Different types of solar surge protection devices are available to protect solar power systems from overvoltage. These are used at different points in the system, both up and downstream of the PV array.
In this article, the types of surge protection devices that installers and solar system owners can use are described. These are based on the location in the system where they are installed.
Surge Protection Device Meaning
An SPD, surge protection device, is an electrical product that is installed in a power system to protect it from voltage surges. Voltage surges are also known as transient voltages and can occur in any type of PV system.
It can be a surge protection device for home electrical systems or a protection device for large-scale solar power plants and other commercial or industrial applications.
Overvoltage protection devices work by diverting or dissipating the excess energy from a voltage surge so that it does not damage the equipment in the system. They are designed to operate within a certain voltage range, and will not work if the voltage exceeds this range.
SPDs can also be used to protect both AC and DC circuits. A DC surge protection device is commonly used in PV systems to protect against lightning strikes, but can also be used to protect against other sources of overvoltage. AC SPD types are also used- on the AC side.
Types of Solar Surge Protection Devices
Because different solar power circuits require different surge protection levels, there is no single surge device that is right for every system. So electricians use different types of surge protectors in the same installation. The types of surge protectors installed depend on the application and the specific needs of the system being protected.
According to the IEC/EN 61643-11 standard on surge protection, there are 3 main types of solar surge protection devices: type 1, type 2, and type 3. Each type of SPD is designed for a specific location in the system and offers different levels of overvoltage protection, as described below.
Type 1 SPD
The type 1 SPD is designed to be installed at the solar panels or at the point where the utility grid is connected to the system, upstream of the inverter. This type of surge protector device is used to protect against voltage surges that come from direct lightning strikes.
Because type 1 surge protection devices are designed for installation at the service entrance, they offer protection from external surges rather than from within the system. They are also typically used in combination with other protection devices, such as fuses or circuit breakers.
Type 1 SPDs are the most effective type of SPD in solar installations. They are usually required for the protection of systems that are located in areas with a high risk of lightning strikes. The surge protection device type 1 has the following characteristics:
- High discharge current capacity
- Current Waveform: 10/350 μs
Type 2 SPD
The type 2 SPD is designed to be installed at the inverter circuit, downstream of the solar panels. This type of surge protector device is used to protect against voltage surges that come from indirect lightning strikes.
Type 2 SPDs are less expensive than type 1 SPDs and will also usually have a lower rating when compared to type 1 SPDs, both in terms of voltage and protection level. The type 2 surge protection device for solar has the following characteristics:
- Medium discharge current capacity
- Current Waveform: 8/20 μs
Type 3 SPD
The type 3 SPD is designed to be installed downstream of the inverter, and near sensitive loads. These types of solar surge protection devices are used where types 1 and 2 types are already installed
Type 3 solar charge devices are, therefore, usually a supplement to type 2 SPD. That means type 2 protectors must be installed before them to dissipate the higher energy surges. A surge protection device type 3 for solar installations will have the following characteristics.
- Low discharge current capacity
- Current waveform: 1.5/50 μs and 8/20 μs
Type 1 vs. Type 2 SPD
While both type 1 and type 2 SPD devices are effective at protecting against voltage surges, there are some key differences between them. These are summarized below.
- Starting with their location within the system, type 1 SPD is installed at the solar panels or utility grid connection, while type 2 SPD is installed at the inverter.
- Because of this difference in location, type 1 SPDs offer protection against direct lightning strikes while type 2 SPDs offer protection against indirect lightning strikes.
- Type 1 SPDs also have a higher discharge current capacity than type 2 SPDs. This means that they can safely divert more surge current away from the system.
- In terms of the current waveform, type 1 SPDs are designed to protect against surges with a 10/350 μs waveform while type 2 SPDs are designed to protect against 8/20 μs waveforms.
- Finally, type 1 SPD is typically more expensive than type 2 SPDs. This is because they offer a higher level of protection and can safely divert more surge current away from the system.
So, when deciding which type of SPD to use in a solar installation, it is important to consider the location of the system, and the level of protection required. Each type of protection device has its best application based on its location and protection level.
Different types of solar surge protection devices can be used in different parts of the system to offer different levels of protection. Type 1 SPDs are typically used where they can protect against direct lightning strikes.
Type 2 SPDs are installed to protect against indirect lightning strikes and are usually used together with type one protectors. Type 3 SPD is usually used close to the load, and usually as additional protection after the type 2 SPD.