Will HV current flow to Earth via Capacitance in this scenario?
ScottH, Sun Mar 12 2017, 07:57PMHypothetical scenario: A man is standing on a rubber mat that has a dielectric strength of 100,000v. It is a thin mat, about 4mm thick (I don't know what kind of rubber that would be). He is planning to work on a tree ajacent to a 7,200v power line. The man, oddly enough, is not wearing any shoes or gloves, and he is using a tall extending aluminum ladder.
The ladder that the man is holding falls sideways and contacts the 7,200v power line. Remember, the man is still standing on the rubber mat that is over good Earth.
Now since it is a large AC current, will the man still get shocked or electrocuted through Capacitance with current flowing through him to Earth?
Re: Will HV current flow to Earth via Capacitance in this scenario?
dexter, Sun Mar 12 2017, 08:56PM
does the ladder is still on the mat? because if so the statement "Now since it is a large AC current" is invalid
as for the current flowing through the capacitor can easily be calculated
calculate the capacitance, calculate the impedance and you'll have the current flowing through the man
my guess is the capacitor is in the pf range which means the impedance is in the GΩ rage and the current is a few micro amps
dexter, Sun Mar 12 2017, 08:56PM
does the ladder is still on the mat? because if so the statement "Now since it is a large AC current" is invalid
as for the current flowing through the capacitor can easily be calculated
calculate the capacitance, calculate the impedance and you'll have the current flowing through the man
my guess is the capacitor is in the pf range which means the impedance is in the GΩ rage and the current is a few micro amps
Re: Will HV current flow to Earth via Capacitance in this scenario?
Hydron, Sun Mar 12 2017, 09:57PM
I have stood a couple of meters below a wire energised to 127kV @ 50Hz (note 127kV line-gnd = 220kV line-line).
Could definitely feel a tingle from the displacement current!
As mentioned above, why don't you make an approximation as to the area in contact with the mat (be generous) and a ballpark dielectric constant for rubber, then use the parallel plate capacitor calculation to work out capacitance to ground.
From this you'll be able to get a rough idea of what current would flow at whatever voltage/freq you'd like!
Hydron, Sun Mar 12 2017, 09:57PM
I have stood a couple of meters below a wire energised to 127kV @ 50Hz (note 127kV line-gnd = 220kV line-line).
Could definitely feel a tingle from the displacement current!
As mentioned above, why don't you make an approximation as to the area in contact with the mat (be generous) and a ballpark dielectric constant for rubber, then use the parallel plate capacitor calculation to work out capacitance to ground.
From this you'll be able to get a rough idea of what current would flow at whatever voltage/freq you'd like!
Re: Will HV current flow to Earth via Capacitance in this scenario?
ScottH, Sun Mar 12 2017, 11:47PM
He's holding it off of the ground to place it.
Contact area is 60 Sq in. for both feet. In this scenario, dielectric of mat is 3 and current is 60hz. The mat is 4mm thick.
ScottH, Sun Mar 12 2017, 11:47PM
dexter wrote ...
does the ladder is still on the mat? because if so the statement "Now since it is a large AC current" is invalid
as for the current flowing through the capacitor can easily be calculated
calculate the capacitance, calculate the impedance and you'll have the current flowing through the man
my guess is the capacitor is in the pf range which means the impedance is in the GΩ rage and the current is a few micro amps
does the ladder is still on the mat? because if so the statement "Now since it is a large AC current" is invalid
as for the current flowing through the capacitor can easily be calculated
calculate the capacitance, calculate the impedance and you'll have the current flowing through the man
my guess is the capacitor is in the pf range which means the impedance is in the GΩ rage and the current is a few micro amps
He's holding it off of the ground to place it.
Hydron wrote ...
I have stood a couple of meters below a wire energised to 127kV @ 50Hz (note 127kV line-gnd = 220kV line-line).
Could definitely feel a tingle from the displacement current!
As mentioned above, why don't you make an approximation as to the area in contact with the mat (be generous) and a ballpark dielectric constant for rubber, then use the parallel plate capacitor calculation to work out capacitance to ground.
From this you'll be able to get a rough idea of what current would flow at whatever voltage/freq you'd like!
I have stood a couple of meters below a wire energised to 127kV @ 50Hz (note 127kV line-gnd = 220kV line-line).
Could definitely feel a tingle from the displacement current!
As mentioned above, why don't you make an approximation as to the area in contact with the mat (be generous) and a ballpark dielectric constant for rubber, then use the parallel plate capacitor calculation to work out capacitance to ground.
From this you'll be able to get a rough idea of what current would flow at whatever voltage/freq you'd like!
Contact area is 60 Sq in. for both feet. In this scenario, dielectric of mat is 3 and current is 60hz. The mat is 4mm thick.
Re: Will HV current flow to Earth via Capacitance in this scenario?
Sulaiman, Mon Mar 13 2017, 11:31AM
the effective area of the capacitor formed by the rubber mat to earth, will be quite large
as urine is conductive.
Sulaiman, Mon Mar 13 2017, 11:31AM
the effective area of the capacitor formed by the rubber mat to earth, will be quite large
as urine is conductive.
Re: Will HV current flow to Earth via Capacitance in this scenario?
Blackcurrant, Mon Mar 13 2017, 03:30PM
That's why they call it earth leakage testing
Blackcurrant, Mon Mar 13 2017, 03:30PM
That's why they call it earth leakage testing
Re: Will HV current flow to Earth via Capacitance in this scenario?
radiotech, Tue Mar 14 2017, 05:27AM
You need the dielectric constant of the mat. Then the area of his two feet.Then the thickness of the mat.
Now get the capacity of the capacitor. Then the Xc.
Divide that into 7200. that will give you the current.
radiotech, Tue Mar 14 2017, 05:27AM
You need the dielectric constant of the mat. Then the area of his two feet.Then the thickness of the mat.
Now get the capacity of the capacitor. Then the Xc.
Divide that into 7200. that will give you the current.
Re: Will HV current flow to Earth via Capacitance in this scenario?
dexter, Tue Mar 14 2017, 05:32PM
does the ladder is still on the mat? because if so the statement "Now since it is a large AC current" is invalid
as for the current flowing through the capacitor can easily be calculated
calculate the capacitance, calculate the impedance and you'll have the current flowing through the man
my guess is the capacitor is in the pf range which means the impedance is in the GΩ rage and the current is a few micro amps
dexter, Tue Mar 14 2017, 05:32PM
does the ladder is still on the mat? because if so the statement "Now since it is a large AC current" is invalid
as for the current flowing through the capacitor can easily be calculated
calculate the capacitance, calculate the impedance and you'll have the current flowing through the man
my guess is the capacitor is in the pf range which means the impedance is in the GΩ rage and the current is a few micro amps
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