Woud reverse passage of current possible if the system is switched off for maintenance of electricit

Thread Starter

jraju

Joined Jul 23, 2017
27
Hi,
i read a news item , wherein an electrical field staff met his death while handling maintenanance work in his area.
The reason set forth , was reverse pass of current while doing and handling maintenance repair.
The system had been switched off, but the current from invertors from the houses and other institutions passed thro the line, he was attending causing of death.
Is it possible that current from invertors, used by general people pass thro, if the main systemis switched off
if that is the case, what is the solultion for this kind of reverse pass
Normally , every prerson would be having invertor now these days.
 

BobTPH

Joined Jun 5, 2013
2,026
A grid tied inverter will not operate if the mains is off.

More likely, someone was illegally backfeeding from a generator or unauthorized non-grid tied inverter. This could happen, and that is why it is illegal.

Bob
 

Thread Starter

jraju

Joined Jul 23, 2017
27
nice reply. but could you elaborate on non rid tied inverer
When the main is switched off, no passage of current in lines ,
what is non grid tied
what is the solution
could not the field staff know, that it is having passage of current
 

Reloadron

Joined Jan 15, 2015
4,510
More likely, someone was illegally backfeeding from a generator or unauthorized non-grid tied inverter. This could happen, and that is why it is illegal.
That would also be my guess. Generators come in a few types including inverter generators.Many people, myself included, use a whole house generator. Some people just use a portable generator. When utility mains power is lost a generator supplies power. This needs to be done correctly and in accordance with published code. Here in the US it's the NEC (National Electric Code).

Starting with residential power distribution here in the US using myself as an example. My residential power enters my home as 240 VAC split phase from a transformer on the utility pole. The transformer is fed by about 7.0 KV in my area. Keep in mind at this point a transformer works two ways. It steps down the 7.0 KV to 240 VAC split phase but if I apply my own generator supplied 240 VAC (back feeding) the transformer feeding me will have 7.0 KV on its primary even though mains utility company power has been removed. Anyone working on that 7.0 KV line thinking power is off can easily be electrocuted.

Grid tie inverter is merely an inverter tied into the power grid. Popular with wind turbines and other power sources. This allows people to return power to the utility company that are not using. However, again, when mains power is lost there must be a disconnect. These disconnects consist of normally two switches which switch between mains power from utility company and locally generated power. They are even normally mechanically linked so only one switch can be on at a time.

Non Grid Tied is just an inverter which is not tied back to the mains power grid and should not be grid tied. There is more to this but again this is simplified.

Any further questions just ask. :)

This is an over simplified explanation but I am pretty sure you get the idea.

Ron
 
Last edited:

crutschow

Joined Mar 14, 2008
23,352
The solution for an illegal converter that is feeding power to the line, is for the workers to measure the voltage before they touch the lines.
Alternately they could short the lines together when working.
That will likely also get rid of any illegal converters. :rolleyes:
 

Reloadron

Joined Jan 15, 2015
4,510
The solution for an illegal converter that is feeding power to the line, is for the workers to measure the voltage before they touch the lines.
Funny you mention that because my wife asked me about that. Why don't they check the line before working on it? This is fine right till you check the line, determine it is not hot, start working and some idiot starts a generator back feeding the line. :)

As to shorting the line? Not quite sure if there is a provision for doing that? :)

Ron
 

Reloadron

Joined Jan 15, 2015
4,510
Yeah, I get it. :) When I questioned a "provision" the linemen work from a procedure, well here in the US anyway. I have no clue where the cited mishap took place of country of origin of the thread starter. My best guess as to the cause is someone or something back feeding a mains distribution line. As to preventing that I guess it depends on any procedures followed before working on or in a power sub station. Yeah, just short the line(s) and remember to remove the short when done. Works for me.

Ron
 

vu2nan

Joined Sep 11, 2014
55
A transfer switch (either operated manually or automatically operated by the incoming mains supply) is mandatory to prevent such accidents.

The following illustrates transfer switch wiring for a domestic generator.

connecting_generator.gif

Domestic inverters have the automatic transfer switch inbuilt.

Regards,

Nandu.
 

MisterBill2

Joined Jan 23, 2018
3,882
The solution for an illegal converter that is feeding power to the line, is for the workers to measure the voltage before they touch the lines.
Alternately they could short the lines together when working.
That will likely also get rid of any illegal converters. :rolleyes:
Certainly this would be effective, and in fact I have had to do that while working in areas where unknowing fools would switch on the power to a machine even despite it being tagged off.
The problem is mostly caused by those who do not let the fact that they do not know what they are doing slow them down at all.
When working with circuits whose status I don;t know, I always treat them as though they are live. That is a wise way to work and avoid all sorts of problems.
 
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