An industrial plant is to be supplied by three identical transformers. A decisio
ID: 2085519 • 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?
1.5 SOURCE CONFIGU 150 A N.C. N.C. N.C. 150 A 150 A 10A 50 A 50 A 100 A 100 A Figure 1.14 Primary Loop System with Reclosers Another option would be to operate the loop in closed mode (with point) and inst ure 1.14. A recloser would be an example of an is upting fault current. Intelligent reclosers capable of compm all isolation devices capable of interrupting faulExplanation / Answer
1. two times 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'coz on the event of failure of one transformer another has to operate to fulfill the load that failled x'mer was provoding.
whereas in sparing x'mer at the time of one transformer failure , spare x'mer will start to operate which designed with same capacity as of operating x'mers. In this case another x'mer will keep continue supplying the the load with same capacity as it was doing before failure occured.
2. Two additional circuit breakers must be purchased to provide the necessary bus tie capability for the secondary selective option compared to the sparing transformer option. (between each two buses).