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Grounding and Lightning Protection in Vaisala Outdoor Installations Technical Reference

Document code
M211786EN
Revision
B
Language
English (United States)
Product
RWS200
RWCC
AWS310-SITE
AWS310
FOC201
AWS430
RME111
Document type
User guide
Recycle all applicable material.

air terminal

An air terminal is part of a lightening protection system that attracts lightening strikes.

air-termination rod, air-termination conductor

See air terminal.

bonding

Bonding is a connection where you connect the electrically conductive parts of systems together galvanically to maintain an as equal as possible electrical potential between the parts. Bonding increases electrical safety and minimizes differential voltages.

conductive plate

A conductive plate is a copper sheet plate used as a special ground electrode on mountain tops or on bare rock when the ground electrode cannot be buried.

conductivity

Conductivity measures the material's ability to conduct electric current. When conductivity is low, resistance is high, and vice versa.

down conductor

A down conductor is part of a lightning protection system that conducts the lightning current from the air terminal to the ground electrode.

earth conductor

Earth conductor is a British English term. See ground electrode.

earth electrode

Earth electrode is a British English term. See ground electrode.

earth plate

Earth plate is a British English term. See conductive plate.

earth rod, earth lead-in rod

Earth (lead-in) rod is a British English term. See ground rod.

earthing

Earthing is a British English term. The American English term is grounding. See electrical safety grounding and grounding.

electrical safety grounding

Electrical safety grounding is grounding that reduces touch voltages in mains powered systems and enables the safety components inside the system to operate properly in fault conditions.

ground electrode

A ground electrode is part of a lightning protection system and has direct electrical contact with the ground, conducting and dispersing the lightning current into the ground. Ground electrode can be implemented by means of ground rods and conductive plates, for example.

ground potential rise

Ground potential rise is the phenomena of a large current flowing to ground through a ground electrode. The potential rise is highest at the point where current enters the ground, and declines with distance from the source. The change of voltage over distance can injure a person due to the voltage developed between two feet, or between the ground on which the person is standing and a metal object. Ground potential rise is a hazard to people and equipment.

grounding

Grounding is the physical connection of an electric circuit to the ground.

grounding resistance

Grounding resistance is the property of the grounding system to ground to conduct current to ground. The goal is to achieve the lowest feasible grounding resistance value for a certain site or application.

impedance

Impedance is the measure of the opposition that is presented to a (lightning) current when voltage is applied. In the context of lightning and grounding, the lower the impedance, the better.

inductance

Inductance is the property of a conductor by which a change in the current flowing through it creates a voltage in the conductor and in nearby conductors.

IT system

An IT system is a power distribution system where there is no connection between the ground and the equipment, except possibly through a high impedance route, and there is a direct connection between the ground and the electrical device being supplied. The letter ‘I’ stands for 'isolation' and ‘T’ stands for ‘terra’ (Latin for ‘earth’). IT system is defined in International standard IEC 60364. In an IT system, the line and neutral are isolated from ground.

lightning protection grounding

The purpose of lightning protection grounding is to attract lightning, disperse the lightning current to different paths, and ground the current.

lightning protection system, LPS

A lightning protection system is a system that reduces or prevents physical damage to a structure due to lightning. An external lightning protection system intercepts direct lightning strikes to the structure, and conducts the lightning current from the point of strike to ground. Equipment of an external lightning protection system include an air-termination system, a down-conductor system, and an earth-termination system (ground electrode system).

LPS

See lightning protection system.

safety grounding

See electrical safety grounding.

soil resistivity

Soil resistivity is the property of soil to conduct electricity. Soil resistivity is dependent on the mineral and moisture content of the soil. Soil resistivity is not homogenous.

step voltage

Step voltage is the voltage between the feet of a person standing near an energized grounded object. Step voltage poses a risk of electric shock. See also touch voltage.

TN system

A TN system is a power distribution system where the connection between the ground and the power-supply equipment is direct and the connection between the ground and the electrical device being supplied is such that there is a direct connection to neutral at the origin of installation.

touch voltage

Touch voltage is the voltage between an energized object and the feet of a person in contact with the object. Touch voltage poses a risk of electric shock. See also step voltage.

TT system

TT system is a power distribution system where there is a direct connection between the ground and the power-supply equipment (such as a generator or a transformer) and between the ground and the electrical device being supplied. The letter ‘T’ stands for ‘terra’ (Latin for ‘earth’). TT system is defined in International standard IEC 60364. In a TT system, the neutral wire is connected to the ground at the supply end (transformer or generator) or on the site.