Calibration of the sphere gap

A series of sparkover voltage calibration tests on sphere gaps using spheres of various sizes up to 200 cm in diameter are reported in this paper. Tests were made with gap spacings ordinarily used in practice, and with 60-cycle and both positive and negative impulse voltages. Since these tests as well as those of other investigators show that some of the A.I.E.E. standard sphere gap calibration curves are in error, it is recommended that those standards be revised. Recommendations are made for the adoption of separate calibration curves for positive and negative impulses and for correcting the 60-cycle calibration curves of large spheres.