Chapter 4 Occupational safety regulations

4.1. Protection from atmospheric electricity. Lightning-proof category and zone type

Lightning is spark discharge of atmospheric electricity between clouds and ground. The streak lightning is frequent and destructive. Streak lightning current produces electromagnetic, thermal and mechanical effect to the object causing damage and fire. To provide protection from lightning for buildings and constructions they use a range of measures.

Every building and construction irrespective to its purpose is protected in accordance to lightning-proof category and zone type (table 4.1). According to the standard “ONTP 24-86” all areas and buildings are divided into 5 categories of fire and explosion risk areas. Data of meteorological station (table 4.2) shows average year’s thunderstorm activity in hours. Table 4.3 contains expected year’s average number of lightning strokes getting into 1 km² of the ground.

Buildings referred to objects of categories I and II are protected from direct lightning stroke, electromagnetic and electrostatic induction, and high potentials transferring in through ground and underground constructions. Objects of category III are protected from direct lightning stroke and transferring in high potentials through ground and underground constructions. External objects referred to the category II are protected from direct lightning stroke and its secondary factors, and those referred to category III are protected only from direct lightning stroke.

Buildings with rooms or areas, which need lightning-proof of the whole building, or building of categories I, II and III are recommended to make lightning-proof following requirements referred to category I. If the area, which needs lightning-proof makes less 30% of the total area of single-store building the whole building can be protected in accordance to category II.

Buildings with rooms or areas, which need lightning-proof of categories II and III are recommended to make lightning-proof following requirements to category II. If the floor area, which needs lightning-proof of category II makes less 30% of the total area of single-store building the whole building can be protected as category III, but protection from transferring high potential into areas of category II through communication system should be foreseen.

Table 4.1 - Lightning-proof equipment category and protection zone type

Building class by RIPF	Location	Protection zone type	Protective equipment category
1. B-I, B-II	All territory of Ukraine	Zone A	I
2. B-Ib, B-Ia	When K10	When N<1 – zone B	II
3. Outside objects of category B-Ig	All territory of Ukraine	Zone B	II
4. P-I, P-II, P-Iia	When K20	For buildings of I and II class of fire resistance when 0.1<N<2 and III, IV and V class of fire resistance when 0.02<N<2 – zone B; when N>2 – zone A	III
5. Outside objects of category II and III	When K20	0.1<N<2 – zone B; when N>2 – zone A	III
6. Objects of fire resistance class III-V, which are not classified by RIPF	When K20	0.1<N<2 – zone B; when N>2 – zone A	III
7. Stacks, towers over 15 m height	When K20	Zone B	III
8. Buildings of 30 m height, remote from the other buildings at distance over 400 m	When K20	Zone B	III

Note: K – average year’s thunderstorm activity in hours per year; N – expected number of lightning strokes buildings and structures which are not equipped with lightning-proof.

Table 4.2 - Average annual thunderstorm activity

Regions	Average thunderstorm activity
1. Crimea Republic	40-60
2. Zakarpattya, Zaporizya, Donetsk	80-100
3. Other	60-80

Table 4.3 - Expected number of lightning strokes at 1 km² of the ground area n depending on thunderstorm activity K

Thunderstorm activity	Expected number of lightning strokes n
10-20	1
20-40	2
40-60	4
60-80	5.5
80-100	7.0
100 and more	8.5

Recommendations improving safety are: grounding electrodes are situated beyond from public places, at the distance over 5 m from roads, under bitumen. To avoid pace voltage grounding should be underground. Conductors are to be mounted in unreachable place.