For the first time today I waited on the southbound line to moorgate
at highbury. I noticed above the track there was what looked like
catenary strung up above the track all the way along and then it
disappeared into the tunnels. It also looked pretty old and given the
lack of any serious insulators theres no way it could be 25Kv. So was
it some abortive attempt at 750v DC overhead or was it something else
entirely?

B2003

On 11 Sep, 09:54, Boltar wrote:
For the first time today I waited on the southbound line to moorgate
at highbury. I noticed above the track there was what looked like
catenary strung up above the track all the way along and then it
disappeared into the tunnels. It also looked pretty old and given the
lack of any serious insulators theres no way it could be 25Kv. So was
it some abortive attempt at 750v DC overhead or was it something else
entirely?

It is an unpowered overrun wire, to guard against a train running with
a raised pantograph. It was installed at the time of the BR takeover
of the line.

On Sep 11, 10:40 am, wrote:
It is an unpowered overrun wire, to guard against a train running with
a raised pantograph. It was installed at the time of the BR takeover
of the line.

How far does it run? I don't remember seeing it at Moorgate.

B2003

On 11 Sep, 11:11, Boltar wrote:
On Sep 11, 10:40 am, wrote:

It is an unpowered overrun wire, to guard against a train running with
a raised pantograph. It was installed at the time of the BR takeover
of the line.

How far does it run? I don't remember seeing it at Moorgate.

B2003

I'll guess not far - as aren't the traction systems interlocked so
that when a driver changes to third-rail at Draytom Park the
pantograph gets lowered. In which case the unpowered overrun line just
needs to exist for as far as the train could coast for until it ground
to a powerless halt!

I don't think any driver doing this would make themselves at all
popular, given the 10 minute service frequency that operates to and
from Moorgate in the Great Northern tunnels!

On Sep 11, 7:26 am, Mizter T wrote:
I'll guess not far - as aren't the traction systems interlocked so
that when a driver changes to third-rail at Drayton Park the
pantograph gets lowered. In which case the unpowered overrun line just
needs to exist for as far as the train could coast for until it ground
to a powerless halt!

The overrun line ends south of Highbury s/b platform.


I don't think any driver doing this would make themselves at all
popular, given the 10 minute service frequency that operates to and
from Moorgate in the Great Northern tunnels!

At least in this case the driver can switch to 750V DC and incur only
a medium delay, as opposed to running entirely off the juice.

On 11 Sep, 19:26, TheOneKEA wrote:
On Sep 11, 7:26 am, Mizter T wrote:

I'll guess not far - as aren't the traction systems interlocked so
that when a driver changes to third-rail at Drayton Park the
pantograph gets lowered. In which case the unpowered overrun line just
needs to exist for as far as the train could coast for until it ground
to a powerless halt!

The overrun line ends south of Highbury s/b platform.

I don't think any driver doing this would make themselves at all
popular, given the 10 minute service frequency that operates to and
from Moorgate in the Great Northern tunnels!

At least in this case the driver can switch to 750V DC and incur only
a medium delay, as opposed to running entirely off the juice.

Yes, stupidly I'd overlooked that! In which case it wouldn't be a
problem - in fact who else apart from the driver and pax would know
about it. Maybe it happens all the time!

In article .com,
(Mizter T) wrote:

On 11 Sep, 11:11, Boltar wrote:
On Sep 11, 10:40 am, wrote:

It is an unpowered overrun wire, to guard against a train
running with a raised pantograph. It was installed at the time
of the BR takeover of the line.

How far does it run? I don't remember seeing it at Moorgate.

I'll guess not far - as aren't the traction systems interlocked so
that when a driver changes to third-rail at Draytom Park the
pantograph gets lowered. In which case the unpowered overrun line just
needs to exist for as far as the train could coast for until it ground
to a powerless halt!

I don't think any driver doing this would make themselves at all
popular, given the 10 minute service frequency that operates to and
from Moorgate in the Great Northern tunnels!

An overrun all the way from Drayton Park to Highbury and Islington?
Surely not?

--
Colin Rosenstiel

On 12 Sep, 00:05, (Colin Rosenstiel) wrote:

An overrun all the way from Drayton Park to Highbury and Islington?
Surely not?

It runs as far as the south end of H&I SB platform.

Having it in the platform means that a train that has entered the
tunnel pan up can be visually inspected, and that the AC-DC changeover
can be cycled through (i.e pan down if still raised, go DC, go AC pan
up onto dead line, go DC.).

In the cab there is a buzzer that sounds if the driver tries to take power with both AC and DC power available. At the Finsbury Park end of Drayton Park there is a button to switch off the buzzer. There is not one at the Moorgate end.

On Sep 11, 10:40 am, wrote:
On 11 Sep, 09:54, Boltar wrote:

For the first time today I waited on the southbound line to moorgate
at highbury. I noticed above the track there was what looked like
catenary strung up above the track all the way along and then it
disappeared into the tunnels. It also looked pretty old and given the
lack of any serious insulators theres no way it could be 25Kv. So was
it some abortive attempt at 750v DC overhead or was it something else
entirely?

It is an unpowered overrun wire, to guard against a train running with
a raised pantograph. It was installed at the time of the BR takeover
of the line.

That's odd; Rails Through The Clay suggested it was installed as an
afterthought when someone forgot to lower the pantograph and ended up
causing a bit of damage.