# EXAMPLE OF CALCULATION. GROUNDING OF A HOSPITAL IN NOVOSIBIRSK

Hospitals and medical center are the most responsible objects from the point of view of grounding quality. To ensure electric safety when using equipment in medical premises, a grounding device with a low resistance value is required. It is taken according to the Technical memo № 24/2009 of the Assosication "Roselectromontazh" and must be not more than 2,5 Ohm and for import equipment - up to 2 Ohm.

ZANDZ Technical Center took part in the calculation of grounding for the "State Novosibirsk regional university hospital". Thanks to modular grounding, which was mounted into clay loam, we managed to achieve the calculated grounding resistance of 2 Ohm on a quite compact territory.

You can get familiarized with the offered technical solution. This example is also remarkable because it was soon mounted after the calculation. You can see the report about the installation at the following link.

## Solution of grounding for a hospital

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

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

• installation of 3 vertical electrodes made of copper-bonded steek 14 mm in diameter, 21 m long, united by the horizontal electrode made of corrosion-resistance copper-bonded steel with a cross-section 4x30 mm 44 m long. Depth of tape laying 0,5m.

Figure 1. Plan with the layout of lightning protection elements and grounding device

## Calculation of a grounding device resistance for a hospital

Resistance of the grounding device should not exceed 0,5 Ohms.

Upon the request of the customer, the design specific resistivity of the soil is assumed to be 100 Ohm m.

Warning. In case of a mistake or ground data limitation presented from the customer the given calculation of the grounding device is considered incorrect. In case of difference between the ground resistivity from the calculated grounding, it is necessary to carry out calculation with a real value. If the normalized resistance of the grounding device exceeds, it is necessary to introduce modifications into the structure.

Grounding calculation was given with the help of software, developed by OJSC "Energy institute to the name of G.M. Krzhizhanovksy" (OJSC "ENIN").

### Horizontal electrode resistance

where p  - soil resistivity, Ohm*m;

b - width of the horizontal electrode tape, m; ;

h - horizontal electrode laying depth, m;

L - horizontal electrode length, m.

### Vertical electrode resistance

where p  - soil resistivity, Ohm*m;

L - vertical electrode length, m;

d - vertical electrode diameter, m;

T - deepening - the distance from the ground surface to the ground electrode system, m;

T=L/2+t;

where t is the depth of the electrode top, m

### Full impedance of the grounding device

where n - number of kits;

kисп гр utilization ratio.

The design resistance of the grounding device is 1.97 ohms, which is less than the required value of 2 ohms

## Components for grounding of a hospital

 № Fig. Product item Product Quantity Grounding device 1. GL-11075-50 GALMAR Copper-bonded tape (30 * 4 mm / S 120 mm²; coil of 50 meters) 1 2. ZZ-005-064 3 3. ZZ-001-065 ZANDZ Copper-coated threaded grounding rod (D14; 1.5 m) 42 4. ZZ-002-061 ZANDZ Threaded coupler 40 5. ZZ-003-061 ZANDZ Starting tip 3 6. ZZ-004-060 ZANDZ Driving head for a jackhammer 9 7. ZZ-006-000 ZANDZ Conductive grease 4 8. ZZ-007-030 ZANDZ Waterproof tape 1 9. ZZ-008-000 ZANDZ Header for a jackhammer (SDS max) 1