T1 T2 T3 surge protector (SPD) Lightning Protection

Surge protector (SPD) Lightning Protection --JUNXELE.COM

January of 2019 UK government come with 18th Edition have require of SPD. So we introduce some basic knowledges of lightning protection.

Lightning Protection

Failures of technical systems and installations cause trouble and economic losses. These require faultless operation from the equipment both under "normal" conditions and in case of thunderstorms.

Reports of insurance companies show clearly that nearly a qurter of the private damage and 45% of commercial damage are due to surge. SPD protection would help to eliminate the damage from the surge.

The Lightning Protection enables designers, constructors and operators to plan, perform and control protection measures. All relevant devices, installations and systems are thus reliably protected with SPDs.

Sources of interference

Surges arising due to thunderstorms are caused by direct or close lightning strokes or distant lightning strokes (Fig. 1).

Direct or close lightning strokes are strokes into the lightning protection system of a structure, into its immediate surroundings or into the conductive systems entering the structure (e.g. low- voltage power supply, telecommunications lines and control lines...).

Due to their amplitudes and energy loads, the arising impulse currents and impulse voltages as well as the corresponding electromagnetic field (LEMP) represent a special risk for the system. '

In case of a close or direct lightning strike, the surges (Fig. 1:Case1.1) are caused by a voltage drop at the impulse earthing resistance and the resulting potential rise of the structure towards the distant surroundings. This is the maximum load on electrical installations in structures.

The characteristic parameters of flowing impulse currents (peak value, rate of — current rise, load, specific energy) can be described with the impulse-current wave form 10/350 us (Fig. 2) and are defined in international, European and national standards as test currents for components and devices for protection against direct lightning strokes. In addition to the voltage drop at the impulse earthing resistance, surges arise in the electrical building installation and systems connected to it and equipment due to the induction effect electromagnetic lightning field (Fig 1: Case 1.2). The power of these induced surges and the resulting impulse considerably lower than the power of a direct lightning impulse c therefore only described with the impulse current wave 8/20 μs(Fig. 2) Components and equipment, which do not have to conduct currents from direct lightning strokes, are therefore tested with impulse currents of 8/20 μs.

Protection philosophy

Distant strokes are lightning strokes from a distance to the object to be protected, lightning strokes into the medium voltage overhead line network or into its immediate surroundings or lightning discharges from cloud to cloud (Fig. 1: Cases 2.1, 2.2 and 2.3).

In analogy to induced surges, the effects of distant lightning strokes on the electrical system of a structure are controlled by devices and components, which are designed accordingly for impulse current wave 8/20 μs.

Surges due to switching operations (SEMP) are caused by e.g.switching off inductive load (e.g. transformers, coils, motors), ignition and interruption of electric arcs (e.g. arc welding device), tripping of fuses.

The effects of switching operations in electrical installations of structures can also be simulated with impulse currents of wave form 8/20 μs for testing purposes.

Power Distribution System