Best practices for protecting ATS
panels and sensitive downstream loads.
Why surge arrestors on the
generator side often overlooked—but critical? It is generally recommended to
install surge arrestors on the generator side of an ATS (Automatic Transfer
Switch) panel, but whether it’s strictly required depends on the installation
environment and protection philosophy. Here’s a detailed explanation:
Why install surge arrestors on the generator side?
- Protect
sensitive loads downstream
When the ATS
switches to the generator supply, any surge coming from the generator (e.g.,
from lightning or switching transients) can damage sensitive equipment like
PLCs, relays, VFDs, etc.
- Generator
switching transients
When generators
start or stop, especially in large systems, they may generate voltage
transients. Surge arrestors help clamp these and protect equipment.
- Outdoor
or exposed installations
If the generator
or ATS is installed in an area prone to lightning or power surges (such as near
an industrial area, water treatment plant, or hilltop), surge protection
becomes critical.
- Compliance
with standards
IEC 61643
recommends surge protection at all power entry points, which includes
generators feeding backup power.
Where to install surge arrestors?
- On the generator output, before entering the ATS
- Preferably in the generator panel or right at the
generator breaker
- Also consider arrestors on both utility and load
sides of the ATS for complete protection
Type of Surge Arrestor
- Use Type 2 SPD (Surge Protection Device) for
generator applications.
- For more exposed environments (like buildings with
external cables or towers), you might add Type 1 + 2 combined SPD.
When might it not be needed?
You might skip it if,
- The generator is small, located indoors, and supplies
only rugged equipment.
- There is already SPD at the load distribution panel
and utility side.
- The installation environment has low lightning risk
and is well shielded.
Recommended practice
Install a surge arrestor on the generator side of the ATS panel for better protection, especially if the generator is in a high-risk or sensitive environment.