Answer / pillay

As the name imply over current means over loading which can
be for a very short time like when switching on a heavy load
or just overloaded slightly by 10 or 20 %.

Short circuit faults are usually of high magnitude when
there is a fault like cable fault or equipment fault.

Answer / girish

over current zone lies between 100 to 400 times the machine
rated current,
but short circuit current zone lies above 400 times and may
extend upto 2000 times the normal rated current

Answer / mahesh katakdhond

overcurrent means just harm equipment slowaly (20to50percent greater than actual current)

shortcicuit means harm suddenly on equipment(it will some multipal value to actual current(4,5,6,7,....*actual current)

When we use air circuit breaker, it has O/L protection ,time delay SC protection, Instataneous SC protection & ground fault protection. They all have some setting range. But what is the suitable/allowable setting for the above protection which will be safe for the equipment? For example-O/L protection setting have a range of (0.4,0.45,0.5,0.55,0.6,0.65,0.7,0.8,0.9,1.0)xIn Time delay SC protection have a range of (1.25,1.5,2,3,4,6,8,10,12)xIn Time delay setting is 0.02,0.1,0.2,0.3,0.4 Instataneous setting is fixed to 20xIn Gound fault setting is given 100A,300A,600A,900A,1200A This setting are for 2500A ACB. So what will be the basic allowable setting for the above protection? is there any formulae to calculate this<

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