An industrial plant is to be supplied by three identical transformers. A decisio
ID: 2085531 • Letter: A
Question
An industrial plant is to be supplied by three identical transformers. A decision must be made whether to purchase a fourth transformer to build a sparing transformer system as shown in Figure 1.16, or to configure the source as a secondary selective system as shown in Figure 1.14. If the secondary selective option is chosen, a. how much larger must each transformer in the secondary selective option be compared to each transformer in the sparing transformer option if each transformer is to be able to supply the full plant load in the event that one transformer fails? b. how many additional circuit breakers must be purchased to provide the necessary bus tie capability for the secondary selective option compared to the sparing transformer option?Explanation / Answer
First Question is not clearly mentioned .
But I will explain you up to which I understood.
In this first Question mentioned if in sparing method any transformer fail , Every transformer can supply full plant load means any time in sparing method each transformer can supply full plant load but the operate at 33.33% of full load or their rated capacity when full plant load is being supplied.If new transformer installed in sparing system and if operated in parallel to existing sparing system then every transformer in that system operates only at 25% of their rated capacity.
Which system might be reliable but not economic.
Hence transformers in secondary selection option are 33.33% of rating of transformer in sparing method to supply full plant load .By adding new fourth transformer identical to existing memang with 33.33% of plant capacity provides a spare of 33.33% power to the system.Assumed previous system operating to its full capacity when plant power demand is full rated.
Second question answer: In sparing system each transformer requires its own circuit braker according to its capacity. Where as in case of secondary selection option as far as two circuit breakers can meet full plant load demand, installing new transformers in between these brakers is not problem at all.
CONCLUSION:Hence no need of any new circuit braker in case of secondary selective option.