For the four bus system as shown in Fig. Determine the fault current when the fault takes place at bus no.3 with fault impedance Z; =0 p.u. The Subtransient reactance of the generators and positive sequence reactance of other elements are given. Assume prefault Votage Egh= 120° p.u Generator X = j0.2p.u ; Transmission line X = j0.23p.u ; Transformer X = jo.42p.u Zth in p.u Fault current l, in p.u 0000- 0000

For the four bus system as shown in Fig. Determine the fault current when the fault takes place at bus no.3 with fault impedance Z; =0 p.u. The Subtransient reactance of the generators and positive sequence reactance of other elements are given. Assume prefault Votage Egh= 120° p.u Generator X = j0.2p.u ; Transmission line X = j0.23p.u ; Transformer X = jo.42p.u Zth in p.u Fault current l, in p.u 0000- 0000

Power System Analysis and Design (MindTap Course List)

6th Edition

ISBN:9781305632134

Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Chapter3: Power Transformers

Section: Chapter Questions

Problem 3.48P: With the same transformer banks as in Problem 3.47, Figure 3.41 shows the oneline diagram of a...

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Q1. The following figure shows the differential protection of power transformers with specifications of 20 MVA, 66/11 KV.Trans is No load.If a two-phase short circuit occurs between phases b and ¢ It is desirable to calculate the currents passing through the CTs and relays R, Y, B. If these relays are three overcurrent relays with inverse characteristics as T=0.63 / log (I / Iset) and Iset =0.5A.Will this work for short circuit relays? If yes, which relay works faster and at what time?
The bus impedance matrix for a three-bus power system has per-unit elements as: Z11 = 0.5 Z12 = 0.4 Z13 = 0.8 Z21 = 1 Z22 = 0.5 Z23 = 0.6 Z31 = 0.5 Z32 = 1.2 Z33 = 1 Prefault voltage is 1 per unit and prefault current is neglected. A three-phase short circuit occurs at bus 3. Determine the subtransient fault current. Round your answer to 2 decimal places.
2. A 100 MVA, 18 kV generator, with per unit reactance of X”d= 0.19, X’d = 0.26, and Xd = 1.3 is connected through acircuit breaker to a transformer rated 100 MVA, 240Y/18 kV,X = 0.10 per unit. It is operating at no load and ratedvoltage when a three-phase short circuit occurs at the highvoltage side of the transformer. Find the initialsymmetrical rms current in the line on the low voltageside.
A generator-transformer unit is connected to a line through a circuit breaker. The unit ratings are: Generator: 10 MVA, 6.6 kV; , and Transformer: 10MVA, 6.9133kV, reactance0.08pu The system is operating no load at a line voltage of 30 kV, when a three phase fault occurs on the line just beyond the circuit breaker' Find (a) the initial symmetrical rms current in the breaker’(b) The maximum possible DC off-set current in the breaker, (c) The momentary current rating of the breaker’ (d) The current to be interrupted by the breaker and the interrupting kVA and (e) The sustained short circuit current in the breaker
16. Which of the following is a solution to the problem of circulating currents?A. Integrating the grounding circuit supplying the equipment with the equipment itselfB. Incorporating surge arresters and surge protection devicesC. Using multiple-point grounding and two power supply systemsD. Connecting the equipment frames to several reference grid structures
Given a 400sq.m single family dwelling unit to be provided with 230V, 1-phase, 2-wire service, and having the following loads: 2-1.5hp A/C, 2-1.0hp A/C, 1-0.5hp water pump, 4-800W water heater, 2-6kW electric range and 2-1kW microwave oven, determine the rating of feeder overcurrent protection in ampere-trip (AT) using inverse time circuit breaker. Write your answer in numerical format without decimal places.
Several natural processes can interfere with the proper functioning of a transmission line, such as the action of winds on the cables, which causes a fatigue process due to vibrations, mechanically limiting them. Are there any provisions capable of reducing such effects? If yes, indicate which ones.
A single circuit 60 Hz transmission line. the conductors are Linnet type with flat horizontal spacing of 17.46 feet between conductors. Determine: (a) Assume that the line is short with a length of 50 miles, calculate the parameters of the line and draw the equivalent circuit. (b) Assume that the line is average with length of 150 miles (Pi-nominal model). draw the pi-nominal circuit for the transmission line and calculate its parameters (Z and Y/2 values, where Z is the series impedance of the transmission line and Y is the shunt admittance).
The impedance seen from the relay side in a distance relay is 10 ohms. Given that the CT ratio is 1000 : 1 and the PT ratio is 100,000 : 110, determine the actual impedance. Given that the line has a resistance of 1 milliohm per km and a reactance of 20 milliohm per km, find the distance to fault. Assume single-phaseline.
At a 220 kV substation of a power system, it is given that the three-phase fault level is 4000 MVA and single-line to ground fault level is 5000 MVA. Neglecting the resistance and the shunt susceptances of the system, (B) And the zero sequence driving point reactance at the bus is: (@)2.2Q (b) 4.84Q (€)18.18 Q (d)22.72Q
1) For the utility radial distribution system shown on figure below (only generator is at 138kV). All impedances are in per unit on a 100MVA base and nominal voltage shown. All transformer connected taps equal nominal voltage shown. All breakers and switches are closed unless marked with N.O. (Normally Open). Calculate fault current magnitudes in rms symmetrical amps at the following locations (faults are bolted, one at a time, not simultaneous.)a. Three phase (3ph), phase to phase, and single line to ground (SLG) at 138kV bus.b. 3ph, and SLG at 34.5kV bus. 138/34.5 transformers have the same Z and are in parallel.c. 3ph, and SLG at 34.5kV at 34.5/12.47 substation high side.d. 3ph, and SLG at 12.47kV buse. 3ph, and SLG at 12.47kV tapf. 3ph, and SLG at 12.47kV end of line (EOL)g. State the 138kV source (generator) amps for the 3ph at 12.47kV EOL fault.
a) Draw the sequence network and calculate the sub-transient fault current for a dead short circuit on one phase to ground at bus 4 with fault impedance j1.78 p.u for the system shown in Fig. The system data's are Machine 1: Xd”=j0.21p.u , X2=j0.4p.u; X0= j0.55p.u ; Machine 2: Xd”=j0.21p.u , X2=j0.4p.u; X0= j0.55p.u ; Transformers T1 and T2 : X1=X2=X0= j1.2p.u The transmission line reactance X1=X2= j0.21p.u and X0=0.97 p.u.