Grounding and lightning protection for a medical center

25.06.15 , , ,

The requests for calculation of grounding and lightning protection that our technicians receive, there are cases and organization of grounding and lightning protection systems for medical institutions: hospitals and medical centers. In addition to the "standard" grounding contour for the entire electricity mains of the building, customers almost always ask to calculate a separate grounding device for the specific equipment (body scanner, X-ray, cardiograph etc).

So we decided to tell you about calculation of grounding and lightning protection for medical institutions on a real example.

It could not have come at a better time, but, recently, our technicians received such a request to identify a set of measures for the protection and operation of equipment at a medical center in Moscow.

Task:

perform lightning protection system (step 6x6 m) and a grounding device (GD) that provides resistance of 4 ohms;
perform separate grounding device with the resistance of 2 Ohm for an X-ray machine.

Type of soil - clay loam (100 Ohm * m), available area for the installation of an independent grounding device - 15x15 m.

The solution is based on the following measures:

Organization of lightning protection mesh with the help of copper-bonded steel wire D = 8 mm.
Arrangement of down conductors with the use of copper-bonded wire D = 8 mm. See figure below.
Installation of the first (4 Ohm) grounding device, which consists of eight vertical electrodes 3 m in length, combined by a horizontal electrode (copper-bonded wire D = 10 mm). The distance from the electrode to the walls of the building is not less than 1 m, embedding 0.5 - 0.7 meters.
Проволока омедненная - copper bonded wire
The second grounding device (2 Ohm) is designed as a grounding mesh (copper-bonded wire D = 10 mm) consisting of four cells with the step of 7x7 m each. Vertical electrodes 6m long are mounted at the intersection points of the horizontal conductor. Embedment to 0.5 - 0.7 m. Distance from the building not less than 10 m. It is necessary to isolate the horizontal conductor (grounding device not more than 2 Ohm) at the to eliminate possible interference. See figure below.

The second grounding device (2 Ohm)

Объект - object

Электрод - electrode

Проволока омедненная - copper bonded wire

Full list of equipment:

1	GL-11149-50	GALMAR Copper-bonded wire (D 8mm / S 50 mm²; coil 50 meters)	13
2	GL-11150-50	GALMAR Copper-bonded wire (D 10 mm / S 80 mm²; coil 50 meters)	2
3	GL-11150-20	GALMAR Copper-bonded wire (D 10 mm/S 80 mm ²; coil 20 meters)	1
4	GL-11551A	GALMAR Clamp for the connection of down conductors (painted galvanized steel)	100
5	GL-11706	GALMAR Holder on a flat roof for down conductor (D8 mm; for bonding, plastic)	500
6	GL-11703A	GALMAR Clamp to the facade of down conductor (painted galvanized steel)	150
7	GL-11562A	GALMAR Contorl clamp for the connection of down conductors wire + tape (painted galvanized steel)	8
8	ZZ-001-065	ZANDZ Copper-bonded threaded ground rod (D14; 1,5 m)	52
9	ZZ-002-061	ZANDZ Threaded coupler	36
10	ZZ-003-061	ZANDZ Starting tip	17
11	ZZ-004-060	ZANDZ Guiding head for a breaker hammer	11
12	ZZ-006-000	ZANDZ Conductive grease	4
13	ZZ-008-000	ZANDZ Breaker hammer header (SDS max)	1
14	ZZ-005-064	ZANDZ Сlamp for conductor connection (up to 40 mm)	20
15	ZZ-007-030	ZANDZ Waterproof tape	5