Surge Impedance Loading Calculation Explained

Added: 2026-06-02

[00:00:00]Let's take 400 kV. Let's take 400 kV and let's put whatever may be the length.

[00:00:05]Search impedance is not really going to be affected by the length because square root of L by C, both are given in ohm per kilometers. So, this value remains same. Let's take a parameter of 0.0001.

[00:00:20]What's the minimum possible value? Then X value let's take 0.4, Y value will take like 3.6. And now, coming back to this L and C, this is a search impedance.

[00:00:31]Right? This is ZN or ZC in ohms.

[00:00:37]And what is the search impedance loading?

[00:00:41]Search impedance loading is V squared by Z.

[00:00:44]400 kV into 400 kV divided by this gives me means what's the search impedance loading? So, kV into kV is 10 power 6, that is like megawatt, like 480 megawatt. So, what I mean, if I put up a 480 megawatt unity power factor load at the receiving end, 480 megawatt, assuming unity power factor, 480 megawatt, right?

[00:01:21]Let's run load flow.

[00:01:24]Now, it will go, right? So, it's crystal clear the losses in the transmission line is 0 megawatt, 0 MVA. The voltage drop is 0%, sending end voltage is 100%, receiving end voltage is 100%.

[00:01:39]Right? So, there is a power flow which exist and this is now search impedance loading. At search impedance loading, sending end voltage is equal to receiving end voltage, real power loss is zero, reactive power loss is zero.

[00:01:54]That means reactive power loss is zero means what? The shunt capacitance, what's the reactive power generated by the shunt capacitance are consumed by the reactive power in the in the inductance of the transmission line.

[00:02:07]Either you increase the line length from 100 km 10 km to 100 km results remain same. Results remain same, right? So, like there is not much change. Since I really couldn't give a value of resistance is zero. That is there is a small values which is coming here, but if the software accepts this R value equal to zero if the software accepts R equal to zero, then like irrespective of the length, you will have zero real power loss, zero reactive power loss, zero voltage drop.

[00:02:41]So, 100% 100% zero megawatt, zero MVAR, whatever may be the power flow here, like it will flows in the receiving end also.