代做EE3004 Test 2代写留学生Matlab语言程序

日期：2024-04-11 05:48

EE3004 Test 2

(Note: this is atake-home test consisting of 5 questions, and the full mark is 100 and each question carries the same mark. The students should independently work on all questions. This test paper will be released on 1:00 pm sharp on 10th April 2024 via learn@PolyU, and submission of your solution via learn@PolyU system is due on 1:00 pm sharp on 11th April 2024)

Q1.  Given an alternating current (AC) circuit where the instantaneous voltage and current are defined as follows:

Voltage, v(t) = 313. 2sin(ωt + 30°) volts

Current, i(t) = 3. 35cos(ωt ? 15°) amps

Perform. the following analyses:

a.   Determine the minimum values of the voltage and current.

b. Calculate the root mean square values for both the voltage and current.

c.   Convert the given time-domain expressions of voltage and current to phasor form. Assume that the current serves as the reference. Please provide the phasor representations in both polar and rectangular coordinates. Sketch a brief phasor diagram that clearly reflects the phase relationships for the voltage and current.

d. Please analyse whether the circuit is inductive or capacitive. Then, calculate the power factor, specifying whether it is leading or lagging.

Q2.

a.   Please draw the diagram of equivalent circuit of a long transmission line.

b. An electrical power system consists of a short transmission line with an impedance Zline = 0. 5 + j1. 0Ω. The receiving end of the line has a voltage ⅤR  = 100kⅤ and a current IR = 100A lagging ⅤR by 30°. Calculate  the  sending end voltage Ⅴs and current Is using the ABCD parameters for the line.

c.   A  medium-length transmission line model has following  parameters: total series impedance Z = 0. 75 + j1. 5Ω and total  shunt admittance Y = 0 + j4 × 10?3s. Theline operates at a voltage of 110kV at the receiving end ⅤR with a power factor of 0.8

lagging and delivers a power of 50MW. Calculate:

(1) The ABCD parameters for the line.

(2) The sending-end voltage Ⅴs and current Is.

(3) The voltage regulation of the line at the given load condition.

(4) The efficiency of the line at the given load condition.

Q3. A DC source of 100 V with negligible resistance is connected through a switch S to a lossless  transmission line, surge impendence ZC=40 Ω. The  line is terminated in a resistance of 80 Ω. If S closes at t =0, Draw the lattice diagram for voltage and plot VR v.s. time t until t=5T, where T is the time for a voltage wave to travel the length of line.

Q4.

a.   Compare the installation features and operational considerations of overhead lines and  underground cables, specifically focusing on voltage and current carrying capacities, size of conductors, safety for living beings, and reliability, etc.

b. Write the frequency domain expression of voltage as a function of distance from the receiving end, and then transform. it into the time domain expression.

c.   Describe the meaning of each parameter in the time-domain voltage expression.

d. Sketch waveforms representing forward and backward traveling voltage waves on a transmission line, indicating their amplitudes and phases due to propagation effects.

e.   If loss neglected (g=r=0), please determine the value of characteristic impedance Zc.

Q5.

a.   In a step-distance relay protection scheme for serial transmission lines AB, BC and CD, what are the typical ranges for the protection coverage of Zone 1, Zone 2, and Zone 3? Besides, what are the general time delays associated with Zone 1, Zone 2, and Zone 3 operations?

b. Please calculate the relay settings for a transmission line system with three interconnected lines. Assume the impedance of these three lines are Z1  = 70∠30。Ω ,

Z2  = 60∠20。Ω,and Z3  = 50∠10。Ω,respectively.

c.   Explain the operational principle of a gas detection system for fault identification in oil-filled transformers.

d. (1) List the three main types of differential protection relays.

(2) For each type of differential relay listed above, sketch the typical arrangement of that relay system in a power system protection scheme.