Neutral Section arcing horns

[Tin Rocket]

Hi,what are the purpose of neutral section arcing horns/catchers? and what is the detrimental effect on the horns when they become burnt?
cheers

 

[Domh245]

Taken from GazK's book pg89

Sacrificial arcing horns are often provided in the event that a train draws power through the dead section.

The detrimental effect is that they are wearing out, but the good news is that they are doing their job.

 

[Tin Rocket]

Taken from GazK's book pg89



The detrimental effect is that they are wearing out, but the good news is that they are doing their job.

How would power be able to be drawn through a neutral section? it's an insulated section isn't it?

 

[thecrofter]

The term Neutral Section is a bit of a misnomer in that it is of course earthed. If a train fails to clear its circuit breaker via the APC magnet and is still drawing current as it enters the NS then it will draw an arc.


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[Tin Rocket]

The term Neutral Section is a bit of a misnomer in that it is of course earthed. If a train fails to clear its circuit breaker via the APC magnet and is still drawing current as it enters the NS then it will draw an arc.


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If the train was still drawing current as it enters the N/S and the N/S had no arcing horns what would happen to the N/S?

 

[Elecman]

Potentially major short circuit to earth and the contact wire parting

 

[Tin Rocket]

Potentially major short circuit to earth and the contact wire parting

The N/S is made up of insulators isn't it? how would the contact wire part?

 

[AM9]

that's right, a full neutral section has a sequence of electrically functioning parts as follows:

1) previous powered conductor
2) in-line insulator (usually made from alternate ceramic and PTFE beads)
3) isolated section of conductor
4) another in-line insulator
5) grounded neutral section of conductor
6) another in-line insulator
7) another isolated section of conductor
8) another in-line insulator
9) following powered conductor​

If the there was repeated arcing from pantographs still carrying load currents, there would be tracking across the insulators at the leading insulator. To prevent that, the 'horns' run parallel to the insulator meaning that the power is transferred to an isolated section of conductor after the insulator has been passed. Any high voltage transients are then dissipated as the pantograph parts company from the horns, (no stress occurs when an isolated conductor is added to the powered circuit). The insulators are rated to handle the maximum voltage spikes caused by the collapse of the current. If there is repeated breaker malfunctioning, the horns will eventually burn a bit but that is well withing the maintenance cycle of the OLE.

 

[Tin Rocket]

that's right, a full neutral section has a sequence of electrically functioning parts as follows:

1) previous powered conductor
2) in-line insulator (usually made from alternate ceramic and PTFE beads)
3) isolated section of conductor
4) another in-line insulator
5) grounded neutral section of conductor
6) another in-line insulator
7) another isolated section of conductor
8) another in-line insulator
9) following powered conductor​

If the there was repeated arcing from pantographs still carrying load currents, there would be tracking across the insulators at the leading insulator. To prevent that, the 'horns' run parallel to the insulator meaning that the power is transferred to an isolated section of conductor after the insulator has been passed. Any high voltage transients are then dissipated as the pantograph parts company from the horns, (no stress occurs when an isolated conductor is added to the powered circuit). The insulators are rated to handle the maximum voltage spikes caused by the collapse of the current. If there is repeated breaker malfunctioning, the horns will eventually burn a bit but that is well withing the maintenance cycle of the OLE.

ok thanks,will the pan be in contact with N/S insulators as it passes through the N/S?and also is there still electrical power in the carriages such as lighting or power points for laptops etc as it passes through a N/S?

 

[AM9]

ok thanks,will the pan be in contact with N/S insulators as it passes through the N/S?and also is there still electrical power in the carriages such as lighting or power points for laptops etc as it passes through a N/S?

As I said above, it will be in contact with the parallel horns until it has passed the insulators. Any arcing will only start when the horns run out and the pantograph breaks contact with them. So long as the horns are still connected to the incoming powered conductor, the train is still getting power. The insulators/isolated conductor neither carry power nor try to ground the pantograph to anything, so no arcing to/through them even when the arc starts at the end of the horns.