Specifications

T4
T4.51
Surge arresters
fig.14
Ground surface more than 4500 m
2
4
Ground surface from 2000 to 4500 m
2
2
Ground surface less than 2000 m
2
1
- The higher the density of the buildings in the area,
the lower the risk of your building being hit with a
lightning strike:
Rural 4
Suburb 2
Downtown 1
- An overhead power supply has a higher risk of being hit
by a lightning strike than an underground supply:
Overhead direct service drop 4
Overhead to facility then underground 3
Underground service from utility substation 2
Metropolitan service grid 1
- Also, the further the infrastructure is away from the
nearest substation, the longer the power supply
cables and thus the higher the risk:
600m to 3km from facility 4
300 m to 600m from facility 2
Less that 300 meters from facility 1
Facility Exposure Risk Level (FER-level)
Determine the facility exposure risk factor by adding
the above scores and looking up the facility
exposure risk level in the table below.
If the total (sum of above) is FER-level
Less or equal to 11 LOW
Between 12 and 18 MEDIUM
Above or equal to 19 HIGH
Step 2: Function and value analysis
- Critical facilities like hospitals, air-traffic control
centres, etc. cannot afford to be out of operation
by losing expensive (sensitive) electronic
equipment:
Mission critical / 24 hours critical 4
Critical / 8 hours critical 2
Non - critical / 8 hours commercial 1
Large concentration of sensitive equipment 4
Sensitive equipment only in certain areas 2
Very limited presence of sensitive equipment 1
- The higher the cost of the equipment to protect,
the better it should be protected:
Above $ 100k 4
$ 100k to $ 30k 3
$ 30k to $ 10k 2
Less than $ 10k 1
- Historical Data
Past history of power problems with damage 4
Past history of power problems without damage 2
No past history of power problems 1
Facility Function and Value Factor (FF&V-factor)
Determine your facility function and value factor by
adding the above scores and looking up the facility
function and value level in the table below
If the total (sum of above) is FF&V-factor
Less or equal to 6 3
Between 7 and 11 2
Above or equal to 12 1