In article <q0emgi$i3j$1@reader2.panix.com>,
David Lesher <wb8foz@panix.com> wrote:
If the ground pole comes off, the bus stops...
BUT with no ground, the chassis must float above ground.
Someone boarding or departing would be straddling the voltage
difference; if they stepped into water, or grabbed a handrail...
It is my impression that trolleybuses can go either way under the
wire, so I doubt they tie either side to the chassis.
I've often wondered about one aspect of trolley-bus technology.
You have a hot pole, and a ground pole. (I believe on some
routes, the hot cat can also serve railed/streetcar vehicles,
but I'm not sure.)
If the hot pole comes off the cat, the bus stops dead.
If the ground pole comes off, the bus stops...
BUT with no ground, the chassis must float above ground.
Someone boarding or departing would be straddling the voltage
difference; if they stepped into water, or grabbed a handrail...
I can think of a few solutions to the bus issue; I just wonder how
it's actually handled.
(I recall reading of a similar fatality in the Princeton area;
she was boarding or disembarking from an Amtrak train, and an
Acela went by at high speed on a parallel track. That raised
train-ground to well above station ground; she was the conductor
between them.)
(I recall reading of a similar fatality in the Princeton area;
she was boarding or disembarking from an Amtrak train, and an
Acela went by at high speed on a parallel track. That raised
train-ground to well above station ground; she was the conductor
between them.)
I've often wondered about one aspect of trolley-bus technology.
You have a hot pole, and a ground pole. (I believe on some
routes, the hot cat can also serve railed/streetcar vehicles,
but I'm not sure.)
If the hot pole comes off the cat, the bus stops dead.
If the ground pole comes off, the bus stops...
BUT with no ground, the chassis must float above ground.
Someone boarding or departing would be straddling the voltage
difference; if they stepped into water, or grabbed a handrail...
I can think of a few solutions to the bus issue; I just wonder how
it's actually handled.
(I recall reading of a similar fatality in the Princeton area;
she was boarding or disembarking from an Amtrak train, and an
Acela went by at high speed on a parallel track. That raised
train-ground to well above station ground; she was the conductor
between them.)
David Lesher <wb8foz@panix.com> wrote:
I've often wondered about one aspect of trolley-bus technology.
You have a hot pole, and a ground pole. (I believe on some
routes, the hot cat can also serve railed/streetcar vehicles,
but I'm not sure.)
If the hot pole comes off the cat, the bus stops dead.
If the ground pole comes off, the bus stops...
BUT with no ground, the chassis must float above ground.
Someone boarding or departing would be straddling the voltage
difference; if they stepped into water, or grabbed a handrail...
I can think of a few solutions to the bus issue; I just wonder how
it's actually handled.
(I recall reading of a similar fatality in the Princeton area;
she was boarding or disembarking from an Amtrak train, and an
Acela went by at high speed on a parallel track. That raised
train-ground to well above station ground; she was the conductor
between them.)
One method used at least on some networks is to have the OHL voltage float
so neither wire is directly grounded. My understanding is trolleybuses are designed with the intention of fully insulating the bus from the traction supply rather than using it for grounding, and attempting to ground the vehicle to the road as best as is possible.
Robin
(I recall reading of a similar fatality in the Princeton area;
she was boarding or disembarking from an Amtrak train, and an
Acela went by at high speed on a parallel track. That raised
train-ground to well above station ground; she was the conductor
between them.)
In article <q0emgi$i3j$1@reader2.panix.com>,
David Lesher <wb8foz@panix.com> wrote:
(I recall reading of a similar fatality in the Princeton area;
she was boarding or disembarking from an Amtrak train, and an
Acela went by at high speed on a parallel track. That raised
train-ground to well above station ground; she was the conductor
between them.)
I grew up in Princeton and never heard of such an incident. The only electrical injury I know of is a student who climbed up on top of the
parked Dinky one night in 1990, grabbed the wire, and was nearly killed. It led to a court case where the student got a lot of money from the
railroad and the university. The guy went on to med school and specializes in hospice care:
https://www.ucsfhealth.org/doctors_and_clinics/features/miller_bj/index.html
I grew up in Princeton and never heard of such an incident. The only >electrical injury I know of is a student who climbed up on top of the
parked Dinky one night in 1990, grabbed the wire, and was nearly killed.
I question that. Given the extensive service of a trackless,
sooner or late those circumstances would occur and someone
get zapped. But I don't think that has ever happened.
I can think of a few solutions to the bus issue; I just wonder how
it's actually handled.
John Levine <johnl@taugh.com> writes:
I grew up in Princeton and never heard of such an incident. ...
I can't recall or cite details. But as an EE, it made sense to
me. ...
I'm not denying that something like that could happen. I'm
just saying that there's no evidence that it actually has.
John Levine <johnl@taugh.com> writes:
I grew up in Princeton and never heard of such an incident. The only >electrical injury I know of is a student who climbed up on top of the >parked Dinky one night in 1990, grabbed the wire, and was nearly killed.
I can't recall or cite details. But as an EE, it made sense to
me. The rails are not grounded through the roadbed as they run,
they are instead isolated by a choke (Wee-Z Bond) and grounded
at the substation. So drawing a lot of current would raise
the rail-to-ground voltage. And thus the train would be above
ground. Usually that's no issue as the train is not drawing high
current. But when the adjacent train is.....
Rails aren't grounded through the roadbed?
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