Primary Services, Power Redundancy, Double-Ended Primary Switchgear and Backup Generators

Posted by PITHOCRATES - July 3rd, 2013

Technology 101

The Higher the Currents the Thicker the Conductors and the Greater the Costs of Electrical Distribution

If you live by a hospital you’ve probably noticed something.  They never lose their power.  You could lose your power in a bad storm.  Leaving you sitting in your house on a hot and humid night with no air conditioning.  No lights.  No television.  No nothing.   And across the way you see that hospital lit up like a Christmas tree.  As if no storm just blew through your neighborhood.  Seemingly immune from the power outage afflicting you.  Why?  Because God loves hospitals.

Actually the reason why their lights never seem to go out has more to do with engineers than God.  And a little thing we call power redundancy.  Engineers know things happen.  And when things happen they often cause power outages.  Something we hate as we’ve become so accustomed to our electric-powered world.  But for us it is really more of an annoyance.  For a hospital, though, it’s not an annoyance.  It’s a life safety issue.  Because doctors and nurses need electric power to keep patients alive.  So engineers design ‘backup plans’ into a hospital’s design to handle interruptions in their electric service.  But first a brief word on power distribution.

Nikola Tesla created AC power transmission and put an end to Thomas Edison’s DC power dreams.  The key to AC power is that the alternating current (AC) allows the use of transformers.  Allowing us to step up and step down voltage.  This is very beneficial for the cost in electric power distribution is a factor of the size of the current carrying conductors.  The higher the currents the thicker the conductors and the greater the costs.  Because power is the product of voltage and current, though, we can reduce the size of the conductors by raising the voltage.  Power (P) equals voltage (E) times current (I).  Or P = I * E.  So for a given power you can have different voltages and currents.  And the higher the voltage the lower the current.  The smaller the conductors.  And the less costly the distribution system.

Neighborhoods typically get a Radial Feed so when we Lose our Power our Neighbors Lose their Power

Generators at power plants produce current at a relatively low voltage.  This power goes from the generators to a transformer.  Which steps this voltage up.  Way up.  To the highest voltages in our electric distribution system.  So relatively small conductors can distribute this power over great distances.  And then a series of substations filled with transformers steps the voltage down further and further until it arrives to our homes at 240 volts.  Delivered to us by the last transformer in the system.  Typically a pole-mounted transformer that steps it down from a 2,400 volt or a 4,800 volt set of cables on the other side of the transformer.  These cables go back to a substation.  Where they terminate to switchgear.  Which is terminated to the secondary side of a very large transformer.  Which steps down a higher voltage (say, 13,800 volt) to the lower 2,400 volt or a 4,800 volt.

We call the 240 volt service coming to our homes a secondary service.  Because it comes from the secondary side of those pole-mounted transformers.  And we can use the voltage coming from those transformers in our homes.  Once you get upstream from these last transformers we start getting into what we call primary services.  A much higher voltage that we can’t use in our homes until we step it down with a transformer.  Some large users of electric power have primary services because the size of conductors required at the lower voltages would be cost prohibited.  So they bring in these higher voltages on a less costly set of cables into what we call primary switchgear.  From that primary switchgear we distribute that primary power to unit substations located inside the building.  And these unit substations have built-in transformers to step down the voltage to a level we can use.

There are a few of these higher primary voltage substations in a geographic area.  They typically feed other substations in that geographic area that step it down further to the voltage on the wires on the poles we see in between our backyards.  That feed the transformers that feed our houses.  Which is why when we lose the power in our house all of our neighbors typically lose their power, too.  For if a storm blows down a tree and it takes down the wires at the top of the poles in between our back yards everyone getting their power from those wires will lose their power.  For neighborhoods typically get a ‘radial’ feed.  One set of feeder cables coming from a substation.  If that set of cables goes down, or if there is a fault on it anywhere in the grid it feeds (opening a breaker in the substation), everyone loses their power.  And they don’t get it back until they fix the fault (e.g., replace cables torn down by a fallen tree).

Hospitals typically have Redundant Primary Electrical Services coming from two Different Substations

Now this would be a problem for a hospital.  Which is why hospitals don’t get radial feeds.  They get redundant feeds.  Typically two primary services.  From two different substations.  You can see this if a hospital has an overhead service.  Look at the overhead wires that feed the hospital.  You will notice a gap between two poles.  There will be two poles where the wires end.  With no wires going between these two poles.  Why?  Because these two poles are the end of the line.  One pole has wires going back to one substation.  The other pole has wires going back to another substation.  These two different primary services feed the main primary switchgear that feeds all the electric loads inside the hospital.

This primary switchgear is double-ended.  Looking at it from left to right you will see a primary fusible switch (where a set of cables from one primary service terminates), a main primary circuit breaker, branch primary circuit breakers, a tie breaker, more branch primary circuit breakers, another main primary circuit breaker and another primary fusible switch (where a set of cables from the other primary service terminates).  The key to this switchgear is the two main breakers and the tie breaker.  During normal operation the two main breakers are closed and the tie breaker is open.  So you have one primary service (from one electrical substation) feeding one end (from the fusible switch up to the tie breaker).  And the other primary service (from the other electrical substation) feeding the other end (from the other fusible switch up to the tie breaker).  If one of the primary services is lost (because a storm blows through causing a tree to fall on and break the cables coming from one substation) the electric controls will sense that loss and open the main breaker on the end that lost its primary service and close the tie breaker.  Feeding the entire hospital off the one good remaining primary service.  This sensing and switching happens so fast that the hospital does not experience a power outage.

This is why a hospital doesn’t lose its power while you’re sitting in the dark suffering in heat and humidity.  Because you have a radial feed.  While the hospital has redundancy.  If they lose one primary service they have a backup primary service.  Unlike you.  And in the rare occasion where they lose BOTH primary services (such as the Northeast blackout of 2003) hospitals have further redundancy.  Backup generators.  That can feed all of their life safety loads until the utility company can restore at least one of their primary services.  These generators can run as long as they can get fuel deliveries to their big diesel storage tank.  That replenishes the ‘day tanks’ at the generators.  Allowing them to keep the lights on.  And their patients alive.  Even while you’re sitting in the dark across the street.  Sweating in the heat and humidity.  With no television to watch.  While people in the hospital say, “There was a power outage?  I did not notice that.”

www.PITHOCRATES.com

Share

Tags: , , , , , , , , , , , , , , , , , , , , , , , , , , , ,

Labor and Energy Costs

Posted by PITHOCRATES - July 1st, 2013

Economics 101

If you want to Destroy an Industry and Kill Jobs all you have to do is Raise the Cost of Labor

What happened to American manufacturing?  The Industrial Revolution swept through the United States and made America an industrial superpower.  By the beginning of the 20th century the United States became the world’s number one economic power.  Immigrants poured into this country for those manufacturing jobs.  Even though some of these jobs may have come out of a Dickens novel.  Because being able to eat had it all over starving to death.  And in America, with a good factory job, you could put food on your family’s table.

Most of those manufacturing jobs are gone now.  Why?  What happened to the once booming textile industry?  The once booming steel industry?  The once booming automotive industry?  Unions happened to them.  That’s what.  These jobs were so horrible and unfit for humans that unions stepped in and organized them.  But the jobs never got better.  Based on the ever more generous union contracts they kept demanding.  Increasing the cost of labor more and more.  Which chased the textile industry out of the country.  And much of the steel and automotive industries as well.

Is there anything we can learn from this?  Yes.  If you want to destroy an industry, if you want to kill jobs, if you want to damage the economy, all you have to do is raise the cost of labor.  The largest cost to most businesses.  Which is why many businesses have been replacing people with machines.  Advanced machines.  Computer-controlled machines.  Robots.  Because they can work 24/7.  They’re never late.  Never hung over.  Never out sick.  They don’t take lunch.  And they will work as fast as possible without ever complaining.  This is why businesses like machines.  For they let them lower their costs.  Making them competitive.  So they can sell at prices lower than their competitors.  Allowing them to remain in business.

Uncompetitive American Manufacturers go to Emerging Economies where they can be Competitive

Labor is a big cost of business.  Especially in an advanced economy.  With a high standard of living.  Where people own houses and cars.  Where those houses have central heat, air conditioning, televisions, sound systems, kitchen appliances, washers and dryers, etc.  These things cost money.  Requiring paychecks that can afford these things.  As well as pay for clothes, groceries, gasoline, utilities, etc.  Common things in an advanced economies.  But not all that common in an emerging economy.  Where factory workers aren’t accustomed to those things yet.  And don’t demand paychecks that can pay for those things.  Yet.

Still, people in developing economies flock to the new factories.  For even though they are paid far less than their counterparts in advanced economies these factory jobs are often the highest paying jobs in their countries.  And those who have these jobs have a higher standard of living than those who don’t.  Even when the occasional factory burns to the ground or collapses killing everyone inside.  As sad as that is.  But if you want to eat and provide for your family these factories often offer the best opportunity.

So this is where American manufacturing jobs go to.  Where labor costs are lower.  Allowing business to stay competitive.  Because if they can’t be competitive no one will buy what they are selling.  And without any revenue they won’t be able to pay their suppliers.  Their employees.  Or their energy costs.  Another large cost of business.  Especially for manufacturers.

Unions and Regulatory Costs haven’t made Emerging Economies Uncompetitive Yet

A lot of houses today come with a 200-amp electric service.  Assuming a house uses about 100 amps on average that comes to 24,000 watts (100 amps X 240 volts).  Now consider a large manufacturing plant.  Like an automotive assembly plant.  That can have anywhere around 8 double-ended unit substations.  Which are pieces of electrical distribution equipment to feed all of the electrical loads inside the plant.  Each substation has two 13,800 volt 3-phase primary electrical services.  If you’re looking at one you will see the following from left to right.  A 600-amp, 15,000 volt switch, a transformer to step down the 13,800 voltage to 480 voltage, a 480-volt main switch, a bunch of 480-volt switches to feed the electrical loads in the plant, a ‘tie’ switch, another bunch of 480-volt switches, another 480-volt main switch another transformer and another 600-amp switch.

The key to a double-ended unit substation are the two 480-volt main switches and the tie switch.  Which normally distributes the connected electric load over the two primary services.  With both 480-volt main switches closed.  And the tie switch open.  If one service fails because a car knocks down a cable pole these switches will sense the loss of that service.  The 480-volt switch on the side of the failed service will open.  And the tie switch will close.  Feeding both sides of the unit substation on the one live primary service.  So each primary service carries half of the connected load.  Or one primary service carries the full connected load.  Assuming each unit substation uses 600 amps on average (2 services at 300 amps or 1 service at X 600 amps) that comes to approximately 13,194,070 watts (600 amps X 13,800 volts X √3 X .92 PF).  Where we multiply by the square-root of 3 because it is three phase.  And assume a 0.92 power factor.  If a plant has 8 unit substations that comes to 105,552,562 watts.  Which equals approximately 4,398 houses with a 200 amp service.  Now to further our crude mathematical approximations let’s take a typical electric bill for a house.  Say $175 on average per month.  If we multiply this by 4,398 that comes to a monthly electric bill for this manufacturer of about $769,654.  Or $9,235,849 per year.

So here is another way to destroy an industry, kill jobs and damage the economy.  By increasing the cost of electric power.  Which is already a very large cost of business.  And ‘going green’ will make it even more costly.  As the Obama administration wants to do.  With their war on coal.  The cheapest source of electric power we have.  By increasing regulations on coal-fired power plants.  Even implementing some kind of a carbon tax.  To punish these carbon emitters.  And to subsidize far more costly green energies.  Such as solar.  And wind.  Going from the least costly to the most costly electric power will greatly increase a business’ electric utility costs.  Easily adding 15%.  30%.  40%.  Or more.  A 40% increase in our example would increase the electric utility cost by $3,694,340 each year.  If a plant has 1,200 workers that’s like adding another $3,000 per worker.  And we’ve seen what higher labor costs have done to companies like General Motors.  Chrysler.  And the textile industry.  By the time you add up all of these new regulatory costs (Obamacare, green energy, etc.) businesses will be so uncompetitive that they will have to follow the textile industry.  Out of the country.  To a country that will let them be competitive.  Such as an emerging economy.  Where unions and regulatory costs haven’t made them uncompetitive.  Yet.

www.PITHOCRATES.com

Share

Tags: , , , , , , , , , , , , , , , , , , , , , , , , , ,