IMPORTANT CONSIDERATIONS OF SUBSTATION DESIGN
Necessary Conditions of Substation Design
1. Safety of personnel and equipment
2. Reliability and Security
3. Electrical design considerations
4. Statutory obligations as per I.E. rules, Environmental aspects
5. Structural design considerations
6. Easy of maintenance
7. Possibility to Expand
System parameters
System parameters are
as shown below in table-8.1.
Table-8.1 System
Parameters
|
Sr.
|
Descriptions
|
400KV
|
220
KV
|
|
1.
|
Nominal System Voltage
|
400KV
|
220KV
|
|
2.
|
Max. Operating Voltage
|
420KV
|
245KV
|
|
3.
|
Rated Frequency
|
50HZ
|
50HZ
|
|
4.
|
Number Of Phases
|
3
|
3
|
|
5.
|
System Neutral Earthing
|
Effectively Earthed
|
|
|
6.
|
Corona Extinction Voltage
|
320KV
|
156KV
|
|
7.
|
Min. Creepage Distance
|
25MM/KV
|
25MM/KV
|
|
8.
|
Rated Short Ckt. Current For 1 Sec.
|
40KV
|
40KV
|
|
9.
|
Radio Interference Voltage At 1MHZ
(For Phase To Earth Voltage)
|
1000MV
(320KV)
|
1000MV
(156KV)
|
|
10.
|
Rated Insulation Levels
|
|
|
|
A. Full Wave Impulse
Withstand Voltage
|
|
|
|
|
For Lines
|
1550KVP
|
1050KVP
|
|
|
For Reactor/ X’mer
|
1300KVP
|
950KVP
|
|
|
For Other Equipments
|
1425KVP
|
1050KVP
|
|
|
B. Switching Impulse
Withstand Voltage (Dry/Wet)
|
1050KVP
|
|
|
|
C. One Min. Power Freq.
Withstand Voltage (Dry/Wet)
|
|
|
|
|
For Lines
|
680KV
|
460KV
|
|
|
For CB / Isolator
|
520KV
(Line
Ground)
610KV
(Open
Terminals)
|
460KV
530KV
|
|
|
For Other Equipments
|
630KV
|
460KV
|
|
Lightning Design
Adequate lighting is necessary for safety of working personnel and
Operation & Maintenance activities
Recommended value of Illumination level
Control & Relay panel area -
350 Lux (at floor level)
Test laboratory -
300 Lux
Battery room -
100 Lux
Other indoor area - 150 Lux
Switchyard - 50 Lux (main equipment)
- 20 Lux (balance Area /
road @ ground level)
Minimum Clearances
Minimum
clearances are as shown in table 8.2
Table-8.2
minimum clearances
|
|
400KV
|
220KV
|
|
Phase to
Earth
|
3500mm
|
2100mm
|
|
Phase to
phase
|
4200mm(Rod-conductor
configuration)
4000mm(Conductor-conductor
configuration)
|
2100mm
|
|
Sectional
clearance
|
6400mm
|
4300mm
|
Bus Bar Design
a.
Continuous current rating. Ampacity calculation as per IEEE:738
b.
Short time current rating (40kA for 1 Sec.) IEC-865
c.
Stresses in Tubular Busbar
d. Natural
frequency of Tubular Busbar
e. Deflection
of Tube
f. Cantilever
strength of Post Insulator
g.
Aeolian Vibrations
Earthing Design
a. Guiding
standards – IEEE 80, IS: 3043, CBIP-223.
b. 400kV
& 220kV system are designed for 40kA.
c. Basic
Objectives:
Step
potential within tolerable
Touch
Potential limit
Ground
Resistance
Adequacy of Ground
conductor for fault current (considering corrosion)
