A solution of a common insulation problem [includes discussion]

Abstract
Problems regarding breakdown and corona voltage arise in the design of transformers and other types of equipment. It is necessary to design the equipment to eliminate or at least minimize the possibility of breakdown or corona. In particular breakdown takes place more readily from sharp corners. Three practical examples of sharp corners from which breakdown or corona may occur are abstracted into one for general use of a sharp corner for discussion purposes. This article is intended to cover possible general methods of solution to such problems. Problems involving square corners are common, and at first sight would seem to be extremely difficult to solve. However, because of the fact that the breakdown or corona value follows from a given voltage drop for a given distance from the corner, the relations for square corners in a single plane are found relatively easily. If breakdown data for the simple reference condition are found, complicated arrangements, still involving square corners, can be solved by the use of form factors. These can be determined mathematically or by field plots. Such determinations may enable experimental work on actual models to be reduced or accomplished more systematically. Although square corners have been emphasized, the development is as easily applicable to corners having any angle and, with more complications, may be extended to cases with rounded corners.

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