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Wednesday, 7 June 2017

Daily lessons-Introduction to substation chapter-3

CHAPTER 3

MISCELLANEOUS

3.1 BATTERIES: -  In electrical power stations and large capacity substations, the operating and automatic control circuits, the protective relay systems, as well as emergency lightning circuits, are supplied by station batteries. The latter constitute independent source of operative dc power and guarantee operation of the above mentioned circuit irrespective of any fault which has occurred in the station or substation, even in the event of complete disappearance of the ac supply in the installation.

Station batteries are assembled of a certain number of accumulator cells depending on the operating voltage of the respective dc circuits. Storage batteries are of two types namely lead acid and alkaline batteries are most commonly used in power stations and substations because of their higher cell voltage and low cost. Detailed description of the storage batteries is beyond the scope of the book and for it, A course in electrical technology volume 1of the same author may be referred.

 

3.2 CONTROL CABLES: -

The control cables and conduit system are required for the automatic controls.

The control system generally operates at 110v or 220v can be employed for these purposes are multi-core cables having 10 or 37 or 61 conductors requirement. For laying these cables generally ducts are run control rods are centrally located from junction box where the conduits are to the required.

 

3.3 EARTH PITS: -

Earth pit resistance should be as low as possible for effective grounding. Earth pit to which power transformer neutral is connected should be more effective. It should be reconditioned periodically. Earth pits should not be used as dust bins. Particularly, oil like liquids should not be allowed into the earth pits. Earth pits should be watered regularly. And the earth pit resistance should be checked periodically. Connections at earth pits should be tightened periodically.

  1. Earth pit for LA should be exclusive to allow immediate discharge of the surge.

  2. Separate earth pit should be provided for the PLLC equipment and it should not be linked with the earth grid.

  3. Earth pit provided for mid-point Earthing of the station battery should not be mixed with the earth grid.


 

 

 

CONCLUSION:

The various factors of substation like classification, selection of site, protection, design and some of the particulars of substation is discussed. Some of the equipment used is delicate and need monitoring. It is better to monitor rather than replacement. The incoming and outgoing sources of this particular substation is also discussed.

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