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Description • • • • • • • • • • Compact DIN rail mounting Broad range 1, 2, 3, & 4 pole versions Replaceable plug cartridges Finger safe 15, 40, 65 & 100 kA versions Three position visual status indication Auxiliary contact for remote signalling UL 1449, File # E238957 & E22406

14Low Voltage Products & Systems
ABB Inc. • 888-385-1221 • www.abb-control.com

14.61
1SXU 000 023 C0201

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General points on lightning and its risks Causes of transient overvoltages

The most serious consequences of lightning are the death of people and farm animals, and the destruction of equipment: telephone lines, transformersconnected to the electrical distribution network, electrical meters, household appliances, etc. At the same time, the growing amount of equipment incorporating very sensitive electronic devices increases the number of incidences linked to lightning. Within companies, if office automation equipment or machines (in factories) are put out of action, it nearly always leads to operating losses, the costof which is much more than that of the damaged equipment. For example, if a bank’s computers are no longer operational, it suffers large operating losses. For the general public, the damage is mainly material: computer, household appliances, home cinema, etc.

ROBUSTNESS OF EQUIPMENT

1950

1970

2000

Causes of transient overvoltages
A transient overvoltage is a voltage peak with amaximum duration of less than one millisecond. There are two possible causes of overvoltages on electrical networks: • natural causes (lightning), • other causes due to equipment or switching devices. Natural overvoltages on low voltage networks are caused by direct lightning strikes. The high level of energy contained in a direct lightning strike on a lightning conductor or an overhead low voltageline leads to considerable damage of the installation. The overvoltage can be over 20 times the nominal voltage. Operating or switching overvoltages linked to a network’s equipment create overvoltages of a lower level (3 to 5 times the nominal voltage) but occur much more frequently, thus causing premature ageing of the equipment. 1950

PROPAGATION OF DISTURBANCES

1970

2000

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Threecategories of overvoltage propagate on low voltage networks:
• direct lightning strikes, • indirect effects of lightning strikes, • operating or switching overvoltages.

Propagation of overvoltages by electrical networks (power and low current)

14.62
1SXU 000 023 C0201

Low Voltage Products & Systems
ABB Inc. • 888-385-1221 • www.abb-control.com

General points on lightning and itsrisks Causes of transient overvoltages

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Overvoltages due to direct lightning strikes
These can take two forms: • When lightning strikes a lightning conductor or the roof of a building which is earthed, the lightning current is dissipated into the ground. The impedance of the ground and the current flowing through it create large difference ofpotential: this is the overvoltage. This overvoltage then propagates throughout the building via the cables, damaging equipment along the way. • When lightning strikes an overhead low voltage line, the latter conducts high currents which penetrate into the building creating large overvoltages. The damage caused by this type of overvoltage is usually spectacular (e.g. fire in the electricalswitchboard causing the destruction of buildings and industrial equipment) and results in explosions.

Direct lightning strike on a lightning conductor or the roof of a building

Direct lightning strike on an overhead line

Overvoltages due to the indirect effects of lightning strikes
The overvoltages previously mentioned are also found when lightning strikes in the vicinity of a building, due to...