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Standard Wiring Practices in Electrical Sub-stations

Standard Practices:

1.           Permanent wiring

2.           Every lead should end at a terminal block.

3.           No junction by twisting.

4.           Copper stranded leads for CT/PT.

5.           ‘O’ lugs for CT, not ‘U’.

6.           Nut with washer is compulsory for CT termination.

7.           TBs shall be stud type and not screw type.

8.           Wherever two DC sources are available, Primary and Back-up protection DC should be from different sources.

9.           Main and Back-up protection should command TC1 and TC2 both for CB tripping on fault.

10.      DC/AC not through different cores of same cable.

11.      DC emergency lightning should be through separate cable.

12.      Negative of DC shall be extended directly, where as positive should be through command.

13.      Lead nos. should be standardized as follow.

a.     A→ CT secondary for main protection

b.     B→ CT secondary for Bus Bar protection

c.      C→ CT secondary for Back-Up protection

d.     D→ CT secondary for Metering

e.      E→ PT secondary

f.       H→ AC supply

g.     J→ Main DC

h.     K→ Control DC

i.       L→ Indication and Annunciation DC

14.      Proper ferruling (numbering).

15.      CT ratio available for the particular feeder should be indicated on panel with connected ratio underlined.

16.      CT core not used (spare) should be shorted by looping at CT secondary box.

17.      Use of appropriate size of glands.

18.      Avoid loose connection.

19.      Wires not used should be removed from panel.

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