Safety Test Switch (STS)
The apex in safety for power systems testing
The ST Switch ensures efficient isolation of the substation devices from the system side equipment by employing disconnect pins. This isolation enables the execution of secondary injection testing, which can be conveniently carried out via strategically positioned banana jacks on the front side of the test block.
To enhance operational transparency, the ST Switch incorporates built-in status windows. These windows enable operators to visually monitor and assess the opening and closing actions of the internal contacts during testing procedures.
- Finger-safe – There are no exposed metallic parts on the ST Switch, greatly increasing safety during testing.
- Keyed Disconnect Pins – Disconnect pins are keyed to the corresponding slots of the test block, preventing mistakes and errors during test.
- Integrated Status Window – Status windows in the front of the ST Switch allow visual inspection of the internal contacts position (open or closed).
- Wire Terminals – Wire terminals are replicated from the FT Switch and offer maximum convenience for technicians and engineers. A screw terminal and a stud terminal version are available.
- Less than 2 mΩ internal resistance – Thanks to the patented construction, ST Switches boast an extremely low internal resistance. This ensures a lighter load on instrumentation transformers and no impact on heat generation within panels.
- Ideal for Retrofit of Older FT Switches – The ST Switch models are available in any even number within the range of 4 to 20-pole configurations. 10-pole ST Switches have the same panel cutout as legacy FT switches. Even the terminal labeling is the same. That means that you can have the increased safety and efficiency from the ST Switch without having to change your engineering drawings.
Closed circuit
An ST Switch contains any even number of poles within the range of 4 and 20, each allocated to a current, voltage, signal or trip circuit. Each circuit is connected through the block via two silver-plated copper contacts, pressed securely together by two pressure springs to create a highly conductive electrical connection. In this situation, a electrical connection is established between the device side (B) and the system side (A).
Open Circuit
To open one of these modular poles, a disconnect pin is removed from its inactive “parking” position and inserted between the silver-coated copper contacts (the “test” position). In this position, the device and system sides of the test block are isolated from each other. For current circuits, the disconnect pins include internal shorting bridges. When the pin is moved back to the “parking” position, the internal springs force the contacts back together, returning the circuit to its normally-closed position. There is no in-between position, completely eliminating the risk of accidents resulting from improperly closed circuits.
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