01․ Condition for maximum voltage regulation

02․ Condition for zero voltage regulation is

03․ Zero voltage regulation is possible only for

Therefore, zero voltage regulation is possible only for leading power factor.

04․ A 1-phase transmission line has an impedance (3+4j) Ω . Find the power factor of the load for achieving maximum and zero voltage regulation?

05․ A transmission line has an impedance of (2+j6) Ω has voltage regulation of 10% at a load power factor of 0.8 lag. Find the voltage regulation for a load of 0.6 lead

06․ A transmission line has 50 km operating at frequency of 500 Hz. Find the type of the line?

Classification of transmission lines:
Short transmission line = Length(L) < 80 km and product of length(L) and frequency(f) L.f< 4000
Medium transmission line = 80 km ≤ L ≤ 200 Km and 4000 ≤ L.f ≤ 10000
Long transmission line = L > 200 km and L×f >10000
Given that
L = 50 km
f = 500 Hz
L.f = 50×500 = 25000
Therefore given line is a long transmission line.

07․ A transmission line has 200 km operating at frequency of 10 Hz Hz. Find the type of the line

Classification of transmission lines:
Short transmission line = Length(L) < 80 km and product of length(L) and frequency(f) L.f< 4000
Medium transmission line = 80 km ≤ L ≤ 200 Km and 4000 ≤ L.f ≤ 10000
Long transmission line = L > 200 km and L×f >10000
Given that
L = 200 km
f = 10 Hz
L.f = 200×10 = 2000
Therefore given line is a short transmission line.

08․ In which of the following transmission lines capacitance effect is negligible?

Short transmission line = Length(L) < 80 km and product of length(L) and frequency(f) L.f < 4000
For short transmission line charging current and leakage currents are very small. So that capacitance effect and conductance are negligible only for short transmission lines.

09․ Communications lines are treated as

Communication lines are operating at the MHz range. So that communication line is represented as long transmission line equivalent circuit. In which all the transmission line parameters are i.e., R,L,C and G are considered.
Classification of transmission lines:
Short transmission line = Length(L) < 80 km and product of length(L) and frequency(f) L.f < 4000
Medium transmission line = 80 km ≤ L ≤ 200 Km and 4000 ≤ L.f ≤ 10000
Long transmission line = L > 200 km and L.f >10000

10․ If the rated receiving end voltage is 33 kV, then what are the limits for safe operation of equipments?

Due to transmission line losses and other losses, we can not get the rated voltage to the equipments. So that equipments are designed to operate at ± 5% or ± 6%.
Therefore, the limits of safe operation of equipments are 31.35 to 34.65 kV. Beyond this limits equipment may damage or not operate.

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