What happens when the Power Meter loses the network connection? (Fail-Safe)

Summary

This article explains the system behaviour when a power meter loses connection to the GATEWAY while all other components (internet, LAN, charging stations) remain operational. It describes how charging power allocation is affected and how you can configure fallback behaviour using the Safety Current setting in HARMON-E.

Scenario

• Power Meter Connection: Lost (one or multiple meters)
• Gateway, LAN, and Charging Stations: Operational
• Protocol: OCPP communication with CPO backend unaffected

Default Behavior

By default, when a power meter loses connection:

• The GATEWAY ****cannot monitor the building's grid consumption.
• To prevent a potential grid overload, the charging limit is immediately reduced to the Safety Current, which is per default set to 0 A.
• This is the most restrictive and safest fallback setting, ensuring the building’s connection is not overloaded.

Behaviour Details

1️⃣ Site with One Power Meter

• The GATEWAY relies entirely on the power meter to safely allocate charging power.
• When the meter disconnects:
  • Charging sessions are immediately reduced to 0 A.
  • New sessions cannot receive power allocation until communication is restored.

Manual Override: Configuring Safety Current

As an Admin user in HARMON-E, you can:

1. Navigate to Assets → Power Meters → Select the power meter → Open Advanced Configuration.
2. Define a static fallback limit (Safety Current), e.g. 16 A or 32 A.
3. Save your settings.

Whenever the power meter goes offline, the system will allocate this static Safety Current instead of defaulting to 0 A.

2️⃣ Site with Multiple Power Meters

• Each power meter belongs to a cluster or sub-cluster of chargers.
• If one meter loses connection, the site or sub-cluster limit is reduced based on its configured Safety Limit.
• This ensures that only the part of the site potentially affected by missing measurements is restricted.

Logic Behind Safety Current Calculation

Formula:

• For a single meter:

  Charging Limit = Charging Limit – (Charging Limit – Safety Limit)

• For multiple meters:

  Charging Limit = Charging Limit – (Charging Limit – Safety Limit PM1) – (Charging Limit – Safety Limit PM2)

Example 1 – Single Power Meter

• Site Charging Limit = 100 A
• PM1 Safety Limit = 50 A
• PM1 offline → Charging Limit = 50 A

Example 2 – Single Power Meter with Safety Limit 0 A

• Site Charging Limit = 100 A
• PM1 Safety Limit = 0 A
• PM1 offline → Charging Limit = 0 A

Example 3 – Multiple Meters

• Site Charging Limit = 100 A
• PM1 Safety Limit = 50 A
• PM2 Safety Limit = 25 A

Results:

• If PM1 offline → Limit = 50 A
• If PM2 offline → Limit = 25 A
• If both offline → Limit = 25 A, clamped to 0 A

⚠️ Important: In multi-meter setups, simultaneous failures may lead to a calculated limit below 0 A, which is automatically set to 0 A for safety.

Recommendations for Customers

1. Always configure a Safety Current:
   • Define a realistic fallback value in HARMON-E for each power meter to avoid a complete site shutdown during outages.
2. Review settings for multi-meter sites:
   • Ensure Safety Limits are correctly sized to prevent unintended zero-allocation during simultaneous meter faults.
3. Monitor power meter connectivity:
   • Repeated disconnections may indicate cabling or hardware issues requiring maintenance.

Key Takeaways

• A loss of connection to a power meter disables load monitoring, triggering restrictive fallback limits to protect the grid connection.
• The Safety Current setting allows defining a static, site-specific fallback allocation instead of 0 A.
• Multi-meter sites require careful configuration to ensure predictable behavior during failures.