Upgrading High Voltage Insulators Using INSILCURE

THIS IS OUR 20th YEAR OF SUCCESSFUL FLASHOVER ELIMINATION

Background

Our partners have significant expertise solving problems for the flashover of overhead line insulation in polluted environments. Replacing conventional insulators with appropriately dimensioned silicon-rubber composite types has considerably reduced this problem. In substations, however, with multiple ceramic insulator, bushing, and housing designs, replacement is not practical, yet the need for a permanent, maintenance-free solution remains. INSILCURE has been developed to solve the problem of pollution flashover.

Summary

The INSILCURE system takes an engineered approach, comprised of:

	A detailed audit of all insulation in the yard to define the characteristics of every insulator and assess its suitability to operate under the existing ambient conditions.
	For insulators identified as under-dimensioned for the pollution severity of the site, the design and application of INSILSHED HTV silicon-rubber shed extenders to create profiles and creepage distances to ensure reliable, maintenance-free performance.
	Coating the insulators and shed extenders with INSILCOTE RTV silicon-rubber to provide the insulator surfaces with uniform hydrophobic properties to further enhance their resistance to flashover.

INSILSHED Extenders

INSILSHED extenders are made of true HTV silicon-rubber material with inherent hydrophobic characteristics and tracking, erosion and UV resistance, and are attached to the insulators by means of an RTV silicon-rubber adhesive. Even uncoated, the sheds are capable of operating in the most extreme environments.

The dimensional design of the extenders and the number and placement in relation to each insulator is critical to the long-term performance. These findings are based on over 25 years' experience in ceramic and polymeric insulation design. All key geometric parameters, such as creepage distance and shed spacing-to-projection ratios, are given due consideration. The upgraded insulators comply fully with the profile requirements of IEC 60815.

INSILCOTE Coating

The INSILCOTE coating has been in used in the harshest environments since its introduction in 1991. Its extremely hydrophobic characteristic prevents the formation of a continuously wet, conductive insulator surface. Even when severely polluted, the low molecular-weight silanes in the coating diffuse into the contaminating layer, maintaining the water repellency and inhibiting leakage current activity.

The coating vastly improves insulator performance and, in many cases, will independently represent a permanent solution to pollution flashover. However, any substation is only as reliable as the weakest insulator in the yard. So for those units deemed grossly under-dimensioned for the prevailing conditions, the combination of shed extenders and coating ensure that all insulators are of adequate standard, and ensure you of acceptable system security.

The life span of the coating depends on how well the insulator design stands up to the severity of the environment in question. Increasing both the quality of the profile and the creepage distance to a suitable level with INSILSHEDS can prevent flashovers well as reduce stress on the coating. Consequently the life span can extend nearly indefinitely.

Eliminating Maintenance

With an insulator-washing program, the cleaning interval must be fairly short, necessitating repeated outages. Live-line washing incurs the danger of precipitating flashovers on surrounding insulators by wetting them with overspray. And uneven wetting of large-diameter current transformers or surge arresters, for example, can also lead to equipment breakdowns.

The main drawback of a washing approach, however, is establishing the right timing. Unless you introduce involving some form of artificial wetting or complex condition monitoring, unseasonal rain or fog can cause unexpected flashover. Further, washing is totally ineffective in areas subject to "instantaneous" pollution, like conductive fog conditions. The upgraded INSILCURE insulator is always prepared for the unexpected climatic event and, with its inherent surface hydrophobicity, resists the effects of marine salt fogs and acidic mists.

The application of silicon grease, with its water-repellent properties and ability to encapsulate contaminants, extends a longer maintenance interval than required by washing. The highly labor- intensive and costly task of replacing the grease, though, makes this by far the most expensive option. Add to this the long outages required, the threat of insulator flashover or damage if the layer is not renewed in time, potential health risks, and environmental disposal problems, and greasing loses any appeal.

Used independently, shed extenders can increase the creepage distance and/or improve the insulator

profile, but expertise in insulator design is required to ensure their correct application. The disadvantage of extenders is that the difference in surface properties of the ceramic insulator and the polymer extender can create severe voltage distortions, which can result in partial discharges and flashover. The INSILCURE system guarantees uniform surface characteristics.

Benefits

Despite a higher initial investment, the life cycle cost of the INSILCURE system is significantly less than undertaking regular insulator maintenance. More important, the INSILCURE system considerably lowers the risk of flashover.

Demonstrated Value

The INSILCURE system:

	Represents a permanent pollution flashover solution for substations, in stark contrast to the limited effectiveness of washing programs and the prohibitive fiscal and environmental costs of greasing.
	Identifies the "weak links" in the yard, and elevates the quality of all the insulators to an acceptable standard.
	Provides insulators with a uniform, highly hydrophobic surface characteristic to prevent flashovers induced by both pre-deposited pollution layers and instantaneous conductive fog contamination.

Contact us

Learn more about how we can help optimize your operations. Send us an e-mail or call and ask for the Insulator Upgrade program.

Contact: infrm@levico.com