Overvoltage

Through voltage is a voltage in the electrical system, which exceeds the tolerance range of the rated voltage. Surges lead to an incident or event of an error when they destroy components or components of the equipment. Overvoltages may be symmetrical (ie, between two leads ) or unbalanced ( both supply lines lead surge to ground) occur.

Causes

Causes of prolonged over-voltages in the range of seconds to hours may be:

• Poor control by the utility
• Sudden load reduction in the energy supply network, generally at a voltage source, for example by Consumer behavior (eg symbolic power saving actions, the end of a football match )
• Power outages in the network neighborhood, eg caused by a lightning strike shutdowns
• Unbalanced load or short circuit of an outer conductor with three phase AC generators, power generators, non -point grounded networks
• Decline in consumption during the night hours

Causes of transient overvoltages can be:

• Shutdown particularly inductive loads switching sparks on the switching contacts, sparking large electric machines (burst, pulse sequences with rise times by 5 ns)
• Lightning in the neighborhood, switching operations in the power supply (surge, pulse rise times of a few microseconds, 10 microseconds pulse duration more )

Also NEMP and caused by solar activity on the Earth magnetic storms cause power surges.

Transient overvoltages can be sources of interference from adjacent capacitively caused ( by induction ) or inductively coupled into the supply or signal lines, as well as by strong radio waves.

Follow

• Punches and damage of insulating materials
• Destruction of semiconductor devices by microscopic thermal overloads
• Temporary malfunction or breakdown of electronic circuits ( latching )

• Thermal overloading of transformers, for example due to increased idle current ( core saturation )
• Premature failure, for example, incandescent lamps

Remedy

Prolonged surges in the power supply can be prevented by the consumer only with an AC controller. However, such network controllers are common and useful only for individual, particularly noise-sensitive and expensive electrical consumers.

Transient overvoltages can be kept with surge arresters of vulnerable components ( see also overvoltage protection):

• In the field of utilities with spark gaps and varistor surge arresters
• At the house with lightning protection, common Erdschienen for the energy, media and communications, and with varistor surge arresters
• In the telecommunications sector with suppressor diodes and gas discharge tubes
• Within electronic devices with suppressor diodes, varistors or protection diodes, as well as interference suppression capacitors

Main supply continues insulation, air and creepage distances to be oversized to avoid an electrical breakdown at high voltage pulses.

Electronic components and electrical terminals for mains voltage operation (partly to 15,000 volts) tested as part of the electromagnetic compatibility assessment of their immunity to transient voltages of 500 to 4000 volts and specified accordingly, or in the case of terminal equipment according to standards for industrial, medical or home application certified. This includes:

• Surge test (pulses of 1.2 / 50 microseconds or 8/20 microseconds rise / fall time)