The photovoltaic disconnection relay is an essential safety component for any grid-connected solar installation. Its main function is to protect personnel and equipment by automatically disconnecting the installation in the event of a disturbance to the electricity grid. This article explores the role, operation, selection, and importance of this key device for the safety and performance of your photovoltaic system.

Key Points to Remember

• The photovoltaic disconnection relay ensures safety by disconnecting the installation from the grid during outages or anomalies, thereby preventing the risk of electrocution for technicians.
• This device reacts to variations in voltage and frequency of the electricity grid, ensuring optimal protection.
• Compliance with standards, particularly NF EN 50549, is mandatory and ensures the safety and proper integration of the installation into the grid.
• The choice of disconnection relay depends on the size of the installation: integrated into inverters for low-voltage systems, external for high-voltage installations.
• Regular installation and maintenance by qualified professionals are necessary to ensure the proper functioning and longevity of the disconnection relay.

Understanding the Role of the Photovoltaic Disconnection Relay

The photovoltaic disconnection relay is an essential safety component for any grid-connected solar installation. Its primary role is to ensure the safety of people and property in the event of an anomaly on the public electricity grid. Without this device, a solar installation could continue to inject current into a disconnected grid, thereby creating a fatal danger for technicians responsible for grid maintenance. It acts as a silent guardian, ensuring that your solar system does not become a source of danger.

The primary function of the disconnection relay is to ensure safety. It is designed to quickly detect any grid disturbance, such as a power cut or an abnormal variation in voltage or frequency. As soon as such an anomaly is detected, the relay immediately cuts off the injection of energy from the photovoltaic installation into the grid. This is an automatic protection measure that prevents dangerous situations. This rapid interruption is vital for the safety of personnel working on the grid.

By cutting off the power supply from the solar installation when the public grid fails, the disconnection relay not only protects technicians who might be working on the lines but also your own installation’s equipment. Without this protection, the inverter could continue to operate by injecting current, which could damage the inverter itself or other sensitive components if the grid returns. It thus provides dual protection: for people working on the grid and for your equipment.

Installing a disconnection relay is not only good practice but also a regulatory obligation in many countries, including France and Europe. Standards are evolving to incorporate ever more safety into electricity grids, particularly with the rise of renewable energies. Complying with these standards, such as NF EN 50549, is necessary for your installation to be compliant and connectable to the public grid. Consulting the documentation of grid operators is a key step to ensure your system’s proper compliance according to local requirements.

Here is an overview of why this device is so important:

• Increased safety: Prevention of electrocution risks for grid technicians.
• Equipment protection: Avoids potential damage to inverters and other equipment.
• Regulatory compliance: Adherence to national and European standards for grid connection.
• Installation reliability: Contributes to the overall stability of the solar system.

Operating Principles of the Disconnection Device

The automatic disconnection device is an essential component for the safety of solar installations. Its main role is to continuously monitor the quality of the electricity grid to which the installation is connected. It acts as a guardian, ready to intervene as soon as an anomaly is detected.

Detection of Electricity Grid Anomalies

This system is designed to quickly identify any deviation from normal grid parameters. This includes voltage variations, whether too high or too low, as well as frequency changes. Precise and continuous measurement of these values is key to its effectiveness. For example, if the grid voltage suddenly drops due to an outage, the device must detect it without delay. Similarly, frequency fluctuations can indicate public grid instability. The ability to react to these abnormal variations is what makes it indispensable.

Automatic Interruption of Energy Injection

When an anomaly is confirmed, the device triggers immediate action: it interrupts the injection of energy produced by the solar installation into the public grid. This disconnection is automatic and aims to prevent several risks. It protects personnel who might be working on the grid without knowing that the solar installation is still injecting current. It also prevents the installation’s energy from being injected into an unstable grid, which could worsen the situation or damage equipment. This is a fundamental safety measure for the protection of people and property.

Response to Voltage and Frequency Variations

The device is configured to react to specific voltage and frequency thresholds, defined by current standards. These thresholds may vary slightly depending on local regulations and grid operators. For example, the NF EN 50549 standard specifies the acceptable voltage and frequency ranges for connection. If the voltage falls outside this range, or if the frequency deviates beyond permitted limits, the disconnection device activates. It is important to ensure that the chosen device complies with these requirements for optimal safety.

Here is a table illustrating typical trigger thresholds:

Parameter	Trigger Threshold (Example)
Voltage	< 0.85 Un or > 1.15 Un
Frequency	< 49.8 Hz or > 50.2 Hz

These values are indicative and must be verified according to the grid operator’s specifications and the applicable standard. The selection of appropriate semiconductors is also important for the performance of these devices.

The proper functioning of the disconnection device relies on constant monitoring and rapid reaction to deviations from normal grid conditions. This responsiveness is paramount for collective safety and the stability of the electricity grid.

Importance of Compliance with Current Standards

Compliance with current standards is an essential step to guarantee the safety and reliability of any photovoltaic installation. These regulations evolve to adapt to new technologies and the stability requirements of the electricity grid.

Evolution of European and French Regulations

Regulatory frameworks, at both European and national levels, are constantly adapting. They aim to harmonise the rules for connecting electricity generation installations to ensure grid safety and stability. It is therefore essential to stay informed of the latest updates to remain compliant.

Application of Standard NF EN 50549

As of 1st January 2025, standard NF EN 50549 will become the technical reference for automatic disconnection devices. This standard, which is part of the European network code, defines the voltage and frequency thresholds to which the system must react. It replaces older directives, such as DIN VDE 0126, which was in force until the end of 2024. Compliance with this standard is mandatory for all grid-connected installations, whether low or high voltage. Ensuring your equipment meets these specifications is a guarantee of safety and proper functioning. For a successful installation, it is advisable to consult relevant technical documents, such as those provided by organisations like Enedis, which offer detailed guides for connecting installations.

Consulting Grid Operator Documentation

Each distribution grid operator has its own specific technical requirements. It is therefore highly recommended to consult their official documentation. These documents provide precise information on connection procedures, required compliance tests, and technical specifications for protection devices. A good understanding of these local directives is essential to avoid any problems during installation and commissioning. For example, the validation of certain processes by labels such as the C2P green list can simplify administrative procedures and certify the technical compliance of your installation.

Compliance with standards is not only a legal obligation but also a guarantee of quality and durability for your photovoltaic installation. It contributes to the safety of all personnel and the stability of the public electricity grid.

Types of Photovoltaic Disconnection Relays

There are several types of disconnection relays, each adapted to specific installation configurations. The choice will depend on the size of your system, its voltage, and the potential presence of a battery storage system.

Integrated Protection in Low-Voltage Inverters

For small and medium-sized solar installations, often low-voltage, the disconnection function is frequently integrated directly into the inverter. This approach simplifies installation and reduces the number of external components required. These devices are designed to meet safety and grid connection standards, as stipulated by NF EN 50549. They detect variations in grid voltage and frequency and cut off energy injection in the event of an anomaly.

External Devices for High-Voltage Installations

Larger-scale photovoltaic installations, particularly those connected to the grid at high voltage, require external disconnection devices. These pieces of equipment are more robust and designed to handle higher power outputs. They act as an additional safety barrier, ensuring a rapid and reliable disconnection from the public grid in case of a problem. The selection of these devices must be made in close collaboration with the grid operator to ensure full compliance.

Specific Solutions for Battery Coupling

When your photovoltaic installation includes a battery storage system, the disconnection relay must be capable of managing this complexity. It must not only provide protection against grid faults but also manage the interaction between the solar installation, the battery, and the grid. Specific relays or advanced energy management systems are often required to coordinate these different elements and ensure optimal safety, even in the event of temporary islanding operation. The objective is to maintain system stability and prevent any risks during transitions between operating modes. For example, the Enphase Q Relay is a solution designed for systems with micro-inverters.

Selecting the Disconnection Relay According to Installation Size

The choice of a disconnection relay heavily depends on the power and configuration of your photovoltaic installation. It is important to correctly size this equipment to ensure safety and compliance.

Criteria for Low-Power Systems

For small residential installations, often single-phase and with a power output below a certain threshold (e.g., 250 kVA), the disconnection function is frequently integrated directly into the inverter. This simplifies installation and reduces the number of components. Nevertheless, it is essential to ensure that the chosen inverter complies with current standards, such as the future application of NF EN 50549. The inverter’s technical documentation must be consulted to confirm this functionality and its precise specifications. A good understanding of the technical characteristics is paramount here.

Requirements for Large-Scale Installations

Larger installations, particularly those connected to high voltage (HTA) or exceeding a certain power threshold, require a dedicated external disconnection device. This type of equipment is designed to handle higher currents and offers more robust protection. It is imperative that this external relay complies with the specific standards applicable to public distribution networks. Consulting the requirements of grid operators, such as Enedis, is a key step in selecting the appropriate equipment. These more complex systems can benefit from specific relays, such as the Enphase Q Relay, which manages the physical disconnection of the solar installation from the electricity grid, ensuring a rapid cut-off in the event of an anomaly.

Adaptation to Single-Phase Systems

For single-phase systems, whether low or medium power, the disconnection relay must be compatible with this type of configuration. It is essential to check the maximum electrical power the device can handle to avoid nuisance tripping due to voltage or frequency variations. Using specialised tools or consulting technical guides can help choose the appropriate electrical power. For example, for a single-phase system, it is necessary to ensure that the relay can handle the nominal current and the expected short-circuit current. Compliance with the VDE standard is often a requirement for these devices.

The choice of disconnection relay must always be based on a precise analysis of the installation size, its electrical configuration (single-phase or three-phase), and local regulatory requirements. Appropriate selection guarantees the safety of personnel and the longevity of the installation, while ensuring compliance with connection obligations.

Here is a summary table of considerations by size:

Installation Size	Recommended Relay Type	Major Points of Attention
Low power (residential)	Integrated into the inverter	Verification of inverter compliance
Medium/Large power (commercial, industrial)	External, dedicated	Compliance with HTA standards, nominal power, short-circuit current
Single-phase systems	Adapted for single-phase	Voltage/frequency compatibility, maximum power handled

Advantages of Integrating a Disconnection Device

Adding an automatic disconnection device to your electrical installation, whether solar or not, brings several notable benefits. It is first and foremost a safety measure that protects people working on the public grid. In the event of an outage or problem on the electricity grid, this system immediately cuts off the energy injection from your installation. This prevents the risk of electrocution, an absolutely vital point.

Beyond personal safety, the device contributes to the overall stability of the grid. It prevents your energy production, even if it is functioning perfectly, from disturbing an already unstable grid. It’s a bit like avoiding throwing water on an already too large fire. This function helps prevent broader problems and maintain a more reliable electricity supply for everyone.

Furthermore, integrating this type of protection greatly simplifies administrative and connection procedures. By complying with current standards, such as the future NF EN 50549 standard, you ensure that your installation is in order. This facilitates relations with grid operators and avoids future complications.

Here are the main advantages summarised:

• Increased safety for technicians working on the grid.
• Improved grid stability by preventing energy injection during disturbances.
• Facilitated regulatory compliance, particularly with European and national standards.
• Overall reliability of your own installation, protecting it from grid overvoltages or undervoltages.

Adopting a disconnection device is not only a regulatory obligation but also a guarantee of safety and proper functioning for the entire electrical system, including your own installation.

Installation and Maintenance of the Disconnection Device

Correct installation and regular maintenance are absolutely necessary for your disconnection device to function as it should. It’s not the kind of thing you can neglect, otherwise it can cause problems.

Importance of Expert Implementation

It is really important that the installation is carried out by someone who knows what they are doing. A bad connection, and presto, it no longer works or, worse, it creates safety problems. For small installations, the function is often already in the inverter, which simplifies things a bit. But for larger installations, especially high voltage ones, external equipment is required, and there, it is really necessary to ensure that everything is done according to best practice. Guides for installing a grid disconnection device can be found, and it’s always a good idea to take a look.

Regular Tests to Ensure Proper Functioning

It is necessary to check from time to time that the device reacts correctly. For example, if there is a variation in voltage or frequency, it must cut off the energy injection. These tests are essential to ensure that the protection is always effective. It’s a bit like checking that smoke detectors work; you never know when you’ll need them. The technical documentation of grid operators, such as Enedis, often provides indications on the tests to be carried out.

Periodic Maintenance to Anticipate Risks

Regular maintenance helps avoid unpleasant surprises. You need to check the general condition of the equipment, ensuring there is no corrosion or visible damage. This helps prevent breakdowns and extends the lifespan of the installation. Remember to integrate these checks into your usual maintenance schedule. For an idea of best practices, the photovoltaic forum can be a useful source of information.

Modern Technologies for Optimised Management

The field of disconnection relays is evolving rapidly, with advancements that make managing your solar installation smarter and safer. We are seeing more and more micro-inverters, such as those in the Enphase range, which directly integrate advanced disconnection functions. These systems don’t just cut off injection in the event of a grid problem; they also offer real-time monitoring. This means you can track your system’s performance and anticipate issues before they become major. It’s a bit like having a technician monitoring your installation 24/7.

For more complex installations or those incorporating batteries, specific disconnection relays exist. These devices are designed to manage more nuanced situations, such as voltage or frequency variations, and to ensure a smooth transition during changes in grid status. The use of automatic reclosing devices can also improve the flexibility and automation of the entire system. These technologies aim to make your installation more reactive and autonomous.

The integration of these modern technologies is not limited to safety; it also contributes to the overall optimisation of your photovoltaic system’s energy performance. Good proactive management helps minimise losses and ensure more stable energy production.

Here are some key points to consider with these new technologies:

• Real-time monitoring: Allows tracking of production and installation status remotely.
• Proactive management: Helps identify and resolve potential problems before they affect production.
• Simplified integration: Solutions integrated into micro-inverters facilitate installation and reduce the number of components.

It is important to stay informed about the latest innovations to choose the most suitable solution for your project. Consulting resources such as specialised forums can help you understand other users’ experiences and make informed choices for your solar installation.

Anticipating Your Installation’s Specific Needs

Each solar project has unique characteristics that influence the choice of disconnection device. It is therefore important to thoroughly analyse these specific features before making your selection. This will allow you to avoid future problems and ensure the optimal performance of your system.

Considering Local Specificities

Environmental conditions and the specific characteristics of the local electricity grid can impact the operation of your photovoltaic installation. For example, in areas prone to frequent voltage or frequency variations, a more sensitive disconnection device might be necessary to react quickly to anomalies. It is also relevant to inquire about the specific requirements of your regional grid operator, as these can vary. A good understanding of the local conditions and rules is the first step towards a successful installation.

Choosing the Appropriate Electrical Power

The power of your installation is a determining factor for the type of disconnection relay to choose. For low-power systems, often single-phase, protection is generally integrated directly into the inverter. However, for larger-scale installations, particularly those exceeding a certain capacity, a more robust and specific external disconnection device will be required. It is necessary to ensure that the nominal power of the relay is significantly higher than the maximum power your installation can produce, to avoid nuisance tripping. For example, for a 4,500 Wp installation, approximately 12 panels would be needed if each panel is 375 Wp.

Guidance from Specialised Tools

To assist you in this process, there are tools and resources available that can simplify the selection process. Online simulators or technical guides can help you assess the necessary power and identify equipment compatible with your configuration. Consulting manufacturers’ technical documentation and professional installers’ recommendations is also a preferred approach. Do not hesitate to use power comparators to find the most suitable equipment for your specific needs. Connection costs, for example, can range from 0 to €1000 (incl. VAT) for installations under 18 kVA, an element to consider in your overall budget.

It is essential to thoroughly understand the specifics of your project to choose the right equipment. An in-depth analysis of local needs, a precise evaluation of the required power, and the use of decision-making tools will guide you towards the most appropriate solution. This will guarantee not only the safety of your installation but also its long-term performance.

Further Resources and Recommended Equipment

To successfully complete your solar installation project and ensure the safety of your system, it is important to rely on reliable resources and certified equipment. Choosing the right components from the outset will save you a lot of hassle later on.

Certified Devices for a Secure Purchase

When purchasing a disconnection relay or any other equipment for your photovoltaic installation, always prioritise products that carry recognised certifications. These certifications attest that the equipment has been tested and meets current safety and performance standards. This gives you assurance regarding the device’s reliability and its compliance with local regulations. For example, brands like Schneider Electric offer integrated solutions that simplify installation while complying with standards, such as the RESI9 Energy Center enclosure for single-phase installations up to 9kWp. It is always good to consult the catalogues of reputable manufacturers to find products adapted to your specific needs.

Technical Information for Equipment Selection

Before making your choice, take the time to consult the manufacturers’ technical documentation. These documents provide precise details on the characteristics of each disconnection relay: operating voltage and frequency range, response time, breaking capacity, etc. Understanding these specifications will help you select the most appropriate device for your installation. It is also advisable to refer to the requirements of grid operators, such as Enedis, as they may have specific connection specifications. A good understanding of the technical requirements is paramount.

Consulting Specialised Forums

Online forums dedicated to photovoltaics are a wealth of valuable information. You will find feedback from other installers and users, practical advice, and discussions on the latest innovations. It’s an excellent place to ask your questions, get opinions on specific products, and stay informed about regulatory or technological developments. Feel free to share your own experiences to contribute to the community. You might find discussions there on topics such as energy injection management or best installation practices.

To go further and find useful information, take a look at our resources. You’ll find plenty of clear explanations about the world of solar energy there. Curious to learn more about photovoltaics? Visit our website to discover all our advice!

In Brief: Safety and Reliability Above All

In conclusion, the automatic disconnection device stands out as a truly important component for any solar installation. Its primary function, which is to disconnect the installation from the grid in case of a problem, protects both equipment and personnel working on the grid. This is a safety measure that should not be overlooked, especially with the evolution of standards like NF EN 50549. Choosing the right equipment, whether integrated into the inverter or external for larger installations, is a key step to ensure compliance and peace of mind. In short, thoroughly understanding and correctly installing this device ensures safer and more reliable solar energy production in the long term.

Frequently Asked Questions

What is a disconnection relay in a solar installation?

It is a safety device that automatically disconnects your solar installation from the public electricity grid if it encounters a problem, such as an outage. This prevents your installation from continuing to send electricity to a grid that doesn’t have it, which is dangerous for people trying to repair it.

Why is this relay so important for solar panels?

It is very important because it prevents serious accidents, such as electrocutions, for technicians working on the grid in the event of a breakdown. It also protects your own equipment against overvoltages or undervoltages that could occur.

How does the relay act when the electricity grid has a problem?

When the relay detects that the grid’s voltage or frequency is no longer normal, it immediately cuts the connection between your solar installation and the grid. Thus, your installation stops injecting electricity.

What is the difference between integrated and external protection?

For small installations, protection is often already in the inverter. For larger or high-voltage installations, a separate protection device must be added, as this is mandatory for safety reasons.

What rules must be followed in France for these relays?

In France, there are standards to be followed. Previously, it was the DIN VDE 0126 standard. Now, from 2025, it is the NF EN 50549 standard, which is aligned with European rules. These standards explain how the relay must react.

What are the main criteria that cause the relay to trip?

The relay trips mainly when it measures that the grid voltage is too low or too high, or when the current frequency is not stable. These are signs that the public grid has a problem.

Does this relay help my solar panels function better?

Yes, by ensuring a stable and secure connection with the grid, it contributes to the overall reliability of your solar installation. This can also help optimise how electricity is managed.

How do I choose the right relay for my installation?

You need to consider the power of your installation. For small ones, an inverter with integrated protection is often sufficient. For larger ones, an external device adapted to the standards is required. It is advisable to seek professional advice.