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ELECTRIALSERVICESSYSTEMFACTSSubject –BUILDING ANDINFRASTRUCTURESERVICES

 

Submitted by:-

Ashutosh Kumar M.B.E.M (2nd 

Sem.) S.P.A New Delhi 

 

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FUNDAMENTALS 

1. Electricity can be generated using the kinetic energy of water, heat energy of

the sun and coal, or from the nuclear energy released from the fission of

nuclear fuel.

2. There are mainly following types of power plant for electrical current

generation :-

Coal based thermal Power Plants

PNG/CNG based thermal power plant

Nuclear Power Plants

Hydro Power Plants

Solar Power Plants

The Wind Power Plant,

Tidal Power Plant

Geothermal Power Plant

Hydel power plants

3. Major Electrical Equipment used in Power Plant are Generation Equipment,

Transformers, Switch Gear, Protection of Electrical Systems. 

4. At the generating plants the energy is produced at a relatively low voltage between

about 2.3 kV and 30 kV, depending on the size of the unit. The generator terminal

voltage is then stepped up by the power station transformer to 400kv supplied to Grid

for transmission for whole country.

5.Transmitting electricity at high voltage reduces the fraction of energy lost toresistance. For a given amount of power, a higher voltage reduces the current

and thus the resistive losses in the conductor. 

6. There are following different range of standard voltage available for electrical

supply :- 12V, 24V, 110V, 220V, 400-440V, 660V, 1100V, 11000V, 22000V,

33KV, 66KV, 110KV, 220KV, 400KV, 600KV, 1000KV. 

7. 12V & 24V are extra low voltage 110V called low voltage 220V- 1100V called

medium voltage and above that are High voltages. Up to 220 voltage Single

phase and above that 3 phase voltage available.

8. In Overhead transmission line, suspension insulators contain a chain of

several disks each rated about 22kv. By multiplying 22 by the number of disks

we can get a good estimation of the voltage in the transmission line.

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SUBSTATION&SWITCHYARD 

9. Substation constitute of HT meter, HT panel, Step down transformer and LT

switch board (which connects to LT Panel).

10. For supply of 11kv, 22kv and 33kv one substation required, but for largerprojects where supply voltage is 66kv or 132 kv then two level of substation

required.

11. Minimum size required for switchyard is 60mX40m with 6m road all around.

The space can be reduced with the use of gas insulated circuit breaker.

12. The site selection criteria for switchyard should be:

a. As near the load center as possible.

b. As far as possible rectangular or square in shape for ease of proper orientation of 

bus– bars and feeders.

c. Far away from obstructions, to permit easy and safe approach / termination of high voltage overhead transmission lines.

d. Free from master plans / layouts or future development activities to have free line 

corridors for the present and in future.

e. Easily accessible to the public road to facilitate transport of material.

f. Preferably fairly leveled ground. This facilitates reduction in leveling expenditure.

g. Above highest flood level (HFL) so that there is no water logging.

13. For control points we provide Automatic circuit breaker and manual Isolators.

These are of three types. Oil filled type, Vacuum type and SF6 type.

14. Provision of adequate earthling system in a Sub Station is extremelyimportant for the safety of the operating personnel as well as for proper

system operation and performance of the protective devices.

15. Transportation and unloading of the sub-station material and equipment at the

location shall be done in a safe manner so that they are not damaged or

misplaced. And inspection required to avoid use of any damaged to insulator

or other fragile equipment due to excessive swing.

16. There are two options available for substation in any building on ground with

the any edge (preferably rear) of the site, or in the Basement. In case of

basement only dry type appliance used in the substation.

17. Right arrangement of components in any substation is as follows :-

C.B

Transformer

DG setsMeter room HT Panel

Isolator

L T panel

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18. All door openings from substation, electrical rooms, etc should open towards

outside.

19. The power supply control to any such substation or transformer (located at

basement levels or upper floors) shall be from a location on ground floor/first

basement level having direct access from outside so that in case of fire, the

electrical supply can be easily disconnected.

20. The minimum height of high voltage switchgear room shall be 3.6 m below the

soffit of the beam.

21. enclose any part of the substation, which is open to the air and contains live

equipment which is not encased, with a fence or wall not less than 2.4 m in

height to prevent, so far as is reasonably practicable, danger or unauthorised

access.

22. Sufficient safety signs of such size and placed in such positions as are

necessary to give due warning of such danger as is reasonably foreseeable inthe circumstances.

23. In case of connected load of 100 kVA and above, the relative advantage of

high voltage three-phase supply should be considered. Though the use of

high voltage supply entails the provisions of space for the capital cost of

providing suitable transformer substation.

24. These are the following advantages are gained by HT line:

Advantage in tariff.

more effective earth fault protection for heavy current circuits; Better control of voltage regulation and more constant supply voltage.

25. It shall be mandatory to provide power factor improvement capacitor at the

substation bus. Necessary switchgear/feeder circuit breaker shall be provided for

controlling of capacitor bank of desired capacity.

TRANSFORMER26. There are two types of transformer available Oil filled type and Dry type.

27. General design objective while selecting the transformer(s) for a substation

would be to provide at least two or more transformers, so that a certain

amount of redundancy is built in, even if a standby system is provided.

28. Minimum separation between two transformers is 2.5m, if provided less than

that they should be separated by firewall.

29. Transformers should be placed on slightly above to ensure no flooding

generally 150mm above placed.

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30. In case of oil filled type transformer base platform must have channel drain to

ensure removal of leaking oil.

31. In case of transformer placed on ground surrounding area should be hard

paving or covered by stone pebble to stop any vegetation and creeper.

32. General requirements for transformer (Tx) room

• Minimum headroom (for equipment & delivery)

• Fire services installation

• Space for maintenance/removal

• Next/Close to main switch room

• No expansion joint & other engineering services

• Independent ventilation

• Generally, no more than 3 Tx in one room

33. Additional requirements for plant room / Transformer room

• A separate & independent staircase to G/F• Also a protected lobby

• Sum pit w/ sump pumps to extract water when flooding

• Hoist beam with pulley for 8,000 kg

• Damp proof course (prevent moisture)

• No dead ends in periphery of the transformer or panel.

34. Major equipment in Transformer rooms

o Power transformer

o Switchgear

May be other equipment like

o LV switchboardo LV capacitor bank

o Battery & charger

o Marshaling boxes

o Meter panel

35. Minimum space around transformer should be 750 mm.

36. Single phase transformer comes in 5kvA, 10kvA, 25kvA and three phase

transformer comes in 63kvA, 100 kvA, 125 kvA, 160 kvA, 200 kvA, 250 kvA,

320 kvA, 400 kvA, 500 kvA, ………….3200 kvA, 4000 kvA.

CABLES ANDBUSDUCTS37. Cable, Armoured — A cable provided with a wrapping of metal (usually in the

form of tape or wire) serving as a mechanical protection. It is used for ouside

underground cabling.

38. Cable, Flexible — A cable containing one or more cores, each formed of a

group of wires, the diameters of the cores and of the wires being sufficiently

small to afford flexibility.

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