Question regarding Ferranti effect

  • Thread starter jaus tail
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In summary, the phasor for Ferranti is used to illustrate the voltage and current relationship in a circuit, specifically the effect of capacitance and inductance. The voltage across the inductor leads the capacitive current by 90 degrees, and this can be seen in diagrams and explained through the concept of electric field and work. In open circuit cases, there is no power generated, but the voltage and current relationship can still be observed.
  • #1
jaus tail
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the phasor for ferranti is

ferranti-effect-in-transmission-line1.gif

Why is BC drawn facing left? I get it's voltage of capactive current across the line inductance. But why is it leading capacitive current by 90 degrees.

Also physically how does receiving end voltage increase without any drop of receiving current? Where does the power come from?
 
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  • #2
In my opinion your sketch is taken from:

http://wangyj.ee.yuntech.edu.tw/PQLAB2_Web/elec_machine/Ferranti%20Effect.pdf

you said:

"But why is it leading capacitive current by 90 degrees."

See [for instance]:

http://www.colorado.edu/physics/phys1120/phys1120_fa09/LectureNotes/Voltage.pdf

you asked:

“Where does the power come from?”

As you see from above articles the voltage it is not "a power" but the work of the force exercised on an unit charge by the electric field on the distance between 2 points of a circuit.

The power is the voltage multiplied by current which is zero [in open circuit case].
 
  • #3
I went through the second link but still didnt understand why the voltage drop across inductor leads capacitive current by 90 degrees. if anything the inductor must cause a lag in phase.
 
  • #4
Icapacitive Xinductive.jpg

The line current- if the end is open and no other load current will flow through- it is only the leakage capacitive

current [neglecting the current through air insulation].

If I [line current] is inductive or capacitive [it does not matter] I*jXL will be 90o leading the current any way.

But, since the current leads the voltage Vr you’ll need to supply less Vs in order to get the same Vr. That means

for the same Vs you'll get more Vr[see the sketch].
 
  • #5
Thanks. That's helpful. in inductor current lags voltage by 90 degrees, so voltage leads the current across it by 90 degrees. gave me a smile at how basic the answer was:)
 

1. What is the Ferranti effect?

The Ferranti effect is a phenomenon in electrical power systems where the voltage at the receiving end of a transmission line is higher than the voltage at the sending end. This is due to the capacitance of the transmission line, which causes a lag in the voltage at the receiving end, resulting in a higher voltage.

2. What causes the Ferranti effect?

The Ferranti effect is caused by the capacitance of the transmission line. As electricity travels through the transmission line, it creates an electric field between the conductors, which results in capacitance. This capacitance causes a lag in the voltage at the receiving end, resulting in a higher voltage.

3. How does the Ferranti effect affect power systems?

The Ferranti effect can have a significant impact on power systems. It can cause voltage instability and fluctuations, leading to potential equipment damage and power outages. It can also affect the accuracy of voltage readings and can be challenging to control and regulate.

4. How can the Ferranti effect be mitigated?

There are several ways to mitigate the Ferranti effect. One common method is to use shunt reactors at the receiving end of the transmission line. These reactors absorb excess reactive power and help to stabilize the voltage. Another approach is to use series capacitors, which can compensate for the capacitance of the transmission line and reduce the Ferranti effect.

5. Can the Ferranti effect be beneficial in any way?

In certain cases, the Ferranti effect can be beneficial. It can help to compensate for voltage drops along long transmission lines, resulting in a more stable voltage at the receiving end. It can also be utilized in power systems to increase voltage levels, reducing the need for step-up transformers. However, the Ferranti effect can also be detrimental, and proper measures must be taken to control and mitigate it.

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