Problem

This is an example of how transient overvoltage is measured when turning on glow fluorescent lighting.

Analysis

A glow fluorescent light incorporates a glow lamp and is widely  recognized as a low-cost fluorescent lighting system. A fluorescent light needs to be warmed-up for its electrodes to be switched on. A glow
lamp is provided for this purpose. It flashes to warm-up the electrodes before the fluorescent light is actually turned on.  Transient overvoltage is generated at the first flash of a glow lamp, which affects electronic equipment located nearby.

Voltage and Transient Waveforms When Turning On the Fluorescent Light

The power is turned on at the voltage waveform peak (128.9V) and the generated transient overvoltage is 103.1V in the negative direction.

When transient overvoltage occurs, a high current flows instantaneously. This example is measured by using a 10-turn coil without a CT ratio setting.The screen shot on the left shows that 0.9602A of current flowed instantaneously in the negative direction.

Source : Guidebook for Power Quality Measurement, HIOKI E.E. Corporation