How to Calculate Lightning to Cable Coupling

Recognize the basic units of measurement used to determine the lightning to cable coupling calculation. This calculation can be determined in terms of both time and frequency.

Assume some basic propositions that make the calculation possible in the first place. For the calculation to even be possible, you have to assume that the overhead line can be considered "loss-less," according to a paper by H.K. Hoidalen at SINTEF Energy Research in Norway. He notes that other basic assumptions must also be made, such as the electrical field is unaffected by the ground, whether it is or not. In other words, the calculation cannot be exact because the researcher has to assume too many variables that have no exact value. You also have to assume that the electrical field is constant.

Solve the calculation for lightning to cable coupling using the finite-difference time-domain method. This is one of the most popular methods used for making this calculation, but it is by no means the only one. As with other calculations used to determine the lightning to cable coupling, the FDTD method can only provide an approximation within a range of possible answers. The answers obtained in the calculation are made on the basis of James Clerk Maxwell's equations, which include a time derivative and a space derivative.

Establish a domain for your calculation. That is to say, the time and space calculations within the FDTD calculation are based on certain limiting factors, including the material in which the process occurs. In the case of lightning to cable coupling, the impedance of the cable has to be taken into account as a limiting factor. Once all the factors have been determined, you can then calculate the time and space components of the function to determine a range of possibilities.

Calculate the values using the MODELS computer language. This method is recommended by Mario Paolone, et. al., in a paper submitted to the Institute of Electrical and Electronics Engineers. Using MODELS allows you to plug in the values and perform multiple calculations at one time.