Power line spikes / surges

Please provide the correlation between the ice and spikes. Unless the lines move far enough to contact another phase, which is extremely doubtful your idea is not valid. All the overhead conductors I have strung were designed to not come in contact with each other, unless something broke.

More likely what is happening the protective devices, or the cap banks on the lines are switching.

We called the Power Company and they indicated "everybody in our area is having the same problem and it is due to frost on the lines". Also, I have never directly seen ice fall from a particular powerline and then noted a surge but I have directly noted a number of times that on days when frost is falling off of the powerlines (sometimes there is a very large amount) we have these surges. I also cannot imagine that they would space the lines inadequately allowing them to contact each other.

On 4 Jan 2006 10:32:18 -0800, snipped-for-privacy@signaturefactory.com Gave us:

Then they have some damn leaky insulators on their high tension lines, or lines are dropping and there are huge current spikes being exhibited as they bounce about on the ground. Likely that latter.

You talked to a PR person certainly no one of any knowledge of the situation. Frost is not a problem with distribution lines. Frost makes pretty pictures on the windows. Icing on the other hand can be a problem. If the ice is falling, it is possible that there could be an electrical path created. Usually the placement of the lines prevents this.

On Wed, 4 Jan 2006 13:48:39 -0700, "SQLit" Gave us:

The way I interpreted what he said was that lines are likely down yet not tripping breakers. That WOULD cause transients as the thing danced around on the ground.

What kind of "spikes and surges" are you getting? How are you measuring it?

Ben Miller

I suppose if you had ice / melting ice creating lowish impedance paths across insulators, spikes and surges could result.

j

Actually you would get sags (voltage drop) not "spikes" and "surges".

Charles Perry P.E.

I agree that would be the normal immediate local result. However, the grid can be very oscillatory. I stand by my comment.

j

Radial distribution lines are not very oscillatory. It is possible to get a voltage swell on one, or two, phases of a multigrounded wye system when one phase faults to ground. Enough fault current flowing for this to happen would trip protective devices on the distribution line.

Now a fault on a transmission line will cause interesting "ripples" all over the system. AEP's operation center in Columbus OH could identify faults in southern Georgia if they happened on the high voltage system! Neat stuff that.

Charles Perry P.E.

Could a single phase utility transformer be left energized, and only the faulted phase trip? Or is it normally 3 phase protection upstream from service transformers?

The whole thing might be a little far fetched, I don't deny that. Someone else might come up with something a whole lot more plausible. I did have some local-ish capacitance in mind, as a possible contributor to oscillatory behavior. It may not be a typical scenario for a utility but perhaps it's a possibility.

Another thought. Some utilities place short circuits to melt ice off wires. Switching these shorts on and off would presumably cause some reactions throughout nearby lines. Maybe this is a culprit. It seems the OP is in Montana, based on a google of signaturefactory.com. Which tells me nothing but maybe you happen to have some lore.

Huh. Local sensing can identify stuff 500+ line miles away from the 'ripples'? That is pretty impressive. For harmonic / transient studies at customer (600V - 24940V) levels, I used to ignore most plant more than 'two transformers away'. Does the system you describe have the ability to identify faults through multiple levels of transformation?

Later,

j

Actually we were seeing sags which were subsequently causing spikes on some of our equipment (as indicated by overvoltage protection on the equip). The spikes might have been locally induced by some of our equipment. We did not measure any of these. The sags were very visible and caused some non-ups connected devices to shutoff.

6473Axy8Dr

Sags are largely what we saw followed by spikes on some equipment which could have been caused locally by the equipment. Ice melting across the insulators seems like a resonable explanation.

I have had similar conditions before on smaller systems, in deep northern climes. Basically -

basic parameters -

1) Potential: Each line has voltage with respect to other line, 2) Physical Path: Both lines are held up by framework, and kept apart on that framework by insulators. 3) Mechanics of frost connection: Frost attaches to dirt (e.g., carbon from burned residue) on the insulators. 4) Conduction: There is a path between lines thru the insulator and frame and thru the other insulator, normally a path of high resistance. There is always some relatively very small conduction between the lines along the insulators. 5) Frost as a parallel path: Frost conducts better than the insulator material, and frost on the insulator creates a parallel path with the insulator. The frost path conducts more than the insulator path. 6) Melted frost (water) as a third parallel path: Water (melted frost) conducts much better than ice (frost) which in turn conducts better than insulator. As frost conducts, per I^2*R it heats and then melts and turns to water, making a third and highly conductive path.

scenario -

a) So when the frost attaches to the system, you have two parallel resistances between the lines -insulator and ice between the lines.

b) Current flows according to the potential and the resistance - but only as long as the paths can handle the power and remain intact. Insulator and frost paths are not self-destructive per se,

-- however-

c) When the ice heats up due to the current leaking between lines through the ice, it melts. That water becomes a thrid path that does conduct, and water on an insulator conducts more than it can handle without self-destructing.

That is -- When the ice melts and becomes water the better conductor, current surges along that new path and vaporizes the water - well before a fuse would react. So the grid stays up, but spikes from current flashing show up.

I suspect what you are seeing are spikes from water paths in the frost being formed and vaporized, and the surges you see are from frost conducting.

(Note that designs to prevent ice damage only limits the paths, and the conditions are not all alike in all places - statistically, some paths conduct a lot better than others.. The cheapest way to clean the lines is let them get melted off by the stray currents. )

fwiw...

(since it's electrical stuff at way too high a high voltage, it's really just magic anyway :-) )

Is