I have a substation package (KIOSK) 1MVA, 11/0.4 KV, 50 Hz. What is the suitable bu-bar current?

Question

I have a substation package (KIOSK) 1MVA, 11/0.4 KV, 50 Hz. What is the suitable rated bu-bar for RMU (M.V.S.G) ?
What is recommended 630A, 800A, 1200A or 1600A? Why?

Answer 1

Rated secondary line current IL = 1000(1000)/1.732(440)
IL = 1312,Therefore, recommended switchgear at the secondary is 1600 amperes, 3poles Allowance for motor starting current= 1600/1312
=1.219 or approximately, 122 percent ofthe rated secondary current.
The primary line current is 1312(11/0.44)= 52.48 amperes.
Normally, line cut-out fuses rated 60 amperes in three lines would be sufficient, but if ypu want a switcgear, the minimum switchgear available at the primary is 630 amperes

Answer 2

Convert the substation transformer rating to amperes at the secondary voltage.

1000 kVA ÷ 0.400 kV ÷ √3 = 1445 amps.

Your secondary cables must have a minimum rating of 1445 amps, therefore the only suitable size is the 1600 A.

Attached is a link to the common bus-bar dimensions and their ampacities.