Year 2000 and Power Transmission
A look at the effect of Y2K on power transmission in the
U.S.
Recently, I have encountered
a few individuals who have proposed the theory that the Year 2000 problem
with computers will immobilize the nation by deenergizing the transmission,
subtransmission, and distribution lines which distribute electricity to
the residences and businesses in the USA. I hope to offer some insight
to this matter as one in position to provide facts and technical expertice
pertaining to power transmission and distribution.
I currently am employed
by a major energy supplier in Nebraska. I have worked for this company
for 10-1/2 years. I earned an AAS degree from Iowa Western Community
College in Electronics Technology and soon thereafter went to work at this
company's nuclear power facility. I completed over 3000 hours of training
while working with this company, most of which was technically oriented
and pertained to Instrumentation and Controls. I worked at
the power plant for 9-1/2 years as an Instrumentation and Controls Technician.
I then worked in the Retail Division as an Equipment Maintenance Technician
(one who performs maintenance and calibrations on power distribution substations
and equipment.) I am currently in the Wholesale Division and am entitled
a Test Technician (one who performs maintenance and calibrations on transmission
and subtransmission substations and equipment.) I have seen most
areas of the power generation, transmission, subtransmission, and distribution
and have worked on a vast array of electrical equipment used in these areas.
First it is necessary to
briefly discuss how it is all tied together. The power is produced
by converting static energy to dynamic energy by using some means of fuel
and comverting it to electricity. This conversion usually takes place
in a nuclear boiler, a coal-fired boiler, an oil or gas boiler, or a gas-fired
combustion engine. Other less conventional forms exist such as solar
power hydro power, and wind power, which actually put dynamic energy to
use directly. These energy sources then turn a generator which converts
the freshly-made dynamic energy to electrical energy and we have the first
phase complete.
The power is now ready to
be transmitted. The power is transmitted from the power plant at
very high voltages. This is the transmission aspect of the power
scene. Transmission voltages are typically 161000 volts to 345000
volts. These voltages are so high due to the high capacity output
of large power plants. Transmission lines are large lines, and suspended
from large, tall structures. Transmission lines are the "backbone"
of the system from which other lines further distribute the power.
Subtransmission voltages
are usually in the range of 69000 volts to 115000volts. The transmission
voltages are "stepped down" by a transformer to a subtransmission voltage
so the power can be sent to regions and areas. Subtransmission requires
smaller structures, smaller conductors, and less ground clearance, resulting
in less cost.
Distribution is the phase
where the power is finally delivered to the user (notice I did not say
consumer; I detest that word used for individuals.) The subtransmission
power is "stepped down" to voltages typically 24900 volts or 34500 volts.
This power is fed to distribution substations where it is "stepped
down" again to distribution voltages. Typical distribution voltages
are 2400, 4160, 7200, 12500 and 13800 volts. These voltages coming
from the distribution substation are once again "stepped down" at the actual
site of the customer.
These power lines, just
like your power system at home, must have a way of deenergizing in the
event that a fault occurs. Have you ever had to reset a breaker or
replace a fuse? Well those breakers and fuses are in substations
for protection as well. They are designed to protect people and equipment
when a problem is sensed. These protective devices are known in the
electrical world as Circuit reclosers and circuit breakers.
Reclosers and breakers were
originally mechanical and/or hydraulic mechanisms. In the rapidly
changing electronics era, breaker and recloser controls have been significantly
improved by using solid-state and even computer controlled controls.
Furthermore, the transmission,
subtransmission, and distribution systems are monitored by control centers
which are also computer oriented.
So the question is, "Will
these computer controls shut down the power lines when the chronometer
rolls over to the new millenium?
Speaking for the Nebraska
system, I will argue that it will not. A look at nuclear plant safety
systems and controls, allows one to see that these plants have been designed
to respond to abnormal occurrences. As such, they are designed using
simple mechanics which will operate predictably at all times. The
mechanical components used in nuclear power rely on the laws of physics
for their function and are maintained by methods which assure that the
components necessary to control the facility are in as-new condition.
To make a long story short, it costs far too much to install state of the
art computerized equipment in place of the existing equipment due to the
safety analyses involved on the part of the equipment manufacturers and
the plant owners. While computerized systems do exist, they are generally
in a non safety-related application. There are exceptions, and the
one at the facility of which I am familiar is the computer-controlled system
which controls the flow of feedwater to the reactor. The computer
only uses times for logging alarms, though, and the time has no bearing
on the control section of the unit.
The other system which indirectly
affects the plant and uses a microprocessor for its functional basis is
the plant alarm system. This system is used to monitor the parameters
of the plant and generate alarms upon receipt of an abnormal condition
and also to log the alarms in real-time. If incapacitated, the plant
is required to declare an "alert" status emergency and commence a safe
and orderly shut-down of the nuclear boiler. This orderly shutdown,
though would allow plenty of time for the company to place its other "peaking"
and standby power generation systems to be activated and replace the absence
of the nuclear facility.
The other plants in the
system are coal fired and gas fired facilities and are controlled by the
Control Center. They are controlled by a computer there, but are
also capable of being switched to manual control at the actual unit.
The nature of these units
allows rapid recovery from a transient. A coal fired facility can
basically start again immediately if taken off the power grid by something
unforseen. Therefore, if the computer controls at the Control Center
were to "dump" the facility, it could be reinitiated manually in minutes;
in seconds for the gas peakers.
Otherwise, the Control Center
is just an "information" gathering device. It receives information
from the substation and monitors them only. The computers do not
control the transmission system automatically, and therefore we must have
men work Sabbaths ans night around the clock to assure the power is distributed
to the customer without interruption.
The substations are mainly
controlled using controls which are electro-mechanical in nature and are
not connected to a computer in any form. There are some exceptions,
as the subs are being slowly updated. These exceptions are in the
form of microprocessor-controlled fault detection relays which have been
installed on some circuit feeds for cities and towns. It is possible
(but doubtful in my view) that these relays could trip off some circuits
at the substation(subtransmission and distribution level.) These
micro-based relays are, however, only installed on about 20% of the circuits
at a given sub and it is possible to switch these circuits onto another
circuit in the same sub or to switch the entire substation to another power
source. In other words, it is just like having six people in two
cars going to the same place; if the driver gets tired, a person in the
same car who is refreshed can take over or the two cars can stop and a
person from the other car could drive for the weary driver. With
this in mind, we can deduce that worse-case, the power would be interrupted
for a short time while the Control Center switched the load to another
source or worse case again, a serviceman was dispatched to switch the circuit
to another.
Now we are at the distribution
level. Distribution systems generally feed a town or a section of
a city through what is termed a "recloser." Reclosers are ased to
break a circuit in the event of a fault just as a circuit breaker, only
the are designed to close on the fault a few times prior to isolating the
line completely. Most reclosers are hydraulic in nature. They
rely on oil in their tank to determine the delay time for reclosing.
This is as high tech as they get, no computers in most. Some reclosers,
however, rely on computers for the timing sequence. The microprocessor
determines the fault current and from this determination, computes a delay
time and reclose time for operation. These are suscetible to time-related
interference, but once again, it is doubtful in my opinion that the time
miscalculation would interfere with anything. If the micro works
the way that it should, the recloser would continue to operate as usual
and if it saw a fault on the line, it would record the fault as occurring
at xx:xx time on jan 1 of 1900, and not 2000. Pretty simple, huh?
Worse case again, if a recloser loses its mind, it generally fails in the
closed mode and the circuit will not be interrupted. Worse-worse
case is if the recloser does open the circuit, it can be bypassed using
an existing bypass switch in place at the substation by utility employees
dispatched to the scene. Power interruption would be for only a few
minutes.
In conclusion, I can say
that the possibility of Y2K affecting the utility industry exists mainly
in the billing arena. Computer programs used to generate bills rely
on dates to properly bill the customer, and would probably be very confused
when switching to the new millenium. The major impact of the Y2K
problem on delivering power is that the events recorders may believe that
it is 1900 instead of 2000. These problems, I assure you, are being
researched by the people who are most intimate with computers and Y2K and
any glitch which may cause perturbations in customer billing or supplying
power to the customer is being resolved.
Any questions regarding
this commentary should be addressed to:
Email: jthol@juno.com
