Fault Level

Hi

the fault level will not only be the reason of not succesfull running of compressor, the compressor is of very big rating, so the regulation of line voltage, total available MW capacity of line, existing load condition and there are many more parameters u have to keep in mind.

as soon as u switch on the motor, because of heavy interia of compressor it draws very high current at low power factor, and if the line capacity is not sufficient, it will result in voltage drop and if voltage drops down more that under voltage relay setting then relay will operates and trips the running plant too,

when i was in IPCL, baroda, In LDPE plant we had compressor motor of 5 MW, 11 kV, in running condition or once the compressor start running there is no any problem but when we had to start is, we had to start our stand by captive power plant of 30 MW in addition with running 60 MW generator and and available power of Electricity board too.

so the inrush current can cause the tripping of the other plant due to operation of under voltage relay,

u can reduce the under voltage relay setting from existing to below just 10 to 15 % and try once.

Best regards

divyesh patel

Thanks Divyesh for the reply. Yes, it is the same with us. Since it is DOL starting, we need to ensure all generator & tie with utilities in closed position. Anyway, i need to know, in what condition will fault level gives impact to motor starting current & capacity calculation. This 'kA' value must higher what value? Starting current? How to calculate the total power required during motor start up? Is is still P=1.732 *V * I * PF ? What value is I. Is it normal running or starting curent? Normally, for DOL, the inrush current is 6/7 times the normal running current. FYI, for start up this motor, it require about 25 second.

Thanks Divyesh for the reply. Yes, it is the same with us. Since it is DOL starting, we need to ensure all generator & tie with utilities in closed position. Anyway, i need to know, in what condition will fault level gives impact to motor starting current & capacity calculation. This 'kA' value must higher what value? Starting current? How to calculate the total power required during motor start up? Is is still P=1.732 *V * I * PF ? What value is I. Is it normal running or starting curent? Normally, for DOL, the inrush current is 6/7 times the normal running current. FYI, for start up this motor, it require about 25 second.

Hello

Fault level by defination refers to the maximum amount of power ( usually put in MVA, but sometimes current is used in KA) that flows at a particular point in a network under fault conditions. Usually this calculation is done for protection purposes, ie to be able to make correct protection settings and for the correct rating of equipment such as circuit breakers. I don't think the issue of fault level will come in when we talk of a compressor tripping on high starting current(DOL). I would buy the idea from the first comment.