POWER June 2010 - 20

increase are diligently enforced by the plant. Achieving these
desired slow ramp rates when raising power levels is difficult
with MG sets due to their unpredictable control stability. That
is, a demand change to an MG set may not result in any speed
increase, or the speed increase may be more than what was originally
requested. With the precise speed control provided by VFDs,
raising power is predicable and power ascension is always within
established limits.
Improved System Reliability
The Siemens VFD was specifically designed for high-availability
applications that require continued operation in the event of an
equipment failure. This particular VFD topology has several layers
of redundancy and robustness designed into the system, including
N + 2 redundancy for the power converter section, fast cell bypass
that will automatically bypass a failed power cell, and redundant
control systems that will automatically switch over to a duplicate
control system in the event of a primary control system failure. The
VFD will continue to run at full power if up to two power modules
fail, a primary microprocessor controller fails, or a programmable
logic controller controlling the system inputs and outputs fails.
Virtually every major component is redundant, which has given
the VFD the ability to operate even after every major system has
a component failure. This process (reactor pump) over product
(VFD) philosophy improves reliability and leads to fewer power
reductions caused by circulation system problems.
Reduced Environmental Issues
Replacing an MG set with a VFD eliminates several other systems
in the plant, including the oil used in the mechanical coupling
between the motor and generator in the MG set. This results in an
environmental improvement, as routine oil disposal is no longer
required. In addition, special fire protection systems that are in
place to protect against potential oil fires can be eliminated. Additional
cost savings associated with eliminating these systems
and maintenance processes may be achievable.
Currently, more than 50 individual VFDs are scheduled for incorporation
into various nuclear plants, primarily in the U.S., in
both boiling water reactors and pressurized water reactors.
-Contributed by Mark W. Harshman, a drive system consultant
with Siemens LDA in New Kensington, Pa.
KEMA Conference Report:
Competition Strengthens as Wholesale
Power Prices Fall
Since the collapse of Enron and the wholesale power markets, the
vitality of competition in retail markets for electricity has waned in
most regions of the U.S., with the exception of Texas. At KEMA's 21st
annual Executive Forum in late March, 300 attendees converged on
Dallas to discuss and debate the dynamics and changes now facing
residential and commercial customers in most regions of the U.S. and
Canada. Founded in 1927, KEMA is a global provider of business and
technical consulting, operational support, measurement and inspection,
and testing and certification for the energy and utility industry.
A summary of the many presentations follows.
During 2009 overall consumption of electricity in the U.S. fell
by 4.2%, the largest one-year drop in 60 years. Concurrently, the
average prices of natural gas (Figure 3) and wholesale electricity
(Figure 4) followed suit and fell more than 50%. Business and
residential customers alike are looking for a better deal on their
electricity purchases, further invigorating an already competitive
buyer's market. Although Texas is still the largest competitive
20
3. Dipping gas prices. The average U.S. regional price of natural
gas dropped from 2008 to 2009. Natural gas prices are shown in $/million
Btu. Source: Derived from Intercontinental Exchange data
Sumas
$3.77
-54%
PG&E
$4.13
-52%
SoCal
$3.62
-54%
HSC
$3.75
-56%
Opal
$3.14
-52%
Panhandle
$3.27
-54%
Henry
$3.92
-56%
AECO
$3.48
-55%
Chicago
$3.92
-55%
TCO
$4.11
-55%
FGT Z3
$3.98
-57%
TZ6 NY
$4.87
-52%
4. The electric slide. Wholesale electricity prices also declined
over the past year. Data shown are 2009 wholesale prices compared to
2008 prices. The electricity price shown is in $/MWh. Source: Derived
from Platts data
Mid-Columbia
$35.66
-45.1%
COB
$38.22
NP 15 -48.5%
$39.29
-51.0%
SP 15
$38.31
-51.7%
Four Corners
$35.38
-50.8%
Palo Verde
$34.77
-51.6%
Minnesota
Hub
$32.09
-52.4%
SPP
$32.94
-52.1%
ERCOT
$26.59
-57.6%
Entergy
$33.57
-51.0%
NI Hub
$34.47
-47.9%
TVA
$34.91
-49.4%
NYPP Zone G
$49.80
-50.7%
PJM West
$44.60
-46.7%
Cinergy
$34.65
-48.2%
Southern
$36.58
-47.8%
Mass Hub
$46.24
-49.5%
NYPP
Zone J
$55.77
-50.9%
Florida
$40.75
-45.4%
market, 2009 brought some significant changes in other competitive
power markets across the U.S.
Maryland
The call for " re-regulation " has subsided in Maryland. With the sharp
fall in wholesale prices, buying electricity from the default providers
now costs about 15% more than competitive power. The rate of
residential customers switching providers is gaining momentum.
Michigan
The current 10% cap on the cumulative amount of competitive
sales in Michigan reached its full subscription in about one year.
Now customers are pushing to increase or remove the cap in order
to encourage companies like Constellation Energy to come to the
state and compete for electricity sales.
California
After deregulating in 2000, California later reregulated while allowing
customers who switched during the open window to stay
with their electricity provider of choice. Senate Bill 528, enacted
in October 2009, has reopened the window for more competitive
power sales. Each of the three major investor-owned utilities must
allow nonresidential customers to switch to an electricity provider
of their choice effective April 16, 2010. However, here's the catch:
Like Michigan, California has established a cumulative cap on the
direct access mandate. So many customers want to change suppliers
www.powermag.com
POWER | June 2010
http://www.powermag.com
POWER June 2010

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