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Working out railway losses

Somewhere along the line there has been a misunderstanding of the context in which the figure of 25 per cent for the losses in Network Rail’s third-rail DC electrification system mentioned by R Eaton (Letters, October 2012) applies.

It cannot be a half-hour average value that could be used for energy budgeting. More likely it applies to short-term peak loads, lasting for a minute or two, in a small part of the system. If a substation delivers 750V, and 25 per cent of the energy is lost, the voltage at the trains would be 562.5V and chaos would ensue. Normally, timetables are designed on the assumption that the voltage available at the trains is 675V.

Calculating losses in 750V DC third rails and the 25kV AC overhead lines is not easy. Very little rolling stock has on-board energy metering, so we have to resort to simulations, running a combined simulation of the electrical network and all the trains that run on it over a period of a few hours. The total energy delivered by the substations is calculated, and the energy used by the trains (net of regenerative braking) calculated.

When I retired from my job in electrification engineering in 2008, Network Rail did not have a good way to do these calculations Recently I succeeded in obtaining a realistic simulation of a part of the South-Western lines from London Waterloo as far as Byfleet and Reading, and the branch lines in between. That area has 37 substations. In the morning peak period, from 6:30 to 9:30, losses are calculated to be between 7 per cent and 11 per cent of the imported energy.

That is not the whole story - there are additional losses within the substations, and in the three-phase cables that connect the substations to the supply points. I have not yet had an opportunity to work those out, but I think that, together, they are between 3 per cent and 4 per cent of the imported energy.

A few years ago I made a similar calculation for an AC electrified line using Network Rail’s OSLO computer program. The calculated losses in the overhead lines did not exceed 3 per cent, except in very arduous scenarios that included the complete outage of an electricity supply point.

Replacing DC third rails with AC overhead lines might save up to 10 per cent of the imported energy, which would be insufficient to justify the cost of making the change. Particular obstacles are the signalling and telecommunications systems, very little of which are compatible with AC electrification.

A more fruitful field of investigation would be the age of the assets. A very large fraction of the existing DC electrical equipment and cables was installed during the 1950s and the 1960s, and some equipment from the 1930s remains in use. Many parts of the signalling and telecommunications systems are elderly.

It would make sense, economically as well as technically, to replace the DC third rails with AC overhead lines if the work were done in a coordinated programme aimed at renewing all of the signalling and telecommunications systems. Clearly it would be necessary to obtain a commitment to provide the required quantities of money at the required times. That would be the really difficult part!

Frank Waterland CEng MIET, Formerly traction power system development engineer, Network Rail



I used to work for Railtrack/Network Rail in the London area, responsible for the section of line from Euston up to, and past, Watford Junction. From Harrow & Wealdstone, London Underground shares the tracks on the suburban line as far as Queens Park, where they disappear underground. The voltage is not 750V DC, but 650V DC. I am sure this ‘sharing’ is similar in other mainline systems which run into London from outside the capital, and makes sense to reduce the need for additional tracks.

There are many positives with removing DC-fed current and replacing it with 25kV, a key one being from a safety perspective. Most traction motors are now heavily energy efficient, use regenerative braking, and high speeds on suburban routes are not that frequent due to the stop/start requirements of frequent stations.

Acceleration would be a benefit, but trains these days have that capability. However, you would not be able to put overhead catenary inside London Underground tunnels - a main location of DC rails - and the cost for converting the remainder would take years to realise.

David Eyley

By email


Britain lagging on patents

Dr Graham Maile makes a valid point about how inventors have become disenfranchised by the commoditisation of patents (Comment, September 2012). What really caught my eye as a patent attorney was the list of notable companies that have recently been involved in high-value transfers of patents. Not one is British. This is consistent with my own experience, with more and more of my work originating from overseas.

It is now quite common to come across British high-technology businesses that have no budget for intellectual property. The result is invariably the same: poor protection and missed opportunities. It seems that many businesses cannot see past the relatively modest cost of obtaining meaningful patent protection and do not realise that this is effectively purchasing exclusive access to a revenue stream that would not otherwise exist. If the idea is any good and well aligned with the business model then it is likely that this revenue stream will pay for the patent many times over.

US and Asian companies seem to understand this point if the volume of patent applications they file is considered as a yardstick. The European Patent Office’s annual report for 2011 indicates that over half of all European patent applications are filed by US and Asian companies, and this has been the case for the last five years at least. On the other hand, the British account for merely 2.6 per cent of all European patent applications filed. This is around three-quarters of the amount filed by the Swiss, around half of the amount filed by the French, and around a fifth of the amount filed by the Germans.

I am sure that many will say that the cost of patent litigation is simply too high for companies, especially SMEs. This argument has some merit, but it is also true that most patent litigation does not end up in court; the other side generally has as much (or as little) interest in going to court as you. Also, there have been significant improvements in the cost of litigating lower-value patent cases with the recent reform of the Patents County Court. Furthermore, and possibly most importantly, the potential cost of patent litigation does not seem to be deterring competitive businesses overseas from protecting their intellectual property.

The amounts of money paid for the patents that Dr Maile cites are certainly eye-wateringly large. But, they are possibly understandable when one considers that the recent spat between Apple and Samsung has resulted in damages of over $1bn being awarded to Apple for infringement of a handful of patents, including some which Samsung contends grant Apple “a monopoly over rectangles with rounded comers”.

David Wraige



Doctor? Who is?

Medical doctors routinely achieve incredible results, particularly in advanced surgical procedures. Consultant surgeons, physicians and other specialists rightly deserve the accolades bestowed on them and the reverence with which they are regarded by members of the public. We call them doctors; we universally approve of them using the title ‘Dr’, but they don’t hold a doctorate degree.

To my mind the term ‘doctor’ is synonymous to ‘nurse’; they are job functions that really mean nothing outside of the workplace. If a doctor is struck from the BMA register for malpractice he can no longer refer to himself as Dr, but a PhD cannot be taken away from its holder, for any reason, because it is a degree. By far the majority of medical doctors only hold bachelor degrees, usually in medicine and surgery.

The title Dr is definitely regarded as a status symbol and it seems unfair to me that similarly qualified engineers cannot call themselves ‘doctor’. With that degree of education, experience, training and responsibility they may become Chartered Engineers (CEng) and even European Engineers (Eur Ing), a much misunderstood qualification, but not doctors.

It is common practice now for dentists, chiropractors, podiatrists, acupuncturists, physiotherapists etc, all with only a bachelor degree, to assume the title of doctor. I have the greatest respect for medical ‘doctors’. However, their skills rely heavily on finely engineered equipment, scanners, surgical instruments and diagnostic devices, but this is largely unseen by members of the public. Give a surgeon the tools from a Victorian naval doctor’s canvas bag and ask him to do a laparoscopic cholecystectomy or a Pterygium excision. He couldn’t! Without engineers his performance is limited, yet he alone enjoys the public admiration and prestige associated with his life-saving achievements. If engineers could equate their status to medical doctors, through adoption of the title Dr, I would consider it to be totally fair.

The question of status for engineers has been bandied around for decades. Could this be a way of correcting that thorny issue? Come on, the IET, at least put it to committee for discussion and maybe engineers will get the status that they have wanted for so long, and so rightly deserve.

EurIng David R Hill CEng FIEE

Wootton Bridge, Isle of Wight

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