Two relays R1 and R2 are connected in two sections of a feeder as shown in Figure Q2. Relay R1: CT ratio = 300/5, plug setting = 2.5A. TMS = 0.3 Relay R2: CT ratio = 500/5, plug setting = 3.75A. A fault at F results in a fault current of 3000A. Find the TMS of R2 to give time grading margin of 0.5s between the relays. The operating time characteristic of the relays is given in the Table Q2.

Two relays R1 and R2 are connected in two sections of a feeder as shown in Figure Q2. Relay R1: CT ratio = 300/5, plug setting = 2.5A. TMS = 0.3 Relay R2: CT ratio = 500/5, plug setting = 3.75A. A fault at F results in a fault current of 3000A. Find the TMS of R2 to give time grading margin of 0.5s between the relays. The operating time characteristic of the relays is given in the Table Q2.

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 3.30MCQ

See similar textbooks

Similar questions

a) Classify the four categories of 3 phase power system faults we experience in our electrical power industry. b) Explain the emergence of such power systems fault as required in (question 1a)? c) Point out each type of fault specified under (a). d) Produce the (1D) design of the three-phase star connected faults stated under(b)
Larger conductors should be used for long runs to minimize the? A. Current B. Voltage drop c. Transformer retio d. Interrupt rating
Why is it necessary to carry out fault calculations? Compare between the p.u. system method and the referred Ohmic impedance method for fault calculations.
8.In a line-by-line failure we can expect Immersive reader A) Currents exist in the ground connections. B) The current values at the ground connections are zero. C) Short-circuit currents exist in all three phases. D) The voltages at the fault point with respect to ground are zero in the faulted phases. E) N. A.
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 And give the below answers For a symmetrical three phase fault on the bus (a).Determine the Thevenin's equivalent circuit which can be used to calculate the fault current. (b) Calculate the fault current contribution from the generator connected to the bus on which you have selected for fault calculation
The 60 mile, 115 kV line GH (Figure P12.8) is operating with the voltages ateach end 30° out of phase when a three-phase fault occurs at 80% of the distance from bus G. This fault has 12 Ω arc resistance. The currents flowing tothe fault are as shown and are in per unit at 100 MVA, 115 kV.d. Determine if the zone 1 mho unit at H set for 90% of the line GH can operate for this fault. Assume that the angle of the mho characteristic is 75°.e. Describe how this three-phase fault can be cleared by the line distance relays.
b) A fault occurs at bus 4 of the network shown in Figure Q3. Pre-fault nodal voltages throughout the network are of 1 + j0 p.u, and the impedance of the electric arc is neglected (Zf = 0 + j0 p.u.). The positive, negative and zero sequence impedance parameters of the generator, transmission lines and transformer are given in Figure Q3. (i) Determine the positive sequence fault current for the case when a three-phase-to-ground fault occurs at bus 4 of the network (ii) Determine the short-circuit fault current for the case when a one-phase- to-ground fault occurs at bus 4. Recall that phasors can be expressed in terms of their symmetrical components as shown in the picture attached. where F stands for any three-phase quantity (e.g., current, voltage) (iii) Determine the short-circuit fault current for the case when a phase-to-phase fault occurs at bus 4 ReplyForward
Given a 3-Ampere, 5-second overcurrent relay having a current setting of 150% and a time setting multiplier of 0.4 connected to the supply circuit through a 300/2 current transformer, a 3500 A fault current was carried through the circuit. Determine its time of operation
A single line diagram of a power system is shown in Figure Q2.1. The neutrals for the generators and transformers are solidly grounded. The motor neutral is grounded through reactance ?? = 0.05 per unit on the motor base. i）Calculate the phase currents in kA following a three-phase fault at busbar 2. ii) Calculate the phase currents in kA when a phase-alpha-to-ground fault occurs at busbar 2.
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.
Data obtained from a short circuit test on a 132 kV 3-phase circuit breaker with earthed neutral are as follows: -the power factor fault was 0.3. -the recovery voltage was 0.75 of the full line value. -the breaking current was symmetrical. -the restriking transient had a natural frequency of 1600 Hz. Estimate the rate rise of the recovery voltage. Assume that the fault is grounded.
Determine the time of operation of a 5-ampere, 3-second overcurrent relay having a current setting of 125% and a time setting multiplier of 0·6 connected to supply circuit through a 400/5 current transformer when the circuit carries a fault current of 4000 A. Use the curve shown in figure below