Electrical Thumb Rules You MUST Follow (Part 4)PostedNOV 15 2013byJIGUPARMARinENERGY AND POWERwith2 COMMENTS

Electrical Thumb Rules You MUST Follow - part 4 (on photo: distribution substation bus on a clear night in February by Eli Nelson) at Flickr

Continued from:Electrical Thumb Rules You MUST Follow (Part 3)

Eight rules to follow:1. Substation Capacity and Short Circuit Current Capacity (As per GERC)2. Substation Capacity and Short Circuit Current Capacity (As per Central Electricity Authority)3. Minimum Ground Clearance and Fault Clearing Time4. Busbar Ampere Rating5. Busbar Spacing6. Sound Level of Diesel Generator (ANSI 89.2 and NEMA 51.20)7. IR Value of Transformer8. Standard Size of MCB, MCCB, ELCB, RCCB, SFU and Fuse1. Substation Capacity and Short Circuit Current CapacityAs per GERC

VoltageSub Station CapacityShort Circuit Current

400 KVUp to 1000 MVA40 KA (1 to 3 Sec)

220 KVUp to 320 MVA40 KA (1 to 3 Sec)

132 KVUp to 150 MVA32 KA (1 to 3 Sec)

66 KVUp to 80 MVA25 KA (1 to 3 Sec)

33 KV1.5 MVA to 5 MVA35 KA (Urban) (1 to 3 Sec)

11 KV150 KVA to 1.5 MVA25 KA (Rural) (1 to 3 Sec)

415 V6 KVA to 150 KVA10 KA (1 to 3 Sec)

220 VUp to 6 KVA6 KA (1 to 3 Sec)

Go back to Rules

2. Substation Capacity andShort Circuit Current CapacityAs per Central Electricity Authority

VoltageSub Station CapacityShort Circuit Current

765 KV4500 MVA31.5 KA for 1 Sec

400 KV1500 MVA31.5 KA for 1 Sec

220 KV500 MVA40 KA for 1 Sec

110/132 KV150 MVA40 KA or 50 KA for 1 Sec

66 KV75 MVA40 KA or 50 KA for 1 Sec

3. Minimum Ground Clearance and Fault Clearing TimeVoltageMin. Ground ClearanceFault Clear Time

400 KV8.8 Meter100 mille second

220 KV8.0 Meter120 mille second

132 KV6.1 Meter160 mille second

66 KV5.1 Meter300 mille second

33 KV3.7 Meter-

11 KV2.7 Meter-

4.Busbar Ampere Rating

For Phase BusbarAluminium 130 Amp / Sq.cm or 800Amp / Sq.inch.

For Phase BusbarCopper 160 Amp / Sq.cm or 1000Amp / Sq.inch

For Neutral BusbarSame as Phase Busbar up to 200 Amp than Size of Neutral Busbar is at least half of Phase Busbar.

5. Busbar SpacingBetween Phase and Earth26mm (Min)

Between Phase and Phase32mm (Min)

Busbar Support between Two Insulator250mm.

6. Sound Level of Diesel Generator (ANSI 89.2 and NEMA 51.20)KVAMax. Sound Level

66KV600M300M150M

22KV to 33KV500M250M125M

6.6KV to 11KV400M200M100M