The AC railway neutral section switch

Solid-state switches, the maintenance-free alternative to mechanical switches

In many railway networks, different sections of a railway line are supplied by different phases of the AC grid. Therefore they need to be isolated from each other. The line section in between two sections with different phases is called neutral section. Often, neutral sections are relatively short and a train can easily coast through them without power supply from the catenary. However, in some railway networks, especially in China, the neutral sections are longer and sometimes in up-hill sections of the railway line. This makes it impossible for the train to coast through without additional power supply. In such case, the neutral sections need to be electrified. This is where the AC railway neutral section switch comes into play.

Electrification of the neutral sections

The electrification is traditionally realized by one-phase mechanical switches at each end of the neutral section. This allows the electrification of the neutral section from either side. The problem with such mechanical switches is that due to frequent traffic on the railway line, the power switching frequency is high. In addition, especially in uphill sections, the locomotives are operating at high power, which leads to high currents in the neutral section. Both together, the high switching frequency and the high switching frequency, leads to fast consumption of the electrodes and short maintenance intervals of the mechanical switches are unavoidable. The fact that the switches are often installed in mountainous regions leads to a further increase of the maintenance cost.

Continuous power supply to the locomotives while passing the neutral section

Like in many other applications, the answer to this problem is solid-state technology. Just as the traditional mechanical solution, the Astrol solid-state railway switch is installed at both ends of the neutral section and allows its electrification from either side. The change-over from Phase A (first side power supply) to Phase B (second side power supply) can be realized seamless within milliseconds, in a way that no interruption of the power during the change-over can be sensed by the train passengers.

The AC Railway Neutral Switch

Applying the AC Railway Neutral Switch results in less component wear and tear and a smoother ride for the passenger.

Platform with customizable current and voltage ratings

The Astrol railway switch is realized as a platform, with customizable current and voltage ratings. It allows every neutral section to be equipped with the optimal amount of power electronics components, but always based on the same qualified power electronics technology.

The AC railway neutral section switch

Typical specifications

  • Rated voltage: 27.5kVAC  50Hz
  • Rated current: 1000A
  • Load profile:    40 seconds on time every 7 minutes
  • Cooling mode: Air-forced cooling with heat pipes

The AC railway neutral section switch in a diagram

The AC railway neutral section switch diagram

At Astrol, we are more than just a design partner. With our commitment to quality, innovation, and customer satisfaction, we are your long-term collaborator in success.

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