Tag: Ben Ross

Theory: Why Our Electric Trains are Grounded and Will Face Future Issues

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Possible Cause: Cost Cutting

 

I have seen a bit of activity, chatter and news going around about our Electric Trains. If you are wondering why they are not running at the moment on the Onehunga Line my Electric Train Fleet Grounded [updated] post gave the heads up on it.

An extract from TVNZ stated:

Fault prompts electric train replacement on Auckland network

Published: 1:15PM Wednesday July 23, 2014 Source: ONE News

A power fault has led to Auckland’s new electric trains being replaced on the Onehunga Line.

Auckland Transport has stressed the faults had not resulted in any safety issues.

The power fault has occurred twice in the last 24 hours and while it could take several days to fix timetables will remain unchanged.

Auckland Transport chief operations officer Greg Edmonds says the organisation intends to get to the root of the issue.

“So as not to inconvenience customers we have decided to run diesel units,” he says.

Mr Edmonds also says issues such as this are expected while phasing in a new train fleet.

….

——

Source: http://tvnz.co.nz/national-news/fault-prompts-electric-train-replacement-auckland-network-6036157

 

After some checking and some chats in regards to the EMU fault I came up with a theory into what MIGHT be causing the issues with our electric trains that has resulted in the grounding of the fleet. Now I stress this is a theory in what possibly might have occurred from deductions and observations. Naturally when such a theory is presented the relevant authority would carry out tests to either prove or disprove the theory. Now we know according to Auckland Transport’s Chief Operating Officer Greg Edmonds that equipment is being installed on the two substations that feed the juice into the electric network for the trains to see if they can find the fault. I hope they do however, I theorise that the fault while found, it can not be remedied if Auckland Transport and Kiwi Rail have done cost cutting with the infrastructure thus we will have continual issues until the proper remedy is in position.

 

The Theory? This is what I have thus far

I have previously picked up on the EMU fault that is plaguing our electric trains resulting in their grounding until further notice.  You can see the post in regards to the fleet grounding: https://voakl.net/2014/07/23/electric-train-fleet-grounded/
My theory on the Electric Train grounding has come from chatter and observations from the saga.  Specifically these three links which have raw information on the problems of our EMU fleet
In short on Sunday (20th July) the problems with the EMU’s shutting down in revenue service (so carrying passengers) got pretty bad. Monday got really bad when two EMU’s broke down causing delays and congestion inside Britomart.
Tuesday AT withdrew the entire fleet.

There is NO problems with the trains (rolling stock) themselves from what I have observed. The fault is with the infrastructure used to run the system. I can not stress this enough to readers!

I have been told by many sources inside the rail industry that the problems of over voltage, surges and train fuses being blown COULD BE caused by what is known as dirty power.
Dirty power being:

Power quality

From Wikipedia, the free encyclopedia

Power quality determines the fitness of electrical power to consumer devices. Synchronization of the voltage frequency and phase allows electrical systems to function in their intended manner without significant loss of performance or life. The term is used to describe electric power that drives an electrical load and the load’s ability to function properly. Without the proper power, an electrical device (or load) may malfunction, fail prematurely or not operate at all. There are many ways in which electric power can be of poor quality and many more causes of such poor quality power.

The electric power industry comprises electricity generation (AC power), electric power transmission and ultimately electricity distribution to an electricity meter located at the premises of the end user of the electric power. The electricity then moves through the wiring system of the end user until it reaches the load. The complexity of the system to move electric energy from the point of production to the point of consumption combined with variations in weather, generation, demand and other factors provide many opportunities for the quality of supply to be compromised.

While “power quality” is a convenient term for many, it is the quality of the voltage—rather than power or electric current—that is actually described by the term. Power is simply the flow of energy and the current demanded by a load is largely uncontrollable.

To use a household appliance like a computer as an example: our household appliances run on 240 volts and usually 3-10 amps at 50Hz frequency. When you have dirty power the Hz frequency jumps all over the place and as a result it will cause your computer to either blow its fuse (same way when there is too much amps coming through) or damage the equipment.
To make things more interesting I have been told of over voltage issues especially around the Onehunga Line where the trains go from receiving its normal 25,000 volts to all of a sudden 27,000 volts. Again this will cause the train to shut down if not blow its fuses.
Now as Greg Edmonds has stated only two sub stations were built to feed and filter power to the network and trains. HOWEVER four if not five substations were meant to be built (as noted by the Better Transport Links above) yet we only have two.
Mr Edmonds said special measuring equipment had been installed at both of the electrification system’s two power supply substations, and on the trains themselves, ready for simulated services to be trialled last night.
As substations act as the surge protector, power feeder, and power filter (to prevent the Hz running all over the show thus giving dirty power that shuts the trains down) we are lacking the full set that would serve the entire network and all 57 EMU trains.
And if we are getting faults now owing to two sub stations ever only being built instead of the 4 or 5 that were meant to be with just 6 EMU trains running then how is the system meant to cope with all 57 by the end of next year?
To make problems more interesting I have been told by reliable sources that there could be issues with the earthing system as well. That is houses near the rail line could have their electronics affected if the rail earthing system is not strong enough. Now I have not heard any complaints from residents or business yet. But if we are getting issues with the substations now then no doubt there will be an issue with the earthing system.

 

Power quality issues (so dirty power) also give harmonics issues which have been mentioned before again here:  http://www.bettertransport.org.nz/forum/viewtopic.php?f=1&t=2460&start=2760 (I think one page back from where that one will open). More on harmonics can be seen here: http://en.wikipedia.org/wiki/Harmonics_(electrical_power) (extract below)

Harmonics (electrical power)

From Wikipedia, the free encyclopedia

Harmonics voltages and currents in an electric power system are a result of non-linear electric loads. Harmonic frequencies in the power grid are a frequent cause of power quality problems. Harmonics in power systems result in increased heating in the equipment and conductors, misfiring in variable speed drives, and torque pulsations in motors. Reduction of harmonics is considered desirable.

…

Effects

One of the major effects of power system harmonics is to increase the current in the system. This is particularly the case for the third harmonic, which causes a sharp increase in the zero sequence current, and therefore increases the current in the neutral conductor. This effect can require special consideration in the design of an electric system to serve non-linear loads.[2]

In addition to the increased line current, different pieces of electrical equipment can suffer effects from harmonics on the power system.

Motors

Electric motors experience losses due to hysteresis and losses due to eddy currents set up in the iron core of the motor. These are proportional to the frequency of the current. Since the harmonics are at higher frequencies, they produce higher core losses in a motor than the power frequency would. This results in increased heating of the motor core, which (if excessive) can shorten the life of the motor. The 5th harmonic causes a CEMF (counter electromotive force) in large motors which acts in the opposite direction of rotation. The CEMF is not large enough to counteract the rotation, however it does play a small role in the resulting rotating speed of the motor.

 

And that is my theory behind the situation resulting in the costly grounding of our electric train fleet. The theory stems from the simple fact that currently only two of the four or five substations that would feed the electrified rail network power as well as filter the power to prevent dirty power and over voltage have been built. We only have 50% of the total supply potential and filtering (or protecting) capacity installed for a 25,000 volt system. Thus because of the reduced capacity to filter, protect and supply we get these problems with just SIX electric trains running let alone the full 57.

 

So the question is what will Auckland Transport do? The remedies that I have seen are quite costly if we are to prevent the entire EMU revenue service fleet being pulled again like last week.

Something that could have been in theory very easily avoided!