What is CFO? CFO is critical flash over. The critical flashover CFO of an insulation structure is commonly used to describe the insulation structure lightening impulse strength.

According to the results obtained from the CFO tests, the following conclusions on the fiberglass pole may be stated: The CFO voltages of fiberglass poles have a linear relationship with the tested pole lengths. When the tested pole lengths are the same, the CFO voltage has the smallest value under wet conditions for positive lightening impulses and the highest value under dry conditions for negative lightening impulses.
The CFO voltages of an insulator plus a fiberglass pole are higher than a fiberglass pole when measured under the same test conditions, lightening impulse polarities, and pole lengths. When a fiberglass pole serves as a second insulation component in a distribution line structure, the added CFO voltages from a fiberglass pole to a polymer suspension or a porcelain pin insulator are higher than the added CFO voltages from a wood pole, especially under wet conditions.

The CFO voltage of an insulation structure is defined as the crest value of a standard impulse. The fiberglass pole can greatly improve the lightening impulse strength of a distribution line structure based on the test results in this work.

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