What Metal-Clad Switchgear Interlocks Must Prove at FAT

Metal-clad switchgear interlocks are mechanical and electrical restraints that keep shutter, truck, earthing, and door operations in a safe order; FAT must prove those sequences under the project wiring and interlocking matrix, not from a brochure alone. Use this page to turn an interlocking matrix into a witnessed FAT checklist for metal-clad panels.

Part 1. What does an interlock prove during FAT?

An interlock proves that a forbidden motion is blocked and that an allowed motion is released only when stated conditions exist. Buyers should ask which actions are mechanical, which are electrical, and which depend on auxiliary power.

Readers searching for metal-clad switchgear interlocks usually need a project checklist, not a catalog slogan.

Part 2. Which mechanical sequences need a witnessed test?

Truck racking, shutter movement, earthing switch operation, and door access usually sit on one matrix. Witness each blocked and allowed path with the serial number of the panel under test.

Part 3. How should electrical and control interlocks be checked?

Electrical interlocking depends on the project control scheme. Confirm coil supply, permissive contacts, and fail-safe behavior when control power is removed.

Important: Do not accept a metal-clad interlock claim from a generic catalog photo. Use the interlocking matrix and witnessed FAT checklist for the offered panel. (Source: IEC 62271 assembly practice / project interlocking drawings.)

Part 4. What must the test position demonstrate?

The test position must show that primary circuits stay isolated while secondary checks can still run. Record how the truck is locked and how shutters behave in that position.

Part 5. Which records make the FAT result usable?

Keep the interlocking matrix revision, witnessed checklist, photos of nameplates, and open punch-list items. A pass stamp without the matrix revision is hard to reuse at site.

Part 6. Which JUBANG routes fit interlock FAT planning?

When the interlocking matrix is attached to the RFQ, discuss metal-clad panel routes with controlled drawings. Selection still requires project voltages, short-circuit data, and witnessed procedures.

• KYN28A-12 Metal Clad Switchgear — metal-clad panel route for interlock FAT planning.

Related articles:
– metal-clad switchgear buyer checklist
– gas insulated switchgear selection guide
– high voltage RMU selection guide

Bring the interlocking matrix to the JUBANG switchgear and ring main unit range discussion, or contact JUBANG with the FAT witness list.

Why not: Do not treat a ring-main unit quote as a metal-clad truck-type interlock package.

Part 7. What are the fit boundaries?

This guide explains interlock witnessing language for metal-clad switchgear. It does not set trip curves, certify type tests, or approve a specific utility package.

FAQ

What are metal-clad switchgear interlocks?

They are mechanical and electrical restraints that enforce a safe order for truck, shutter, earthing, and access operations.

Which interlocks should be witnessed during FAT?

At minimum: truck travel, shutters, earthing switch, door rules, and control-power-loss behavior stated in the matrix.

Why is the test position important?

It separates primary isolation from secondary testing so checks can run without re-energizing the main circuit.

Can a key interlock replace a mechanical interlock?

Only when the project matrix assigns that role. Keys do not automatically replace truck or shutter mechanics.

What happens if auxiliary power is unavailable?

Record the fail-safe state. Buyers should know which permissives disappear when control power is lost.

What FAT records should the buyer retain?

Matrix revision, witnessed checklist, nameplate photos, and remaining punch-list items.

Does this page certify the switchgear?

No. Final acceptance needs project documents, responsible engineers, and verified factory records.

References

• IEC webstore — high-voltage switchgear publications
• IEEE Standards Association
• Electrical Engineering Portal