lightening arresters and poor soil 2

[andykippo]

I am working at a utility company in which lightnening is the major cause of outages and damage to pole mounted transformers.The terrain is hilly and the soil is poor.can any one recommend any practices that they may have done in the past. Also, if arresters are placed on each phase will this mitigate the damages done to the transformers?

 

[Kiribanda]

andykippo,
The lightning arresters will help to ground travelling waves propergated along the line due to INDIRECT LIGHTNING STROKES,there by protecting the end equipment.Therefore,the line has to be shieled with a properly designed shielding conductor bonding each tower top.

 

[rbulsara]

Arresters will help, but you still need good grounding electrode system to create low impedance path to earth. There are many ways to deal with poor soil conditions, ranging from use of ground mats, adding electrolytes (salt and charcoal)to ground pits, using concrete encased rods and using chemical rods, etc.

You may want to use services of an experienced professional engineer and some grounding system experts (mfrs/vendor) who deal with such issues.

Rafiq Bulsara

http://www.srengineersct.com

 

[andykippo]

can any one recomend some proven practices used to improve grounding resistance on power company feeder circuits in rocky and mountainous location.Please and thank you.

 

[ronbert]

Go to:

http://www.iaei.org/magazine/?p=63

 

[jghrist]

The arrester connected across the transformer insulation will limit the voltage across the insulation regardless of how poor the soil is. Poor ground resistance will reduce the lightning performance of the line insulation, but transformers will still be protected. The important point is to limit the length of leads from the arrester to the transformer bushing and ground.

Overhead shield wires are usually not cost effective for MV distribution lines. Many lightning flashovers on MV lines with limited BIL are caused by strokes to ground and objects near the line inducing voltage above the line BIL on the line. OH shield wires will not stop these. With low BIL, backflashes from direct strokes to the shield wire will also occur.