please solve correctly Question-5: A three-phase, 60 Hz distribution system oper

Question

please solve correctly

Question-5: A three-phase, 60 Hz distribution system operates at 10.65 kV line to line and serves three balanced, linear, three-phase loads all at one location Load 1: Load 1: Load 1 The true power factor listed for each load is entirely displacement power factor. The three-phase short circuit duty at the load location is 61 MVA. Assume that the system impedance is entirely inductive 2.0 MW with a lagging power factor of 0.75 1.0 MVA with a lagging power factor of 0.80 0.5 MW with a lagging power factor of 0.85 What is the combined displacement power factor of the three loads? What is the largest three phase shunt capacitor bank that can be installed at the load location using a combined of 100 kVAr (single phase) capacitor units if the steady-state voltage rise when the capacitor bank is switched on can not exceed 390 What is the combined displacement power factor of the three loads and the capacitor bank of 80 kVAr (single phase)? What will be the frequency of the switching transient when the capacitor of 80 kVAr (single phase) is switched on? What will be the peak amplitude inrush current into the capacitor bank when it is switched on? a. b. c. d. e.

Explanation / Answer

a. We need to know the MVA and MW of each load individually at the same time. The combined Displacement power factor would be the sum of MW divided by the sum of MVA.

By using the formula MW = MVA x pf, we have (Please note you took all three loads as load 1,load 1and load 1,but I have taken load 1,load 2 and load 3)

Load1- 2.0MW and 2.66MVA

Load 2- 0.8MW and 1.0MVA

Load 3- 0.5MW and 0.588MVA

Total MW= 3.3MW

Total MVA= 4.248MVA

So combined displacement power factor of three loads will be = (3.3/4.248) = 0.778

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