SKEE4683: As part of your role in the electrical engineering design department of a multi-national consultancy you have been allocated an activity: POWER SYSTEM DESIGN AND OPERATION Assignment, UTM, Malaysia

Power System Generation, Transmission, and Distribution

Ql. As part of your role in the electrical engineering design department of a multi-national consultancy you have been allocated an activity as part of a new transmission line project. The project has been commissioned by ‘Powa-Grid’ who are the leading utility infrastructure company in a particular eastern european country. You have been provided with the following specification data:

You are required to complete the following tasks in preparation for the next client liasion meeting.

(a) Sketch a nominal ‘7″ equivalent circuit and calculate the component values (R, Xi, Z, Yo) of the given transmission line.

(b) Due to existing capacity issues the line is being commissioned to support, amongst other applications, a major leisure and retail development with an existing load of 40 MW. If the load has a lagging power factor of 0.8 and assuming the customer voltage is 132 kV, calculate:

i) The sending end current

ii. The sending end voltage

iii. The sending end power factor

iv. The transmission line efficiency

Q2. As part of the main ‘Powa-Grid’ project you are also required to perform design calculations to supplement a tender document. This aspect of the project is at distribution level and the client has provided an illustration of the simple radial distribution system for your inborn.

as shown in Figure Q2. The scheme is described by a generator feeding a 10 MVA electrical load at 0.8 power factor lagging. The two buses are connected by a cable with an impedance of Z= 0.01 + p.1 per unit on 210 MVA base. The client has also specified an iteration tolerance of 0.0002 and has requested the following tasks to be completed.

(a) Using an appropriate method, compute the load bus voltage for the specified iteration tolerance. (A maximum of five iterations should be completed).

(b) Compute the complex power for bus 1.
(c) Determine the complex power absorbed by the cable.

Q.3. A client to your consultancy firm has an existing installation which requires fault level analysis; and to enable you to complete the necessary calculations they have provided an illustration, as shown in Figure Q3, and relevant data. The generating station identified as feeding a 220 kV system.

(a) Sketch a single line reactance diagram, including component values, to represent Figure Q3. For the three phase bolted fault illustrated determine: (b) The total fault current in kA.

(c) The fault level in MVA

(d) The fault current supplied by each generator in kA

Q4. When used in the context of Electrical Power System Protection.
(a) Define the following terms:

i) Sensitivity

ii) Discrirnation

(b) Describe, with the aid of a diagrarn, how an over-current protection scheme is formed using a current transformer, relay and circuit breaker.

(c) A client to the consultancy company where you are working has an existing installation which is utilising a three phase vacuum circuit breaker on a 33kV line.

They have provided the following data regarding the rating of the device; 1500A, 1000MVA and 3s. Given the data, your client has requested the following:

i) Normal rated current

ii) Breaking capacity

iii) Rated symmetrical breaking current

iv) Rated making current (Based on IEC 62271-100 which specifies that the first initial peak of the fault current on closing should not be less than 2.55 x rated symmetrical breaking current).

v) Short time rating

Answer

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