ikram shehzad said:
Dear all,is ther any body who can tell me about the setting of ACB(air circuit breaker ). what kind of it,s setting is and how to do it,s setting. also please tell me the setting of VCB(vaccume circuit breaker) . please tell me their setting,s.i will b very thank ful to all of u.Thank,s and Regard,s.Muhammed Ikram.
Dear Mr. Ikram ;
An ” ACB ” is a circuit breaker dedicated to protcet the Electrical Low Voltage Networks, that are equiped of many kind of protections noting that are all Electronic Protection installed in the ACB and internaly connected with ” Current Transformers ” that are also istalled in the ACB, these protections are :
– Thermal Protcetion against ” Overload faults ” : it can be adjusted ” Ir : 0.4 to 1 x In “, where ” In ” is the nominal current of ACB like : 2500A or 3200A or 4000A, so, if we adjusted it at ” 0.5 ” for ” ACB – 4000A “, the thermal protcetion value is ” Ir = 0.5 x 4000 = 2000A “
– Magnetic Protection for ” Short Circuit Faults ” : it can adjusted ” Isd : 1.5 to 10 x Ir ” or for some manufacters to ” 12 “, so, if we adjusted for the same ACB at ” 6 “, the magnetic protection value is ” Isd = 6 x 2000 = 12000A “.
– Earth Fault Protection against direct fault between any phase and the protection line, it can be adjusted ” Ig : 0.3 to 1 x In “, so, if we adjusted it for the same ACB at ” 0.7 “, the earth fault protection value is ” Ig = 0.7 x 4000 = 2800A “.
-Residual Protection against ” Residual Faults ” that means against indirect fault where the fault current's value is normaly small ( a few Amps ), it can asjusted ” IΔn : 0.5 to 30A “.
– Instantaneous Protection against ” Short Circuit Faults ” when the fault's current value will be very big, and in the same time we want that ACB trip quickly without delaying, it can adjusted ” Ii : 2 to 15 x In ” and we can also switched-off, so, if we adjusted it for the same ACB at ” 6 ” the instantaneous protection value is ” Ii = 6 x 4000 = 24000A “.
In some ACB there's also a ” Timing Delay ” for the thermal protection and for the magnetic protection, where the ” Timimg delay ” for thermal protection can be adjusted is ” Seconds “, but the ” Timing Delay ” for the magnetic protection can be adhusted in ” mili-Seconds “, and we use these ” Timing Delay ” in ACB to realize the ” Discrimination or Selectivuty ” between 2 ACB's or between ACB and MCCB .