Originally posted by phishybongwaters
The power plants and transportation systems, on the other hand, would be damaged.
The only thing that can be damaged by GIC at a power station is the step up transformer that ties the generators to the transmission system.
Lets go over the basics of why GIC’s can be a threat to long distance power systems. When the magnetic fields move, they induce currents into the
crust of the earth. But the earth’s crust is a poor conductor. The power lines are far better conductors. Current takes the path of least
resistance. If the line is grounded at both ends, then current will go down the line, instead of through the earth’s crust.
The currents are not high enough to damage the wires themselves. The problem comes at the ends of the wires. If the wire is grounded to the earth at
each end through the transformer’s windings, then the GIC will flow from ground, through one transformer, down the line, then out through the other
transformer, back to ground.
The current flow has such long cycles of oscillation that it is basically DC as far as the equipment is concerned. AKA “quasi dc”
How it threatens the transformer is the fact that a dc current flow through the windings of a transformer will saturate the transformer’s core. By
it’s self the DC saturation will not damage a thing. The problem comes when you have a transformer that is still operating at full AC service
voltage while saturated. That will cause core heating and winding heating. The heating will continue until the insulation breaks down. A short will
form and the fault detection system will kick the transformer off line. End of story. No explosions, no leveling of everything within a half mile.
That above scenario is assuming a long three phase transmission line with grounded wye transformers at each end.
But……… and a big But………. Standard Operating Practice is that you have a grounded wye secondary on the transformer that supplies the line,
and an ungrounded delta primary on all three phase transformers that run off that line. That is SOP.
Usually, any substation transformer running off the transmission system will be using an ungrounded delta primary. Remember a key point here, is that
the only way current can flow is if the line is grounded at both ends through the transformer. In the standard installation, it is only grounded at
The majority of all standard substation transformers will not be bothered by GICs. The situations that invite damage from GICs are large grids where
there is multiple power stations at different ends of a single line. Each power station is a “source” So it has a “grounded wye” at it’s
connection to the line. If the two power stations are connected at both ends, then you have a complete circuit and GICs can flow. You need a grounded
wye at each power station because each power station has the ability to supply the line by it’s self. If it didn’t have a grounded wye and it was
the only station on the line, then the line would be floating, and I will just state that a “floating line” is not something you want to have.
Basic rule of thumb is that if you island the distant power stations from each other with their own share of the loads, you will negate any GICs.
The only other area of the power grid that is at risk is the distribution side. In the distribution environment, you have single phase transformers
that connect between the ground and the hot lines along the path of the line. Most smaller lines in the cities are too short to be bothered by GICs.
It will more likely affect the ones in the rual areas. And they will only be affected if the power is on.
If there is no AC power, then no more units will be damaged. Remember, DC saturation will not damage a transformer by it’s self. The only time you
get damage is when you try to apply operating voltage to a saturated transformer.
And, as I have pointed out on other threads, when the first couple big transformers go, the power will drop across the entire united states. Look at
the north eastern blackout that happened after ONE big transformer went. Do you honestly think that the power will stay on after 5%, 10%, or 20% of
the power distribution spontaneously drops off line from transformer damage, or other GIC induced fault conditions? Once the power goes out, then no
more damage. Find out what broke, fix it, wait until the GICs calm down, then turn the power back on. You may have to tell people to limit their usage
for a few weeks until the damaged stations get back on line, but that will be it.
Our power grid is too fragile to stay on long enough for a sizable percentage of the transformer stock to damage it’s self. And that is a good
Originally posted by phishybongwaters
I recall hearing years back during an Ice Storm that wreaked havoc on the Eastern US and Canada that a single power transformer takes months to
(Holds my head in my hands while mumbling unrepeatable things to myself)
For normal day to day repair and maintenance, you DON’T build a NEW transformer when the old one is damaged. You REBUILD it!!!!!!! That is why there
is such a long turn around for new ones. They are not regular production items. They are normally built for a project that is on a schedule. There is
plenty of lead time. No one is in a hurry. I can assure you that if you really needed one, then you could get one built in way under a month. You
could get an old damaged one rebuilt in less than a week.
Heck. Give me the required copper, a couple big spools of fish paper, spooling system, and a hoist system, and I would easily be able to rebuild a
couple MW transformer in less than a month with my own two hands!!!
Heck, ditch the spooling system and I still would be able to do it with time to spare.
It isn’t freaking rocket science. All you need is something to lift the large parts as you break it down, and put it back together.
And all that is assuming that there will be nobody on duty, or no automated safety systems watching the instrumentation and equipment to see the fact
that something strange is happening that needs to be stopped.
As I have posted before, there is always people on watch. Overseeing the power grid and it’s operation.
I don’t know how I can be more clear on this……. There are people that watch over the operation of “the grid” They are paid to watch over
their company’s assets 24/7/365. They breathe, eat, and sleep the power grid. They know what they are doing. They will be the first ones to see
strange stuff happening. They are the ones that decide if the lights get turned off. Or what measures need to be taken to keep the lights on. Not some
politician in some stupid movie.
They are there to maintain a proper and timely operation of the power grid, and the protection of the assets that make up the grid, if, and when,
necessary. If they deem that there is a threat to the grid that warrants the cessation of operations, or islanding of generation until the threat
clears, then they will be the one making the decision, and pulling the switches. No one else!
edit on 14-1-2011 by Mr Tranny because: (no reason given)