Lightning Season Prep: What Factories Should Do Before Summer Storms

Summer lightning can trigger voltage sags, which are short drops in supply voltage. A sag lasting only a few cycles can stop variable frequency drives, PLCs and servo systems even when no outage is logged. Before the storm season, facilities should check grounding and surge protection, review sag records from their power quality meters, and compare each machine’s tolerance against the sags they actually see. For sites where equipment is sensitive but the sag is too deep to ignore, a battery-free voltage sag protector can fill that gap.

A familiar scene: an afternoon storm passes, the breakers are closed, and no outage appears in the logs. Yet a line of drives and controllers faults within seconds. The cause is often a sag that lasted a fraction of a second, which the equipment could not ride through.

How lightning produces sags

Lightning can strike a line directly or induce surges nearby. When protective relays detect a fault, breakers operate and system voltage drops briefly. If the line recloses, the equipment downstream sees that dip for the duration of the event.

Lightning is one contributor to voltage sags, and its share depends on local weather and grid topology. Site-level logs are more useful than industry averages when you plan for the summer season.

How much sag can equipment take?

Two references are commonly used to judge equipment tolerance. The ITIC (CBEMA) curve is a published envelope that maps voltage magnitude against duration and shows the region where equipment is expected to keep operating normally.

Semiconductor tools are typically evaluated against SEMI F47. Per SEMI F47, the ride-through points are:

• 80% of nominal voltage for 1 second
• 70% of nominal voltage for 0.5 seconds
• 50% of nominal voltage for 0.2 seconds

These figures are a starting point, not a final answer. Drive undervoltage trip settings are often stricter than the tool specification, so the real limit is the lowest threshold in the chain. Confirm it with the manufacturer’s documentation and, where possible, a controlled test.

Pre-season checklist

1. Grounding resistance. Measure and record it so lightning current has a low-impedance path to earth. Inspect bonding connections for corrosion and looseness.
2. Surge protective devices. Check indicator status, signs of degradation and protection level. Schedule replacement for aging units.
3. Power quality logs. Compile the past year’s sag count, duration and timestamps, then match them against equipment stop records.
4. Drive and PLC undervoltage settings. Review trip thresholds and restart behavior. Confirm that automatic restart fits your process safety rules.
5. Standby generators and UPS units. Run automatic start tests and check battery condition.
6. Data protection. List which work data and equipment states could be lost on an unexpected stop.

What a sag compensator does

A voltage sag compensator bridges the short window of a sag with stored energy, keeping the load-side voltage up. TSP® (The Second Power) is a voltage sag protector and compensator for low-voltage systems up to 1 kV. Systems at 3.3 kV and above are outside its scope.

TSP uses an EDLC ultracapacitor and no battery. The energy storage is designed for a 10-year service life, so periodic battery replacement is not part of the maintenance plan. Compared with battery-based UPS systems, this reduces maintenance workload and lifetime cost for sag protection.

Two specifications are easy to confuse and should be read separately. Switchover time is the transfer from the grid to EDLC discharge, which is within 2 ms. Compensation time is how long the support lasts: 1 to 3 seconds for small and mid-size units, and 3 seconds for large units. Match the compensation time against the sag duration your equipment requires. Because it lasts seconds, it does not replace a generator for extended outages.

Key takeaways

• Summer sags are short enough to escape outage logs. Start by capturing sag data from your power quality meters.
• Map each machine’s tolerance using the ITIC curve, SEMI F47 points and manufacturer specifications, then compare with actual records.
• Check grounding, surge protective devices and drive undervoltage settings before the rainy season.
• Separate switchover time (2 ms) from compensation time (1 to 3 seconds) when evaluating a compensator. A battery-free TSP® is one option to evaluate for low-voltage systems.

Frequently Asked Questions

Q. What should a factory check first before summer lightning season?

Start with grounding resistance and the condition of surge protective devices (SPDs), then review the voltage sag records from your power quality meters. Without those records, it is hard to tell when and why equipment stopped.

Q. How is a voltage sag different from a momentary interruption?

A voltage sag is a short drop in supply voltage below normal levels. A momentary interruption is a drop close to zero volts. Both can stop drives, PLCs and servo systems.

Q. Is TSP the same as a battery UPS?

No. TSP is a voltage sag compensator, not a UPS. It uses an EDLC ultracapacitor with no battery and applies to low-voltage systems up to 1 kV. It is an option for sites that want sag protection without battery replacement cycles.