JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD

Prerequisite

Dielectric and Insulation Engineering

Course objectives:

• To know the transmission line properties and its successive reflections coefficients.
• To understand the lighting mechanism and its mathematical modeling.
• To understand the high voltage ac circuit breakers and it protection schemes.
• To know the different types of insulation characteristics and it co-ordination methods

Course Outcomes

After Completion of this course, student will be able to:

• To understand the basic modeling on transmission lines in various cases.
• Follow the various standards for best practice in switching over voltage techniques.
• To understand the high voltage circuit breakers and its requirement in transmission lines.
• To know the general protection schemes against over voltages.
• Basic ideas to avoid the failures occur in insulators and co-ordination methods in EHV substation.

UNIT - I

Traveling Waves: Transmission line equation, attenuation, distortion, types of traveling waves, Reflection of traveling waves at a transition point, typical cases. Successive Reflections: Reflection lattice, line with different terminations, line-cable connection, line-cable-transformer connection.

UNIT - II

Lightning: Mechanism of the lightning stroke, Mathematical model of lightning stroke. Over voltage due to lightning. Power frequency over voltages, over voltages due to faults. Switching over voltages, switching over voltage reduction techniques.

UNIT - III

High voltage AC circuit breakers: Opposing forces during closing and opening operation, inter locks, indication and auxiliary switches, CB time, auto re-closure, transient recovery voltage, single frequency transient, double frequency transient, rate of rise of TRV, resistance switching, damping of TRV, opening resistors.

UNIT - IV

Protection of power system against over voltages: General principles of lighting protection, ground wires, surge arresters, counter poises, tower footing resistances, protection of rotating machines against surges.

UNIT - V

Insulation characteristics of long air gaps: Types of electrode geometries, breakdown characteristics of long air gaps, breakdown models of long gaps with non uniform fields, CFO and withstand voltages of long air gaps. Insulation Coordination: Protective characteristics of rod gaps, surge arrestors, insulation withstand voltage characteristics, correlation between insulation and protective levels, and illustration of insulation coordination in an EHV substation.

TEXT BOOKS:

• 1. “Traveling waves of Transmission systems”, by LV Bewley.
• 2. “Insulation Co-ordination ELBS in H.V. Electrical Power Systems”, by W.Diesendorf, Butter worth publications, London, 1974.

REFERENCE:

• 1. “E.H.V. Transmission Engineering”, by Rakosh Das Begamudre, Wiley Eastern Ltd., New Delhi, 1986. M. Tech – I Year – II Sem. (PS H.V. Engg. / H.V. Engg.)