Strang phenomena on 380 kV In-Out Arrangement OHTL
Strang phenomena on 380 kV In-Out Arrangement OHTL
(OP)
Hi all,
It has been reported to our department that a new substation has supply by in-out arrangement from an existing double circuit 380kV OHTL, experiences frequent FLASHOVER on the two suspension towers adjacent to the tapping point, the flashovers occured almost at same time daily it is around 6 a.m., where the weather is very humid, i have investigated various causes assuming that the suspension insulators ( Vee Type ) on the existing towers had been slightly tilted during stringing of the cut conductors to the new terminal tower, field investigation by binoculars proofs perfect alignment...the Trip log showed both differential and distance relay trip on all phases on one side, and on center phase - (Blue) on the other phase, one two different days.
I think that some trapped charge is accumulating between the two lines ( continuous and cut one ), and unbalance due to the diffraction angle of the exiting towers ( about 3 degrees ), caused this (potential) over-voltage on certain adjacent towers,...
Any ideas?
It has been reported to our department that a new substation has supply by in-out arrangement from an existing double circuit 380kV OHTL, experiences frequent FLASHOVER on the two suspension towers adjacent to the tapping point, the flashovers occured almost at same time daily it is around 6 a.m., where the weather is very humid, i have investigated various causes assuming that the suspension insulators ( Vee Type ) on the existing towers had been slightly tilted during stringing of the cut conductors to the new terminal tower, field investigation by binoculars proofs perfect alignment...the Trip log showed both differential and distance relay trip on all phases on one side, and on center phase - (Blue) on the other phase, one two different days.
I think that some trapped charge is accumulating between the two lines ( continuous and cut one ), and unbalance due to the diffraction angle of the exiting towers ( about 3 degrees ), caused this (potential) over-voltage on certain adjacent towers,...
Any ideas?






RE: Strang phenomena on 380 kV In-Out Arrangement OHTL
RE: Strang phenomena on 380 kV In-Out Arrangement OHTL
RE: Strang phenomena on 380 kV In-Out Arrangement OHTL
Properly designed insulation shouldn't flash over, even with fog, so the first suspect as a recurring voltage event. Do you have a voltage recorder?
Alan
----
"It's always fun to do the impossible." - Walt Disney
RE: Strang phenomena on 380 kV In-Out Arrangement OHTL
This is correct, TL must survive fogs, this is correct for the existing line " erected about 20 years ago ", but,when the modification took place, the flashover occured on the two adjacent towers only, this flashover took place for about 4 days ,at 6 a.m. everyday, the flashover was possible to be seen by naked eye from the SS operator.
We are going to check the voltage log on both the new SS and the remote ends ( sending & receiving ), however, the network in this region is comparatively stable where no load rejection is probable to occur.
RE: Strang phenomena on 380 kV In-Out Arrangement OHTL
What are the lengths and are there any Shunt reactors at the substation!!
RE: Strang phenomena on 380 kV In-Out Arrangement OHTL
RE: Strang phenomena on 380 kV In-Out Arrangement OHTL
Check also the "dry band". Mechanism. This could be more significant than the humidity for F0.
RE: Strang phenomena on 380 kV In-Out Arrangement OHTL
Doesn't seem to be the cause here, but I had to share.