Reducing the effects of high-frequency surges on central office grounding networks

The author discusses different ways in which the high-frequency components of ground faults or disturbances affect the performance of the grounding network, with emphasis of the roles of inductance and reflected waves. Due to the high-frequency nature of ground faults, a grounding network must provide electrical paths that exhibit not only a low DC resistance, but also, and more importantly, a low inductance. In most cases, the inductance will be the main component of the total ground impedance and must therefore be reduced to a minimum by direct routing of conductors. Bends should be used only when absolutely necessary and even then they should be formed with a large radius. Plastic clamps or ties should be used to support conductors instead of using metal clamps. With the network, there are a multitude of points where wave reflections may occur. In many cases, it is not practical to eliminate these reflective points. However, splice reflections can be reduced to a minimum by properly selecting the type of connector used. The test results suggest that, if an in-line low-profile connector is used, the reflective effect may be minimal, if detectable at all in actual service conditions. Therefore, when splices are required, it would be preferable to use this type of connector instead of parallel splices, lap-type, or other types of bulky, large-profile connectors.<
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