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? Q1. The following figure shows the differential protection of powertransformers with specifications of 20 MVA, 66/11 KV.Trans is Noload.If a two-phase short circuit occurs between phases b and cIt is desirable to calculate the currents passing through the CTs andrelays R, Y, B. If these relays are three overcurrent relays withinverse characteristics as T=0.63/ log (I/ Iset) and Iset =0.5A.Willthis work for short circuit relays? If yes, which relay works fasterand at what time?66 kV11 kV200/12000/120 MVAA9090 AB9090 A000

Answered: Image /qna-images/answer/df89bb05-d334-4b73-9949-e00b395a19aa.jpg

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 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?

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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Consider a single-phase electric system shown in Figure 3.33. Transformers are rated as follows: XY15MVA,13.8/138kV, leakage reactance 10 YZ15MVA,138/69kV, leakage reactance 8 With the base in circuit Y chosen as 15MVA,138kV determine the per-unit impedance of the 500 resistive load in circuit Z, referred to circuits Z, Y, and X. Neglecting magnetizing currents, transformer resistances, and line impedances, draw the impedance diagram in per unit.
A Y-connected load bank with a three-phase rating of 500 kVA and 2300 V consists of three identical resistors of 10.58. The load bank has the following applied voltages: Vab=184082.8,Vbc=276041.4, and Vca=2300180V. Determine the symmetrical components of (a) the line-to-line voltages Vab0,Vab1, and Vab2, (b) the line-to-neutral voltages and Van0,Van1, and Van2, (c) and the line currents Ia0,Ia1, and Ia2. (Note that the absence of a neutral connection means that zero-sequence currents are not present.)
Consider the single-Line diagram of a power system shown in Figure 3.42 with equipment ratings given: Generator G1: 50MVA,13.2kV,x=0.15p.u. Generator G2: 20MVA,13.8kV,x=0.15p.u. Three-phase -Y transformer T1: 80MVA,13.2/165YkV,X=0.1p.u. Three-phase Y- transformer T2: 40MVA,165Y/13.8kV,X=0.1p.u. Load: 40MVA,0.8PFlagging,operatingat150kV Choose a base of 100 MVA for the system and 132-kV base in the transmission-line circuit. Let the load be modeled as a parallel combination of resistance and inductance. Neglect transformer phase shifts. Draw a per-phase equivalent circuit of the system showing all impedances in per unit.
Consider the single-line diagram of the power system shown in Figure 3.38. Equipment ratings are Generator 1: 1000MVA,18kV,X=0.2perunit Generator 2: 1000MVA,18kV,X=0.2p.u. Synchronous motor 3: 1500MVA,20kV,X=0.2p.u. Three-phase -Y transformers T1,T2,T3,T4,: 1000MVA,500kV,Y/20kV,X=0.1p.u. Three-phase YY transformer T5: 1500MVA,500kV,Y/20kVY,X=0.1p.u. Neglecting resistance, transformer phase shift, and magnetizing reactance, draw the equivalent reactance diagram. Use a base of 100 MA and 500 kV for the 50-ohm line. Determine the per-unit reactances.
Figure 3.39 shows a oneline diagram of a system in which the three-phase generator is rated 300 MVA, 20 kV with a subtransient reactance of 0.2 per unit and with its neutral grounded through a 0.4- reactor. The transmission line is 64km long with a cries reactance of 0.5-/km. The three-phase transformer T1 is rated 350MVA.230/20kV with a leakage reactance of 0.1 per unit. Transformer T2 is composed of three single-phase transformers, each rated 100 MVA, 127/13.2kV with a leakage reactance of 0.1 per unit. Two 13.2kV motors M1 and M2 with a subtransient reactance of 0.2 per unit for each motor represent the load. M1 has a rated input of 200 MVA with its neutral grounded through a 0.4- current-limiting reactor, M2 has a rated input of 100 MVA with its neutral not connected to ground. Neglect phase shifts associated with the transformers. Choose the generator rating as base in the generator circuit and draw the positive-sequence reactance diagram showing all reactances in per unit.
Consider the oneline diagram shown in Figure 3.40. The three-phase transformer bank is made up of three identical single-phase transformers, each specified by X1=0.24 (on the low-voltage side), negligible resistance and magnetizing current, and turns ratio =N2/N1=10. The transformer bank is delivering 100 MW at 0.8 p.f. lagging to a substation bus whose voltage is 230 kV. (a) Determine the primary current magnitude, primary voltage (line-to-line) magnitude, and the three-phase complex power supplied by the generator. Choose the line-to-neutral voltage at the bus, Va as the reference Account for the phase shift, and assume positive-sequence operation. (b) Find the phase shift between the primary and secondary voltages.
With the same transformer banks as in Problem 3.47, Figure 3.41 shows the oneline diagram of a generator, a step-up transformer bank, a transmission line, a stepown transformer bank, and an impedan load. The generator terminal voltage is 15 kV (line-to-line). (a) Draw the per-phase equivalent circuit, aounting for phase shifts for positive-sequence operation. (b) By choosing the line-to-neutral generator terminal voltage as the reference, determine the magnitudes of the generator current, transmiss ion-line current, load current, and line-to-line load voltage. Also, find the three-phase complex power delivered to the load.
Transmission line conductance is usually neglected in power system studies. True False
The single line diagram of a power system is shown in Figure Q2.1 includinggenerator and transformer winding connection and earthing details. The parametersfor this system have been calculated on a common 100 MVA base and are given inTable Q2.1. All resistances and shunt susceptances are neglected. This systemexperiences a single line to ground fault at a point F on line L1. The point F is at adistance d from Bus 4 along the line L1. The total length l of the line L1 is 50 km.Note that the location of d is not drawn to scale in Figure Q2.1. The fault current atthe fault point F is measured to be 6.106 kA. i) Determine the zero, positive, and negative sequence Thevenin equivalentimpedances as seen at the fault point F. These should be evaluated in per unitand shown as a function of d.ii) Use the sequence impedances calculated in part (i) to determine the distance dof the fault (in km) from Bus 4. It's different from the answer, please don't send it
1- Conductor cables are considered the active elements of a transmission line, as they carry current. Such elements must exhibit some characteristics, what are they? Is there an element that meets all these requirements? 2- 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. 3-We have an aerial bifilial transmission line, powered by a constant voltage source of 700 V. The values for the inductance of the conductors are 2.348x10-3 H/km and the capacitance values are 6.325x10-9 F/km. Assuming an ideal (no loss) line and its length of 130 km, determine the impedance line natural.
At the end of the 8 km overhead line given in the figure below, there are two distribution transformers, one of which is 800kVA and the other is 1200kVA, operated with power coefficients of 0.6 and 0.8, respectively. The end-of-line voltage is 6kV. Find the required rated cross section and line head voltage so that the power loss on the line is less than %pk = 10.
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).