# Calculation example: lightning protection and grounding of solar electric power plant (panels)

July 24, 2017

Like any other power generation facilities, solar power plants need grounding and lightning protection systems. The ZANDZ Technical Center has received a request to design such a system. Let's study what solution was proposed by our specialists for solar (photoelectric) station in a region in Russia.

Initial data:

1. The soil resistivity in the solar power plant location is 60 Ohm*m.

2. Dimensions and arrangement of PES are shown in Figs. 1 and 2.

Figure 1. Dimensions.

Фотоэлектрический модуль - Photoelectric module
Отражатель - Reflector
Распределительный щит - Distribution panel

Figure 2. PES layout.

# How to make lightning protection and grounding for a solar power plant?

Protection of the buildings and structures against lightning strikes is provided by using lightning arrester. Lightning arrester is a device that is elevated over the protected facility through which the lightning current goes into the ground bypassing the protected facility. It consists of a lightning rod that directly accepts the discharge of a lightning , a current collector, and a grounding electrode.

A set of arrangements ensuring compliance with the lightning protection requirements is based on the following solutions:

2. The facility is classified as Category III in terms of lightning protection. The required system's reliability is 0.9..

3. The lightning protection for the solar power plant is made using 4 x 6 m lightning arresters installed on the concrete foundation. The embedded parts for the foundation are included in the lightning rod set.

4. For grounding of solar panels, 3 m vertical electrodes are used from each lightning rod. The lightning rods are interconnected using steel copper-plated bar GL-11075 with the cross-section of 30 x 4 mm along the PES contour. The distance to the solar panels is at least 1 m. Depth is 0.5 to 0.7 m. Strips and electrodes are connected using clamps ZZ-005-064.

Results of the calculations performed by using the software developed by OJSC Krzhizhanovsky Energy Institute (OJSC ENIN):

Intensity of lightning discharge into the ground is 6 strikes/square km/year;

The total number of strikes into the system is 0.019 (once every 52 years);

The total number of breakouts into the system is 0.00087 (once every 1,149 years);

The system's reliability is 0.954;

The probability of breakout into all facilities of the system is 0.046.

Ground terminal resistance calculation:

М - M
Верт - Vert
Ом - Ohm
Гор - Hor
ЗУ - GA

The estimate resistance of the grounding arrangement is 1,41 Ohm..

Figure 3 shows equipment layout.

Рисунок 3 - Расположение оборудования.

Условные обозначения - Legend
- Молниеприемник-мачта с закладными под фундамент (6 метров)- Lightning mast with embedded parts for the foundation (6 meters)
- Зажим для соединения проводников - Clamp for connecting conductors
- Вертикальный заземлитель длиной 3 м - 3 m vertical grounding electrode

Figure 3 - Equipment layout.

The list of necessary materials is given in Table 1.

 № Fig. Part number Name q-ty, pcs 1. ZZ-201-006 ZANDZ 6 m vertical lightning rod (galvanized steel; with parts embedded under the foundation) 4 2. ZZ-001-065 ZANDZ Copper-plated threaded grounding rod (D14; 1.5 m) 8 3. ZZ-002-061 ZANDZ Threaded connecting coupling 5 4. ZZ-003-061 ZANDZ Takeoff Tip 4 5. ZZ-004-060 ZANDZ Guide head for jackhammer attachment 2 6. ZZ-005-064 ZANDZ Conductor connection clamp (up to 40 mm) 50 7. ZZ-006-000 ZANDZ Conductive grease 1 8. ZZ-007-030 ZANDZ Waterproofing tape 13 9. ZZ-008-000 ZANDZ Attachment to the jackhammer (SDS max) 1 10. GL-11075-50 GALMAR Copper-plated strip (30 * 4 mm / S 120 mm²; 50-meter strip bundle) 5

Our solution will provide a reliable protection for a solar power plant against direct lightning strike and high-quality grounding of the installation having resistance of 1.41 Ohm with the shown initial data.

Do you want to know more about lightning protection and grounding of the alternative power generation facilities? Please, contact the ZANDZ Technical Center!