For most applications, ground rods of +++++ diameter, and length of +++++, are used where bedrock is beyond a depth of ++++++.
1.90 cm (3/4 inch), 3.0 meters (10 feet), three meters (10 feet).
The metal framework of buildings may exhibit a resistance to earth of less than __ ohms, depending upon the size of the building, the type of footing, and the type of subsoil at a particular location.
Class A bond:
Class B bond
Bolting or clamping
Class C bond
Bridging using a metallic strap
DC resistance across bonding and grounding junctions shall not exceed +++ ohms for electrical safety
RF impedance across bonding and grounding junctions shall not exceed ++ ohms at ++ megahertz (MHz)
The earth electrode subsystem rods are interconnected with No. +++ AWG, or larger, bare copper cable
Other structures located greater than ++++ feet, are provided with a separate earth electrode subsystem
6m (20 feet)
If there is more than one earth electrode subsystem, they are interconnected with two bare No.__ AWG copper cables that use independent routes
Measure the resistance to earth every +++ months after the initial 12-month period of installation using the FALL-OF-POTENTIAL
Determine if the resistance of the earth electrode subsystem to ground using the FALL-OF-POTENTIAL METHOD is less than
Determine if the wideband noise with respect to earth ground measures less than 100 mV p-p, with periodic noise burst not
exceeding+++ V p-p, and occasional bursts up to +++ V p-p or greater
Measure the resistance to earth of all equipment, structures, fences and gates that are required to be bonded to ground and meets requirements of being less than +++ ohms
MIL-STD-188-124B recommends that ++++ be installed on 120-volt, single-phase, 15- and 20-ampere receptacles of C-E facilities.
Generally, less than ___ A is acceptable within a facility fault protection subsystem.
An average lightning strike consists of about three strikes, with the first strike discharging an average of +++
Subsequent lightning strikes will discharge about ____ the current of each preceding lightning strike.
Five effects of lightning
For this reason, metal objects within +++ feet of lightning down conductors should be electrically bonded to the down
The high voltage of a lightning strike may be high enough to cause a flashover to conducting objects located as
close as +++ inches away.
Roof and down conductors must be a separate ++++ AWG cable, continuous, un-spliced and installed in as straight a line as possible in order to provide a low-impedance path from the highest conductive surface (air terminal) to the main ground connection point
The tip of the air terminal should be at least +++ inches above the structure you are protecting.
If a building has a sloping roof then air terminal placement should be on the corners and edges where terminals that are:
Less than 24 inches in height are spaced a maximum of 20 ft apart
Equal to or greater than 24 inches in height are spaced a maximum of 25 ft. apart
If a building has a pitched roof then air terminal placement should be within +++ feet of ridged ends
If a building has a flat roof then air terminal placement should be +++++++++++
on the corners or edges
Any critical stuctures within a ++:++ cone of protection do not require lightning protection.
Any non-critical structures within a ++:++ cone of protection do not require protection
The maximum DC resistance of a 75-foot or less copper-clad steel down conductor shall not be greater than +++++ ohms per 1000 ft.
The maximum DC resistance for a 75 foot or more, copper-clad steel down conductor shall not be greater than ++++ ohms per 1000 ft.
The conductivity of copper-clad steel shall not be less than ___ of a solid copper conductor with an equivalent cross-sectional area.
The bend radius of a down conductor should not be less than ++++ inches.
The angle of any down conductor bend shall not be less than ++++ degrees
An air terminal must have at least ++++ paths for discharging the lightning to ground
At least +++ down conductors shall be placed on any structure
On structures exceeding 250 ft. in perimeter, an additional down conductor is required for each additional +++ ft. of perimeter.
The ground rod shall be at least +++ feet long and +++ inch in diamete
Ground rods are constructed of:
copper-clad steel, solid copper, hot-dipped galvanized steel, or stainless steel
The lightning protection subsystem should be inspected visually every +++ months and mechanically every +++ months per NETA guidelines.
The +++++++ ground configuration is preferred for Communications Electronics (C-E) facilities
Signal reference subsystem grounding configurations for all of the equipment in a facility falls into one of three grounding configurations: