Sub Station Abstracts

Sub Station Equipments and Safety Clearance

Rating of Lighting Arrestor:

  • Size of L.A = 1.5 X Phase to Earth Voltage    OR   
  • Size of L.A =1.5 X system Voltage/1.732       OR
  • Size of L.A = 0.81 X highest System Voltage

Lighting Arrestor Protection Radius:

  • Protection Radius (Rp) = Sqrt (H X (2D-H)+L(2D+L))
  • H= Actual Height of L.A
  • D= 20 meter, 40 meter or 60 meter
  • L= V X T (T=Discharge Time & V= 1m/ms)

Creepage Distance:

  • 18 mm to 22 mm /KV for Moderate Polluted Air.
  • 25 mm to 33 mm /KV for Heavily Polluted Air.
  • In HVDC System The value is double from above value.

Lighting Arrestor Rating:

Rated Voltage

Highest Voltage

L.A Rating

132kv

145kv

120kv To 132kv

220kv

245kv

198kv To 216kv

400kv

420kv

336kv

Location of Lighting Arrestor:

Rated Voltage

Max Distance from Equipment

132kv

35 meter To 45 meter

220kv

Closed To Transformer

400kv

Closed To Transformer

 Size of Corona Ring:

Rated Voltage

Size of Corona Ring

Less than 170 KV

160mm Ring Put on HV end

170KV To 275KV

350mm Ring Put on HV end

More than 275KV

450mm Ring Put on HV end

More than 275KV

350mm Ring Put on HV end

 Capacity of Sub Station as per GERC:

Size of S/S

Electrical Load

66 KV

80 MVA

132 KV

150 MVA

220 KV

320 MVA

400 KV

1000 MVA

 Breaking / Short Circuit Capacity of Sub Station:

Size of S/S

Short Circuit Current

66 KV

25 KAmp  for 1 or 3 sec

132 KV

31.5 KAmp  for 1 or 3 sec

220 KV

40 KAmp  for 1 or 3 sec

400 KV

40 KAmp  for 1 or 3 sec

 Fault Clear Time:               

                Size of S/S

Fault Clear Time

66 KV

300 mili Sec

132 KV

160 mili Sec

220 KV

120 mili Sec

400 KV

100 mili Sec

 Normal Type of Conductors:

Voltage

Main Bus

Auxiliary Bus

11KV

Twin ACSR Zebra

ACSR Zebra

33KV

ACSR Zebra

ACSR Zebra

132KV

ACSR Zebra

ACSR Panthers

220KV

Twin ACSR Zebra

ACSR Zebra

400KV

1/14.2 mm Dia Alu Pipe

Twin ACSR Moose

 Number of Disc Insulator:

System

Number

Strength (KN)

11KV

4

120KN

33KV

4

120KN

132KV

10

120KN

220KV

14

70KN

220KV (Anti  Fog)

2 X 15

120KN

400KV (Anti  Fog)

2 X 25

120KN

 Minimum Clearance:

Voltage

Phase to Earth Wire

Phase to Phase

Section Clearance

2.2KV

28cm

33cm

27.45cm

33KV

380cm

43cm

27.7cm

132KV

107cm

12cm

25cm

220KV

178cm

20.6cm

42.8cm

400KV

350cm

40cm

65cm

 Ground Clearance:

                Voltage

Meter

33KV

3.7meter

66 KV

6.1meter

132 KV

6.1meter

220 KV

7.0meter

400 KV

8.8meter

 Conductor Spacing:

Voltage

Highest Voltage

Lighting Impulse Level (Kvp)

Min Clearance

Ground Clearance

Safety working Clearance

Phase to Earth

Phase to Phase

11KV

12kv

70

178mm

229mm

3700mm

2600mm

33KV

36kv

170

320mm

320mm

3700mm

2800mm

132 KV

145kv

550

1300mm

1300mm

4600mm

3700mm

220 KV

245kv

950

2100mm

2100mm

5500mm

4300mm

400 KV

420kv

1425

3400mm

4200mm

8000mm

6400mm

  Earthing Resistance Value:

Particular

Max Earthing Resistance

Power Station

0.5Ω

EHT Sub Station

33KV Sub Station

Double Pole Structure

Tower foot Resistance

10Ω

Distribution Transformer

220KV Sub Station

1Ω To 2Ω

400KV Sub Station

0.5Ω

 Losses in 11 kv Transformer at 75c (As per CBIP):

Transformer

No Load Loss(kw)

Load Loss (kw)

% Impedance

3.15MVA

2.9

20

6.25

4MVA

3.2

27

7.15

5.3MVA

3.9

31

7.15

6.3MVA

4.5

37

7.15

 Losses in 66 kv Transformer at 75c (As per CBIP):

Transformer

No Load Loss(kw)

Load Loss (kw)

% Impedance

6.3MVA

6

40

8.35

8MVA

7.1

48

8.35

10MVA

8.4

57

8.35

12.5MVA

9.7

70

8.35

20MVA

13

102

10.0

 Standard Rating of 66KV Transformer (As per CBIP):

Transformer

KV

Type of Cooling

6.3MVA

66KV/11KV

ONAN

8MVA

66KV/11KV

ONAN

10MVA

66KV/11KV

ONAN

12.5MVA

66KV/11KV

ONAN / ONAF

20MVA

66KV/11KV

ONAN / ONAF

 % Impedance for Transformer (As per IS 2026):

33KV Transformer

66KV Transformer

MVA

%Impedance

MVA

%Impedance

1MVA

5%

6.3MVA

8.35%

1.6MVA

6.25%

8MVA

8.35%

3.15MVA

6.25%

10MVA

8.35%

4MVA

7.15%

12.5MVA

8.35%

5MVA

7.15%

20MVA

10%

6.3MVA

7.15%

16MVA

10%

8MVA

8.35%

25MVA

10%

10MVA

8.35%

31.5MVA

12.5%

MVA

%impedance

Less Than 1MVA

5%

1MVA To 2.5MVA

6%

2.5MVA To 5MVA

7%

5MVA To 7MVA

8%

7MVA To 12MVA

9%

12MVA To 30MVA

10%

More Than 30MVA

12.5%

  Bus Bar Materials:

Description Bus Bar and Jumper Material
400 kV Main Bus 114.2 mm dia. Aluminium pipe
400 kV equipment interconnection 114.2 mm dia. Aluminium pipe
400 kV overhead bus & droppers in all bays. Twin ACSR Moose
220 kV Main Bus Quadruple / Twin ACSR Zebra / Twin AAC Tarantulla
220 kV Auxiliary Bus ACSR Zebra
220 kV equipment interconnection Twin ACSR Zebra / Single ACSR Zebra
220 kV overhead bus & droppers in all bays. Twin ACSR Zebra / Single ACSR Zebra
132 kV Main Bus ACSR Zebra
132 kV Auxiliary Bus ACSR Panther
132 kV equipment interconnection ACSR Zebra / ACSR Panther
132 kV overhead bus & droppers in all bays. ACSR Panther
33 kV Main Bus ACSR Zebra
33 kV Auxiliary Bus ACSR Zebra
33 kV equipment interconnection, overhead bus and droppers:  
(i) Bus coupler & transformer bay ACSR Zebra
(ii) Feeder bay. ACSR Panther
11 kV Main Bus Twin ACSR Zebra
11 kV Auxiliary Bus ACSR Zebra
11 kV equipment interconnection, overhead bus and droppers:  
(i) Transformer bay Twin ACSR Zebra / Single ACSR Zebra
(ii) Bus coupler ACSR Zebra
   

About Jignesh.Parmar
Jignesh Parmar has completed M.Tech (Power System Control), B.E(Electrical) from Gujarat University. He has more than 13 years experience in Power Transmission-Power Distribution-Electrical energy theft detection-Electrical Maintenance-Electrical Projects(Planning-Designing-coordination-Execution). He is Presently associate with one of the leading business group as a Deputy Manager at Ahmedabad,India. He is Freelancer Programmer of Advance Excel and design useful Excel Sheets of Electrical Engineering as per IS,NEC,IEC,IEEE codes. He is technical Author for "Electrical Mirror" and "Electrical India" Magazines. He is Technical Blogger and Familiar with English, Hindi, Gujarati, French languages. He wants to Share his experience & knowledge and help technical enthusiasts to find suitable solutions and updating themselves on various Engineering Topics.

30 Responses to Sub Station Abstracts

  1. bhargav says:

    Thank u very much for providing valuable material. It is very helpful to me.

  2. Dharminder says:

    Thanks for this upload

  3. asif says:

    Thanks a lot Mr: Jignesh. The datas was very helpful

    Asif KM
    Saudi Electricity Company

  4. ritu says:

    very very good!!!

  5. kaveesh (power engr.) says:

    very helpful..

  6. Shivakumar Kinni says:

    I have request could you please provide the standard/code reference for Earthing Resistance Values.
    Thanks in advance.

    • Earthing Resistance Value:
      Power Station = 0.5 ohm.
      Sub Station Major=1.0 ohm.
      Sub Station Minor=2.0 ohm.
      Distribution T/C=5.0 ohm.
      Transmission Line=10 ohm.

      As per My knowledge.There is not exact value for Earthing Resistance in any Standard ,It depend upon Soil but There is a guideline in Some Code that it should be less than 5 ohm and in some code it is given less than 10 ohm.

  7. balaji Gir says:

    hi!

    i want know how to calculate the LA (lightining Arrestor) rated voltage.

    any formula

  8. Fernando Campos Merino. says:

    Would you please to told me what’s meaning GERC and CBIP??
    Thanks a lot

  9. Its very good. Thank you very much.

  10. vinod says:

    could i get a detailed article on power transformer testing including the purpose

  11. AIJAZ RAINA says:

    VERY INFORMATIVE .PLEASE PROVIDE INFORMATION ABOUT PROTECTION DIAGRAMS

  12. vilas k says:

    Dear Sir , we are thankful to you for the exhaustive information u provide in collective manner. Pl provide some article on DC Battery chargers & DC Batteries used in EHV sub stations.

  13. dharmraj says:

    Thank u, it is very useful

  14. Sanjeevikumar says:

    than u ,
    i need megger value is any standard.

  15. John bosco says:

    Do you have any formula for calculate clearance phase to phase ,phase to earth ,sectional clearance without reference of standards

  16. arnab says:

    hello sir,

    I would like to go through a simplified, detailed substation design procedure guide. Please help me in this regard.

  17. jainy says:

    can u tell me about sub conductor spacing in twin zebra conductor

  18. sameer says:

    Dear Sir
    thank you for above article
    can you please tell or mail me the types of tests performed in substation or detailed notes on testing and commissioning methods carried din substation

  19. vishnu vyas says:

    dear sir, i need your help i am doing a 220 kV s/s project in tanzinia pl tell me what Clarence i should kept . can i used CBIP ???

  20. lliayan says:

    i need one information why choose in twin conductor in susstation

  21. yuvan says:

    dear sir,

    i need the substation design calculation formula

  22. Rahul Bundel says:

    Sir how the ratings of lightning arrester is decided????

  23. Waqas Khalid says:

    I very much appreciate the valuable data being provided by you and your knowledge. Please respond to my following queries:
    1. Why 02 nos. Surge Arresters are normally used in a 145 kV or more voltage level in a single bay of GIS switch-gear?
    2. Kindly also refer international applicable standard(s) against values/data being provided by you.
    Regards,
    Waqas Khalid

  24. Vijay says:

    Sir name And type of holo conductor used in 132 KV yard

  25. rizwan says:

    hii sir i think there is some mistakes in minimum clearance table ( 400 KV phase to phase clearance only 40 cm and in 220kv 20 cm and in 132kv 12cm )

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