Repairs have to be carried out on HV cir- cuit breaker No. 6 shown in Fig. 26. If the three 220 kV lines must be kept in service, which disconnecting switches must be kept open? HV LINE 1 220 kV lightning 2 current transformer arrester HV disconnect grounding switch HV disconnect 30 HV circuit breaker 32 KA HV tie line HV disconnect motorized disconnect 8 33 34 lightning 10 11 grounding arrester 36/48/60 MVA, 60 Hz Y= mig 220 kV/24.9 KV. grounding transformer $12 switch 13 lightning arrester 35 36 MV circuit breaker 25 kA 14 MV disconnect 15 MV tie line 17 HV LINE 2 220 kV 37 382 HV LINE 3 220 kV h 117 11- line circuit breaker 12 kA reactor 16 17 Автово Котово 197 feeder 18 T24 табатын китоб Котово роботою натов 25 ротобионт втобо 20 26 коловон 21 4ьтово нотовонароботок матово втово 22 237 T29 -

From figure below, if 3 phase bolted fault occurs. Using Zbus method to choose a suitable rating of C.B's. Data are as follows: Gl: 100 MVA, 22 Kv,Xgi" = 0.2 pu G2: 100 MVA, 22 KV, X2"=0.15 pu TR1: 100 MVA, 22/220 KV, XTr1 =0.1 pu TR2: 100 MVA, 22/220 KV, XTR2 =0.1 pu CB TR1 1 ZTL-J50 ohm TR2 св св G2 3 Zload =(0.2 + j0.1) pu CB

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In a short-circuit test on a 3-pole, 110 kV circuit breaker.  Power factor of the fault= 0.4. Recovery voltage= 0.95 times (full line voltage)   The breaking current was symmetrical the restriking transient had a natural frequency of 15000 c/s. Determine the average rate of rise of restriking voltage. (The natural is grounded and the fault involves earth). Explain in details.

Calculate the neutral current in a 120/240-volt, single-phase system when the current inphase A is 20 amperes and the current in phase B is 40 amperes. The load is resistive.  Calculate the neutral current in a 208Y/120-volt, 3-phase, 4-wire system when thecurrent in phase A is 0, in phase B is 40, and in phase C is 60 amperes. The load isresistive

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c.1. Which of the following is one of the three essential functions of an equipment grounding conductor?A. Provide an arc-fault current pathB. Establish groundingC. Establish bondingD. Ensure the system is groundedc.2. What's another name for the three-point method of Earth resistance testing?A. Fall-of-potentialB. Line surgeC. Spatial shieldingD. Leakage current c.3. If the National Electrical Code provides a requirement to ground equipment, it generally implies thatthere will be a direct connection to the Earth of a connection through a/anA. grounding electrode conductor.B. equipment grounding conductor.C. equipotential bonding conductor.D. bonding conductor.

Why are circuit breakers and fuses ineffective in protecting against transient over voltage due to lighting and switching surges?

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Figure 2 shows the circuit of a simple power system. The ratings of the generators, transformers and the motors are as shown in the figure. The reactance of lines 1 and 2 are 40 ohms and 50 ohms respectively. Assume that system is unloaded, and the generators are generating their rated voltage. Select the generator G₁ ratings as base values. Choose the fault location in bus 1, bus 2, or bus 3.( Only one bus location) And give this answer For a symmetrical three phase fault on the bus 1.Draw the reactance diagram for the fault with all the reactances marked in per unit. 2.Determine the Thevenin's equivalent circuit which can be used to calculate the fault current. (3) Calculate the fault current in ampere and fault power in MVA. (4) Calculate the fault current contribution from the generator connected to the bus for fault calculation.