Boiler house power supply

Explanatory Note

1.1. Calculation of components of the lightning protection system of the boiler room is made in

compliance with CO 153 - 34. 21. 122 – 2003.

1.2. Expected number of lightning losses in the boiler room for Kulebaki, Nizhny Novgorod Region with an average duration of thunderstorms of 40 - 60 h/year

N = 4

1.3. In accordance with Table 2.2 (p. 9) we accept the level of protection - III with the reliability of protection against direct lightning strikes 0.9 (Table 2.2) based on the customer's specification.

When using a metal pipe (ht = 12 m) with a pin with a length of 1 m (h = ht + 1 = 13m) as a single rod lightning connector, the protection radius at the roof height rx with protection reliability 0.9 (Table .2) will be

h0 = 0.85 • h = 0.85 • 13 m = 11.05 m,

r0 = 1.2 • h = 1.2 • 13 m = 15.6 m,

rx = r0 (h0 hx/h0) = 15.6 • (11.05 - 3 )/11.05 = 11.365 m,

which overlaps the dimensions of the boiler room.

1.5. Resistance of grounding device of lightning protection system is not more than 10 Ohm.

As vertical earthing electrodes we take rods from steel angle

50 x 50 x 2500 mm, connected by steel horizontal strip 40 x 4 mm (Table 3.1).

Number of vertical grounding conductors - not less than 3, distance between vertical

by at least 5 m of electrodes.

1.6. Required number of vertical rods can be specified after

direct measurements of grounding circuit resistance.

1.7. When entering the boiler room, skid protection shall be provided

high potential for underground and ground metal communications by combining them (by welding) with a steel strip of 40 x 4 mm and connecting to the ground device of the lightning protection system.

1.8. At the commissioning of the boiler room, protection against secondary lightning effects - the internal lightning protection system - must be performed by installing an overvoltage protection device.