Popularity of Solar Energy Systems

Nowadays, solar panel become more and more popular as an alternative or even primary source of household energy. In the last few years, various researches focus on how to improve Photovoltaic (PV) Solar Panel efficiency, reliability, and even availability during all seasons or even at night. Moreover, because installation of photovoltaic solar system is in outdoor it shall also endure outer severe weather condition, animal intervention, and also electrical events such as surge and lightning.

Solar power is becoming the go-to option for people across the world to meet their energy needs.

Understanding Of DC SPD For Solar

A DC surge protection device prevents power surge in solar PV systems. 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.

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

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.

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.

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.

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.

Even the slightest voltage spike can damage every electronic device drawing power from a solar panel array if it has no surge protection. This is aside from the fact that any energy-saving investment you make would be rendered useless without lightning protection since lightning is one of the main reasons solar panels malfunction.

What Happens When Lightning Strikes a Solar PV System?

Lightning poses significant risks of complete or partial destruction to solar farms either immediately from a direct strike or results in degenerative damage from an indirect strike.

Overvoltages can impact a solar panel system installation in different ways:

- From direct strikes to the external lightning protection system of a structure, near it, and even to the PV installation itself
- From lightning-induced currents distributed into the electrical network
- From overvoltages transmitted from the electrical network of atmospheric origin (lightning) and/or due to operations
- From variations of the electric field due to lightning
- From the grid, if lightning hits medium or low voltage conductors
- From the earth, if lightning hits close to the PV’s inverter
- From the DC side, if lightning hits the PV modules

When lightning strikes a solar panel array, it causes an induced transient current within the system’s wire loops that lead to the failure of the insulation, panels, inverter, and communication equipment. Other components within the solar power system, such as the combiner box and MPPT (maximum power point tracker device), have the highest chances of failure.

Some solar PV systems might withstand physical or circuit damage to their panels; however, their circuit controls and energy storage devices will be instantly unusable after a lightning strike.

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 to Protect the Solar System with the DC SPD?

DC surge protector solar protect the circuit control and energy storage devices by limiting the surge and send it to the ground. A lightning strike on a solar panel array causes induced transient currents in the system’s cable loops, damaging insulators, panels, inverters, and communication equipment. Other electronic components in the photovoltaic system, such as the combiner box and MPPT (Maximum Power Point Tracker Device) are the most likely to fail. DC surge protective device provide surge protection by limiting the amplitude of the overvoltage and divert the current wave to the earth. This DC surge arrester shall be installed not only in DC component but also in AC component. The overall number of DC SPD for solar PV system depends on the distance between the modules and the inverter, and also the number of inverter and DC line.

How To Choose The Right DC SPD For Solar?

Flash Density:

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. 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.

How Many Surge Protectors Do You Need in a Solar Farm?

A surge protection network should be installed throughout a solar power system’s DC and AC power distribution network to safeguard critical circuits. The overall number of SPDs needed in a solar PV system varies depending on the distance between panels and inverter.

We recommend the installation of SPDs on DC inputs and AC outputs of a solar PV system’s inverters while grounding both positive and negative DC lines. Combiner circuits, control circuits, monitoring systems, and tracking systems must also be protected to prevent electrical interference and data loss.

- In AC lines, surge protection should be deployed on each power conductor to the ground.
- If the cable length between solar panels is under 10 meters, 1 SPD should be installed by the inverter, combiner boxes, or closer to the solar panels.
- In installations with DC cabling over 10 meters, more surge protectors will be needed at both the inverter and solar modules end of the cables.
- In a residential solar power system with microinverters that has short DC cabling but longer AC cables, SPDs should be installed at the combiner box to protect the home from transient 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.

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.

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.

Does a solar farm need a lightning protection system?

Surge protection is a necessary component in any electrical installation, but by no means does it replace a proper lightning protection solution.

If you want to protect your investment, surge protection is not an option, it is a necessity, but if you want total protection and peace of mind, a lightning protection system can make the difference between the success and failure of large-scale solar power installations.

A lightning protection system not only protects the solar PV system but also provides reliable protection to your entire property and assets while safely diverting transient currents to the ground.

A simplified way to look at lightning protection vs surge protection is to view surge protection as the second line of defence against indirect lightning strikes.

In contrast, a complete lightning protection system that includes air terminals (lightning rods), down conductors, surge protectors, equipotential bonding, and an earthing system is the first line of defence against a direct lightning strike.

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.