transmission line 1

[2000Kvar]

Does anyone know how determine how much charge remains on a transmission line once the circuit has been opened but not brought to ground? I have a 7 mile long 69kV (nominal) transmission line that was opened up and never grounded.

 

[davidbeach]

It depends on many factors. Are there other lines in the vicinity that can induce voltage on the line in question? No such thing as a dead line unless it is visibly grounded, but what charge might be trapped on it depends on the specifics of that installation.

 

[waross]

Are there any other lines nearby of any voltage?
How long has the line been de-energised?
respectfully

 

[2000Kvar]

There is 230KV line in the vacinity. It is comprised of paralelled 954kcmil conductors

 

[davidbeach]

With another line in the vicinity the trapped charge will be renewed as fast as it can dissipate and the line will remain energized at some voltage. A quick EMTP study would tell you what kind of voltage to expect.

 

[Bahram7]

The DC voltage trapped on the line will decay through the line insulators. In good weather it may stay there for few minutes.

Bahram7

 

[davidbeach]

In my last post, I probably misused the term "trapped charge". The trapped charge becomes a DC component once the driving AC source is removed. What will happen with this line is that when the line is disconnected for its source the other line(s) in the vicinity will continue to induce voltage in the subject line. The induced voltages will reach a steady-state level and the line will remain energized at some level.