ECN Forum Forums General Topics of the Trade General Discussion Area Wild oscillations of line voltage Aug 14th.

ok therefore i did work on power companie before ( both usa and france) and the proper way to reengerize the line is start the low deamand area then ramp up by turning on the remote breakers ( they have to be recharge the switching devices )and load the line gradually to advoid sudden surge and alot of time when we engerized the breakers it will buzz for few sec then quiet down after the load stablized but if get too much surge we will disconnect then try it again in short time later and alot of line act like capatior (hold charge or load or both) and try to enerized the voltage will dip montartly but if keep dipping and surge like crazy we can pull the swtich off fast to advoid more damge but surge that diffrent matter it can do more damgae than good the last time i have nasty surge it did blew the large breaker pretty good so most power plants have compacated electronc control but i know few older one use the simple controls anyway that one way we do that and also keep in mind the 3 phase line have to be scyorized to engized properly if not it will kick breaker out

if need more info ask me


merci marc

Bjarney,

You speak in a language I can readily understand.

That was beautiful, I got it (or I think I do) right away.

Thank you very much.

As for bringing it back on line, I was under the impression that the switches at the substations are remote controlled.

I thought someone would sit at a control center, open all switches, energize the feeds to the substations, then start bringing on the load in a controlled fashion.

Now after reading Marcs post I wonder if you need guys out in the field to do this.

If you need field guys to do this work it seems IMO that some more money should be spent on automation of local cutouts.

Thanks all, Bob

This sounds not unlike a situation we had happen over here, in the late 80's.
It's called "hunting", where a series of Alternators will speed up and slow down and cause a really huge variation in Output Voltage, this is caused by a gross loss in loading and can seriously damage the windings in an Alternator, due to back EMF currents/voltages, which for a 11kV alternator, can be HUGE!!.
I'd invite the comments of CaOperator on this one!.

[This message has been edited by Trumpy (edited 08-16-2003).]

yes bob most power compaines do have automatic cutoff switching devices but there are some area have to engerzed by manually for safety reason and also when get some power surge espcally with hevey loaded lines expect some of the cut off fuse or breakers to kick out and some reclosers will cycle up to 4 time before locked out that why some peoples can see light came on then go out for a few sec then back on due the recloser cycling if too much current going tru especally with hevey loaded transmmion lines it dont matter what voltage it willbe and alot of power company do have big bullten board or large map where all the lines run and some have with display lights to tell which one is on or off or locked out and with today techolgy more recloser and few other cutoff devices can controled by computer now i know my area after power outage the recloser will delay for few sec before closing to make sure the voltage is on line ( on line side) before enegerized

sorry for long winding chat here but need more let me know i will try to set up the seperate thread if other members do agree with me


merci marc

Before and after:



Note: These are from a satellite image, with the number of colors severely reduced to lower the image size.

Source (original filesizes are large): http://www.noaanews.noaa.gov/nightlights/blackout081403-20hrsbefore-text.jpg

and
http://www.noaanews.noaa.gov/nightlights/blackout081503-7hrsafter-text.jpg

[This message has been edited by ThinkGood (edited 08-16-2003).]

Yes, Long Island was sure Dark!
I'm near the center, where the Arrow is pointing. It was very strange driving around familiar roads and not being able to see landmarks set back off the road, or even where the intersections were because there was no light.

Bill

I need to add a comment related to Subsynchronous Resonance conditions, which imply a rather sustained condition, as opposed to a shorter duration or somewhat transient event.

Another potentially disastrous effect on generators and electrical transmission is an Out-Of-Step condition. SSR is typically thought of as a more oscillatory/periodic condition {like waves on a lake.} OOS is sort of the severe rotating-shaft equivalent of stripped gears that couple the hypothetical water wheel to the giant shaft.

You want to know what else is weird about not having power for a few days. Noise!!. The fridge doesn't run, the pump doesn't run, the furnace doesn't run, the freezer doesn't run, no tv or radio in the background. Flicking the switch when you come in even though the lights haven't worked for days. I live in a rural area,my nearest neighbor is 600 ft away, so is the nearest road,lots of trees in between. The silence was eerie

Let me add 2 cents here. I am in northern NJ and we have the POCO called JCP&L. Well they were bought out by GPU from PA. awhile back and just recently GPU was bought out by First Energies. (OR is it Energys?) Anyway, I still had power during the black out. I was happy to see the JCP&L did OK this time. We have been having a lot of trouble with the POCO as of late. They are trying to cut back more and more to save money. They lay off all of their own people, then sub out to independent contractors. Now I don't mind anyone making a buck, this country is good for that. however what use to take an hour to fix, now takes a 1/2 day. What use to take a 1/2 day now takes 2 days. The Powers that be, think they can run the POCO here in NJ like they do in other states. I don't think that it is working. NJ and NY are very busy places and there are a lot of people here. the towns/cities all almost work on a 24 hr/ 7 days a week schedule. Well I was proud of the POCO til today, because now I hear the rumor that the problem started out in Ohio in a First Energy plant. I don't know if it is true yet, but time will tell. I can see where companies have to try and make a Co. profitable, but not when service suffers. Maybe they shouldn't have dereg the utility co. when they did. It seems that they are cutting back too many people and the service is getting just rotten.

Another problem with restoring power is that the plants themselves can only pick up load at a relatively slow rate. When the lines trip, the plant will not have anywhere to put the power they are generating and will have to shut down. Then when the dispatch center is ready to start restoring power, the plant will have to have power to run auxilliary equipment. Some plants will have small units that can be black started, and the output from these is used to provide enough power to get a larger unit online. If the plant does not have any black start capability it will need outside power for a while to get rolling. Our units are fairly small, and the loading rate is only about 2 megawatts every 5 minutes. The time between load increases is necessary to allow the boiler a chance to catch up with the higher load being placed on it. If a gas turbine (jet engine) is being used they can be loaded a bit quicker, but you still have to allow time for temperatures to equalize between load changes.

Anyway, a major factor in restoring power is finding a way to add load slowly enough that the equipment can keep up. It can be a game of trial and error, since it is very difficult to know exactly how much load is waiting when you close in a feeder.

Also, on the electrical grid, frequency is the controlling factor. When the frequency dips, the generators will automatically pick up load to try to correct it, and when the frequency rises, the generators will reduce load to correct it. If the frequency is too low the units will trip on underspeed and have to be restarted.

Boy oh boy, sorry folks, I could go on for hours here.

Anyway, I hope that might help a bit.