11-06-2013, 01:02 PM
SEMESTER EXAMINATIONS FOR EXTRA HIGH VOLTAGE TRANSMISSION
EXTRA HIGH VOLTAGE.pdf (Size: 55.27 KB / Downloads: 18)
Answer any five questions
All questions carry equal marks
1.a) Give ten levels of transmission voltages that are used in the world.
b) What are the important and useful conclusions can be drawn for preliminary understanding of trends relating to power-handling capacity of a.c. transmission lines and line losses?
2.a) Derive the expression for Single-phase line inductance calculation and Multi-conductor line for calculation of Maxwell's potential coefficients.
b) The configurations of some E.H.V. lines for 400 kV to 1200 kV are given. Calculate req for each.
(i) 400 kV : N = 2, d = 2r = 3.18 cm, B = 45 cm
(ii) 750 kV : N = 4, d = 3.46 cm, B = 45 cm
(iii) 1000 kV : N = 6, d = 4.6 cm, B = 12 d
(iv) 1200 kV : N = 8, d = 4.6 cm, R = 0.6 m
3. Explain the following
a) Maximum surface voltage gradient of bundle with more than 3 sub conductors,
b) Mangolt formula.
4.a) Define compensation and explain Cascade connection of components of shunt series compensation with generalized equations and chain rule.
b) Explain the audible Noise frequency spectra for ac and dc transmission lines. Also give the limits for audible noise?
5. Explain how Harmonics injected into network by TCR under
a) Harmonic Injection by TCR in to high voltage system
b) Connection of TCR to delta and Ύ connected transformer windings
c) Voltage and current wave forms for α=90°, α>90° for calculations of harmonics.
6.a) Design of Filters for Suppressing Harmonics Injected into the System
(i) Actual connection to transformer secondary.
(ii) Inductive and capacitive reactance referred to primary by turns ratio a.
b) Filter inductance used is 2 mH. Filter Capacitance =211.6 μF. which have limited the 5-th harmonic Injected into the line to 1% of the generated 5-th harmonic:
(i) Calculate the 7-th harmonic injected into the line;
(ii) If the 7-th harmonic generated by the TCR = 2.586% of fundamental, as calculated for the value of α =4π/7 = 102.9°mn in the previous section, calculate the % of 7th harmonic injected into the line on base of fundamental current I obtained when the firing angle α= 90°
7. Derive the Line capacitance calculation for
i) Two conductor line
ii) Capacitance of multi conductor lines
iii) Potential coefficients for bundled conductor lines.
8.a) Give Power-Handling Capacity and Line Loss for different Transmission lines.
b) Among HVAC and DC Transmission which one is best transmission, also mention the advantages and disadvantages of it.