV Circuit #1 P. PowerFactory Earth Wire Circuit Circuit # BOCKMAN SUBSTATION Project: 030 INSULATION COODINATION STUDY Graphic: Brockman Date: /3/011 Annex: ~ Nodes Branches 1 Case Studies Stroke Current Waveform Summary Current Heidler Function Test Case Waveform η T 1 T n Direct Stroke 0 ka 1./50 us E E-05 8 Ideal First Stroke(AS 1768) 150 ka 4.6/40 us E E yrs MTBF design 11 ka.5/91 us E

12 Case 1 esults - Direct Stroke 6.3E+6 X = 0.87 us 5.0E+6 3.8E+6.5E+6 1.3E E [us] Flash_P1_1PhA: Vinsulator Flash_P1_1PhA: Vstrength 5 X = 0.87 us 1.6E kv 8.0E+ 4.0E kv kv kv -4.0E [us] P1_1: Phase Voltage A in kv P1_1: Phase Voltage B in kv P1_1: Phase Voltage C in kv P1_E: Phase Voltage A in kv 5 Case1: 0kA 1./50us, Phase A, Milstream Line, 300m span P1_Insulator Date: 8/11/008 Annex: 030 /11 3 Case 1 esults - Direct Stroke Stroke Current: Current, Magnitude A in ka _earth_p1: Line-Ground Voltage Phasor, Magnitude/Terminal i in kv E E E+ 1.00E+ 1.00E+ 1.00E _earth_p1: Phase Current A/Terminal i in ka E+ _earth_p1: esistance (Input) in Ohm 5 Case1: 0kA 1./50us, Phase A, Milstream Line, 300m span P1_Earth Date: 8/11/008 Annex: 030 /1 4 1

13 Case 1 esults - Direct Stroke BIL=1016 kv Y = kv Y = kv B_Gantry1 0kV: m:u:a B_Gantry1 0kV: m:u:b CB1_1: m:u:a CB1_1: m:u:b B_Gantry1 0kV: m:u:c CB1_1: m:u:c BIL=1161kV BIL=1016kV Y = kv Y = kv T10001: n:u:bushv:a T10001: n:u:bushv:b IS3_1: m:u:a IS3_1: m:u:b T10001: n:u:bushv:c IS3_1: m:u:c Case1: 0kA 1./50us, Phase A, Milstream Line, 300m span 0kV Side Date: 8/11/008 Annex: 030 /1 5 Case 1 esults - Direct Stroke X = us 0.03 MWs MWs [us] SA1 ABB PEXLIM Q88-XV45SE: MO absorbed Energy in MWs SA ABB PEXLIM Q88-XV45SE(1): MO absorbed Energy in MWs SA3 ABB PEXLIM Q88-XV45SE: MO absorbed Energy in MWs us Y = ka [us] SA1 ABB PEXLIM Q88-XV45SE: MO Current A in ka SA ABB PEXLIM Q88-XV45SE(1): MO Current A in ka SA3 ABB PEXLIM Q88-XV45SE: MO Current A in ka 197. Case1: 0kA 1./50us, Phase A, Milstream Line, 300m span SA_Summary Date: 8/11/008 Annex: 030 /

14 Case esults - Ideal Stroke 150 ka 4.6/40us 3.0E us Y =03.33 kv.0e+3 1.0E+3-1.0E [us] P1_1: Phase Voltage A in kv P1_1: Phase Voltage B in kv P1_1: Phase Voltage C in kv P1_E: Phase Voltage A in kv 5 Case: 150kA 4.6/50us, Phase A, Milstream Line, 300m span P1_Insulator Date: 8/11/008 Annex: 030 /10 7 Case esults - Ideal Stroke 150 ka 4.6/40us Stroke Current: Current, Magnitude A in ka _earth_p1: Line-Ground Voltage Phasor, Magnitude/Terminal i in kv _earth_p1: Phase Current A/Terminal i in ka 5 _earth_p1: esistance (Input) in Ohm 5 Case: 150kA 4.6/50us, Phase A, Milstream Line, 300m span P1_Earth Date: 8/11/008 Annex: 030 /

15 Case esults - Ideal Stroke 150 ka 4.6/40us us Y = kv BIL=1016 kv Y = kv B_Gantry1 0kV: Phase Voltage A in kv B_Gantry1 0kV: Phase Voltage B in kv 5 CB1_1: Phase Voltage A in kv CB1_1: Phase Voltage B in kv 5 B_Gantry1 0kV: Phase Voltage C in kv CB1_1: Phase Voltage C in kv BIL=1161kV BIL=1016kV Y = kv Y = kv T10001: Phase Voltage A/HV-Side in kv T10001: Phase Voltage B/HV-Side in kv 5 IS3_1: Phase Voltage A in kv IS3_1: Phase Voltage B in kv 5 T10001: Phase Voltage C/HV-Side in kv IS3_1: Phase Voltage C in kv Case: 150kA 4.6/50us, Phase A, Milstream Line, 300m span 0kV Side Date: 8/11/008 Annex: 030 /1 9 Case esults - Ideal Stroke 150 ka 4.6/40us 8 BIL=73kV 0 Y = kv 4 15 Y = kv Y = kv 10 5 Y =-8.60 kv -4 -BIL= -73kV [us] T10001: Phase Voltage A/LV-Side in kv T10001: Phase Voltage B/LV-Side in kv T10001: Phase Voltage C/LV-Side in kv [us] T10001: Phase Voltage A/MV-Side in kv T10001: Phase Voltage B/MV-Side in kv T10001: Phase Voltage C/MV-Side in kv BIL=73kV 0 BIL=165kV 4 15 Y =1.014 kv Y = kv 10 5 Y = kv -4 -BIL = -73kV [us] B_11kV: Phase Voltage A in kv B_11kV: Phase Voltage B in kv B_11kV: Phase Voltage C in kv [us] Brockman 33kV: Phase Voltage A in kv Brockman 33kV: Phase Voltage B in kv Brockman 33kV: Phase Voltage C in kv Case: 150kA 4.6/50us, Phase A, Milstream Line, 300m span MV+LV Side Date: 8/11/008 Annex: 030 /

16 Case esults - Ideal Stroke 150 ka 4.6/40us X = us 0.1 MWs MWs MWs [us] SA1 ABB PEXLIM Q88-XV45SE: MO absorbed Energy in MWs SA ABB PEXLIM Q88-XV45SE(1): MO absorbed Energy in MWs SA3 ABB PEXLIM Q88-XV45SE: MO absorbed Energy in MWs us Y =.184 ka [us] SA1 ABB PEXLIM Q88-XV45SE: MO Current A in ka SA ABB PEXLIM Q88-XV45SE(1): MO Current A in ka SA3 ABB PEXLIM Q88-XV45SE: MO Current A in ka 5 Case: 150kA 4.6/50us, Phase A, Milstream Line, 300m span SA_Summary Date: 8/11/008 Annex: 030 /14 31 Case 3 esults - Earth Wire Stroke 11 ka.5/91us.5e+3 X =.455 us.0e kv 1.5E+3 1.0E kv 5.0E kv -5.0E P1_1: m:u:a P1_1: m:u:b P1_1: m:u:c P1_E: m:u:a Case3: 11kA.5/91us, Phase A, Milstream Line, 300m span P1_Insulator Date: 8/1/008 Annex: 030 /

17 Case 3 esults - Earth Wire Stroke 11 ka.5/91us [us] Stroke Current: Current, Magnitude A in ka [us] _earth_p1: Line-Ground Voltage Phasor, Magnitude/Terminal i in kv [us] _earth_p1: Phase Current A/Terminal i in ka [us] _earth_p1: esistance (Input) in Ohm Case3: 11kA.5/91us, Phase A, Milstream Line, 300m span P1_Earth Date: 8/1/008 Annex: 030 /11 33 Case 3 esults - Earth Wire Stroke 11 ka.5/91us.783 us Y = kv.983 us BIL=1016 kv Y = kv [us] B_Gantry1 0kV: Phase Voltage A in kv B_Gantry1 0kV: Phase Voltage B in kv B_Gantry1 0kV: Phase Voltage C in kv [us] CB1_1: Phase Voltage A in kv CB1_1: Phase Voltage B in kv CB1_1: Phase Voltage C in kv BIL=1161kV BIL=1016kV Y = kv Y = kv [us] T10001: Phase Voltage A/HV-Side in kv T10001: Phase Voltage B/HV-Side in kv T10001: Phase Voltage C/HV-Side in kv [us] IS3_1: Phase Voltage A in kv IS3_1: Phase Voltage B in kv IS3_1: Phase Voltage C in kv Case3: 11kA.5/91us, Phase A, Milstream Line, 300m span 0kV Side Date: 8/1/008 Annex: 030 /

18 Case 3 esults - Earth Wire Stroke 11 ka.5/91us 8 BIL=73kV 0 Y = kv 15 4 Y = kv Y = kv 10 5 Y = kv -4 -BIL= -73kV [us] T10001: Phase Voltage A/LV-Side in kv T10001: Phase Voltage B/LV-Side in kv T10001: Phase Voltage C/LV-Side in kv [us] T10001: Phase Voltage A/MV-Side in kv T10001: Phase Voltage B/MV-Side in kv T10001: Phase Voltage C/MV-Side in kv BIL=73kV 0 BIL=165kV 15 4 Y = kv Y = kv 10 5 Y = kv -4 -BIL = -73kV [us] B_11kV: Phase Voltage A in kv B_11kV: Phase Voltage B in kv B_11kV: Phase Voltage C in kv [us] Brockman 33kV: Phase Voltage A in kv Brockman 33kV: Phase Voltage B in kv Brockman 33kV: Phase Voltage C in kv Case3: 11kA.5/91us, Phase A, Milstream Line, 300m span MV+LV Side Date: 8/1/008 Annex: 030 /13 35 Case 3 esults - Earth Wire Stroke 11 ka.5/91us X = us 0.07 MWs MWs MWs [us] SA1 ABB PEXLIM Q88-XV45SE: MO absorbed Energy in MWs SA ABB PEXLIM Q88-XV45SE(1): MO absorbed Energy in MWs SA3 ABB PEXLIM Q88-XV45SE: MO absorbed Energy in MWs us Y = ka [us] SA1 ABB PEXLIM Q88-XV45SE: MO Current A in ka SA ABB PEXLIM Q88-XV45SE(1): MO Current A in ka SA3 ABB PEXLIM Q88-XV45SE: MO Current A in ka 5 Case3: 11kA.5/91us, Phase A, Milstream Line, 300m span SA_Summary Date: 8/1/008 Annex: 030 /

19 Conclusions This paper introduces modelling techniques to achieve more accurate results when executing lightning insulation coordination studies using PowerFactory. Thank you 37 19

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