The faculties like easy installation and maintenance, accessibility, connectivity to grid, the longevity, and so forth have been making the solar PV technology more and more adaptable. And, financial assistance and friendly solar schemes accelerate this technology to become easily accessible to the majority of people, especially in India. India shows good insolation or average full sun hours per year. So it has got an auspicious opportunity to utilize the sun’s energy for electrical power. But that is not enough because there is another thing that makes this technology this reliable and accessible. And, that is all about safety.
Safety and Protection-
Safety is the foremost point of concern whenever you go for any electrical or electronics system. With poor safety electrical or electronics systems, precarious and dangerous situations come. A solar PV system may come to face some kinds of uninvited faults, indeed. So Protection should be provided to protect the solar systems from unwelcomed events, such as overload, short circuit, sky lighting, ground fault, frequency fault, etc. With smart protection devices, it becomes rather easy for customers to go solar. These devices are becoming smarter and cheaper with time. That cannot only render a healthier solar plant but also save maintenance costs.
What do protective devices do?
Two levels of protection play their roles in a solar PV system – primary and backup protection. The operation of primary protective devices is to trip down involved all circuit breakers to get rid of faulty conditions. The backup protection comes into the picture when the primary protection gets out of order or fails.
Hazardous Scenarios for a Solar PV Plant and Preventions:
1. Overloading/ Short Circuit
Safety is the foremost point of concern whenever you go for any electrical or electronics system. With poor safety electrical or electronics systems, precarious and dangerous situations come. A solar PV system may come to face some kinds of uninvited faults, indeed. So Protection should be provided to protect the solar systems from unwelcomed events, such as overload, short circuit, sky lighting, ground fault, frequency fault, etc. With smart protection devices, it becomes rather easy for customers to go solar. These devices are becoming smarter and cheaper with time. That cannot only render a healthier solar plant but also save maintenance costs.
Prevention from Overloading-
Overload relays, fuses, and MCBs are taken as shielding devices from overloading conditions. And, an over-current relay is used for getting rid of an overcurrent condition. But MCBs work in both situations. A miniature circuit breaker (MCB) is a guard system for all connected pieces of equipment, wirings, and appliances from over current.
This protection device can be used on both sides DC and AC based on requirements. Many times we use a fuse panel between panels and inverter. When current steeps beyond the limit of the miniature circuit breaker, then Molded Case Circuit Breakers (MCCBs) takes charge.
They ensure a strong shielding against overload and short circuit current of higher value. These are employed where a large capacity of solar PV plants is installed. These protection devices have a very high current rating and breaking capacity. That is why they are applied in the industrial sector very frequently. On the other hand, MCBs are the first choice for domestic solar PV systems.
2. Sky Lightning
Sky lighting is the discharge of static electricity that occurs through the thunder clouds. The structures for the solar plants are built with the help of various metallic components made up of galvanized iron, steel, and aluminum. Most of the parts of metallization is disclosed to the atmosphere that can be susceptible to strikes of sky lightning. That could be detrimental for panels. Efficient and necessary protections are required in such cases.
Prevention from Sky Lightning-
Protection from sky lightning is handled by lightning arresters and SPDs. In a solar plant, more than one lightning arrester may be required. They capture the lightning and give a path towards the earth by using a poor resistive cable. Earth has zero potential. One end of the arrester is grounded at 3 to 4 meters of depth from the earth’s surface.
This depth may vary from location to location.
To make the earth are low resistive GEMs are used. GEM stands for ground enhancement material. These materials create moisture at 3 to 4 meters of depth to enhance the conductivity of that area.
Sky lighting can strike in two ways directly and indirectly. For direct capture, arresters are employed.
If it strikes your solar plants indirectly or side flash, then surge protection devices (SPDs) deal with that. More than two SPDs can be used as per the requirement of the plant. These devices are the most important to implant in every solar PV system.
There are three types of SPD available for solar photovoltaic power systems – Type 1, Type 2, and Type 3. These have different usages. Type 2 SPD is the most frequently used device.
3. Current Leakage
When a current flows through a line, then phase and neutral terminals have the equal value of that current. But sometimes neutral terminal does not have the same value of current as the live terminal has. This deficiency of current leads to leakage current.
In the rainy and wet weather, it is likely to see the problem of current leakage through the metallization of panels.
The issue with a large scale of current leakage is that invitation for unexpected accidents or electric shocks to those, who come in contact directly with the apparatus.
Prevention from Current Leakage –
For effective protection from leakage current, grounding is provided. Grounding renders two functions. One is protection from leakage current and another is entire system safety.
Grounding of any PV system is crucial because it prevents you from electric shock due to leakage of electric current.
4. Ground Fault
Failure of insulation leads to ground fault. This fault may also occur due to physical damage of wires and underground cables, and water flows in the cables.
Prevention from Ground Fault –
A ground fault is detected by the current relay.
5. Frequency Fault in PV System
Frequency match is paramount for every grid-tie solar PV plant. If the frequency at the output of the inverter is not the same as the frequency of the grid, then exporting electricity to the grid cannot be done. But sometimes the frequency of the grid does vary that can cause frequency fault especially in the case of multi-inverters interfacing.
Prevention from Frequency Fault –
Frequency fault occurs from the grid side that is detected by frequency relay. If the frequency of the PV system varies beyond ±1% of the range of frequency of the grid, then frequency relay trips off. After that, resynchronization is needed to deal with.
6. Failure of Circuit Breakers
Circuit breakers are the primary protective devices. But in some hazardous situations, they may also break down or fail.
If you are someone who is curious to know how the solar PV system will be reliable when you will own it, this article is then for you.
You may have heard about some safeguarding systems like MCB, electrical grounding or earthing, and fuses.
But some of them you may not have heard of. These are MCCB, lightning rod, overcurrent relay, SPD, etc. These protection devices and systems have noteworthy importance and applications.
These devices cannot be ignored to employ. If they are ignored, then unfavorable accidents and losses can occur. They ensure the reliability of the system.
Have a glance through it, and you will find all that you need to know about protection systems and their magnificent roles in protecting you and your solar power plant.