basics of electrical supply

[shekhar_dandya]

Hi All,
I wanted to know that is neutral wire connected to earth at some point ?
If not then how do we get shocked,since to get shocked,current must flow from live to neutral?
-Shekhar

 

[audioguru2]

Hi Shekhar,
The neutral is connected to ground probably in the transformer down the street from your home.
I think they ground it to provide a path to ground for lightning, and for any leakage current.

If you worry about being shocked, then you should have Ground-Fault-Interrupters installed on receptacles located near grounded objects like in bathrooms and for outside. They disconnect the power when they detect a tiny current to ground. ;D

 

[Raver2097]

Hi Shekhar,
As said by audioguru, the neutral is effictively connected to ground in the transformer. This is made to allow the differential interruptors to work when a leakage appears in the circuit.

 

[shekhar_dandya]

But,if neutral is not connected to ground,and there is no special protection circuits around,is it that we never will get shocked when we hold a live wire?

 

[audioguru2]

If your electrical wiring didn't have a ground, then it might spark all around your house during lightning storms, causing your house to catch on fire.

 

[Alun]

I don't know about the US but here in the UK the neutral is connected to ground where the mains enters the building just before the consumer unit, the

 

[ante1]

This might explain a few things, or it might not! ;D

[attachment deleted by admin]

 

[shekhar_dandya]

I think my basic question remains unanswered as far as theory goes:
"But,if neutral is not connected to ground,and there is no special protection
circuits around,is it that we never will get shocked when we hold a live wire? "

 

[audioguru2]

Yesterday my son touched a 120VAC live wire and felt a small shock even though he wasn't grounded (lucky for him!).
I guess some current flowed through his capacitance to ground.

He asked, "Why don't the birds get shocked when they perch on a high voltage wire?" I explained that they are small so have a very low capacitance to ground, and are stupid like him.
Actually, it was the electrician who wired the breakers for my home who was stupid. They weren't marked and the breaker box is upside down. My son turned off nearly everything but not the correct one.

 

[ante1]

Why is it called “live” when it easily can cause the opposite?  ;D

 

[prateeksikka]

hi audioguru!
i think your son must have touched ground. is it possible for the mid air to ionize at mere 120V and cause breakdown(fee movement of charges!) ?
i dont think so....................

;D

 

[audioguru2]

I won't try it but I think a person's capacitance to ground passes enough current from a live mains wire to be felt as a mild shock. It is enough current to light an NE2 neon bulb in your hand. We use the extremely high mains frequency of 60Hz over here!
Long ago, the mains frequency was only 25Hz. If you got a shock you vibrated so much that it knocked your teeth out. Transformers and motors were huge. ;D

 

[prateeksikka]

Ive heard a few kilo volts is enough to knock u down even without ground.but if grounded gosh..
60-70V will do the job.
Air's ionization potential is a few thousand volts and it can only cause u a shock if air ionizes and circuit is completed.
;D

 

[aakaash]

I think my basic question remains unanswered as far as theory goes:
"But,if neutral is not connected to ground,and there is no special protection
circuits around,is it that we never will get shocked when we hold a live wire? "

Hi
Shekhar
i joined this room today only and read  it  n  felt  ur  basic qu  is  remained unanswered.  Coz  u  forgot the basics of current flow. The nutral  n  grnd  wire  have  nothing to do with  shock.  If  u  hold  live (phase) wire in hand the current will flow thru  ur  body  to  ground  and  u  r  bound  to  get  good  shock  ;D .
Aakaash

 

[ec_deepak]

HI SHEKAR,
    i think so that there is no any quite difference between the neutral and the earth wire, as we know that the earth wire is gronded , hope so yhe same at uor home power supply.

 

[prateeksikka]

hi aakash!
the topic has remained same nd we are now discussing the amount of voltage u need in case there is no direct connection between u and ground.

 

[MP1]

Shekhar,
In most geographical regions, code requires the Neutral to be connected to ground in your service breaker box. If you have the opportunity to look inside, you will see that they are all connected by a buss bar and all of the grounds are connected to the same place. The wires in a receptacle are open loop and thus waiting for something to complete the circuit. If you touch the Hot wire, you can become a path to ground and this is how you can get zapped. The only way that a Neutral wire will give you a zap is if you are a better path to ground than the Neutral circuit where it connects to the buss in the service box. Yes, if you have a loose Neutral wire in the breaker panel, you could get zapped by touching this side of the circuit. This is not uncommon. One way to find such a faulty circuit is by measuring voltage from Neutral to Ground at the receptacle. If it is greater than zero, you have a loose wire or corrosion, or something causing a weak connection of one of the circuits to ground. In other words, if the wire where it is connected to the buss bar is not at ground potential due to looseness or corrosion or rust, etc, you might be a better ground potential than the connection in the service box.

hope this helps you in your quest.

MP

 

[aakaash]

hi aakash!
the topic has remained same nd we are now discussing the amount of voltage u need in case there is no direct connection between u and ground.

Hi
Pratik
In direct touch to ground also "amount of shock " is decided by many things like if ur hand is wet , the resistance of skin decreases  n  more current flows thru ur body  n  u  get  life-spoiling shock. This body resistance varies person to person. Some hav xcptnal high so they can easily handle live-wire!! But normally few milliAmps can damage u severly. So its not the voltage but body-resi to decide. So in case of open ckt (not touching grnd) along with body resi , wet or dryness of body , humidity of air ,  wetness of ground  ,  etc  r  also imp along with high volt to make flow those killing few  milliAmps  thru ur body after breaking high resi of open air inbetween.
Aakaash
India     

 

[Alun]

The frequency also plays a part, 50/60Hz will stop your heart but 100kHz will just make your hands warm (or bun you if there's enough power) as the nerves in your body can't resond to high frequencies.