Surge Impedance in power transmission is the natural impedance of a transmission line that determines how power waves propagate through it. It is used in the study of power systems, especially when analyzing wave propagation and surge phenomena, such as lightning strikes or switching surges. Surge impedance defines how voltage and current waves behave along a transmission line and helps engineers design transmission systems that efficiently manage power flow and surges.
Key Points about Surge Impedance
Power Flow in Transmission Lines - When a transmission line is terminated by its surge impedance, there is no reflection of the wave, which results in efficient transmission of power (maximum power transfer). This condition is called surge impedance loading (SIL).
Wave Propagation - When a surge, such as a lightning strike or switching operation, travels through a transmission line, the surge will be reflected and transmitted based on the impedance mismatches. Surge impedance is critical in understanding how these surges will behave.
Typical Values - For overhead transmission lines, surge impedance typically ranges between 200 to 400 ohms. For underground cables, it is lower, usually around 40 to 60 ohms, due to different inductance and capacitance characteristics.
Surge Impedance Formula |
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| Symbol | English | Metric |
| \( Z_s \) = Surge Impedance | - | \(ohm\) |
| \( L \) = Inductance per Unit Length of the Transmission Line | - | \(H\) |
| \( C \) = Capacitance per Unit Length of the Transmission Line | - | \(F\) |
