Lightning Arrester Ppt 4f1c3l

LIGHTNING ARRESTERS AND INSULATION COORDINATION

BY S.RAGHAVENDRA & T.REVANTH KUMAR

CONTENTS  INTRODUCTION

 LIGHTNING ARRESTER  LIGHTNING ROD  BASIC INSULATION LEVELS (BIL)

 TYPES OF L.A.

INTRODUCTION

 Veltoor 400kv substation is a secondary

transmission interconnecting type of substation.  Incoming to the substation consists of two 400kv lines and outing consists of a 220kv and a 33kv lines.  For incoming the conductors used are Twin Moose conductors.  The conductor used for outgoing is a 1 Moose conductor.

 In 400kv we use a tie breaking system.

 Here four conductors are used for bus-bars.  With the help of tie breaking system the equipment

on both sides of the breaker are protected.  In every line the starting equipment is a lightning arrester.

LIGHTNING ARRESTER

 A lightning arrester is a device used on electrical

power systems to protect the insulation on the system from the damaging effect of lightning.  Metal oxide varistors (MOVs) have been used for power system protection since the mid 1970s.  The typical lightning arrester also known as surge arrester has a high voltage terminal and a ground terminal.  When a lightning surge or switching surge travels down the power system to the arrester, the current from the surge is diverted around the protected insulation in most cases to earth.

LIGHTNING ROD

 A lightning rod or lightning conductor is a

metal rod or conductor mounted on top of a building or tower and electrically connected to the ground through a wire, to protect the building or equipment in the event of lightning.  The above picture shows the lightning tower used to hold the rod in a 400kv station.  In VELTOOR 400kv station, the 360 degrees protection is done by lightning towers to ensure that it grounds the lightning strokes anywhere in and near to the station zone.

BASIC INSULATION LEVELS (BIL)  Having decided the voltage that are required to be created at

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any substation it is necessary to establish a common insulation level for all items of equipment of each system voltage. It is to be ensured that the breakdown or flashover strength of all insulation (particular voltage) in the station will exceed the selected level. After the development of station type lightning arresters the B.I.L’S have been determined on the basis of the protective characteristics of the lighting arresters. These levels help us in the selection of proper equipment. The protective devices are then so selected that their flashover values are considerably lower than the B.I.L of the apparatus, thereby leaving sufficient margin of protection.

BASIC INSULATION LEVELS (BIL)

TYPES OF L.A.

 Rod Gap Type  Expulsion type Lightning Arrester  Valve Type Lightning Arrester

Rod Gap Type  This type of protective device is very simple and

robust.  It is, however, rarely used on circuits of some significance because it does not fulfill the basic requirements of a true protective device.  It does not cut off power voltage after it has been flashed over by a surge.  This would mean a short circuit on the system every time a surge causes a flashover across the rod gap.

Expulsion type Lightning Arrester

Valve Type Lightning Arrester

Valve Type Lightning Arrester

Rated Voltage

Development of lightning Arrester

Tests  In IS: 3070-1965, the tests are classified as

 Type tests,  Acceptance test, and  Routine tests.

The time required for the currents to reach their crest values

Co ordination of Insulation in Stations of A.G.E. System

Standard Insulation Levels as per Practice of M.S.E.B.