Voltage sag

Related notions

Swell

Causes

• Since electric motors draw more current when they are starting than when they are running at their rated speed, starting an electric motor can be a reason of a voltage sag.
• When a line-to-ground fault occurs, there will be a voltage sag until the protective switch gear operates.
• Some accidents in power lines such as lightning or a falling object can be a cause of line-to-ground fault and a voltage sag as a result.
• Sudden load changes or excessive loads can cause a voltage sag.
• Depending on the transformer connections, transformers energizing could be another reason for voltage sags happening.
• Voltage sags can arrive from the utility but most are caused by in-building equipment. In residential homes, voltage sags are sometimes seen when refrigerators, air-conditioners, or furnace fans start up.