Part 1 Part 2 Part 3 Part 4 Part 5

Synopsis PART III

Voltage Surges / Transients, Over Voltages And Grounding / Earthing Practices

This part is complementary to Part II and provides technical support to switchgear assemblies and machines fed by them for surge and over-voltage protection. It is a very useful part for all those handling HV and EHVpower systems and their surge and over-voltage protection.

. The part deals with the BIL of a system, protective margins and insulation coordination. LV surge protection and surge protection devices (SPDs)

. It also deals with electric motors as they are typical for their surge behaviour and protection.

. It also covers the steepness of TRVs, their significance and methods of taming them. Reflections of travelling waves and surge transferences are also described.

. This part specifically considers the application and selection of surge capacitors and surge arresters. Since the internal causes of surge generation are a consequence of switching operation and type of interrupter, this part provides details of the various types of interrupters in use, their switching behaviour, current chopping and quenching of arc plasma. It also makes a detailed comparison of the various types of interrupters available in the market to facilitate their selection and adaptation to a more appropriate surge protection scheme. Gas insulated switchgears (GIS). HV and LV vacuum contactors.

. Temporary over-voltages are different from surges as are their causes. Therefore temporary over-voltages also form an important parameter in a system design and its grounding method. This topic is therefore complementary to surge protection and has been dealt in detail to make a practising engineer or engineering student more aware of the behaviour of an HV system, particularly on a ground fault.

. Exposure of a human body to touch and step voltages and methods to deal with these are also covered. Grounding and ground fault protection schemes are described in detail with illustrations to help an engineer select the most appropriate grounding method and ground fault protection scheme for a machine or a system.

. The use of CBCTs is covered.

. Grounding systems, their choice and protection from transferred surges and over-voltages

. Grounding practices of industrial installations and power generating stations. 

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