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QUESTION: 1

A Δ -ΔT/F having rating 132KV/66KV, 50 MVA, the base impedance on primary side

Solution:

QUESTION: 2

The impedance of a Δ- Y 11000/400V 3-ΔT/F of capacity 100 KVA as on its name plate as z = (0.02 + j0.07) pu. The ohmic impedance in Ωreferred to primary (11000 V) side

Solution:

QUESTION: 3

take 6.6 KV, 20 MVA on G side, the pu impedance of line is

Solution:

QUESTION: 4

The sequence voltage of a 3φ system is given as

0.87 pu = V_{a1}

-0.33 pu = V_{a0}

-0.54 pu = V_{a2}

What is the phase voltages on 11KV

Solution:

V_{a} = V_{a0} + V_{a1} + V_{a2} = 0

V_{b} = V_{a0} + α^{2}V_{a1} + αV_{a2}

= -0.33 + 1 ∠240 (0.87) + (1∠120) (-0.54)

= 1.232 ∠-97.69 KV

V_{c} = V_{a0} + αV_{al} + α^{2}V_{a2}

= 1.317 ∠112.6^{0} pu

V_{a}(KV)= 0KV

V_{b} (KV) = V_{b} (pu) x KV_{basd/pm}

= 8.36 KV

V_{c} (KV) = 8.36 KV

QUESTION: 5

An unsymmetrical fault on a transmission line gives the sequence voltage and sequence current

V_{a1} = 0.837 pu

V_{a2} = -0.45 pu

V_{a0} = -0.2 pu

and sequence current I_{1} = I_{2} = I_{0} = -j1.2 pu. What is the type of the fault.

Solution:

As all the sequence current is

same, fault is LG.

*Answer can only contain numeric values

QUESTION: 6

What is fault impedance value on the base of 11KV, 20 MVA

Solution:

QUESTION: 7

|V_{1}| = |V_{2}| =1pu , what is the maximum power flow in this Network.

Solution:

= 55 pu

Notice that without capactior pr.

QUESTION: 8

In which of the following condition the system is stable (ω is speed)

Solution:

For stability, speed must never

be continuously increase or

decrease so

QUESTION: 9

An alternator having E = 1.2 pu connected to ∞ bus through a power network. The transfer reactance between alternator and ∞ bus before fault, during fault, and after clearing fault are X_{1} = 0.5, X_{2 }= 2.0, X_{3} = 1.5 pu. If initially P_{m0} = P_{eo} = 1 pu then what is δ_{cr} made by rotor such that system is stable?

Solution:

as p_{m} is 1 pu, which is greater than

p_{max3}, even if fault is cleared,

mech. input will always be

higher. System will remain

unstable.

QUESTION: 10

A 50 bus system with 200 transmission line. How many zeroes are in Y bus matrix.

Solution:

QUESTION: 11

For a 3 bus network

a shunt capacitor of -j0.5 is added at 2^{nd} bus, Y_{22} new = ?

Solution:

z_{22} new = -j15 + j2 = -j13

QUESTION: 12

A Network having postive, negative and zero sequence bus impedance matrix as

what is the LG fault current at bus 2 with z_{f} = j0.1 pu. Pre-fault voltage at bus 2 is 1.05 pu

Solution:

QUESTION: 13

A 3φ load of 50 MW, 0.6 pf, is operating at 33KV, what is capacitance per phase required by the capacitor bank connected in Δ to improve pf to 0.8 lag.

Solution:

QUESTION: 14

what is reactive power support required at bus 2.

Solution:

As at load, no imaginary term is

given. This is active power only

= -0.267

as only active load is present a

capacitor must be installed to

get reactive power zero

so, θ_{required} = 0.267

QUESTION: 15

A Network containing 20 voltage controlled bus, 10 reactive power support bus, a generator bus, 5 fixed shunt capacitance bus, total voltage controlled bus is

Solution:

Shunt capacity is not voltage

controlled bus,

Total no. of voltage controlled

bus

= 20 + 10 + (9 - 1)

= 38

QUESTION: 16

A transmission line of length 300 km operating at 50Hz, the receiving end voltage under no load V_{S} = 1pu is

Solution:

QUESTION: 17

A transmission line of length 600km, has a phase shift in degree of

Solution:

QUESTION: 18

A generator having H = 6 MJ/MVA is connected to generator having H = 4 MJ/MVA. A fault reduce the pr. out put to 0.6 pu which was initially 1 pu. Find angular acceleration in elect degree/S^{2}

Solution:

QUESTION: 19

A transmission line has impedance (3 + j4) Ω/phase. The power factor of the load for maximum V.R.

Solution:

For maximum V.R

= 0.6

QUESTION: 20

A 3φ transmission line has ABCD parameters as A= 0.75 ∠0° = D, B = 100∠90°Ω, C = 0.5 x 10^{-6} ∠90° ℧ operating at V_{s} = 200 KV, V_{R} at no load, and shunt reactor for compensating Ferranti-effect

Solution:

*Answer can only contain numeric values

QUESTION: 21

In previous question, the charging current at no load is_____

Solution:

QUESTION: 22

A TL has z_{S} = 400Ω is terminated with a cable with z_{L} = 50Ω. A rectangular pulse of 100KV is travelling towards the cable. The transmitted volt will be

Solution:

QUESTION: 23

A 3φ transmission line having a surge impedance of 400Ω is operating at 400 KV line is compensated with 30% of shunt capacitor at the load end. The other end is connected to a generator which is delivering power at 200 MW. SIL of the above system is

Solution:

= 400 MW

QUESTION: 24

In above question, SIL after compensation is

Solution:

QUESTION: 25

A TL supported by 3 insulation disc, the maximum voltage of each disc is 25 KV. Find the operating voltage per phase of the line given efficiency η = 78%

Solution:

as (V_{1} + V_{2} + V_{3}) is per phase voltage

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