One,  grounding engineer description

50MWsolar-fishing complementary project grounding engineer:more hard surrounding terrain of the power station,water  in the fish pond is sea water, more serious  corrosion to the grounding material. In order to ensure the safe operation of the booster station, The resistance of the grounding grid of power station must meet the requirements of <4Ω,, high strength of the ground material is needed to counter the severe corrosion of the sea water to achieve full life grounding system. Thus make the following grounding engineering solutions.

Two, design base of grounding engineering

1, DL/T621 Grounding for AC electrical apparatus

2, DL/T620 Over voltage protection and insulation coordination of AC electrical apparatus

3, GB50169 Code for construction and acceptance of grounding device for installation of electrical equipment

4, GB 50057 Design code for protection of structures against lightning

5, State Power Grid Corp: Eighteen major anti accident measures of power grid

6, GB50065 Code for grounding design of AC electrical equipment

Three, project description

According to the design requirements of the national standard: The resistance of the grounding grid of power station must meet the requirements of <4Ω, because it is solar-fishing project, so the surrounding soil resistivity is relatively low. Soil resistivity ρ= 50Ωm, Then, use a similar traditional grounding method, such as : grounding area S=0.25·ρ2/R2,, the calculated S value is a very small number of square meters, so the resistance reduction for the power plant will not be a big problem. According to the actual situation of the surrounding terrain of the power station, a good potential and fault current drain channel should be considered after satisfying the requirement of the resistance of the grounding grid and to meet the design life of the use, to prevent the corrosion of the sea water. According to the GB50057 and GB50065 mentioned in the severe corrosion area , after economic analysis , copper plated steel can be used as a grounding material, so in our whole project in the grounding part, we use copper plated steel in line with the national standard of as a grounding material.

Four, detailed  construction scheme

(1)、Horizontal grounding line: according to the drawings, now we make a specific grounding plan for the plot one and plot four. In the horizontal grounding line of land one and four, we choose to use the red line along the extension of the two plots, and extend 1-1.5 meters to the land to do horizontal grounding line, horizontal ground wire excavation trench -80 to -100cm, placing a horizontal ground wire in the grounding trench. Using two horizontal grounding lines between the plot one and plot four to connect the two plots,  in order to reach the potential connection of all areas. The level ground wire is a diameter of 10 mm copper bar, and customize the length according to the need. The connection of horizontal grounding wire uses exothermic welding , the wire length is produced according to the real site of the construction of the ground, as far as possible to reduce the welding point, to achieve rapid and efficient construction.

(2)、The equal potential connection of power station: according to the drawingsΦ8 copper plated steel is used as the equal potential connecting in the power plant. According to the field situation, we complete installation of 6 equal potential wires from east to west and 7 equal potential wires from south to the north in plot one. In the plot four to complete the installation of individual two potential connection lines for east-west and north-south direction.

Each of the equal potential connecting wires are connected with the two ends of the horizontal grounding wire, and the middle section is connected with the fastening bolt of the base bracket, to form a grid

in the entire plot one and plot four. Copper plated steel of diameter 8 is used in both ends of the bracket and the nearest connection line to achieve consistent potential of the whole base brackets in the power plant.

(3)、The jump connection of bracket and bracket ,the connection between each group of bracket and the adjacent bracket is connected by BVR10 yellow copper wire in plot one and plot four.

(4)、In the vertical grounding, in the land bound point of equipotential connection line and the ground level, to lay the vertical grounding rod, vertical grounding electrodes useΦ16/2.5 copper plated steel grounding electrode, each point lay 2 grounding electrodes. The grounding electrode is connected with level grounding wire .The distance between two grounding rods is not less than 5 meters, each grounding and connection point distance is greater than or equal to 2.5 meters, in order to reach the effect of discharge current and tensile isoelectric line.

(5) Grounding observation well, in order to observe the grounding wires after completion of the project, we set four observation wells in the project . We set three observation wells in the plot, three wells are located in the north, west, east three directions. The specific location of electrode placement arrangements according to the scene.We can directly observe the level grounding wires and vertical grounding rods etc. grounding equipment in the ground observation wells. In the plot four reserved a observation well, located in the south of the plot four, same as plot 1, placed in the vertical grounding location to convenient for observation.

(6) According to the drawings, the second plot and third plot are for the reserve position. if in the site construction, the tow plots are need to use in accordance with the situation , then make changes according to the scene.

(7) Specific construction site can be made appropriate changes

 according to the actual situation .

Five, methods for check and acceptance

Party A and Party B shall be present at the scene, and Party B shall issue the grounding resistance test by the instrument through the national inspection standard.

Six, After-sale service

Within one year of the project, the grounding resistance of the grounding grid rises (can not meet the requirement), Party B should free rectification until to meet the requirement.