Abstract: This paper is a continuation of the work reported during the 2004 Daycor users meeting. The electric field measurement method has been explored to determine its potential for timely detection of defects in nonceramic insulators. Various types of defects were simulated and the external electric field was computed. It is shown that the electric field method used presently is not sensitive enough to permit early detection of defective. There is a need for an improved method, perhaps periodic corona inspection could be the answer.
S. Gorur and S. Sivasubramaniyam
Abstract: This paper presents results and analysis of corona studies performed on NCI removed from service as well as on new materials in the laboratory. It has been shown that it is possible to quantify the corona degradation and this could be used to answer important questions like remaining life. The approach can also be used to develop a rapid screening method for evaluating the corona resistance of materials used for NCI housings.
B. Pinnangudi and R. S. Gorur
Defects in Nonceramic Insulators: Can They be Detected in a Timely Manner?
Abstract: This paper is a continuation of the work reported during the 2004 Daycor users meeting. The electric field measurement method has been explored to determine its potential for timely detection of defects in nonceramic insulators. Various types of defects were simulated and the external electric field was computed. It is shown that the electric field method used presently is not sensitive enough to permit early detection of defective. There is a need for an improved method, perhaps periodic corona inspection could be the answer.
S. Gorur and S. Sivasubramaniyam
Abstract: This paper presents results and analysis of corona studies performed on NCI removed from service as well as on new materials in the laboratory. It has been shown that it is possible to quantify the corona degradation and this could be used to answer important questions like remaining life. The approach can also be used to develop a rapid screening method for evaluating the corona resistance of materials used for NCI housings.
B. Pinnangudi and R. S. Gorur
Effect of Corona on Nonceramic Insulator Housing Materials
Abstract: This paper presents results and analysis of corona studies performed on NCI removed from service as well as on new materials in the laboratory. It has been shown that it is possible to quantify the corona degradation and this could be used to answer important questions like remaining life. The approach can also be used to develop a rapid screening method for evaluating the corona resistance of materials used for NCI housings.
B. Pinnangudi and R. S. Gorur
Transmission Line Insulator Condition Monitoring
Transmission line insulator condition monitoring is of increasing interest with the ageing of many transmission lines constructed since the 1950s. Porcelain and toughened glass and more recently polymeric insulators all have characteristic degradation and pollution modes that must be considered by asset managers. Following the recent inspection of some 220 kV Transmission Line Insulators it is useful to summarise current understanding of ceramic insulator degradation and condition assessment.
B. David Stuart McLennan – SP AusNet
Corona Rings: Are They Needed?
Mar 1, 2010 12:00 PM
By Raymond Ferraro, Public Service Enterprise Group; Emilie Dohleman, Public Service Company of New
Modeling predicts corona levels based on configuration, hardware and line voltage. (march 2010 | www.TDworld.com )
The Feasibility of Using Daytime Corona Inspection to Identify Contaminated Insulators That Need to Be Washed
Abstract
In areas plagued by contamination related flashovers, it is a challenge to decide when to was the transmission line or substation insulators. An experimental study has been performed to investigate the feasibility of using daylight corona detection as a means to identify insulators that needs to be washed.
During this study comparative observations have been performed on six artificially contaminated suspension insulator strings that were exposed to natural wetting conditions. The degree of contamination on the insulators were chosen according to a classification of (1) No need for washing—two strings; (2) Borderline case—one string and (3) Needs to be washed—three strings. A DAYCOR camera was used to do the inspections.
Six typical discharge patterns have been identified according to which the observations could be classified. These are described and explained in terms of the development of discharge activity on contaminated surfaces. Also the natural wetting conditions are explained and ranked according to its severity. An analysis of the observed discharge activity and other parameters measured was performed to determine whether this technology offered an unambiguous detection of insulators with a critical contamination level.
The main conclusions are as follows:
- The observed discharge activity is a function of both the contamination severity on the insulator as well as the degree of wetting prevalent at the time
- No corona activity is observed on clean insulators, irrespective of the rate of wetting
- Corona activity is observed on all contaminated insulator bells
- Arcing activity may be observed on insulators with a critical level of contamination. This arcing activity is often intermittent with long quiet periods in-between
- Insulators do not always exhibit arcing activity. This may be due to:
- The level of contamination is too low
- The wetting rate is too low
- A large dry band is established on the insulator and it prevents any discharges taking place
Detection criteria were established based on an analysis of the experimental results. Visual discharge detection cannot be used as an unambiguous technique for the identification of critically contaminated insulator units unless cameras are permanently installed and monitored. However, if scintillation activity or dry band arcing is observed on insulator units it is a positive indication that the insulators are contaminated enough to pose a real risk for flashovers.
