DSLP CALCULATION BY LM.pdf

DOCUMENT NO. : ICML/SOLAR/GUJ/ELECT/DSLP-0022

DIRECT STROKE LIGHTNING PROTECTION CALCULATION FOR 66kV GRID SUBSTATION AT KUTCH GUJRAT Reference: Direct stroke lightning protection calculation is based on the procedure given in "High Voltage Engineering" by Prof. D.V.RAZEVIG , chapter 31, translated from Russian by Dr. M.P.CHOURASIA.

1

Height of Lightning Spikes

2

Height of the livepart to be protected:

h

a. Transformer height Height of the livepart to be protected 

hx

=

16.0 m

=

5.9 m

=

5.9 m

II. Formulae Used: 1

Protective radius (r x) :

If , hx <= (2/3)h and h > 30m:-

⎛ 

h

r x = 1 . 5 h × ⎜⎜ 1 − ⎝ 

If , hx <= (2/3)h and h <= 30m:-

0.8h

⎛ 

h

⎝ 

0.8h

r x = 1 . 5 h × ⎜⎜ 1 −

2

Co-efficient for the Lightning Lightning Mast Height

P

x

x

=

 ⎞ ⎟⎟ P  ⎠

m

 ⎞ ⎟⎟  ⎠

m

5.5/

=

3

Allowable distance between two LMs

Where ha= h - hx m

s

=

for h >30 m

h

1

7

×

h

a

×

P

m

for h <=30 m

Midway point protective Height (ho) and Midway Point Protective Distance (bx)

4

⎛  s  ⎞ ⎟ ⎝ 7 × P ⎠

h0 = h − ⎜

m

If hx < (2/3)ho and ho > 30 m :b x

⎛  h  ⎞ = 1.5ho × ⎜⎜1 −  x ⎟⎟ × P 0 . 8ho  ⎠ ⎝ 

b x

⎛  h  ⎞ = 1.5ho × ⎜⎜1 −  x ⎟⎟ ⎝  0.8ho  ⎠

m

⎛  h  ⎞ = 0.75 ho × ⎜⎜1 −  x ⎟⎟ ⎝  ho  ⎠

m

m

If hx < (2/3)ho and ho < 30 m :-

If hx > (2/3)ho and ho < 30 m :b x

III Legend:

Symbol

Description

Unit

h

Height of Lightning Spikes

m

hx

Height of Livepart to be protected

m

ho

Mid way p oin t pr otective heigh t bet. two LM's

m

P

Coefficient for the LM height

-

s

Allowable Distance between two LM's

m

Midway point protective distance bet. two LM's

m

 bx

IV Calculation Transformer level The protective zone between two lightning masts have considerably greater dimensions than the sum of protective zones of two single lightning masts. If two lightning masts are located at a distance less than S=7 * ha, the point of ground surface which lies midway between the two lightning mast will not be struck by lightning. In otherwords, a fictitious lightning mast will be formed in  between two lightning masts at midpoin t with a height ho h

h

0.8h

0.8h ho

1.5h

0.75h

hx

s

T14

0.75h

T14

1.5h

r x  bx T14

T14 P=

1

S=

7 x ha x P

m Where ha = ( h - h x )

ha = s

Allowable Distance between two LM's

Distance between LM1 & LM2 Protective radius

rx

Midway point protective height between two LM's ho

Midway point protective distance between two LM's bx

m

10.1 m

=

7 x 10.1 x 1

=

70.7 m

=

7.6 m

=

1.5 x h x ( 1-h x / 0.8 h)

=

1.5 x 16 x ( 1 - (5.9 / ( 0.8 x 16))

=

12.9 m

=

h - s / 7P

=

16 - (7.6 / (7 x 1 ))

=

14.91 m

=

1.5 x ho x ( 1-hx / 0.8x h o)

=

1 .5 x 13 .91 x ( 1 - ( 5. 9 / (0 .8x 13. 91) )

=

11.31 m

m m

m

DSLP Protection with shield wire

Reference 'Direct stroke lightning protection calculation is based on the procedure given in "High Voltage Engineering" by Prof. D.V.RAZEVIG , chapter 31, translated from Russian by Dr. M.P.CHOURASIA. As per the above diagram H= hx= S= S1= hx1= hx3=

12 4.2 7.6 8.8 6.4

mtr. mtr. Mtr mtr mt r.

5.9 mtr.

Height of the Tower   Height of the equipments from Ground Level Distance between two Towers. Distance between two Towers. He ight of the li ne conduct or/ Mai n bus conduct or from Ground Le ve l Height of Power Transformer from Ground Level For hx

Now 7.6 < 48 i.e. S1 < 4H  Now the shield wires will protect the object upto a height 'Ho' between them Ho1= ( H - S/4) = 12-(7.6/4) Ho1=

10.1 mtr.

Now 8.8 < 48 i.e. S1 < 4H  Now the shield wires will protect the object upto a height 'Ho' between them Ho1= ( H - S/4) = 12-(8.8/4) Ho1=

9.8 mtr.

4.2 < shield wire will protect distance bx from its centre bx= 1.2H( 1 - hx/0.8H)

8.00 i.e hx< 2H/3

= 1.2*12*(1-(4.2/(0.8*12)) bx= 8.1

mtr.

For hx1 6.4 < shield wire will protect distance bx from its centre bx1= 1.2H( 1 - hx1/0.8H) = 1.2*12*(1-(6.4/0.8*12))  bx1= 4.8

mtr.

shield wire will protect distance bx from its centre  bx2= 0.6H( 1 - hx2/H) = 0.6*12*(1-(9.2/12)  bx2= 7.2

mtr.

8.00 i.e hx< 2H/3

For hx3 5.9 < shield wire will protect distance bx from its centre  bx3= 1.2H( 1 - hx3/0.8H)

8.00 i.e hx< 2H/3

= 1.2*12*(1-(5.7/(0.8*12))  bx3= 5.55

mtr.

Since Ho > hx2, Jack bus conductor is protected Since the lightning protection have been achieved by shield wire at 12 Mtr. height, so all other equipment/ parts below the shield wire level will also be protected. Since Power Transformer end is at a distance of 7.6m, the protection distance is 5.55m hence it cannot be protected by shield wire hence spike shall be used to protect the Power Transformers

DIRECT STROKE LIGHTNING PROTECTION CALCULATION FOR 66kV GRID SUBSTATION AT KUTCH GUJRAT Reference: Direct stroke lightning protection calculation is based on the procedure given in "High Voltage Engineering" by Prof. D.V.RAZEVIG , chapter 31, translated from Russian by Dr. M.P.CHOURASIA.

1

Height of Lightning Spikes

2

Height of the livepart to be protected:

h

a. Transformer height Height of the livepart to be protected 

hx

=

14.0 m

=

5.9 m

=

5.9 m

II. Formulae Used: 1

Protective radius (r x) :

If , hx <= (2/3)h and h > 30m:-

⎛ 

h

r x = 1 . 5 h × ⎜⎜ 1 − ⎝ 

If , hx <= (2/3)h and h <= 30m:-

0.8h

⎛ 

h

⎝ 

0.8h

r x = 1 . 5 h × ⎜⎜ 1 −

2

Co-efficient for the Lightning Mast Height

P

x

x

=

 ⎞ ⎟⎟ P  ⎠

m

 ⎞ ⎟⎟  ⎠

m

5.5/

=

3

Allowable distance between two LMs

Where ha= h - hx m

s

=

for h >30 m

h

1

7

×

h

a

×

P

m

for h <=30 m

Midway point protective Height (ho) and Midway Point Protective Distance (bx)

4

⎛  s  ⎞ ⎟ ⎝ 7 × P ⎠

h0 = h − ⎜

m

If hx < (2/3)ho and ho > 30 m :b x

⎛  h  ⎞ = 1.5ho × ⎜⎜1 −  x ⎟⎟ × P 0 . 8ho  ⎠ ⎝ 

b x

⎛  h  ⎞ = 1.5ho × ⎜⎜1 −  x ⎟⎟ ⎝  0.8ho  ⎠

m

⎛  h  ⎞ = 0.75 ho × ⎜⎜1 −  x ⎟⎟ ⎝  ho  ⎠

m

m

If hx < (2/3)ho and ho < 30 m :-

If hx > (2/3)ho and ho < 30 m :b x

III Legend:

Symbol

Description

Unit

h

Height of Lightning Spikes

m

hx

Height of Livepart to be protected

m

ho

Mid way p oin t pr otective heigh t bet. two LM's

m

P

Coefficient for the LM height

-

s

Allowable Distance between two LM's

m

Midway point protective distance bet. two LM's

m

 bx

IV Calculation Transformer level The protective zone between two lightning masts have considerably greater dimensions than the sum of protective zones of two single lightning masts. If two lightning masts are located at a distance less than S=7 * ha, the point of ground surface which lies midway between the two lightning mast will not be struck by lightning. In otherwords, a fictitious lightning mast will be formed in  between two lightning masts at midpoin t with a height ho h

h

0.8h

0.8h ho

1.5h

0.75h

hx

s

T14

0.75h

T14

1.5h

r x  bx T14

T14 P=

1

S=

7 x ha x P

m Where ha = ( h - h x )

ha = s

Allowable Distance between two LM's

Distance between LM1 & LM2 Protective radius

rx

Midway point protective height between two LM's ho

Midway point protective distance between two LM's bx

m

8.1 m

=

7 x 8.1 x 1

=

56.7 m

=

7.6 m

=

1.5 x h x ( 1-h x / 0.8 h)

=

1.5 x 14 x ( 1 - (5.9 / ( 0.8 x 14))

=

9.9 m

=

h - s / 7P

=

14 - (7.6 / (7 x 1 ))

=

12.91 m

=

1.5 x ho x ( 1-hx / 0.8x h o)

=

1 .5 x 13 .91 x ( 1 - ( 5. 9 / (0 .8x 13. 91) )

=

8.31 m

m m

m