Generator Voltage & Frequency Dip Setting

[faresos]

What is the recommended setting for the voltage and frequency dip when sizing a generator? let's say it's an office building with no fire pump. The software sizing program has default of 30% for voltage and 20% for frequency. Would it make a different if it was emergency or standby generator?

Thanks,

Sam

 

[Bugman1400]

I'd be more interested in the duration of the transient than the percentage of dip. Although it may not apply here, you could view IEEE 1547 for some guidelines on both voltage and frequency dips.

 

[templdl]

I'd be more interested in the duration of the transient than the percentage of dip. Although it may not apply here, you could view IEEE 1547 for some guidelines on both voltage and frequency dips.

I agree. The term 'dip' is relative just like 'hot' etc. What the length of time that the dip we would last? If you had a 'brief 'dip' did you want to Immediately start the genset and make a transfer to the emergency source and when is it acceptable to transfer to the normal source? You may end up with nuisance transfers.

 

[wirenut1980]

What is the recommended setting for the voltage and frequency dip when sizing a generator? let's say it's an office building with no fire pump. The software sizing program has default of 30% for voltage and 20% for frequency. Would it make a different if it was emergency or standby generator?

Thanks,

Sam

Are you talking about what voltage and frequency settings should the transfer switch have for deciding on when to transfer from normal power to generator power? Or are you talking about how to size a generator so that inrush currents from large motors don't cause a voltage or frequency deviation larger than X?

 

[kwired]

I'm guessing OP is asking about dip in voltage/frequency when generator is running and a sudden load change occurs, also to consider is sudden rise in voltage/frequency when a heavier load is switched off.

I don't believe there is a one answer fits all to the question. Types of loads supplied and sensitivity of certain loads will be factors in what is acceptable. If anything a more sensitive load may be better off being supplied through some sort of power conditioner, maybe a UPS type of device.

Otherwise if you have say a 15 kVA generator and try to start a 10 hp motor with across the line starting method, you are very likely going to have an unacceptable drop in voltage/frequency for a wide variety of other loads, yet if this generator is only intended to supply the one motor it will be just fine.