Shiden Kukan

[Ronny]

I've a question for the forum.

Yesterday I was watching the second episode of the anime Tetsuko no Tabi and at 15 min 29 sec the protagonist spoke of "Shiden Kukan" about the transition from DC to AC, can someone explain to me the meaning? I know that Japan has both lines AC and DC, but the discussion of the anime seems strange to me. Here's a link of the episode on Youtube https://youtu.be/iCu19p9K7r0?t=15m29s

Thanks.

Edited August 27, 2015 by Ronny

[railsquid]

Not an expert, but it's a section of unpowered wire for the transition between AC and DC sections, presumably longer than the train so you don't have one pantograph on DC and another on AC. The train has to coast without power like this:

 

 

The subtitles on that anime aren't correct, it says "Depending on the time of day or climate" systems change, which is BS; what was actually said is "地域によって", i.e. depending on the region.

Edited August 27, 2015 by railsquid

[Kabutoni]

This is called a 'dead section' in railway terminology. You can find lots about this here: http://deadsection.image.coocan.jp/

 

 

The train has to coast without power like this:

 

Only old types have this problem. New types like the E531 and TX2000 don't have to deal with a 'power out' any more. I'm not sure about the E501, as I've only ridden it once or twice, but IIRC it also didn't flicker when going through a dead section.

[bikkuri bahn]

Language-wise, the katakana term "dead section" is used more than "shiden kukan", which is a rather inelegant phrase and likely is more the stuff of manga and anime worlds than real life. The somewhat softer term "muden kukan" also exists, along with another rough-sounding "shikukan" (dead or "death" section). 

Edited August 27, 2015 by bikkuri bahn

[kvp]

The flicker is seen only on units that drive the lights directly from the main traction supply. Early trains had no low voltage auxiliary systems with battery backup and even when they did, it was only for control systems and marker lights. Most modern trains have some form of static converter that provides power for the train lighting and it's battery backed, meaning even in case of a power failiure, the interior lights stay on for some time.

 

The dead sections are an old way to transition from one power district to another and have to be at least as long as the two most distant connected pantographs to ensure that the two districts are not connected together and give enough time for the driver to switch over. An alternative is to have a very short isolation and require the trains to lower their pantographs until they cross the boundary. This can be automated with trackside markers.

 

For a DC to DC or an AC to AC transition and on modern trains, the same pantographs can be used, but older trains had separate AC and DC pantographs with different subsystems and different level of electrical isolation. The reason is that it was easier to connect the transformers to the AC pantographs in a fixed fashion and the through train DC cable to the DC pantographs and select them by raising the right one. Modern systems use common pantographs and the board electronics select the right conversion method. This also has the added benefit of having all high voltage cables and systems isolated for the highest supported voltage.

 

For really modern trains, the isolated section can be as short as the width of the pantograph and each pantograph can have its own subsystem with automatic selection between standards. This means the driver can leave them up and the control electronics handle the rest. It also means the through train traction power bus is behind the control electronics, so it's impossible to connect two districts through the bus and the pantographs.

 

ps: For many 3rd rail systems, the high voltage systems were never connected, so the length of the dead sections could be limited to either shoe or pantograph width. The benefit of this is that only one pickup and its associated power bogie falls out during the crossing and the system is simple and safe even without driver control and the lights only blink during a crossing. The benefit of a through train connected system is that if there is gap that is not a section boundary (which is very common for 3rd rail), the lights and the motor power will be continous on the whole train, even if one of the pickups stops over a gap. In exchange, if there is a boundary, then the powerless time will be higher as seen on the video above.

[Ronny]

"Depending on the time of day or climate" was what I did not understand, is "depending on the region" that have sense. In Italy there're dead section too between the AC high-speed lines and the DC classic lines.

Thanks to all.

[Sacto1985]

The best example I've seen online demonstrating the transition from DC 1500 V to AC 20,000 V overhead power on a Japanese railway is this video I've posted before from YouTube member saremya:

 

 

The description (in Japanese) starts at 33:35 into video as the JR West 475 Series EMU approaches Itoigawa Station, complete with a small inset video to show the transition as the interior lights are switched off and on, and you can see the "dead section" overhead wiring around 34:00 in the video.