Overview
The FKN12-12D/T630-20 type indoor AC high-voltage load switch is a three-phase high-voltage switching device with a rated voltage of 12 kV and a rated frequency of 50 Hz. It is used for switching on and off load current, loop current, no-load transformer current and cable charging current, as well as closing short-circuit current.
The load switch equipped with an earthing switch can withstand short-circuit current, so it can be used where the earthing position must carry fault current for the duration of the protection operation.
The FKRN12-12D/T125-31.5 type AC high-voltage load switch-fuse combined electrical appliance is an indoor high-voltage switching device formed by combining the FN12-12D load switch with the S□LAJ-12 (XRNT□-10) high-voltage current-limiting fuse.
Key Features
- Load current switching — the FKN12-12D/T630-20 load switch switches on and off load current, loop current, no-load transformer current and cable charging current.
- Short-circuit current closing — the load switch is also rated for closing short-circuit current.
- Earthing switch withstand — the load switch equipped with an earthing switch can withstand short-circuit current.
- Combined switch-fuse appliance — the FKRN12-12D/T125-31.5 appliance combines the FN12-12D load switch with the S□LAJ-12 (XRNT□-10) high-voltage current-limiting fuse.
- Any overcurrent reliably broken — the load switch breaks the working current and the fuse breaks the short-circuit current, so together they break any overcurrent between the working current and the full short-circuit current.
- Striker tripping — when the fuse operates it makes the load switch open through its striker.
Technical Specifications
| Load switch model | FKN12-12D/T630-20 |
|---|---|
| Switch-fuse appliance model | FKRN12-12D/T125-31.5 |
| Product type | Indoor AC high-voltage load switch / switch-fuse combination |
| Rated voltage | 12 kV |
| Rated frequency | 50 Hz |
| System type | Three-phase |
| Load switch rated current | 630 A |
| Switch-fuse rated current | 125 A |
| Rated short-circuit breaking current | 31.5 kA (switch-fuse combination) |
| Combined load switch | FN12-12D |
| Combined fuse | S□LAJ-12 (XRNT□-10) high-voltage current-limiting fuse |
| Switching duty | Load current, loop current, no-load transformer current, cable charging current, and closing short-circuit current |
| Earthing switch | Available; able to withstand short-circuit current |
| Tripping | Fuse striker operates the load switch to open |
Applications
- Distribution networks — switching of load current and loop current in medium voltage feeders.
- Transformer circuits — switching no-load transformer current and protecting transformer feeders.
- Cable circuits — switching cable charging current.
- Industrial and commercial installations — medium voltage switching inside substations and distribution rooms.
Installation Conditions
- The devices are indoor high-voltage switching devices, installed in a distribution room or switchgear enclosure.
- Where an earthing switch is fitted, it is able to withstand short-circuit current, so it can be used in circuits where the earthing position must carry fault current.
- In the switch-fuse combination, the striker of the fuse is linked to the load switch mechanism, so the striker linkage must be set correctly during installation for the tripping function to operate.
- Allow space for access to the fuse for replacement after operation.
How to Select
- Whether a load switch alone or a load switch-fuse combination is required.
- Rated current required — 630 A for the load switch or 125 A for the switch-fuse combination.
- Rated short-circuit breaking current required — 31.5 kA for the combination.
- Whether an earthing switch is needed, and whether it must withstand short-circuit current.
- Main circuit configuration and the switching duty of the circuit.
FAQ
What currents can the FKN12-12D load switch handle?
It switches on and off load current, loop current, no-load transformer current and cable charging current. It is also rated for closing short-circuit current.
What is the difference between the load switch and the switch-fuse combination?
The load switch alone handles load and loop current switching. The switch-fuse combination adds an S□LAJ-12 (XRNT□-10) high-voltage current-limiting fuse, so it can break short-circuit current as well.
How do the load switch and fuse work together?
The load switch breaks the working current and the fuse breaks the short-circuit current. Together they reliably break any overcurrent between the working current and the full short-circuit current.
What happens when the fuse operates?
The fuse makes the load switch open through its striker. This means the circuit is opened by the load switch and not left relying on the fuse alone.
Can the load switch be fitted with an earthing switch?
Yes. The load switch can be equipped with an earthing switch, and that earthing switch is able to withstand short-circuit current.
Which fuse is used with the combination appliance?
The FKRN12-12D/T125-31.5 appliance is formed by combining the FN12-12D load switch with the S□LAJ-12 (XRNT□-10) high-voltage current-limiting fuse. The rated current of the combination is 125 A and the rated short-circuit breaking current is 31.5 kA.
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