High temperature arc resistant coating/material

Siemens is seeking an electroconductive material/coating that is resistant to electrical arcs.

During a high current/voltage switching operation an electrical arc occurs. These arcs can cause functional failures of the electrical system.

Siemens is looking for a new solution to ensure safe switching of high currents and high voltages.

The present solution prevents the evaporation/damage of the contact areas through electrical arcs when switching. 
Siemens would like to find a new solution with a reasonable lead time.

The three-position switch-disconnector is used in a three phase gas-insulated, metal-enclosed, medium-voltage switchgear acc. to Norm IEC 62271-1-200.

The switch has the functions switch-disconnector and make-proof earthing switch.
The operation is carried out via a rotary bushing welded gas-tight into the front of the switchgear vessel.

Mode of operation:
The operating shaft forms one unit together with the three contact blades.
During the closing operation, the operating shaft with the moving contact blades changes from the “OPEN” to the “CLOSED” position.
During the earthing operation, the operating shaft with the moving contact blades changes from the “OPEN” to the “EARTHED” position.

The force of the spring-operated mechanism ensures a high operator-independent closing speed and a reliable connection of the main circuit.

These criteria are essential for success:

• High temperature resistant coating of electrolytic copper.
• The coating/material has to be electroconductive.
• Defined coating adhesion strength necessary.
• After heat input (5x ~20ms ~5000-10.000 kelvin) a damage/evaporation of the coating/material is permitted.

From our experience, the following criteria are recommended (high probability that these criteria need to be fulfilled):

• Roughness max. Rz10
• Hardness ~85 HBW 2,5/62,5
• The mechanical load must not cause a detachment of the coating.

For the three-position switch-disconnector (CLOSED-OPEN-EARTHED) the following criteria have to be fulfilled:

Switching capacity for general-purpose switches according to IEC /EN 62271-103/ VDE 0671-103

• Rated voltage Ur kV36
• Test voltage Utest kV38
• Rated short-circuit making current* Ima 60 Hz up to kA 65
• Number of short-circuit making operations with Ima/Classification n=5/E3

Switching capacity for make-proof earthing switch according to IEC /EN 62271-102 / VDE 0671-102

• Rated voltage Ur kV36
• Test voltage Utest kV38
• Rated short-circuit making current* Ima 60 Hz up to kA 65
• Number of short-circuit making operations /Classification n=5/ E2

Number of mechanical operating cycles (CLOSED-OPEN-EARTHED-OPEN-CLOSED) with no-load n=1000

*Making capacity is the maximum current which the switch can conduct at the instant of closing.

Siemens is open to all solutions that meet the success criteria.

We are looking for concise, non-confidential proposals. The proposal should:

• Describe the technical approach
• Provide information on the performance of the technology (if available)
• Include a description of the responding organisation or team and their experience.

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