1. Presented by: Nguyen Phan Thanh Southern Taiwan University of Science and Technology

2. FEEE Ensuring Enhanced Education 2 Objective  To protect the distribution substation from lightning overvoltage, the lightning arrester is installed at the high voltage side of transformers.  If the lightning arrester is installed at the terminals of transformers, the transformer will be protected safety.  However, lightning arrester must to protect for all insulation of the substation’s components.  Thus, the determination of reasonable distance between lightning arrester and terminals transformer to protect efficiency the transformer and switching devices of the substation is very necessary.

3. FEEE Ensuring Enhanced Education 3  This project presents a new method for calculating the separated distance and the Mean Time Between Failure (MTBF) of the transformer with different configurations to make sure that the life of transformer according to first requirement, considering the affected factors such as the shielding factor of the object, areas ground flash density, the inductance value of connected wires.  The OPSOLA program is built to help the users easily determine the appropriate installed position of lightning arrester and check MTBF for the existing configuration of substation. Objective

4. FEEE Ensuring Enhanced Education 4  The previous protection methods  The proposed protection method  The OPSOLA Program  Result Content

5. FEEE Ensuring Enhanced Education UnUn kV17,52436 BILkV95125170 UpUp kV57,279,9117,6 5 1.The simple protection method The maximum distance: Table 1. BIL and U p (Với: D = a + b) a : The maximum separation between J and pole- mounted transformer, m b : Distance between J and surge arrester, m U t : Arrester residual voltage, kV C: Velocity of wave propagation, C = 300 m/  s. BIL: Basic Insulation Level of Transformer (KV) I. The previous protection methods

6. FEEE Ensuring Enhanced Education 6 2. The improved protection method (J. R. Lucas Method) D O : Point of lightning stroke S 0 : Rate of rise at O, kV/µs I 0 : Lightning stroke current, kA X :Distance in which a surge with an infinite slope will decay to slope S A at A, m S A : Rate of rise of surge voltage at A, kV/µs  : Reflection coefficient at transformer E t : Peak surge voltage at transformer, kV S f : Shielding factor (0,3 ÷ 0,5) N : The number of direct stroke into line, times/100km/year h : Height of nearby objects, m b : Horizontal span between outermost conductors, m N g : Number of stroke per km 2 per year LF: Lifetime of transformer, year FR: Failure rate of transformer, % N f : Number of lightning surges arriving at A /year, with slope higher S A T : Wave front time,  s k : Corona damping constant, kV.km/  s. I. The previous protection methods

7. FEEE Ensuring Enhanced Education 7 D O : Point of lightning stroke S 0 : Rate of rise at O, kV/µs I 0 : Lightning stroke current, kA X :Distance in which a surge with an infinite slope will decay to slope S A at A, m S A : Rate of rise of surge voltage at A, kV/µs  : Reflection coefficient at transformer E t : Peak surge voltage at transformer, kV S f : Shielding factor (0,3 ÷ 0,5) N : The number of direct stroke into line, times/100km/year h : Height of nearby objects, m b : Horizontal span between outermost conductors, m N g : Number of stroke per km 2 per year LF: Lifetime of transformer, year FR: Failure rate of transformer, % N f : Number of lightning surges arriving at A /year, with slope higher S A T : Wave front time,  s k : Corona damping constant, kV.km/  s. 2. The improved protection method (J. R. Lucas Method) I. The previous protection methods

8. FEEE Ensuring Enhanced Education 8 The previous methods: Accounting for influence elements with some experiment parameters Just considered to single transformer substation The proposed method: Determining surge arrester‘s location for 3-line, 2-transfomer substation based on:  IEEE Std C62.22.2009  Influence elements (can be calculated)  Mean Time Between Failure (MTBF ) of Transformer I. The previous protection methods

9. FEEE Ensuring Enhanced Education 9 S.1. Eliminate 1 transformer and determine the line which the lightning wave transmitted into. S.2. Define the following parameters: - J, the common point between transformer, surge arrester and the line identified in step 01. - D1, distance from J to pole-mounted transformer - D2, distance from arrester to ground (3-line, 2 - transformer substation) The proposed protection method based on IEEE Std C62.22.2009 S.3. Eliminate all line connected to D 1 S.4. Calculate SJ, kA/  s A, B, C: Line A, B, C. T 1,T 2 : Transformer T 1 and T 2 D 1 : Separate distance between T 1 and line, m. D 2 : Separate distance between T 2 and line, m. N tt : Number of identified lines II. II. The proposed protection method d 2 =

10. FEEE Ensuring Enhanced Education 10 S.5. Distance : stroke - substation, km S.6. Voltage of Arrester B: insulation equipments. d 1 : distance between line and arrester, m. D 2 : distance between arrester and ground, m. S : slope wave, kA/  s. MTBF: mean time between failure, year FR: acceptable failure rate, % N : number of stroke into line, times /100 km/year K c : corona damping constant, kV.km/  s V a : Mức bảo vệ đầu sóng của chống sét van tại 0,5  s, kV Z : line impedance,  L : Inductance,  H. with: The proposed method based on IEEE Std C62.22.2009 II. II. The proposed protection method

11. FEEE Ensuring Enhanced Education 11 S.7. Determine D 1 and D 2 : D 1 = min (D 1 _T 1 _Line A ; D 1 _T 1 _Line B ; D 1 _T 1 _Line C) D 2 = min (D 2 _T 2 _Line A ; D 2 _T 2 _Line B ; D 2 _T 2 _Line C) II. II. The proposed protection method The proposed protection method based on IEEE Std C62.22.2009

12. FEEE Ensuring Enhanced Education 12 Shielding Factor Distance from objects to line (DO = x), m (S f ) Object ‘s Height H = 10m: S f = 5,013.10 - 7.x 3 – 6,051.10 -5.x 2 – 0,003655.x + 0,4813 H = 14m: S f = – 6,047.10 - 12.x 5 + 1,452.10 - 8.x 4 – 3,332.10 - 6.x 3 +0,3459.10 - 3.x 2 – 0,0247.x + 0,9982 Nonlinear regression technique Curve Fitting Matlab Build 16 relationships S f, H và DO S f = S fL + S fR S fL : S.F at left side S fR : S.F at right side II. II. The proposed protection method

13. FEEE Ensuring Enhanced Education 13 The number of stroke into line The inductance line which connect to surge arrester, times/100km/year - The inductance at line (length 1 m),  H/m - The inductance line which connect to surge arrester,  H Which:, m II. II. The proposed protection method

14. FEEE Ensuring Enhanced Education 14 Check MTBF of transformer II. II. The proposed protection method (1) (3) Nonlinear regression technique Curve Fitting Matlab Build 6 relationships S f, H và DO MTBF (year) N g (times/km 2.year)