A utility company plans to install capacitor banks in a newly built 230 kV substation. According to load flow and dynamic stability studies, the power system needs about 160 Mvar of additional reactive power to accommodate system changes (such as new lines and loads). Due to the design of the substation and reactive power requirement, it is decided to split the reactive power demand into two stages. Thus there will be two three-phase capacitor banks, each rated at 80 Mvar. The following data is available, • The system three-phase short circuit capacity at the substation is 11,500 MVA. • Each phase of the three-phase 80 Mvar capacitor bank is contructed using the fol- lowing arrangement (see Fig. 5.5): There are 6 parallel units in each series group. 190 ELECTRICAL TRANSIENT PHENOMENA -There are 8 series groups. Each capacitor unit is rated at 800 kvar and 19.92 kV (see Table 5.1) Capacitor banks are configured as grounded wye. Figure 5.41 below shows the one-line diagram of the capacitor banks along with the substation. Note that Bank #2 is energized only when Bank #1 is already online. Bank #2 is 120 feet away from Bank #1, and the bus bar inductance is 0.342H/ 230 kV substation MVA-11,500 Bank #1 Proposed at 80 Mvar CB Bank #2 Proposed at 80 Mvar Figure 5.41 A 230-kV substation with the proposed 2 x 80 Mvar three-pahse capacitor banks. Note that Bank #2 is energized only when Bank #1 is already online. A bank. Determine the rated reactive power and capacitance of each three-phase capacitor B Determine the rated per-phase voltage and current of the capacitor banks. C The system normal operating voltage is 230 kV. Let us suppose that Bank #1 will be automatically energized when the substation voltage is 0.98 pu. Determine the actual reactive power injected by Bank #1. D What is the steady-state voltage at the substation after Bank #1 is online? How about when both Banks #1 and #2 are online? E Determine the worst case energizing scenario for energizing Bank #1. What is the maximum transient overvoltage and the corresponding switching frequency? F For the worst case switching scenario, determine the maximum inrush current peak when Bank #1 is energized. G Suppose Bank #1 is energized when the instantaneous system voltage is at zero volt- age. Compute the maximum transient overvoltage, inrush current, and the corresponding switching frequency. H Bank #2 is energized only when Bank #1 is already in service. Show an equivalent circuit during the fast transient of the back-to-back capacitor energizing. Determine the worst case peak inrush current and its transient frequency when energizing Bank #2. Should the results raise concerns? Please explain your rationale. Proble In capac 5.14 ener capa rate 5.15 (Ba inc ba 5. lin