The positive sequence current for an L-L fault of a 2kV system is given as 1400A. This means that during the fault, the current flowing through both the line conductors is in phase and has the same magnitude.


The corresponding current for an L-L-G fault is given as 2220A. In an L-L-G fault, one of the line conductors comes in contact with the ground, resulting in a fault current flowing through the faulted phase and the ground.


The zero sequence impedance of a power system represents the impedance seen by the zero sequence current, which flows in a closed loop through the neutral conductor and the ground during a fault. It is denoted by Z0.

The zero sequence impedance can be calculated using the fault current values and the system voltage. The formula to calculate the zero sequence impedance is:

Z0 = V / (3 * I0)

Where:
Z0 = Zero sequence impedance
V = System voltage
I0 = Zero sequence current

In this case, we are given the positive sequence current for an L-L fault (I1 = 1400A) and the corresponding current for an L-L-G fault (I2 = 2220A). To calculate the zero sequence impedance, we need to find the zero sequence current (I0).

The zero sequence current can be determined using the following relation:

I0 = (3 * I1 - I2) / 2

Substituting the given values:

I0 = (3 * 1400A - 2220A) / 2
I0 = 4200A - 2220A / 2
I0 = 1980A / 2
I0 = 990A

Now we can calculate the zero sequence impedance using the formula:

Z0 = V / (3 * I0)
Z0 = 2000V / (3 * 990A)
Z0 ≈ 0.674 ohms

Therefore, the zero sequence impedance of the system is approximately 0.674 ohms.