Searching \ for '[EE] Shunt Trip' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/index.htm?key=shunt+trip
Search entire site for: 'Shunt Trip'.

Exact match. Not showing close matches.
PICList Thread
'[EE] Shunt Trip'
2007\02\01@125007 by Mark Peterson

flavicon
face
I'm working on a 480V distribution relay protection project that
requires the application of a shunt trip device at the time of an
overload condition.  I need to detect when the load exceeds 500A, and at
that time apply a short across the 480V source in order to force the
circuit's 2000A main breaker to trip.  This is similar to using a
grounding switch as the initiator for a transfer trip scheme in the
electric utility world.  Crude, but simple and effective.  I have argued
for other methods but this method has been dictated by the client, the
government client.

Detecting the current is no problem.  My effort now is to determine the
best method to apply the short.  The available fault current is in the
neighborhood of 50kA.  A near-zero ohm short would be ridiculous.  A
fault current of approximately 3000A is sufficient and it can be limited
to that magnitude if I use a 425uH (160mohm) inductor for the shorting
conductor.  Such an inductor would be roughly 15cm in diameter and 30cm
long, with 90 turns of wire that is capable of withstanding the 3000A
surge current for a maximum time of about 10 cycles, or 160 ms.

The question now is:  What is the best way to switch the inductor across
the 480V supply?  Traditional clapper or mercury wetted relay?  Triac?
SCRs?  Whadayathink?

Thanks.  M. Peterson
The preceding e-mail message (including any attachments) contains information that may be confidential, or constitute non-public information.
It is intended only for the designated recipient.  If you are not the named addressee, you should not disseminate, distribute or copy this e-mail.
If you have received this e-mail by mistake,  please notify the sender immediately by replying to this message and delete this e-mail from your system.
Use, dissemination, distribution or reproduction of this message by unintended recipients is not authorized and may be unlawful.

2007\02\01@142922 by Vasile Surducan

face picon face
On 2/1/07, Mark Peterson <spam_OUTmpetersonTakeThisOuTspamcannontech.com> wrote:
> I'm working on a 480V distribution relay protection project that
> requires the application of a shunt trip device at the time of an
> overload condition.  I need to detect when the load exceeds 500A, and at
> that time apply a short across the 480V source in order to force the
> circuit's 2000A main breaker to trip.  This is similar to using a
> grounding switch as the initiator for a transfer trip scheme in the
> electric utility world.  Crude, but simple and effective.  I have argued
> for other methods but this method has been dictated by the client, the
> government client.

You have argued for a good reason. I was working on 6/30KV plant for
almost 10 years but I never seen this solution in my country (and it
was a big plant with an equivalent electrical distribution equipment
of a city with 200.000 people). All current breakers have a DC
connectig-disconnecting coil driven by an automation which is
measuring the current using a current transformer and disconect the
breaker exactly at the programmed current.


{Quote hidden}

Forget about any triac or SCR. I have doubts there is any mercury
relay rated at 3KA. Such switchers are usualy mechanical, having
different switching and conducting plates (contacts), just because the
peak to peak current is impossible to be predicted (even using a
calibrated inductor in series) and the switching contacts are
producing huge flames, so it require a special chamber to purge the
flame.


best wishes and take care,
Vasile

2007\02\02@001340 by Rich

picon face
Have you considered SCR.  There are huge SCRs with massive heat sinks (which
you will need).  The physical size will be appreciable.  The SCR timing
would fit with your requirement.  Just a thought.  You would have to
consider a dynamic load so that you don't short the system too fast.  Just
some food for thought.

{Original Message removed}

2007\02\02@001539 by Rich

picon face
Why forget about SCRs? Could not a dynamic circuit be designed with banks of
SCRs?


----- Original Message -----
From: "Vasile Surducan" <.....piclist9KILLspamspam@spam@gmail.com>
To: "Microcontroller discussion list - Public." <piclistspamKILLspammit.edu>
Sent: Thursday, February 01, 2007 2:29 PM
Subject: Re: [EE] Shunt Trip


{Quote hidden}

> --

2007\02\02@002437 by Rich

picon face
Some high current switching (Contacts) are encapsulated in nitrogen.  I
don't know off hand how high ampacity rating.  It seems that mechanical
switching would be subject to bouncing and increase the arcing and
transients.  An excited Xenon chamber would provide a short, but the heat
would be immense.  Another method would be variable inductive coupling so
that coupling the energy from one inductor to another having a low Z load.
Just another hare brain idea.

{Original Message removed}

2007\02\02@014517 by Vasile Surducan

face picon face
B

On 2/1/07, Rich <EraseMErgrazia1spam_OUTspamTakeThisOuTrochester.rr.com> wrote:
> Why forget about SCRs? Could not a dynamic circuit be designed with banks of
> SCRs?

I'm not sure what will be the purpose of this shunt device described.
Imagine it will be mounted on an infinite energy power line (like
could be considered any low voltage line which delivers more than
20kA) with a variable power factor (cos fi) between 0.3 inductive and
0.9 capacitive...
If one of the SCR from banks is dying the whole bank worth nothing.
Current equilibration in a SCR high power bank and turning ON
synchronised it's a problem. Not talking about turning the SCR OFF
with inductive load at controlled moments.

OK, let say for the sanity of discussion that SCR is OK. Could you
suggest exactly a type and a schematic ?

What I can't imagine, is what government want to create deep trouble
on it's own power mains when the protection switch is working...
>
>
> {Original Message removed}

2007\02\02@033852 by Forrest W Christian

flavicon
face
Mark Peterson wrote:

>I'm working on a 480V distribution relay protection project that
>requires the application of a shunt trip device at the time of an
>overload condition.  
>
Are you sure you understand what the client is asking for?

Shunt trip does not mean short out the lines, shunt trip means apply
some sort of control signal to the "shunt trip breaker" which has such
an input.  Generally what it does is provide an alternative way to trip
the breaker.   This is often used for emergency power off switches or
similar.  Generally you only need a few amp closure at the control
voltage (which may be 480V, but more likely is someting like 277 (1
phase of 480) or 120 or 24 or 12VAC).

I cannot envision any situation where you would want to try to trip a
2000A breaker by shorting it out.    The danger in doing this is far in
excess of anything you could ever imagine.  I've seen what 277 to ground
will do, at just a few amps.  Typical screwdrivers vaporize without even
a thought of tripping a breaker.   You could do serious damage to
everything in the entire system, including killing nearby people.   This
is *dangerous stuff*.  You really need to google "arc flash protection"
(including the quotes).  At a bare minimum look at
http://www.bussmann.com/library/docs/spd02/SPDSection15.pdf , and the
3rd page of the PDF.

Someone somewhere is misunderstanding or misstating the requirements.

-forrest



2007\02\02@064131 by Rich

picon face
Yes, I see the problem with SCRs as a method.  Shorting out such power is
extraordinary.  I have never heard of it before.


{Original Message removed}

2007\02\02@084124 by Aaron

picon face


Mark Peterson wrote:

>I'm working on a 480V distribution relay protection project that
>requires the application of a shunt trip device at the time of an
>overload condition.  I need to detect when the load exceeds 500A, and at
>that time apply a short across the 480V source in order to force the
>circuit's 2000A main breaker to trip.  
>
No, no, no!

You want a breaker with a shunt trip option.  See page 55 of this link:
http://www.cutler-hammer.eaton.com/unsecure/cms1/2C12060.PDF

I quote:

   3-8.1 PLUG-IN ELECTRICAL ACCESSORIES
   ...
   Shunt Trip - The shunt trip is an optional device on circuit
   breakers (Figures 3-48 and 3-49). It opens the circuit
   breaker instantaneously when its coil is energized
   by a voltage input (Table 3.3). A total of two shunt trips
   can be mounted on a Magnum circuit breaker.

I think there is a fundamental misunderstanding between you and your
customer.  And if not, somebody needs to read NFPA 70E regarding arc
flash safety.

Aaron

2007\02\02@092808 by Steve Smith

flavicon
face
In HV terms that's a fault thrower. They are SF6 and have miles of wire to
the feed breaker. A shunt trip is a small coil in the feed breaker. That
opens it on command by an over current for instance.

Don't short the phases the triping device wont last very long if you do..
Steve
{Original Message removed}

More... (looser matching)
- Last day of these posts
- In 2007 , 2008 only
- Today
- New search...