Infrastructure problems in Thames Valley causing disruption elsewhere - ongoing, since Oct 2014

[whole diary]

[onthecushions]

Now advising disruption until 2359, apparently NR^» (Network Rail - home page) have identified the problem & are fixing it.

Two replacement fuses have both blown shortly after installation, so sections of the signalling being isolated one at a time to trace where the fault is.

Still using fuses?

OTC

[Electric train]

Now advising disruption until 2359, apparently NR^» (Network Rail - home page) have identified the problem & are fixing it.

Two replacement fuses have both blown shortly after installation, so sections of the signalling being isolated one at a time to trace where the fault is.

Still using fuses?

OTC

What is wrong with fuses?
 
Fuses BS88 (HRC^▸ (High Rupturing Capacity)) fuses are very reliable, can handle high fault levels, work as well with dc and ac and are not susceptible to nuisance tripping due to mechanical vibration like MCBs^▸ (Miniature Circuit Breaker) also easy to grade in terms of discrimination.

MCB are used in places and the new signalling power supplies (650V) uses VCBs^▸ (Vacuum Circuit Breaker - electrification) and a auto reconfigurable system, however for the lower voltage parts of the system fuse are the most reliable.

The incoming supply from the DNO^▸ (Distribution Network Operator) or internal railway high voltage transformers will be a BS88 (type) fuse.

[TaplowGreen]

Due to engineering works not being finished on time between London Paddington and Slough:

Train services running to and from these stations may be delayed or revised. Disruption is expected until 09:30 18/09.

[broadgage]

Now advising disruption until 2359, apparently NR^» (Network Rail - home page) have identified the problem & are fixing it.

Two replacement fuses have both blown shortly after installation, so sections of the signalling being isolated one at a time to trace where the fault is.

Still using fuses?

OTC

Fuses have a lot to be said for them, especially in adverse conditions such as lineside equipment cabinets. MCBs^▸ (Miniature Circuit Breaker) are somewhat temperature sensitive and may trip prematurely in very hot conditions, or allow an over current to persist for longer than it should in very cold conditions.
Most types of MCB are not sealed and the internal parts are vulnerable to rust etc.

Fuses are often preferable to MCBs in complex circuits were a number of fuses or MCBs are required in series.
If a 16 amp MCB and a 32 amp MCB are in series then a fault may well trip both.
A 16 amp fuse and a 32 amp fuse OF THE SAME TYPE in series will normally blow the smaller one before the larger one.

The main drawback of fuses is the absolute requirement for an ample stock of spares, an intermittent fault can blow a surprising number of fuses before it is located.
IMO^▸ (in my opinion), a prudent minimum stock of spare fuses is 2 for each circuit AND a dozen extra regardless of how many or how few circuits use that type. So if a control panel contains 8 fuses of the same type, the spare stock should be 2 for each circuit =16 AND another 12 or 28 in total.
For equipment that is of great importance, or that has a history of blowing fuses for unknown reasons, twice as many should be provided.

[IndustryInsider]

The main drawback of fuses is the absolute requirement for an ample stock of spares, an intermittent fault can blow a surprising number of fuses before it is located.

As demonstrated on Friday afternoon.

[Adelante_CCT]

Two replacement fuses have both blown

As demonstrated on Friday afternoon.

Would you be referring to the electrical equipment or the commuters? 

[onthecushions]

What is wrong with fuses?
 
Fuses BS88 (HRC^▸ (High Rupturing Capacity)) fuses are very reliable, can handle high fault levels, work as well with dc and ac and are not susceptible to nuisance tripping due to mechanical vibration like MCBs^▸ (Miniature Circuit Breaker) also easy to grade in terms of discrimination.

MCB are used in places and the new signalling power supplies (650V) uses VCBs^▸ (Vacuum Circuit Breaker - electrification) and a auto reconfigurable system, however for the lower voltage parts of the system fuse are the most reliable.

The incoming supply from the DNO^▸ (Distribution Network Operator) or internal railway high voltage transformers will be a BS88 (type) fuse.

I suggest we ask ourselves how we would prefer critical electrical circuits to be protected in civil airliners.

There's about three minutes to rectify a problem.....

OTC


Edit to correct format only

[Electric train]

The main drawback of fuses is the absolute requirement for an ample stock of spares, an intermittent fault can blow a surprising number of fuses before it is located.

As demonstrated on Friday afternoon.

What is wrong with fuses?
 
Fuses BS88 (HRC^▸ (High Rupturing Capacity)) fuses are very reliable, can handle high fault levels, work as well with dc and ac and are not susceptible to nuisance tripping due to mechanical vibration like MCBs^▸ (Miniature Circuit Breaker) also easy to grade in terms of discrimination.

MCB are used in places and the new signalling power supplies (650V) uses VCBs^▸ (Vacuum Circuit Breaker - electrification) and a auto reconfigurable system, however for the lower voltage parts of the system fuse are the most reliable.

The incoming supply from the DNO^▸ (Distribution Network Operator) or internal railway high voltage transformers will be a BS88 (type) fuse.
[/quote]

I suggest we ask ourselves how we would prefer critical electrical circuits to be protected in civil airliners.

There's about three minutes to rectify a problem.....

OTC
[/quote]

The biggest problem I have come across in my 40 years as an electrical engineer is you can only reset a MCB a number of times after it has cleared a fault (typically after 5 faults) this is because the contacts get pitted and burnt and then there is the risk of contacts welding, also MCB are expensive compared to the humble "red spot" BS88.

The railway signalling system and many other critical system has hundreds of thousands if not millions of fuse 99.9% of them sit there passively for their working life for 30, 40 even 50 years doing their job and retire without a rupture, the ones that do rupture do so because there has been a fault.

A fault is just that something has gone wrong and its not the fuse that ruptured because it felt like it its because a cable or component has failed, to get a system up and running new fuse are put in if they rupture again then the fault has to have detailed investigation because if you just keep putting fuses in more and more damage is done and can even lead to loss of life or fire

[patch38]

Is this the first time we've heard this as a reason for delays - damage to overhead line equipment in the Burnham area causing delays into and out of Paddington this morning. On the relief lines, according to TM^‡(resolve).

[ChrisB]

Looks as the lady in her mobility buggy isn't going quietly (see thread elsewhere!)

[TaplowGreen]

Is this the first time we've heard this as a reason for delays - damage to overhead line equipment in the Burnham area causing delays into and out of Paddington this morning. On the relief lines, according to TM^‡(resolve).

..............the shape of things to come!!! 

[sanfrandragon]

Is this the first time we've heard this as a reason for delays - damage to overhead line equipment in the Burnham area causing delays into and out of Paddington this morning. On the relief lines, according to TM^‡(resolve).

So ironic, and they're not even in use yet, but damage causing slow running trains anyway.

[Jason]

Due to damage to the overhead electric wires at Burnham the line towards Reading is blocked.
Impact:
Train services running through this station may be cancelled, delayed by up to 30 minutes or revised. Burnham and Taplow will not be served. Disruption is expected until 11:00 27/09.

I took a 15 minute hit on an High Speed Train (HST^▸ (High Speed Train)) from Reading to Paddington.

Edit: VickiS - Clarifying Acronym

[patch38]

From my casual observation (i.e. looking out of passing HST^▸ (High Speed Train) windows), I don't believe the wires are even installed there yet. So presumably the damage is to a gantry or some other piece of support infrastructure?

[paul7575]

Is this the first time we've heard this as a reason for delays - damage to overhead line equipment in the Burnham area causing delays into and out of Paddington this morning. On the relief lines, according to TM^‡(resolve).

It isn't the first report of this nature, there were reports of 'damage to OHLE' causing delays west of Tilehurst some time ago, which turned out to be something used temporarily during installation hanging into the path of traffic on the main lines. 

Possibly something similar this time - IIRC^▸ (if I recall/remember/read correctly) the reasons for delay automatic announcements are chosen from a menu, so there probably won't be one that covers 'installer error'...   

Paul