Cascade Overload Protection: What is it and what impact does it have?

Protecting the fuses between your main connection and your charging stations, not just the main connection itself.
What is Cascade Overload Protection?

Cascade Overload Protection is an extension of regular Overload Protection. In short: it lets you set an extra current limit on the circuit of a secondary distribution panel (for example a sub-board feeding a group of charging stations), so that panel's own fuse is protected too, on top of the protection already offered on the main breaker.

When demand on that secondary panel gets close to its limit, Cascade Overload Protection automatically reduces the charging speed of the connected charging stations, so the panel's fuse is never exceeded.

Diagram showing Cascade Overload Protection: main GRID fuse plus a separate current limit on a secondary distribution panel

Requirements

  • GRID measurement
  • Circuit measurement on the secondary panel(s)
  • Only Smappee charging stations connected (other brands aren't compatible with this feature)
  • Maximum amperage configured for the main fuse and for every secondary breaker panel
  • The measurement hierarchy correctly set up in the Smappee Dashboard
Critical: double-check that the phase mapping is correct for every measurement in the hierarchy. Incorrect phase mapping is the most common cause of Cascade Overload Protection not working as expected.

Multi-Gateway setups are supported (optional): in that case, Cascade Overload Protection is configured on the Multi-Gateway parent.

All configuration happens in the Smappee Dashboard. For the step-by-step setup, see Configuration of the Cascade Overload Protection.

What impact does it have?

Example setup used below:

  • GRID (main fuse): 63A max
  • Secondary panel for the charging square: 16A max
  • 1 EV Base connected directly on the main distribution board
  • 3 EV Wall Business units connected on the secondary distribution board

Visual representation of the example: EVbase directly under the GRID, three EVwall Business units under the secondary distribution panel

In the visual, blue is the EV Base, connected directly under the GRID, unaffected by the secondary panel's limit. Turquoise and green are two of the three EV Wall Business units managed through the secondary panel. Here's how a real overlap plays out:

Moment EV Base (main board) EV Wall session 1 EV Wall session 2
Before 8:00 Charging at full speed (16A/phase, 3-phase) Charging at 16A (single-phase), already at the secondary panel's 16A limit on its own Not started yet
8:00 Still full speed, unaffected Throttled to 8A Starts, throttled to 8A
Just after 9:00 Still full speed, unaffected Session ends Ramps back up to the full 16A
Why this matters: the combined demand of all three sessions never comes close to the 63A GRID limit, so without Cascade Overload Protection nothing would stop session 2 from also charging at 16A. But two sessions at 16A each on a panel rated for 16A total would exceed that panel's own fuse, with no protection catching it. Cascade Overload Protection is what recognises this and throttles both sessions to 8A each until there's room again.

Chart showing the EVbase charging at full speed while the two EVwall sessions are throttled to 8A each until one session ends

See also: How does overload protection work? and How do I activate overload protection? How can I change my max grid current?

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