Voltage sags from cause to sizing. Read in order: from "why does it trip" to "what size do I need."
Most sags come from outside the plant. Prevention means riding through.
Voltage dips to 10–90% for ~0.1 s. Power stays on, tools stop. 6 causes and 2020–2025 incidents.
Storm trips are usually sags, not surges. Arresters can't stop sags.
6 steps: log incidents, cost them, prioritize, cheap fixes, POC, purchase specs.
Three test points, the IEC 61000-4-11 / 4-34 test procedure, a/b/c pass criteria, and 6 things to check when you get a test report.
A few weak parts cause most trips. Harden the relays, contactors and power supplies — not the whole tool.
Capacitor protectors, voltage conditioners, online and offline UPS, flywheels: depth, duration, standby power.
Only the controls that reset: measure, convert to kVA, add margin, check inrush.
Book a voltage sag risk assessment. We use trip records and on-site measurements to find the equipment that really needs protection, then decide how to protect it.