Tecnical calculation of a conventional grounding device made of angle steel for a UTS 10/0,4 kW

Appendix № 1 to "Economic justification of using ZANDZ modular grounding"

The activities were carried out in accordance with the EIC 7 th ed. Chapter 1.7.

The object of the protective grounding installation a unit transformer substation (UTS) with the voltage of 10/0,4 kW. According to the customer's data, the ground in the intended place of grounding devices installation is clay loam. Specific soil resistance is taken equal to 100 Ohm ∙ m.

In accordance with the EIC p.1.7.96, 1.7.97 and 1.7.104 for electric installation with the voltage above 1 kW in networks with the isolated neutral (35-10 kW), the grounding device resistance should not exceed 4 Ohms.

In accordance with EIC 1.7.101 the resistance of the grounding device, to which the neutrals of the generator or transformer or single-phase current supply terminals are connected, should not exceed 4 ohms at any time of the year at the line voltage of 380 W of a three-phase power source.

The set of measures to ensure the necessary requirements to the grounding device is represented by the following solutions:

• installation of 30 vertical electrodes 3 m long of angle steel of 50x50x5 mm (GOST 8509-93), united by a horizontal contour of steel tape with the cross-section of 5x32 mm (GOST 103-2006), laid around the UTS. Depth of the tape burial 0.7 m;
• a horizontal ground electrode 1 meter long is laid to the wall of the UTS (copper-bonded tape with cross-section of 5x32 mm).

Arrangement of elements of the grounding device is shown on Figure 1.

Figure 1 - grounding device elements layout

Условные обозначения – code designations

Вертикальный электрод длиной 3 м – vertical electrode 3 m long

Горизонтальный электрод – horizontal electrode

Calculation of a grounding device resistance:

Horizontal electrode resistance:

ρ  - soil resistivity, Ohm* m;   
b - horizontal electrode tape width,m;
L_гор - horizontal electrode length, m.

Vertical electrode resistance:

ρ  - soil resistivity, Ohm* m;    
b - horizontal electrode tape width,m;
h- depth of horizontal mesh laying, 

Lгор - horizontal electrode length, m.
 

t – deepening of the electrode top, m

Impedance of the grounding device:

Where n - number of kits;
kисп - utilization ratio;

The design resistance of the grounding device is 3.55 ohms.

The list of required materials:

See further - Appendix № 2. Local costing № 030 (application of ZANDZ modular grounding of vertical stainless steel rods with the diameter of 16 mm and 1,5 long).
Do you need to make the project on grounding and lightning protection? Order it by contacting the ZANDZ Technical Center!

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