Victron G98 and G99 Settings for Loss of Mains Protection and Grid Codes

Key Takeaways

• Loss of Mains (LOM) detection is a critical safety feature to prevent back-feeding the grid.
• Disabling LOM detection requires a password from your dealer and external safety equipment for grid-connected systems.
• High impedance grid connections can cause instability in the LOM detection algorithm, leading to system shutdowns.
• Ensure your Victron inverter/charger is running VE.Bus firmware 419 or later for proper grid code functionality.

What are Victron G98 and G99 settings, and why are they important?

Victron G98 and G99 settings relate to Loss of Mains (LOM) detection and grid codes, which are essential safety and regulatory requirements for inverter/chargers connected to the utility grid. LOM detection is an automatic process that identifies when the mains supply is lost. After detection, the inverter/charger will open its back-feed relay, ensuring no live AC voltage remains on its AC-inputs. This prevents unsafe conditions, such as an electrician working on a disconnected utility line that could be energized by your solar system.

Victron Multis, Quattros, MultiCompacts, and MultiPlus-II models are certified for use in the UK, which includes compliance with G98 and G99 grid codes. The MultiPlus-II is also certified for installation in Germany without external anti-islanding safety devices (ENS). These grid codes dictate how grid-tied inverters must behave to ensure grid stability and safety.

Diagnosing Loss of Mains Detection Issues

If your Victron system is experiencing unexpected shutdowns or unstable operation when connected to the grid, LOM detection settings or grid conditions may be the cause.

Diagnosis Steps

1. Check Firmware Version:

• • Observable Check: Verify the VE.Bus firmware version of your Victron inverter/charger.
  • What it Means: VE.Bus firmware 419 and later is applicable for these functions. If your firmware is older, an update may be necessary to ensure proper LOM detection and grid code compliance.

2. Observe System Behavior:

• • Observable Check: Note if the system experiences overload shutdowns or continuous increases and decreases in frequency, especially during periods of high load or fluctuating grid conditions.
  • What it Means: Overload shutdowns can indicate instability in the LOM detection algorithm due to a high impedance grid connection, such as a weak utility connection or a long extension cable. Continuous frequency shifts can also point to a too-weak connection to the utility, causing LOM detection to trigger repeatedly and temporarily disable feed-in.

3. Review Grid Connection Quality:

• • Observable Check: Assess the quality of your grid connection. Is it a stable utility supply, or are you connected to a generator or a particularly long or undersized cable?
  • What it Means: High impedance grid connections can cause the LOM detection algorithm to become unstable. Improving the grid connection quality can resolve these issues.

Common Causes and Fixes for LOM Detection Instability

Configuring Grid Codes and LOM Detection

Victron inverter/chargers use the VEConfigure software to manage grid codes and Loss of Mains (LOM) detection settings. These settings are crucial for compliance and safe operation.

Using VEConfigure for Grid Settings

To access and modify these settings, you will use the VEConfigure application.

1. Open VEConfigure: Launch the VEConfigure software and connect to your Victron inverter/charger.
2. Navigate to the Grid Tab: Within VEConfigure, locate and select the "Grid" tab. This section contains the relevant settings for grid codes and LOM detection.
3. Configure LOM Detection:

• • Setting to "None": You can change the LOM detection setting to "None". This action requires a password. Contact your Victron dealer to obtain this password.
  • Setting to "Disabled": Alternatively, you can choose "Disabled" in the LOM options. This also requires a password from your dealer.

4. Select Grid Code:

• • Country-Specific Codes: In the Grid tab, you can select specific country grid codes, such as "UK" for G98/G99 compliance.
  • Other Options: Options like "None" or "Other" are also available, depending on your installation requirements.
  • Germany Specific: For installations in Germany, you might select "Germany: VDE-AT-N 4105:2018-11 external NS protection" if external anti-islanding is used.

Remember that disabling LOM detection has significant safety implications and should only be done under specific conditions with proper external safety equipment. For detailed guidance on system design and installation, refer to the Victron Energy System Design and Installation Manual.

Safety: Loss of Mains Detection and Anti-Islanding

Loss of Mains (LOM) detection is a fundamental safety feature in grid-tied inverter/chargers. Its primary purpose is to protect personnel and equipment by preventing the inverter from feeding power into a disconnected grid.

The inverter/charger's role is to open its back-feed relay when it detects a loss of the mains/network/grid supply. This ensures there is no live AC voltage on its AC-inputs, which is critical for the safety of utility workers. Imagine an electrician working on a street, disconnecting a house; they need to be able to safely work on the wiring without risk of electrocution from a back-feeding solar system.

Disabling LOM Detection: Critical Safety Considerations

Disabling LOM detection carries significant risks and is subject to strict regulations.

• With a Generator: There is no regulatory need to install external anti-islanding equipment when disabling LOM in combination with a generator. However, it is crucial to install clear signs and other means to ensure that any installer working on the generator is fully aware that they must also switch off, or otherwise disconnect, the inverter/charger system.
• With a Utility Connection: Disabling the LOM on an input connected to the grid is only allowed when other external safety equipment is installed. This typically means using an anti-islanding safety device. Without such a device, disabling LOM creates a dangerous situation where your system could energize a supposedly disconnected grid.

Always prioritize safety and adhere to local electrical codes and regulations. Consult with a qualified electrician or your Victron dealer before making any changes to critical safety settings like LOM detection.

When to call a technician instead

While some troubleshooting steps can be performed by the system owner, certain situations require professional intervention. You should call a qualified technician if:

• You are unable to resolve overload shutdowns or persistent frequency instability after checking basic grid connection quality.
• You need to disable LOM detection for a grid-connected system and require installation of external anti-islanding safety devices.
• You do not have the password to change LOM detection settings in VEConfigure, as this must be obtained from your dealer.
• You are unsure about the implications of modifying grid code settings or the safety requirements for your specific installation.
• Your Victron inverter/charger is running VE.Bus firmware older than 419 and you are not comfortable performing a firmware update, or if the update process encounters issues.

Attempting to bypass safety features or improperly configure grid-tied systems without the necessary knowledge or external equipment can void your warranty and, more importantly, create hazardous conditions.