20090909Assessment of System.pdf

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09/01/2009 2009 SEP -8 M1 9: 05
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Keith Hessing
Idaho Public Utility Commission
472 W Washington
Boise, ID 83720-0074
Subject: Atlanta Power Assessment
Introduction:
On August 28, 2009 Idaho Power performed an assessment of the Atlanta Power's system at the request
of the Idaho Public Utility Commission and the Atlanta Power Company. The goal was to monitor the
power quality in the town of Atlanta and provide the results to Atlanta Power and the IPUC. This
Assessment is not inclusive of all the problems on the Atlanta Power's generation and delivery system,
this assessment only includes the our findings and observations.
Safety:
Several safety issues were observed while on site. Public safety issues should be repaired first and
foremost.
1. A complete line patrol should be performed of the primary overhead system, pole by pole.
loose hardware, broken equipment, broken or loose guy wires should be noted, prioritized and
repaired.
2. Broken guy wires and conductor that are within reach of the general public should be removed
or repaired to avoid contacting live wires.
3. The facilities should also have a grounding inspection and maintenance performed.
System Single Line and Inventory:
The system should have a single line diagram showing the location of the equipment, phasing, distance,
conductor size, number of conductors, what phase transformers are connected to etc. This makes it
easier to balance load, voltage and troubleshoot problems and is also needed to calculate system
performance. This also improves safety when personnel not familiar with the system are work on it.
The single line can simply be hand drawn on llX17 paper with the assistance of a hand held gps.
Frequency Regulation:
The governor was slow to respond to regulation causing the frequency of the generator to vary
constantly from 58 to 65 Hz, about once per minute with an average of 62 Hz. The maximum and
minimum frequencies throughout the recording period were 68 and 57.8 Hz respectively.
1. The governor control appeared to have significant room for improvement. The drive chain had
slack causing more delay in reacting to frequency change.
2. The set point of the frequency is too high; the frequency should average 60 Hz during operation,
not 62 Hz.
3. The bandwidth of the frequency is too broad; recommend setting high limit to 61 Hz and low
limit at60 Hz.
4. The delay should also be shortened to make the system more responsive to frequency changes.
5. New equipment could be purchased that is dedicated to frequency regulation for this type of
system.
6. Care should be taken to keep the frequency from dropping below 59 Hz. It appears there is no
voltage regulation on the unit. If this is the case, the voltage is frequency controlled; dropping
below 59 Hz causes a significant output voltage drop. The Voltage vs. Frequency chart below
displays the relationship.
Freq.
66
64
62
60
58
56
54
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~~ ~ ~~ ~ ~~ ~ ~~~~ ~ ~ ~ ~ ~~~~ ~ ~ ~~~ ~ ~~ ~~~~~~ ~ ~ ~ ~ ~ ~~ ~ ~~~~ ~ ~~~ ~~ ~ ~ ~~ ~~~ ~ ~ ~ ~~~~~00000000000000000000000000000000000000000000000000000000000000000000~ ~ 00 ~ ~ ~ ~ ö ~ M Ö ~ M m ~ N m ~ N 00 ~ ~ 00 ~ ~ ~ ~ ö ~ M Ö ~ M mNMM~~~ OM MNMM~ ~~OOMNNM~~~OOMN NM~~~~NN N NN N ~ ~ ~ ~ ~ ~~ ~ ~ N N N N N NN N N MM M M MMMMM MMMMMMM
118
116
V 114
112o110
I 108
t 106
s 104
102
100
Voltage vs. Frequency'''-'''-Avg. Town Volts -Freq.
65
63 F
61 r
59 e
q
57
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Voltage Issues:
Voltage at the resort was too high. The cause appears to be the 3 phase transformer bank serving the
ranch. The core of the transformer appears to be saturating causing voltage flat topping and distortion.
1. It appears that the transformer bank has internal taps that are raising the voltage approximately
15% too high, or more. The transformers should be taken down, opened and taps adjusted to
raise the voltage 5%, not 20% from nominaL. The percentage of adjustment can be made to
provide the ranch with 120/208 three phase voltage.
2. If there is no taps then the transformer bank is rated for a different primary or secondary
voltage. New or salvaged transformers with taps should be purchased and installed that are
rated for the application.
Voltage at the generator fluctuated from 108 to 123 volts, using a base of 120 volts. The average output
voltage was 120 volts. With the dynamics of the system we could not coordinate the voltage fluctuation
at the generator with any load variation.
1. We did not expect or believe the voltage output should fluctuate significantly. Voltage
fluctuation is most likely caused by the frequency variation.
2. The voltage fluctuation could be caused by malfunctioning generator voltage regulation. The
voltage regulation should compensate for changes in load etc. We did not look or inquire about
the voltage regulation on the generator. If the voltage regulation is fixed or has no feedback
control we would expect to see about 6% voltage change from no load to rated load.
3. The voltage at the generator should be set (if possible) at 123 to 124 volts, using a 120 volt base.
This wil allow for the voltage drop of the step up transformers, line loss to town, loss stepping
the voltage down and service drop. Increasing the output voltage will compensate for the
system losses.
Load Balance:
The load at the generator became more unbalanced as the day progressed. load on C phase peaked
about 84 amps while load on A phase was running 45 amps. B phase during this same interval was
running 60 amps.
1. Move about 10-15 amps of load from B-C phase to A-B.
Voltage Regulation:
The voltage at Steve's house averaged 117.5 volts and amax of 121.7.
Steve's Voltage
125
115
120
110
105
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The voltage at the lodge averaged 113.8 volts and a max of 116.2.
Voltage Lodge
125
120
115
110
105
100 ~~ ~ ~ ~ ~ ~~~ ~ ~~~~ ~~ ~~~~~ ~~~~~ ~~~~~~~~~~ ~ ~~ ~ ~~~ ~~~ ~~ ~~ ~ ~~ ~~ ~ ~~~ ~ ~~~~~~~~00000000000000000000000000000000000000000000000000000000000000000000~ m ~ m M 00 M ~ N ~ ~ ~ ~ ~ Ö ~ m ~ m M 00 M ~ N ~ ~ ~ ~ ~ Ö ~ m ~ mMMNNM M ~~~~OOMMNNNMM~~ ~~OOM MNNMMM~~~~ ~~ ~ ~ ~~~~NNNNNNNNNNNNNMMMMMMMMMMM
The voltage on the hill averaged 117 volts and a max of 119.
Voltage on hill
125
120
115
110
105
100
~~ ~ ~ ~ ~ ~ ~ ~~ ~ ~~ ~ ~ ~ ~ ~~ ~~~ ~ ~ ~~ ~~ ~~ ~~~~~ ~ ~ ~ ~ ~ ~ ~~ ~ ~~ ~ ~ ~ ~ ~~ ~ ~ ~ ~~ ~~ ~~ ~ ~ ~~~000000000000000000000000000000000000000000000000000000000000000000~ m M 00 N ~ ~ ~ m ~ 00 N ~ ~ ~ Ö ~ 00 M ~ ~ ~ Ö ~ m M ~ N ~ Ö ~ m M~ ~OOM MNN NMM~~ ~ ~OOO M M NNMMM~ ~ ~~OOOM~ ~NN N N NN NNNNNN NMMMMMMMMMMMMMM~ ~~ ~
1125
115
110
105
100
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ .~ ~~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ Cl ~ ~ ~ ~ ~ ~ ~ ~000000000000000000000000000000000000000000000000000000000000000000~ 00 N ~ m N ~ m M ~ Ö M ~ Ö ~ ~ ~ ~ 00 ~ ~ 00 N ~ m N ~ m M ~ Ö M ~~ ~ 000 M M M N N MM M ~ ~ ~ ~ ~ ~OO 0 M M M NN N MM~ ~ ~~ ~ N N N N N N N NN N N N N NNNNMM M M M M MM M M MMM M
Customer Equipment:
The size of customer equipment, especially motors should be limited. The system is not capable of
starting motors without impacting other customers on the system. The system cannot readily handle
the sudden changes in load. Motors of approximately 10 Hp or greater should have soft start
equipment installed.
Customer clocks should keep better time once the frequency is more accurately regulated.
Electronic devices that are malfunctioning should have the voltage checked at the device. The line to
neutral voltage, line to ground voltage and neutral to ground voltage should be checked. line to neutral
voltage at the device should be within ANSI range A utilization voltage while operating 108 - 125V.
Neutral to ground voltage should not exceed 2 volts at the equipment. Equipment needs to have proper
grounding and neutral to ground bond at the main paneL.
The line to neutral voltages should be checked at the meter base at the same time the equipment is
checked. Voltage at the meter base should be in ANSI range A limits 114-126V. These are steady state
conditions, not the voltage when equipment is starting.
Closing:
1. Significant improvement can be made to the quality of the power delivered with small
investments and labor. The area with the most room for improvement is the frequency
regulation. Improving the existing regulation or investing in a new regulator is recommended.
The existing regulation wil always be "chasing" the frequency causing system performance and
frequency to have marginal performance.
2. System single line diagram and drawing is needed to properly operate the system.
3. The transformers at the ranch should be addressed. The overvoltage and voltage distortion is
affecting the customer's equipment.
4. Maintenance on the existing system for public safety should also be performed as soon as
possible.
5. load should be balanced; this will improve voltage balance also.
Equipment could be added at the generator that provides real time displays and data logging capability
for voltage, amperage, kw, kva and frequency. The data is stored internally to the equipment and can
be downloaded and reviewed on regular bases to determine changes in operating characteristics. (Note:
is appears as if this system has always operated in this fashion.) Also this equipment can continually
download the data into a local or remote computer. This same equipment could also provide better
frequency control. Idaho Power makes use of this type of permanent monitoring equipment frequently
to know how our system is operating. The addition of data logging equipment allows for better control
of the system. Trends can be established over time to determine what needs to be adjusted or if
something is malfunctioning.
Shane Woods
Senior Power Quality Engineer
Jon Roholt
Principal Power Quality Engineer