Series Impedance Guide
Series impedance per unit length describes the opposition in a line section. It combines resistance and inductive reactance. Engineers use it for cables, feeders, bus runs, and overhead conductors. The value is normally written as R plus jX. R shows real loss. X shows magnetic energy storage. Together they affect voltage drop, short circuit current, and power flow.
Why This Value Matters
A long conductor does not behave like a small jumper. Every meter adds resistance. Every meter also adds inductance. At higher frequency, inductive reactance grows. This calculator helps compare materials, routes, and operating conditions before a layout is finalized. It can also estimate total impedance for a selected length. That is useful for quick studies and report checks.
Main Input Ideas
Enter resistance per length when it is available from a datasheet. Enter inductance per length when your design guide provides it. You may also use the geometry option. It estimates inductance from conductor spacing and GMR. Temperature correction adjusts resistance from a reference value. A skin or proximity factor can be added when alternating current raises effective resistance.
How To Read Results
The calculator returns R, X, magnitude, angle, and total impedance. R is the loss part. X is the reactive part. Magnitude shows the combined size. Angle shows how inductive the line is. Positive angle means the impedance is inductive. Total values are found by multiplying the per length value by the entered route length.
Practical Notes
Use consistent units. Check whether a cable table lists ohms per kilometer, mile, meter, or foot. For three phase transposed lines, use equivalent spacing. For bundled or parallel conductors, use a suitable equivalent value from design standards. The geometry estimate is a practical approximation. Final engineering work should use manufacturer data and accepted design rules.
Common Use Cases
Power studies often need quick line models. A designer may compare copper and aluminum. A technician may check a replacement cable. A student may test frequency effects. The same method supports low voltage feeders, medium voltage cables, and simple transmission examples. Results can be exported, so another person can review the assumptions. Keep notes with every value, especially when data comes from mixed sources. This improves checking and future reuse later.