LBSCR Overhead electrification - what if...?

[mike57]

A bit of an odd one this... A what if?

The LBSCR began electrification using 6000v AC (and 25Hz I think). If this system had prevailed over the 3rd rail system what effect would it have had today.

To start the thoughts:

Would we have 25kV or would 6kV supplied sufficient power for a modern railway?

Would higher speeds have developed more quickly?

Would we have more or less electrification today, or would it not have made any difference?

Was it a technically better system back in 1923, just that there was more 3rd rail on the LSWR?

Any other thoughts welcome

 

[daikilo]

As this appears to be a historical question I suggest it be moved to that section.

As to its future, it disappeared when the decision was made to standardise Southern lines on 600V DC third rail. Had that not happened, then 6600V AC may have become a standard until 25kV AC became possible.

 

[SpacePhoenix]

Had it survived in use would some of the LBSCR OLE have been able to be re-used for 25Kv or would it have still required all brand new OLE?

 

[Domh245]

Had it survived in use would some of the LBSCR OLE have been able to be re-used for 25Kv or would it have still required all brand new OLE?

From what I understand, a lot of the 6.25kV sections on the original 25kV schemes were converted with no alterations to the equipment (having originally been introduced to allow for reduced clearances under bridges) so it could have probably gone over with a minimum amount of work, at least for clearances. Things like insulators and other parts of the design may have had to have been altered.

 

[Glenmutchkin]

Was it a technically better system back in 1923, just that there was more 3rd rail on the LSWR?

Any other thoughts welcome

Blame Herbert Walker.

 

[daikilo]

Had it survived in use would some of the LBSCR OLE have been able to be re-used for 25Kv or would it have still required all brand new OLE?

From what I have seen it was close to a tramway-type OHLE and thus probably not suitable for speed. Equally, I doubt it had sufficient insulating characteristics to allow higher voltages.

 

[AM9]

From what I understand, a lot of the 6.25kV sections on the original 25kV schemes were converted with no alterations to the equipment (having originally been introduced to allow for reduced clearances under bridges) so it could have probably gone over with a minimum amount of work, at least for clearances. Things like insulators and other parts of the design may have had to have been altered.

The 6.25kV 50Hz ac electrification on the GEML used all of the original 1500VDC OLE, just changing the feeder equipment. The 1500VDC insulators were found to be OK for a nominal peak voltage of over 8kV. Many of the insulators that replaced them for the 6.25 to 25kV conversion in the '70s were of similar size to the original DC types due in main to the development of better materials and construction in the intervening 30 years.

 

[AM9]

From what I have seen it was close to a tramway-type OHLE and thus probably not suitable for speed. Equally, I doubt it had sufficient insulating characteristics to allow higher voltages.

Although the trains had simple bows that looked a little like some light railway rolling stock instead of pantographs, the OLE design was far from simple or basic. It was unusual as it had twin catenary wires supporting a single conductor wire in an unusual vee configuration. The dynamics of the LB&SCR OLE was probably fine for speeds on the line before WW2 and the OLE portals, some of which survived as structures until the '60s or '70s, were substantial giving clearances compatible with current 25kV requirements. It would also have been simple to rewire using the original portals at the same time as compensated tensioning to allow modern running speeds.

 

[gimmea50anyday]

The 6.25kV 50Hz ac electrification on the GEML used all of the original 1500VDC OLE, just changing the feeder equipment. The 1500VDC insulators were found to be OK for a nominal peak voltage of over 8kV. Many of the insulators that replaced them for the 6.25 to 25kV conversion in the '70s were of similar size to the original DC types due in main to the development of better materials and construction in the intervening 30 years.

Same with the former woodhead routes. In some places around the ardwick-ashburys-Gorton area the original catenery wires are still in use.

 

[edwin_m]

Although the trains had simple bows that looked a little like some light railway rolling stock instead of pantographs, the OLE design was far from simple or basic. It was unusual as it had twin catenary wires supporting a single conductor wire in an unusual vee configuration. The dynamics of the LB&SCR OLE was probably fine for speeds on the line before WW2 and the OLE portals, some of which survived as structures until the '60s or '70s, were substantial giving clearances compatible with current 25kV requirements. It would also have been simple to rewire using the original portals at the same time as compensated tensioning to allow modern running speeds.

The important thing is the voltage, frequency and clearances. If the OLE itself was inadequate for higher speeds, heavier trains etc then it could be upgraded with relatively little disruption while the original trains continued to use it. If you change the voltage or frequency you need new trains and that is much more disruptive. If the clearances were insufficient then structures would have to be re-built.

I imagine the clearances would in fact have been enough, given the conservative approach adopted in early schemes until actual viable clearances had been established. 6kV provides a viable upgrade path to 25kV by using a multi-tap transformer as was done on the early 25kV schemes, but changing the frequency might have been a bigger problem as transformers are optimised for a particular frequency. So if this scheme had survived we might have ended up with 25kV but at a low frequency.

 

[apk55]

I could well imagine that in the 30s that the lines would be converted to 15KV 16.7Hz standard as adopted by Switzerland Germany etc. A lot of similar lines in Germany for example were electrified on a similar system such as Hamburg suburban lines and converted to the standard system

 

[HSTEd]

The question then becomes - would 25kV have ever been adopted if there had been a ~6kV 25Hz installed base comparable in scale to the third rail systems that were installed by the time it was concieved?

 

[AM9]

The question then becomes - would 25kV have ever been adopted if there had been a ~6kV 25Hz installed base comparable in scale to the third rail systems that were installed by the time it was concieved?

Probably for trunk out of urban areas. On a trunk route, the 6kV 'ish level still requires frequent feed points when power demands are high. For example, the GEML had five neutral sections beteeen Liverpool St and Shenfield, so that averages one for every four miles. I can't recall all the feed arrangements but either each section would need national grid feeds or high voltage feeds along the formation for phase distribution. The cost of frequency conversion would be similar to ac/DC conversion so when the rest of the world started adoption of 25kV/50Hz, the lower overall costs would probably prompt gradual conversion to the global standard. There wouldn't be the infrastructure issues if the pre WW2 installations were along the lines of the LB&SCR schemes, as adequate clearance would already be generally available.

 

[HSTEd]

Probably for trunk out of urban areas. On a trunk route, the 6kV 'ish level still requires frequent feed points when power demands are high. For example, the GEML had five neutral sections beteeen Liverpool St and Shenfield, so that averages one for every four miles. I can't recall all the feed arrangements but either each section would need national grid feeds or high voltage feeds along the formation for pNhase distribution.

Installations of low frequency AC of similar vintage in the US (the 11kV system) utilised autotransformer feeding - I think any significant expansion of the 6kV system would have done the same.

National grid feeds would probably not have been used, instead of the Railway would likely have maintained its own single phase traction supply network, as the railways in the 15kV portion of the world.

Utilising a single phase system does significant simplify the feeding arrangements.

The cost of frequency conversion would be similar to ac/DC conversion so when the rest of the world started adoption of 25kV/50Hz, the lower overall costs would probably prompt gradual conversion to the global standard. There wouldn't be the infrastructure issues if the pre WW2 installations were along the lines of the LB&SCR schemes, as adequate clearance would already be generally available.

However BR was at the forefront of 25kV adoption, it is not clear it would have been such a dominant standard if it had not been.
And it is not clear that 25kV 50Hz would have triumphed over either 6kV or some sort of higher voltage 25Hz standard if the installed based had been already present.

Additionally considering the early unreliability of the arc rectifiers in the first 25kV locomotives - there would be a significant incentive for avoiding the whole rectification mess by simply utilising the universal motors used in the low frequency practice.

 

[edwin_m]

Would phase distribution have been an issue though? Surely the traditional answer would have been to have a rotary converter in each feeder station with a 50Hz three-phase motor driving a lower-frequency single phase alternator? Modern installations would have solid state inverters. Either would balance the load across the phases and it might even be possible to have the entire network running synchronously without neutral sections.

 

[mike57]

Probably for trunk out of urban areas. On a trunk route, the 6kV 'ish level still requires frequent feed points when power demands are high. For example, the GEML had five neutral sections beteeen Liverpool St and Shenfield, so that averages one for every four miles. I can't recall all the feed arrangements but either each section would need national grid feeds or high voltage feeds along the formation for phase distribution. The cost of frequency conversion would be similar to ac/DC conversion so when the rest of the world started adoption of 25kV/50Hz, the lower overall costs would probably prompt gradual conversion to the global standard. There wouldn't be the infrastructure issues if the pre WW2 installations were along the lines of the LB&SCR schemes, as adequate clearance would already be generally available.

The question is where would the driver for 25kV 50Hz come from, if there were a lot of successful implementations of 6kV 25Hz, which would have been running since around 1910 would the French have pioneered 25kV 50Hz. I could imagine 1500v DC would not have been as popular, as there would already be an installed base of suppliers for the 6kV 25Hz system. My belief is that the electrification map of Western Europe may have looked very different

 

[HSTEd]

I could see a ~24kV standard being deployed on the WCML - but it would almost certainly would just have been 25Hz.

The overall objective would have been the entire electrification system being synchronous and parallelled at all times.

 

[edwin_m]

The question is where would the driver for 25kV 50Hz come from, if there were a lot of successful implementations of 6kV 25Hz, which would have been running since around 1910 would the French have pioneered 25kV 50Hz. I could imagine 1500v DC would not have been as popular, as there would already be an installed base of suppliers for the 6kV 25Hz system. My belief is that the electrification map of Western Europe may have looked very different

There would still be some energy saving - quadrupling the voltage reduces the losses by a factor of 16 other things being equal. In fact the benefit would probably have been taken in the form of fewer and more widely spaced feeder stations - more of an issue if each one has to contain a rotary convertor.

 

[HSTEd]

There would still be some energy saving - quadrupling the voltage reduces the losses by a factor of 16 other things being equal. In fact the benefit would probably have been taken in the form of fewer and more widely spaced feeder stations - more of an issue if each one has to contain a rotary convertor.

Well there is little reason for feeder stations to all have rotary converters - since you could just use transformers to supply power at high voltages and low frequency.

This is why the traction energy network exists in Germany.
(And sometims you can avoid rotary converters entirely by having a traction energy power station that can support much of the country)

 

[ianhr]

A lot of the LBSCR AC equipment was AEG and so the supply of many parts dried up during WW1 and extensions beyond Crystal Palace and West Croydon could not be completed. If it were not for the war the catenary could well have reached Brighton by the early 1920s and this was the original intention. The Coulsdon and Sutton scheme, which was not commissioned until after the grouping, used motor luggage vans usually positioned in the centre of the train. These were effectively prototype electric locomotives for longer distance mainline services. The decision to standardise on 600v DC third rail was in the end largely political as the LSWR personnel, Walker, Jones etc. dominated the Southern and Philip Dawson of the LBSCR was sidelined. Even at this time the AC technology, while primitive by modern standards, was almost certainly more efficient for distances beyond the suburban area.

 

[36270k]

The New Haven Railroad in 1908 had similar triangular catenary to the LBSC but the voltage was 11000.
The Pennsylvania also used 11000 Volts 25hz. As this was long before any national grid, The Pennsylvania had there own distribution network at 132000 volts single phase.
Some of the power stations generated current at 25hz. eg Safe Harbour dam hydro station.

 

[edwin_m]

Well there is little reason for feeder stations to all have rotary converters - since you could just use transformers to supply power at high voltages and low frequency.

This is why the traction energy network exists in Germany.
(And sometims you can avoid rotary converters entirely by having a traction energy power station that can support much of the country)

Duplicating the National Grid doesn't seem to make too much sense, though perhaps it would have happened if the railway was there first.

 

[HSTEd]

Duplicating the National Grid doesn't seem to make too much sense, though perhaps it would have happened if the railway was there first.

Well that depends, a simple pole line from an appropriate power plant is going to be much less maintenance intensive than multiple rotary converters scattered alone a line potentially miles from anything.
Indeed it might even be less expensive - this is especially true if the Glasgow Area scheme had been carried forward at 6kV - a relatively short power line would have provided access to a hydroelectric generating site powerful enough to provide all normal operating demands by itself.