Transmission line ceramic insulator flash over ?

[sparky1976]

Dear Forum,

I've tried to find the similar trhead but unfotunately there is no thread discussing this matter.
We have 150 kV transmission line double circuit distance 16 km with average load 110 MW.
Recently we experinced flash over on some of ceramic insulator and trips both lines, the weather was misty rain and foggy.
For short term remedy we wash (energized wash) the ceramic insulator.

For long term remedy I still need more input.

The suspect of this event are : changing season from long dry season to wet season, the line near(you can see the coast line from the towers)wind with salty water from sea.

My option are :
1. add more ceramic insulator
2. coating with silicone which I already proved not make any improvement with my MV O/H line right near the sea, and the coating will peeled if we do the energized washing.
3. Chopper energised washing.

Is any one on the forum experince similar problem ?
If any one has some suggestion ?
I'm scraching my head,pulling my hair this last couple weeks to find good resolution to make sure this not happen again.

Thanks
Pitat

 

[2000sp]

Dear Friend !
Our Option is : 1 )Add more number of insulators.
2 )Increase voltage rating of the insulator.
Our experience:
Our 33 kv Outdoor substation is nearby seashore. All the supporting insulators are designed for 66 kv . So there is Flash over of Insulators. No need for frequent maintenance.

 

[Macnee]

I have a suggestion to use silicone rubeer insulators which on our first recent experience seems to be working well.
May be you might have difficulties in expenses. But as we changed the ceramic insulators to silicone rubeer type the tripping on coastal lines (MV) (and on hills where humidity is high) have reduced drastically prooving the point. Yet we are still to pass the first cycle. Also these insulators do not require hot line washing.

 

[sparky1976]

Macnee,
I dont understand "Yet we are still to pass the first cycle", Please explain ?

Thanks
Ilyas

 

[Macnee]

I mean we have not completed one cycle of seasons yet..>> not a full year completed. completed about 4/5 months with new insulators with peak loads & results are satisfactory

 

[urja]

I think you problem can be solved only by increasing Creepage Distance (i.e. by adding some more insulator) or more prefarebly to avoid this kind of problem use solid core insulator which is having very little failure rate.

 

[Outback]

I would suggest replacing the porcelin with polymer insulators and increase the airspace.
Check with Hastings or S&C for the polymer types and ratings.

 

[jbartos]

Suggestion: Adding more insulators or insulator length could potentially impact the spacing distance between the transmission line phases. If there is high wind, the conductors tend to rotate and approach to each other very closely. Also, the forces imposed on longer insulators are bigger. Therefore, the better solution is to research or redesign the insulator shape, i.e. increase their diameter by increase offsets.