Introduction:
In electrical power systems, faults can occur due to various reasons such as insulation breakdown, equipment failure, or external factors. These faults can result in abnormal current flow, which needs to be analyzed and mitigated to ensure the safe operation of the system. One way to analyze faults is by using sequence impedance, which helps determine the fault current and its characteristics.

Sequence Impedance:
Sequence impedance is a way to represent the impedance of a power system during different types of faults. It is used to calculate the fault current and determine the behavior of the system during abnormal conditions. There are three types of sequence impedances - positive, negative, and zero sequence impedances.

Positive Sequence Fault:
A positive sequence fault occurs when two phases (L-L) are short-circuited together, while the third phase remains intact. The positive sequence impedance represents the impedance seen by the positive sequence of currents during this fault condition.

Given that the current for a L-L fault is 1400 A, we can use this information to determine the positive sequence impedance.

Negative Sequence Fault:
A negative sequence fault occurs when all three phases are short-circuited together, resulting in a balanced fault condition. The negative sequence impedance represents the impedance seen by the negative sequence of currents during this fault condition. However, this information is not provided in the given problem statement.

Zero Sequence Fault:
A zero sequence fault occurs when all three phases are short-circuited together, with a ground fault present as well. The zero sequence impedance represents the impedance seen by the zero sequence of currents during this fault condition.

Calculating Zero Sequence Impedance:
To calculate the zero sequence impedance, we need the current for a L-L-G fault. In this case, the given current is 2220 A.

The zero sequence impedance can be calculated using the formula:
Zero sequence impedance (Z0) = V / I0

where V is the system voltage and I0 is the zero sequence current.

Given that the system voltage is 2 kV (2000 V) and the zero sequence current is 2220 A, we can substitute these values into the formula to calculate the zero sequence impedance.

Z0 = 2000 V / 2220 A = 0.90 ohms

Therefore, the zero sequence impedance for the given system is 0.90 ohms.

Conclusion:
In electrical power systems, faults can occur due to various reasons, resulting in abnormal current flow. Sequence impedance is used to analyze these faults and determine the characteristics of the fault current. By using the given information of the current for a L-L-G fault, we were able to calculate the zero sequence impedance of the 2 kV system, which was found to be 0.90 ohms.