Overvoltage Protection

Overvoltage Protection:

Lightning : An electric discharge between cloud and earth, between clouds or between the charge centres of the same cloud is known as lightning. Lightning is a huge spark and takes place when clouds are charged to such a high potential (+ ve or – ve) with respect to earth or a neighbouring cloud that the dielectric strength of neighbouring medium (air) is destroyed. There are several theories which exist to explain how the cloud to be charge. The most accepted one is that …


Surge Diverter  | Lightning Arrester Types: The earthing screen and ground wires can well protect the electrical system against direct lightning strokes but they fail to provide protection against travelling waves which may reach the terminal apparatus. The Lightning Arresters or surge diverter provide protection against such surges. A lightning arresters or a surge diverter is a protective device which conducts the high voltage surges on the power system to the ground. Lightning Arrester Working: Fig. 24.8 (i) shows the basic form of a …


Types of Lightning Strikes : There are two Types of Lightning Strikes may strike the power system (e.g. overhead lines, towers, sub-stations etc.), namely; Direct stroke Indirect stroke 1. Direct stroke: In the direct stroke, the lightning discharge (i.e. current path) is directly from the cloud to the subject equipment e.g. an overhead line. From the line, the current path may be over the insulators down the pole to the ground. The overvoltages set up due to the stroke. may be large enough to …


Types of Surge Absorber : The travelling waves set up on the transmission lines by the surges may reach the terminals apparatus and cause damage to it. The amount of damage caused not only depends upon the amplitude of the surge but also upon the steepness of its wave front. The steeper the wave front of the surge, the more the damage caused to the equipment. In order to reduce the steepness of the wave front of a surge, we generally use …


Voltage Surge or Transient Voltage : A sudden rise in voltage for a very short duration on the power system is known as a Voltage Surge or Transient Voltage. Transients or surges are of temporary nature and exist for a very short duration (a few hundred μs) but they cause over Voltage Surge on the power system. They originate from switching and from other causes but by far the most important transients are those caused by lightning striking a transmission line. When lightning