There are two types of transmission system; HVAC and HVDC system. In this article, we will make comparison between HVAC and HVDC system.
Comparison between HVAC and HVDC system
Sr No |
Title |
HVAC system |
HVDC system |
|
1 |
Effect of capacitance | Because of the effect of capacitance charging current produced in the line. The length of the line is limited due to the charging current. | There is no effect of capacitance in the case of DC. Hence, the charging current is not produced. So, there is no restriction on the length of a line. |
|
2 |
Skin effect |
In the HVAC system, the skin effect produced due to the non-uniform distribution of charge in a conductor. The power loss increases due to the skin effect. | There is no skin effect and power loss. |
|
3 |
Supports | Heavy supports needed. So the cost is more. | The cost is less because of the use of lightweight support. |
|
4 |
Corona effect
|
Corona effect is more in the HVAC system. Which results in the power loss and disturbance to the communication line. | Less effect of the corona. Power loss is less and no disturbance to the communication line. |
|
5 |
Reactive loss | There is a net reactive loss. | There is no reactive loss. |
|
6 |
Number of line wire | For bulk power transmission, six conductors used. | Only two conductors required. |
|
7 |
Ferranti effect | In this system, the Ferranti effect produced. | In this system, the Ferranti effect is absent. |
|
8 |
Power factor | The transmission line behaves as an inductor. Therefore, the power factor is lagging. Synchronous condenser or FACTS devices used to improve the power factor. | There is no question of the power factor in the case of DC. |
|
9 |
Intermediate substation | Every 300km, one substation required. | No requirement of intermediate substation. |
|
10 |
Use of earth return | It is not possible to use earth or marine as a return path. | It is possible to use earth or marine as a return path. |
|
11 |
Line loss | Due to reactive power, line loss increases. | Line loss is less in this system. |
|
12 |
Stability | The stability of this system is less. The length of a line is limited. | This system is more stable. |
|
13 |
Voltage regulation | Poor | Good |
|
14 |
Asynchronous tie | It is not possible to connect two tie line which has a different frequency. | There is no question for frequency. |
|
15 |
Overload capacity | More | Less |
|
16 |
Possibility of system failure | Less | More |
|
17 |
Volume of conductor | More | less |
|
18 |
Power transfer and control | Slightly difficult | Quick control of line |
|
19 |
Short circuit level | Increases | Fault level remains the same |
|
20 |
Complexity of system | Less | More |
|
21 |
Cost |
Less | More |
|
22 |
Maintenance | Easy to maintain | Difficult to maintain and highly qualified staff need to maintain |
|
23 |
Change the voltage level | Possible | Not possible |