system interruptions has been one of the major cause of concern for power system engineers across the globe. The problem adds on to the

severity critically in urban areas where power outages

directly implies severe financial crunch

1

Diagnostics for Non-ceramic Insulators in

Harsh Environments

2

Abdul Aziz 28Md Azam 27Nadeem Ahmad 30

appendix• Need for Insulator Pollution Diagnostic• Why non – ceramic insulators• Objective of the presentation• Charecteristic of non ceramic insulators• Corona Inspections• Measurement of electric-field

distributuion along the insulators.• References and source of information.

3

Need for Insulator Pollution diagnostic1. Sharp radii of curvature is avoided to

reduce electrical stress.

2. Porcelain insulators to be glazed and made free from rough particles and unevenness

3. Internal bubbles that allow partial discharge and put the insulator at risk of explosion and failure needs to be avoided.

4. Shed and creepage play such a vital role that in areas of high pollution, areas of airborne sea salts, icing and bird risk areas  are varied to accommodate for the environmental effect on the same.

4

Need for Insulator Pollution diagnostic

1. Effects a) the radius of curvatureb) Creepage Length

and Hence Insulation

2. In severe circumstances it may lead to the …development of holes or pores in the …insulators curbing the entire purpose of …insulators.

Ever Growing Pollution Damage to the Insulators.

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In highly polluted areasutilities must perform preventative maintenance, otherwise systemoutages will occur. Some ceramic insulators are being

used in highly polluted areas but erosion on these insulators has limited their use in these regions.

Main reason for use of Non- ceramic insulators- reduction of maintenance needed to keep a line in service in polluted regions

Analysis of air pollution on Insulator efficiency

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Objective of the presentation

the useful lifetime of the insulatorsdepends largely on the pollutionConditions

toinspect the insulators on a regular

Cycle becomes all the more important

The presentation discusses severaldiagnostic techniques that can be appliedto detect risky conditions beforeFailure.

To ensure insulator prevention and diagnostic of environmental effect on the same is the

core of the presentation7

Characteristics of Nonceramic Insulators Installed.

8

Characteristics of Nonceramic Insulators Installed.

The insulators installed on a 230-kV line in polluted regions

Is as shown in the table

The line operates at a maximum of 245kV phase-to-phase and this voltage is used for calculating the creepage distance (mm/kVp-p)

Insulators on two structures in the region of highest pollution level were monitored for leakage current, the number and magnitude of leakage current peaks are logged using custom monitor

9

The Salt – Fog Analysis Test Salt-fog tests at 14 and 112 kg/m3 and clean

fog tests were done on insulators removed after 8, 18, 25, 36 and 45 months of service.

It was verified that the flashover voltage waslower when the ESDD and the corresponding leakage currentmeasurements were lower.

10

CORONA- Inspection

Definition - An electric discharge on account of ionization of a fluid around a conductor which in turn takes place on account of high voltage.

The first corona inspection- Used a DayCor II corona camera showed no corona on any of the transmission line insulators.

Inspection of 2004 revealed corona around thehigh voltage end of type NC-2 and NCI-3 insulators as shown

No corona was evident on type NC-1 insulators

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CORONA- Inspection

In 2006, the inspection identified corona activity on the sameinsulators, as shown

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Measurement of electric-field distributuion along the insulators.

Basic Principle- Insulator damage is assumed to affect the electric field. An

example of electric field measurement is as shown.

The composite insulator tester can be used

The measured data are stored in the memory of the tester which is later transferred to a computer.

According to the shape of the curve it may be determined if the insulator is damaged.

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A close-up Inspection of the insulator Damage

2006 Analysis

2003 Analysis

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Simulation of Electric Field along the Insulators

Without Pollution

Figure-

15

Simulation of Electric Field along the Insulators

Without Pollution

Figure-

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CONCLUSIONThe effect of pollution on Electric field

distribution in non ceramic insulators can be studied, analysed and timely replacement of insulator is feasible.

The results obtained indicate that the useful life of non-ceramic insulators installed in polluted regions depends largely on the actual conditions of pollution

The reason for using non-ceramic insulators inpolluted regions is the reduction of maintenance.

It is advisable to inspect the insulators on a regular cycle.

These inspections will help detect insulators at risk of failing and help maintain the reliability of an overhead line. 17

ReferencesReferences[1] G. Montoya-Tena, R. Hernandez-Corona, and I. Ramirez Vazquez, “Experienceson pollution level measurement in Mexico,” Electr. Power Syst.Res., vol. 76, pp. 58–66, 2005.

[2] R. Hackam, “Outdoor HV composite polymeric insulators,” IEEE Trans.Dielectr. Electr. Insul., vol. 6, pp. 557–585, 1999.

[3] R. S. Gorur, E. A. Cherney, and J. T. Burnham, Outdoor Insulators. Phoenix,AZ: Ravi S. Gorur, Inc., 1999, pp. 131–144. 18

References[4] Working Group 22.03: Insulators, “Review of in service diagnostic testingof composite insulators,” Electra, no. 169, pp. 105–119, 1996.

[5] Guide for the Selection of Insulators in Respect of Polluted Conditions,IEC 60815, 1986.

[6] J. L., Fierro-Chavez, I. Ramirez-Vazquez, and G. Montoya-Tena, “Online leakage current monitoring of 400 kV insulator string in polluted areas,”

[6] IEEE Electrical Insulation Magazine Vol 25, 2009, Pg No – 28-33 19

Thank You20