[Lightningrod]

We have had several occurrences over the last year of a fault out on the line passing back through our Oil Reclosers to cause 1 or 2 of the 3 power fuses to blow on the power transfomer protection in a 69Kv wood pole sub.

My question is the OR'S have been brought and all have checked out alright in the test shop, this is happening at the same sub every time and this sub has had all it's grounding stolen prior to this starting (repaired right away).......... so do you think something has happened to the sub TX's or something freaky with grounding or imbalances that are blowing the power fuses.

[wood stabber]

We have had several occurrences over the last year of a fault out on the line passing back through our Oil Reclosers to cause 1 or 2 of the 3 power fuses to blow on the power transfomer protection in a 69Kv wood pole sub.

My question is the OR'S have been brought and all have checked out alright in the test shop, this is happening at the same sub every time and this sub has had all it's grounding stolen prior to this starting (repaired right away).......... so do you think something has happened to the sub TX's or something freaky with grounding or imbalances that are blowing the power fuses.

Could like you say be a problem with the ground? Maybe not the same resistance with the new ground set up,ie. compaction,depth,conductor size,????

[GreatDestroyer]

We have had several occurrences over the last year of a fault out on the line passing back through our Oil Reclosers to cause 1 or 2 of the 3 power fuses to blow on the power transfomer protection in a 69Kv wood pole sub.

My question is the OR'S have been brought and all have checked out alright in the test shop, this is happening at the same sub every time and this sub has had all it's grounding stolen prior to this starting (repaired right away).......... so do you think something has happened to the sub TX's or something freaky with grounding or imbalances that are blowing the power fuses.

Have the ground on the ct's been verified on the ocr? Also have the fault duties increased. It sound like the issue is showing up on a phase to phase fault indicating possibly that the settings on the ocr are to slow, or the primary fusing has been changed to a fuse with the curves to quick.

[Lightningrod]

We have had several occurrences over the last year of a fault out on the line passing back through our Oil Reclosers to cause 1 or 2 of the 3 power fuses to blow on the power transfomer protection in a 69Kv wood pole sub.

My question is the OR'S have been brought and all have checked out alright in the test shop, this is happening at the same sub every time and this sub has had all it's grounding stolen prior to this starting (repaired right away).......... so do you think something has happened to the sub TX's or something freaky with grounding or imbalances that are blowing the power fuses.

Have the ground on the ct's been verified on the ocr? Also have the fault duties increased. It sound like the issue is showing up on a phase to phase fault indicating possibly that the settings on the ocr are to slow, or the primary fusing has been changed to a fuse with the curves to quick.

I had the OR taken down and brought in for for a complete check over by the electro-mechanics and all the settings and internal connections checked out 100%. The OR actually has almost 1 MW less load on it now then it did as we shifted it over to another sub for load balancing. The fuses at the sub are 65E on 69KV.

[GreatDestroyer]

We have had several occurrences over the last year of a fault out on the line passing back through our Oil Reclosers to cause 1 or 2 of the 3 power fuses to blow on the power transfomer protection in a 69Kv wood pole sub.

My question is the OR'S have been brought and all have checked out alright in the test shop, this is happening at the same sub every time and this sub has had all it's grounding stolen prior to this starting (repaired right away).......... so do you think something has happened to the sub TX's or something freaky with grounding or imbalances that are blowing the power fuses.

Have the ground on the ct's been verified on the ocr? Also have the fault duties increased. It sound like the issue is showing up on a phase to phase fault indicating possibly that the settings on the ocr are to slow, or the primary fusing has been changed to a fuse with the curves to quick.

I had the OR taken down and brought in for for a complete check over by the electro-mechanics and all the settings and internal connections checked out 100%. The OR actually has almost 1 MW less load on it now then it did as we shifted it over to another sub for load balancing. The fuses at the sub are 65E on 69KV.

I think I would start with earth resistance testing, and verify that the ground on the unit, as well as the substation grid is good.

My guess would be its a coordination issue. Could the 65 E's have the incorrect curve. For example S&C SMD1A fuses have 3 curves Standard 153.1 Slow 119.1 Very Slow 176.1. I have run into this in the past. It's easy to miss especially when it's the middle of the night with battling wind and snow. I would also verify the reclosing time. I have seen where a recloser is set to reclose to quick not letting the primary fuses cool off between shots blowing the primary fusing.

I have only been in substations for the last year so I would love for someone to chime in here with a little help.
Good luck