Bissoy.com
Doctors Medicines MCQs Q&A

Which of the following options is correct regarding the advantages offered by high-voltage direct current (HVDC)?

Which of the following options is correct regarding the advantages offered by high-voltage direct current (HVDC)? Correct Answer System control stability is high

  • High voltage direct current (HVDC) power systems use D.C. for transmission of bulk power over long distances.
  • For long-distance power transmission, HVDC lines are less expensive, and losses are less as compared to AC transmission.
  • It interconnects the networks that have different frequencies and characteristics.
  • HVDC transmission is economical only for long-distance transmission lines having a length of more than 600kms and for underground cables of length more than 50kms.

 

Economic Distance For HVDC transmission lines:

  • DC lines are cheaper than the AC lines, but the cost of DC terminal equipment is very high as compared to AC terminal cables as shown in the figure below. Thus, the initial cost is high in the HVDC transmission system, and it is low in the AC system.
  • The point where two curves meet is called the breakeven distance. Above the breakeven distance, the HVDC system becomes cheaper. Breakeven distance changes from 500 to 900 km in overhead transmission lines.


[ alt="F1 U.B Deepak 22.01.2020-D7" src="//storage.googleapis.com/tb-img/production/20/02/F1_U.B_Deepak_22.01.2020-D7.png" style="width: 380px; height: 251px;">

Advantages of HVDC transmission:

  • A lesser number of conductors and insulators are required thereby reducing the cost of the overall system.
  • It requires less phase to phase and ground to ground clearance.
  • Their towers are less costly and cheaper.
  • Corona loss is less as compared to HVAC transmission lines of similar power.
  • Power loss is reduced with DC because fewer numbers of lines are required for power transmission.
  • HVDC system uses earth return. If any fault occurs in one pole, the other pole with ‘earth returns’ behaves like an independent circuit. This results in a more flexible system.
  • HVDC acts as the asynchronous connection between two AC stations connected through an HVDC link, i.e. it interconnects two substations with different frequencies.
  • Due to the absence of frequency in the HVDC line, losses like skin effect and proximity effect does not occur in the system.
  • It does not generate or absorb any reactive power. So, there is no need for reactive power compensation.
  • Very accurate and lossless power flows through the DC link.

 

Disadvantages of HVDC transmission:

  • Converter substations are required at both the sending and the receiving end of the transmission lines, which result in increasing the cost.
  • Inverter and rectifier terminals generate harmonics which is reduced using active filters which are also very expensive.
  • The inverter used in Converter substations has limited overload capacity.
  • Circuit breakers are used in HVDC for circuit breaking, which is also very expensive.
  • It does not have transformers for changing the voltage levels.

 

Conclusion:

  • Considering all the advantages of DC, it seems that HVDC lines are more proficient than AC lines. But, the initial cost of the HVDC substation is very high and their substation equipment is quite complicated.
  • Thus, for long-distance transmission, it is preferable that power is generated in AC, and for transmission, it is converted into DC and then again converted back into AC for final use.
  • This system is economical and also improves the efficiency of the system.

 

Difference between HVDC and HVAC transmission system

HVDC Transmission System

HVAC Transmission System

Low losses.

Losses are high due to the skin effect and corona discharge

Better Voltage Regulation and Control ability.

Voltage regulation and Control ability are less.

Transmit more power over a longer distance.

Transmit less power compared to an HVDC system.

Less insulation is needed.

More insulation is required.

Reliability is high.

Low Reliability.

Asynchronous interconnection is possible.

Asynchronous interconnection is not possible.

Reduced line cost due to fewer conductors.

The line cost is high.

Towers are cheaper, simple, and narrow.

Towers are bigger compared to HVDC.

Related Questions

Consider the following advantages with respect of HVDC transmission: 1. Long distance transmission 2. Low cost of transmission 3. Higher efficiency Which of the above advantages are correct?
In a class, 30% of the students offered English, 20% offered Hindi and 10% offered both. If a student is selected at random, what is the probability that he. has offered English or Hindi ?
In a class, 30% of the students offered English, 20% offered Hindi and 10% offered both. If a student is selected at random, What is the probability that he has offered English or Hindi ?
Read the passage carefully and choose the best answer to each question out of the four alternatives.
In mid-2012 I completed my first massive online open course, or MOOC, the kind widely offered by Coursera, EdX, Udacity and so on in partnership with different educational institutions. It was on clinical trials and ethical practices, offered by Johns Hopkins, on Coursera. This was shortly before the MOOC sensation hit India, and when Coursera, which was founded by two Stanford professors, itself was just a few months old. The MOOC bug had bit me. The course Id completed was mainly designed for health care professionals who would be involved in actual clinical trials, not college students who had no prior knowledge of that area. I decided to enroll in the course because it was the only biology related course open at the time. However, I did see hope in that sometime in the future Id be able to get a glimpse of what classes are like in the hallowed halls of major educational institutions around the world. By early 2013, Coursera and EdX had partnered with so many educational institutions and expanded their course offerings to include everything from food and nutrition to Greek mythology to business, that I was spoilt for choice. I spent hours going through course catalogues and poring over course descriptions, almost delirious with excitement at the fact that I was actually going to be able to take classes offered by universities I had only dreamt of attending.
Which of the following is the name of a university and not an online education delivery company?
Read the passage carefully and choose the best answer to each question out of the four alternatives.
In mid-2012 I completed my first massive online open course, or MOOC, the kind widely offered by Coursera, EdX, Udacity and so on in partnership with different educational institutions. It was on clinical trials and ethical practices, offered by Johns Hopkins, on Coursera. This was shortly before the MOOC sensation hit India, and when Coursera, which was founded by two Stanford professors, itself was just a few months old. The MOOC bug had bit me. The course Id completed was mainly designed for health care professionals who would be involved in actual clinical trials, not college students who had no prior knowledge of that area. I decided to enroll in the course because it was the only biology related course open at the time. However, I did see hope in that sometime in the future Id be able to get a glimpse of what classes are like in the hallowed halls of major educational institutions around the world. By early 2013, Coursera and EdX had partnered with so many educational institutions and expanded their course offerings to include everything from food and nutrition to Greek mythology to business, that I was spoilt for choice. I spent hours going through course catalogues and poring over course descriptions, almost delirious with excitement at the fact that I was actually going to be able to take classes offered by universities I had only dreamt of attending.
The C in MOOC stands for which word?
Read the passage carefully and choose the best answer to each question out of the four alternatives.
In mid-2012 I completed my first massive online open course, or MOOC, the kind widely offered by Coursera, EdX, Udacity and so on in partnership with different educational institutions. It was on clinical trials and ethical practices, offered by Johns Hopkins, on Coursera. This was shortly before the MOOC sensation hit India, and when Coursera, which was founded by two Stanford professors, itself was just a few months old. The MOOC bug had bit me. The course Id completed was mainly designed for health care professionals who would be involved in actual clinical trials, not college students who had no prior knowledge of that area. I decided to enroll in the course because it was the only biology related course open at the time. However, I did see hope in that sometime in the future Id be able to get a glimpse of what classes are like in the hallowed halls of major educational institutions around the world. By early 2013, Coursera and EdX had partnered with so many educational institutions and expanded their course offerings to include everything from food and nutrition to Greek mythology to business, that I was spoilt for choice. I spent hours going through course catalogues and poring over course descriptions, almost delirious with excitement at the fact that I was actually going to be able to take classes offered by universities I had only dreamt of attending.
The course the author completed on MOOC was related to which subject?
Read the passage carefully and choose the best answer to each question out of the four alternatives.
In mid-2012 I completed my first massive online open course, or MOOC, the kind widely offered by Coursera, EdX, Udacity and so on in partnership with different educational institutions. It was on clinical trials and ethical practices, offered by Johns Hopkins, on Coursera. This was shortly before the MOOC sensation hit India, and when Coursera, which was founded by two Stanford professors, itself was just a few months old. The MOOC bug had bit me. The course Id completed was mainly designed for health care professionals who would be involved in actual clinical trials, not college students who had no prior knowledge of that area. I decided to enroll in the course because it was the only biology related course open at the time. However, I did see hope in that sometime in the future Id be able to get a glimpse of what classes are like in the hallowed halls of major educational institutions around the world. By early 2013, Coursera and EdX had partnered with so many educational institutions and expanded their course offerings to include everything from food and nutrition to Greek mythology to business, that I was spoilt for choice. I spent hours going through course catalogues and poring over course descriptions, almost delirious with excitement at the fact that I was actually going to be able to take classes offered by universities I had only dreamt of attending.
Coursera was founded by professors from which university?
Read the passage carefully and choose the best answer to each question out of the four alternatives.
In mid-2012 I completed my first massive online open course, or MOOC, the kind widely offered by Coursera, EdX, Udacity and so on in partnership with different educational institutions. It was on clinical trials and ethical practices, offered by Johns Hopkins, on Coursera. This was shortly before the MOOC sensation hit India, and when Coursera, which was founded by two Stanford professors, itself was just a few months old. The MOOC bug had bit me. The course Id completed was mainly designed for health care professionals who would be involved in actual clinical trials, not college students who had no prior knowledge of that area. I decided to enroll in the course because it was the only biology related course open at the time. However, I did see hope in that sometime in the future Id be able to get a glimpse of what classes are like in the hallowed halls of major educational institutions around the world. By early 2013, Coursera and EdX had partnered with so many educational institutions and expanded their course offerings to include everything from food and nutrition to Greek mythology to business, that I was spoilt for choice. I spent hours going through course catalogues and poring over course descriptions, almost delirious with excitement at the fact that I was actually going to be able to take classes offered by universities I had only dreamt of attending.
What aspect of MOOC excited the author?
The average of fruits offered in a temple in a week was 75. The average of fruits offered in six days excluding Tuesday was 72. How many fruits were offered on Tuesday?
In the question given below, four sentences are given which may or may not be grammatically correct. From the given options, choose the grammatically correct sentence. A. The members-only zone on the top of the ship has its own luxurious accommodations including suite, private lounges and dining options. B. The members-only zone on the top of the ship has its own luxuries accommodations including suites, private lounges and dining options. C. The members-only zone along the top of the ship has its own luxuries accommodations including suites, private lounges and dining options. D. The members-only zone on the top of the ship has its own luxurious accommodations including suites, private lounges and dining options.