Please solve the two highlighted questions bellow by hand , i\'m having a hard t

Question

Please solve the two highlighted questions bellow by hand , i'm having a hard time undersanding it.

A utility feeds to a step-up transformer T1 that supplies a 6 miles transmission to a step-down transformer T2. Transformer T2 feeds to a switchgear and its downstream loads in a commercial building. A 500 kVA standby generator provides the power to certain loads in the building through an Automatic Transfer Switch (ATS) when the utility power is not available. Pertinent data for all equipment is provided below Utility Data 3-Phase Fault Line-to-Ground Fault 60 Base rated MVA 60,000 A 60,000 A 100 12 12 Base rated Voltage (L-L) 5,000 Transformers Data Transformer KVA Impedance Z% Primary Secondary ID Rating Voltage Connection Voltage Connection 1,000 1,000 225 KV 5.0 13.8 Y Grounded 0.48 kV 13.8 0.48 0.208 Y Grounded T1 T2 T3 3.6 3.1 4.3 Y Grounded Transmission Line Data AmpacityLength Miles Positive Sequence Zero Sequence Xc 100 6 0.888 0.88231 0.173369 1.1742 3.093637 0.410707 Generator Data 500 kVA Generator Rating Transient Steady State Parameters Stator Resistance Ra 0.0072 puDirect axis sub-transient short circuit time constant26 ms Direct axis sub-transient short circuit time constantTd 420 ms Synchronous Reactance 2.75 pu DC Time Constant Tde PU Subtransient Impedance 93 ms Transient Reactance Xd' 0.29 Positive Sequence Negative Sequence 0.15 0.15 X/R Ratio 20 20

Explanation / Answer

2 ) Transformer T2 Primary Voltage is V1=13.8kv , V2= 480V

For 150 Hp motor (1 hp = 746 Watts) So it is 111KW

The Formula for 3 phase power is

P=1.732*V*I*Cos phi

111KW = 1.732*480*I*0.8

Full load Amps I= 170A

3 size of the feeder

110 KW Feeder is enough from Switch gear to 150hp motor

  

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