T 3.5 Inadvertent damaging of cables

The less protection afforded to cables when installed, the greater the risk of inadvertent damage. Such damage does not necessarily result in the immediate failure of connections. It is also possible that unauthorised connections could be established accidentally, for example when cable sheathing or insulation is not completely intact any more after being damaged. The following are typical examples of such damage to cables within buildings:

• When cables are placed loosely on the floor and are exposed, employees or visitors can trip over the cables and disconnect the devices.
• Conductors can break in a device connection cable when office furniture is rolled over the cable.
• Concealed cables can be damaged by drilling or hammering nails in the wrong location.
• Water can cause damage, for example when water permeates into the cable ducts in window sills or floors due to cleaning crews or an open window when it's raining.
• Surface-mounted cables can become damaged when transporting heavy, bulky objects.
• Cables can become damaged when they are unplugged from the socket by pulling on the cable instead of the plug.
• Equipment can become overloaded when, for example, the total load placed on a power distributor by the connected devices exceeds the permissible limit.

Outside of buildings, cables can become damaged by the following events, for example:

• Cables can be damaged during excavation work, either by shovels when excavating manually or by an excavator.
• Water can penetrate into underground cable ducts or buried cables.
• Rodents can chew on cables and damage them.
• Ducts and cables can be damaged by roots (tree roots are strong enough to crush cables).
• The permissible traffic load limits can be exceeded (this can cause broken conduits or sheared cables).
• Vehicles can drive over the plug connections of cables laid temporarily for tools and machines.

Example:

In a pedestrian zone, the cleaning person employed by a small shop had a habit of pouring waste water into the cable inspection manhole directly in front of the shop door. The water always evaporated with time, but it took a lot of time and effort to remove the dirt and soap residue deposited on the cables whenever there was work to be done on the cables.