Touch Potential, Step Potential & Touch/Step Potential

There are three basic pathways electric current travels through the body 1) Touch Potential (hand/hand path) 2) Step Potential (foot/foot path) 3) Touch/Step Potential (hand/foot path) Figure illustrates these groups and the path of current through the body. 1) Touch Potential (hand/hand path) In a touch potential contact, current travels from one hand through the … Read more

Voltage Transformer or Potential Transformer

Voltage or Potential Transformer Q. State the specifications of PT as a protective transformer. Voltage transformers (potential transformers) are used for measurement and protection. They may be either single phase or three phase units. Voltage transformers are necessary for voltage, directional, distance protection. Primary of voltage transformer is connected to power circuit between phase and … Read more

Practical Considerations in using Gases for Insulation Purpose

Practical Considerations in using Gases for Insulation Purpose Air has great advantage of being low in cost, therefore it found some application at increased pressure in condensers, cables and other insulation constructions. But it does not satisfy the second requirement, since ionization of air is accompanied by emission of ozone, nitrous and nitric oxides causing … Read more

Control of Over Voltages due to Switching and Power Frequency

Control of Over Voltages due to Switching and Power Frequency (a) Energization of TL in or more steps by inserting resistances and withdrawing them afterwards It is normal practice to have a series resistance with the circuit breaker contacts during switching ON and then but short circuiting this resistance after a few cycles. (b) Eliminating … Read more

Distribution of Switching Surges (EHV and UHV Systems)

Distribution of Switching Surges (EHV and UHV Systems) Switching surges originate when there is sudden release of internal energy stored in the electrostatic form (in the capacitance) or in the electromagnetic form (in the inductance). This can happen in following situations :     (i) Current chopping phenomenon : Interruption of magnetizing currents (transformers/reactors re switched … Read more

Switching Surges due to External and Internal factors

Switching Surges due to External and Internal factors The above all were the protection systems against the direct lightning strokes which is purely natural and we are not having any control over it. Switching surges are the over-voltage stresses applied on the traction system, and are generally transient in nature. The surge voltage is defined … Read more

Conventional Lightning Protection System

Conventional Lightning Protection System There are various conventional or principle provide protection against components to conventional lightning strokes. (A) Air Termination Network The primary function of termination network, is to arrest the an air terminal or air lightning strike to a preferred point, so as to make sure that the discharge current can be safely … Read more