Toughened Glass insulator advantages and benefits

Toughened Glass insulator advantages and benefits include solving internal current effects, preventing pollution accumulation, protection of the metal end fittings against corrosion, and other benefits.

Toughened Glass insulator

Toughened Glass insulator advantages:
High Resistivity Toughened Glass to solve internal current effects

Adapted glass shell design to prevent pollution accumulation:
The specific pollution conditions of DC applications require that the insulators be designed with care to reduce the risk of excessive dust accumulation resulting from unidirectional electric fields. (See IEC 60815 part 4).
Test laboratory and field experience have largely demonstrated that the bottom of the insulator is of prime importance in this regard. The best insulators will offer an adapted leakage distance distributed in a way that will prevent both dust nests as well as rib to rib arc bridging.
In this regard, Sediver has been able to adapt the shape of the glass shell to DC specifics, made possible thanks to the glass pressing and toughening processes which:
- avoids arc bridging,
- reduces dust accumulation,
- maintains self-cleaning.

Protection of the metal end fittings against corrosion:
Pin protection:
Under DC stresses, the galvanized coating of the pin deteriorates over time leading to the corrosion of the pin itself which in the long term can lead to significant reduction of the mechanical strength.
In order to prevent this form of pin damage, Sediver HVDC insulators are equipped with a corrosion prevention sleeve made of high-purity zinc.

Cap protection:
In HVDC, arcing activity and corrosion can also take place around the cap leading to rust deposits on the top surface of the skirt.
While no mechanical risk is expected from this phenomenon the generation of a conductive path on the insulators can substantially reduce the overall leakage distance of the entire string and therefore its electrical performance.
In order to avoid this type of corrosion, Sediver, went beyond the IEC specification in the early 80’s and patented a specific zinc collar design to protect the cap.

Toughened Glass insulator (HRTG) developments and User benefits:
Internal current:
HVDC stress: consequence Ionic migration Thermal runaway
Risk: Dielectric breakdown
HRTG solution: High Resistivity Toughened Glass imparting high resistance to localized thermal stresses and ion flow
User benefit: No puncture = less maintenance

External current:
HVDC stress: Pollution accumulation, Metal parts corrosion
Risk: String flashover, String flashover Mechanical failure
HRTG solution: Adapted glass shell design with wide spacing between ribs and increased leakage distance; Protection of the metal end fittings with pure zinc collar bonded to the cap and pure zinc sleeve bonded to the pin
User benefit: High pollution efficiency = less maintenance; Longer life expectancy

The condition of DC insulators after 30 years in service has been monitored jointly with Utilities. Today millions of HRTG insulators have proven their outstanding performance and reliability under all kinds of environmental conditions.

Toughened glass suspension insulators:
Ball & Socket coupling DC Fog type

Toughened Glass insulator on HVDC T/L in the World:
Over 4 million toughened glass DC insulators are installed all around the world
More than 48 years of experience up to 800 kV DC

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