A Full Guide To DC Surge Protection Devices (SPD) For Solar

As a DC surge protector specialist, I have discussed how to choose the right DC SPD for solar. And the importance of DC SPD for solar, their phase connections, protection modes, and many more. Read till the end to find out.

 

Understanding Of DC SPD For Solar

A DC surge protection device prevents power surge in solar PV systems. It redirects the current from the system’s component and prevents it from getting damaged. However, to be more precise, the DC SPD contains a metal oxide varistor.

So, when a surge occurs in the circuit, the metal oxide varistor absorbs the extra voltage and lets the current flow through it. As the metal oxide varistor has high resistance, the circuit doesn’t get harmed by the flow of current.

Instead, it reverts to normal functioning when the surge has passed. Furthermore, the process is done in nanoseconds only so that there is no risk of a surge in the system.

Understanding Of DC SPD For Solar

Understanding Of DC SPD For Solar

 

Why do Solar Systems Need DC Surge Protection Devices (SPD)?

  • Safety

The voltage surge can occur for multiple reasons, such as lightning or internal changes in voltage use. So, as solar PV systems are susceptible to damage, voltage surges destroy the solar power’s photovoltaic (PV) system components.

This voltage surge also creates burning holes in the PV panels and degrades inverters. So, a DC surge protection device can prevent the current from overflowing into the circuit and save these components from getting damaged.

  • System Performance

When a power surge occurs, it stops the system from running at its optimal level. Sometimes, it also ruins the PV system components badly. So, when you install a solar surge protector on the PV system, it helps the system run smoothly without sudden surges. As a consequence, the system delivers a better and more consistent performance.

  • Lifespan

Sudden power surges lead the PV system components to degrade with time. It gradually reduces the life expectancy of the solar power system. So, a surge protection device will ensure the well-being of these components. Additionally, this device will increase the life expectancy of the solar power system for a longer period.

  • Saving

As lightning strikes the solar power PV system, it can severely damage inverters, controllers, or panels. Repairing these damages can often make you pay for more than the investment in the long term. Sometimes, you might need to replace these components, which is quite expensive.

So, a DC SPD will make sure you don’t spend extra money and will help you to save more in the long term. Therefore, investing in the DC SPD is really worth it.

How To Choose The Right DC SPD For Solar?

  • Type

There are three types of DC SPD available for solar. So, you need to choose the DC surge protection device based on your needs.

Types

Use Application

Type 1

The type 1 surge is designed to handle direct lightning strikes. This device is installed at the primary inlet of the power supply. Additionally, it protects a wide area. However, this device saves the solar power’s PV system from only external surges.

You can install them for areas where there is a high chance of lightning strikes.
Type 2 The type 2 DC SPD device is installed at the junction box. This device helps protect solar power’s PV system from indirect lightning. To be precise, sometimes, lightning strikes through a ground current. So, it can travel to the solar panel’s PV system circuits and damage the components.

Best to install in solar power plants that are mounted inside households or buildings.

Type 3

The type 3 device is installed downstream of the inverter. This device can handle both direct and indirect lightning. So, basically, it is a combination of type 1 and type 2. Furthermore, it is installed as a supplement to type 2 DC SPD in case of sensitive loads. You can install type 3 DC SPD for industrial environments where solar power plants are installed.

Check our top-grade DC surge protection devices to boost your solar PV system’s productivity

The lightning flash density is the number of lightning strikes to the ground per square kilometer. It is measured on the basis of a year. This flash density helps you to know how much lightning is occurring in a particular area. So, you can choose a DC SPD based on how many flashes it can take on average.

For example, you can choose type 1 DC SPD if lightning is occurring too much in a particular area, as this device is specially designed to save components from lightning strikes.

  • System Operating Temperature

The system operating temperature is the operating limit of the device at which the physical component might fail. So, you should know the system operating temperature of the DC SPD you will choose. For example, a type 3 DC SPD can run ranging from -40/+85°C. A better system operating range will make sure that the DC SPD is running safely.

  • System Voltage

The system voltage is the maximum voltage rating at which the DC SPD will run. It means that if the current overflows more than the rated current, then the DC surge protection device might degrade. It can also cause permanent damage to the device. So, make sure that the DC SPD you choose has a high voltage rating.

DC SPD Phase Connections and Protection Modes

Specifications

 Protection

Applications
1P 1-phase protection line and the earth

Household appliances

1+ NPE

1-phase protection line, neutral, and the earth Industrial uses
3P 3-phase protection line and the earth

Industrial uses
3+ NPE 3-phase protection line, neutral, and the earth

Commercial uses

  • 1p

The 1P refers to the single-phase connection where the DC SPD will protect only one pin. Additionally, it will protect the earth connection, which is used for safety purposes. However, if you don’t know what the earth connection is, it is the connection of the electric power system with the ground. This earth connection directs the current to a space where accidents cannot occur.

  • 1+NPE

The 1+ NPE means that the device protects a single-phase connection. Additionally, it protects the connection between the neutral and the earth. However you have known about the earth connection, but what is the neutral connection? This neutral line provides a return path to balance the voltage in a circuit.

  • 3P

The 3P means that the device will protect a three-phase and an earth connection. Here, the three-phase connection transmits the extra voltage to the earth connection. Then, the Earth connection redirects the flow of electricity so that no surge happens.

  • 3+NPE

The 3+ NPE means that it contains a three-phase connection line, an earth connection, and a neutral line. Here, the phase line carries the current, and the neutral line redirects the current back to the panel. And lastly, the earth connection is used to save the solar power system from power surges.

 

What Are The Components Of DC SPD For Solar Power?

Various types of resistors prevent surge strikes on solar power plants. So, your DC SPD can contain any of these resistors. Here, I have written about their inner working and how they prevent power surges. Please check it out :

 

  • Metal Oxide Varistors

The metal oxide varistor is a type of resistor that helps electrical devices avoid over-voltage or power surges. This varistor is placed at the entrance of the circuit. This resistor ensures that extra voltage from the primary circuit can be transient easily.

However, its resistance changes based on the voltage. This means that if the voltage increases, the resistance will decrease. As a result, the current flow will be higher in the DC SPD circuit, which will help balance the voltage.

Metal Oxide Varistor

Metal Oxide Varistor

 

  • Gas Discharge Tubes

Gas Discharge Tubes (GDT) are lightning protection tubes. When this tube detects a rise in the voltage, it releases the inert gas, which forms a low resistance channel due to ionization. Further, it passes the current to the ground line. This way, the gas discharge tube avoids power surges in solar power plants.

Gas Discharge Tube

Gas Discharge Tube

 

  • Sensitive Resistors

There are some sensitive resistors, such as transient voltage suppressors (TVS). These voltage suppressors can act quickly to transient the voltage. At first, when the diodes of TVS detect voltage in the circuit, they convert into a low transition state. Then, they transmit the extra voltage to the ground. Sometimes, the extra voltage can also pass through the TVS diodes.

Sensitive Resistor

Sensitive Resistor

 

How Overvoltage Disrupts Solar Panel System?

  • Damage Solar Cells

The voltage overload in the circuit puts pressure on the solar cells. As a result, it starts overheating. It ultimately leads to the materials getting burnt out or damaging the cell. Sometimes, it can lead to irreparable damage to the solar cell. As a consequence, you might need to change the solar power plant completely.

  • Create a Fire Hazard

When the voltage gets overloaded, the materials start overheating. Sometimes, excessive overheating can lead the materials to explode. This will, as a result, create a huge fire hazard in solar power plants. Furthermore, as these power plants are interconnected with each other, it can ruin the whole solar power panel installation system. It can risk the lives of people as well.

  • Interrupt Power Supply

The voltage overloading prevents the circuit from delivering consistent performance. These regular surges gradually make the solar power plant incapable of functioning smoothly. As a result, the consumers receive reduced system performance from their end. So, if proper steps are not taken at the right time, it won’t take long for the whole system to get damaged.

 

How Many Surge Protection Devices Are Needed For Solar?

  • If the DC cable is less than 10 meters, then you should install one SPD at the solar modules.
  • If the DC cable is more than 10 meters, then you should install the first SPD at the inverter. Then, you can install a second SPD at the solar module.

 

Pre-Installation Tips Of DC SPD For Solar

  • You must make sure that the SPD you install has a higher voltage rating than the solar power plant’s expected voltage rating.
  • You should ensure that there is sufficient space in the DC SPD enclosure so that equipment can be installed properly and does not malfunction due to disruption in connections.
  • If you are going to install more than one DC SPD, make sure that the gap between these surge protection devices is manageable.

How To Install DC SPD For Solar?

Step 1: Connect The DC SPD To Solar System

First, you need to position the DC SPD at the place where there is a possibility of surge. The location can be at the inverter or solar modules based on the cable size. Once you have found the location, turn off the electrical connections of the solar panel’s PV system to reduce the risk of getting an electric shock while working on it.

Now, you need to take the cables from the solar power plant’s photovoltaic system’s modules and connect them to the DC SPD terminals. These terminals can contain single-phase pins to three-phase pins.

To make it more precise, if it’s a single-phase connection, you need to connect the positive marked cable to the positive terminal and the negative marked cable to the negative terminal.

The last cable marked PE will be connected to the earth line. Now, make sure that cables are connected to terminals properly so that there are no loose connections.

Step 2: Select Enclosure

First, select an enclosure where you can place the DC SPD. However, you can also customize the enclosure to place the equipment. Make sure that there are vents in the enclosure box so that heat can get out of the box.

Step 3: Attach The DC SPD

Place the DC SPD in the enclosure. Make sure the terminals are attached inside correctly. Furthermore, you can place these terminals backward down so that there is no dust accumulation in the connections.

Step 4: Route Cables

Now, you can route the PV module’s cables to the enclosure. Besides, you have to use cable clamps to secure the edge of the circuit so that it doesn’t get in contact with other components and create any potential hazard. Then, you can close the enclosure.

Step 5: Test The PV System

Now, you can run the PV system and check if the DC SPD is giving adequate protection from surges and if the solar power plant is performing well.

How To Maintain DC SPD For Solar?

Regular Check: You should regularly monitor the DC SPD and check for loose connections. If you find any loose connection, then secure it back tightly. Besides, check for dust accumulation on cables. Sometimes, dust accumulation can degrade wires and damage them ultimately.

Routine Replacement: When you check for the DC SPD, make sure that all components are fresh and intact. However, if you see any damage in the cable or component, then replace it immediately.

 

DC SPD Vs. AC SPD For Solar: The Differences

Specifications

DC SPD

AC SPD

Current Type

Direct current Alternating current

Connection

 Solar PV modules, junction boxes, or inverters Utility grid and load equipment
Voltage 1500 V

120V – 480V

Clamping Properties

Unidirectional voltage surges Bidirectional voltage surges
Applications Solar photovoltaic systems, battery storage systems, telecommunication infrastructure

Traditional power distribution systems, buildings, and facilities

Conclusion

If it’s for direct lightning, you can choose type 1. If it’s for indirect lighting, then you can choose type 2. But if there is a chance of both direct and indirect lighting strikes, then you can choose type 3.

However, LETOP is a  DC SPD manufacturer providing customers with DC surge protection devices with our 20 years of expertise. So, if your application needs a DC SPD, then contact us right away to get our premium service ready for you.

FAQs

1.  What is the maximum voltage of DC SPD for solar?

The maximum voltage of DC SPD for solar is 1000V. It means that the power can run at a maximum of 1000V in the circuit. In addition, the DC SPD voltage rating defines the maximum rate at which the device can run. If the device exceeds this rating, then the DC SPD will get damaged.

 

2. Which DC SPD for solar is better?

Various types of DC SPD are designed mainly for different applications. So, choosing DC SPD depends on the location of the application. However, type 1 DC SPD is generally better for solar as it is specially designed to handle direct lightning strikes.

 

3. Is DC SPD for solar expensive?

Yes. Usually, DC SPD for solar is a bit expensive, but it is worth it in the long term consideration. Additionally, you won’t have to spend unnecessary money on repairs if you go for it. However, it can cost $100-$300 on average to buy a DC SPD for solar.

 

4. How long does DC SPD last?

A DC SPD can last ranging from two years to five years on average. However, if you are regularly taking maintenance of the device, then it can last longer than five years.

 

5. What should the DC wire size of the solar cable be?

The wire size can be 4 mm, 6mm, or 10 mm, depending on the solar system you use. For example, if the DC SPD is for photovoltaic systems, then using a 4 mm solar cable is suitable. It helps to balance the current carrying capacity of the solar power plant. 

 

Beite X
Beite X

Hello guys! This is Beite X. I have 10 years of working experience in the electrical control field. I have participated in many world-renowned brand OEM projects, helping solve problems such as packaging, product advantages, differentiation and unique selling points, and promoting product success together. Hope my sharing can help you!