Is the Neher-Mcgrath method the only way to calculate underground ampacity?
No. Neher-Mcgrath method is the industry standard calculation but there are situation where the Neher-Mcgrath method falls short. The Neher-Mcgrath method is based in ampacity that is static over a given time period. In a Dynamic current situation the Neher-Mcgrath method is a bit conservative. A Dynamic current analysis is best done using the KEMA model. This model is designed for transmission grade power and is applicable to medium voltage and high voltage cables where the operator (typically a utility company) needs to know how much current they can push through a given cable over the next 24 hours. The model can be used to predict cable temperatures in the future (based on an expected loading) or to calculate the maximum ampacity for the next hours or days. By using these mathematical techniques in a control room setting, for example, the following can be calculated: • The current the cable can transport over the next 24 hours. • The length of time the cable can transport a given a
