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Kresimir Bakic, CIGRE & ELES, Slovenia
Beograd, 6 November 2014
SLOVENIJA 2014
STATE-OF-THE-ART FOR DYNAMIC LINE RATING TECHNOLOGY
Future Vision
"Maintenance and recovery of HV electricity transport
systems and aerospace assistance"
Plan of presentation
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1. INTRODUCTION – Why we need DLR?
2. POSIBLE SENSORS FOR DLR
3. WHAT IS THE KEY ISSUE FOR LINE MONITORING? STATIC VALUE, DYNAMIC VALUE, +++ PREDICTIONS
4. TECHNOLOGY BASED ON WEATHER STATIONS
5. TECHNOLOGY BASED ON TENSOR CELLS
6. TECHNOLOGY BASED ON CONDUCTOR TEMPERATURE
7. TECHNOLOGY BASED ON CONDUCTOR VIBRATION
8. TECNOLOGY BASED ON FIBER OPTIC
9. TECHNOLOGY BASED ON SAG MONITORING DEVICE
10. TECHNOLOGY BASED ON DGPS – SATTELITE MONITORING
11. MY VISION ON SATELLITE AIDED OHL MONITORING - CONDUCTOR: SAG, TEMPERATURE, ICING
- TOWER: TENSION, SAG
- CORRIDOR: VEGETATION MANAGEMENT
- WEATHER CONDITION ??? GROUND LEVEL WIND FLOW ???
- RECOVERING SUPPORTS DURING LARGE WEATHER STORMS, SPACE STORMS
Kresimir Bakic, CIGRE Slovenia
INTRODUCTION
3 Kresimir Bakic, CIGRE Slovenia
100
%
200% C
AP
AC
ITY
IN
CR
EA
SE
COST
Base Case:
New Line:
Cost = 100%
Capacity=100% 100%
0 25% 50%
75% 3
4
5
300%
1, 2
6
1 Real Time Monitoring
2 Probabilistic Rating
3 Conductor Retention
4 Conductor Change
5 Voltage Increase
6 Conversion to DC
CIGRE WG
B2/C1 - 19
TECHNOLOGIES FOR INCREASING
CAPACITY OF OHLs - DLR solution - cheapest
- Older OHLs with high loads
- Carefuly with losses
New HTLS conductors
(ACCC) could be more
competitive than investment
in non-reliable monitoring.
Why we need DLR?
4 Kresimir Bakic, CIGRE Slovenia
INTRODUCTION Criteria for decision
of Technology
1. ECONOMY 2. RELIABILITY (supply method, ICT – transmission) 3. ACCURACY (± 5 A) and for SAG (± 20 cm) 4. PLACING (with or without switching off line)
Economy of cable or OHL Capacity of Cable or OHL
Source: CIGRE WG B2/C1 - 19
5 Kresimir Bakic, CIGRE Slovenia Source: EPRI, Future Inspection of OHL, 2008
TECHNOLOGIES FOR OHL MONITORING
Main parts of technology:
- sensors,
- information transmission.
Monitoring of
- electrical, thermal, mechanical
and atmospheric parameters.
SENSORS TECHNOLOGIES: - optical, infrared, ultra-violet, satellite imagery, - surface acoustic waves (SAW), - vibration sensors, conductor temperature sensors, - LIDAR (Laser Imaging Detection And Ranging), - tensor load cells, strain sensors, - wind measure with ultrasonic anemometers, etc.
6 Kresimir Bakic, CIGRE Slovenia
rp
sp
RI 2
cp
mW cooling Radiation-
mW cooling Convection -
mW heatingSolar -
mW heating Joule -
mW
r
c
s
j
rcsj
p
p
p
p
pppp
Condition State Steady Under
Direct or BeamSolar Radiation
Sky or Diffuse Solar RadiationImaginary BoundaryRepresenting Sky andSurrounding
Portion NotAbsorbed byConductor
Horizontal ConductorOriented in Air with WindNormal to Conductor
Win
d
rp
sp
2
cp
mW cooling Radiation-
mW cooling Convection -
mW heatingSolar -
mW heating Joule -
mW
r
c
s
j
rcsj
p
p
p
p
pppp
Thermal balance equation
Main atmospheric parameters are wind, wind direction, ambient temperature and solar
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Temperature in atmosfere
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WHAT IS THE KEY ISSUE FOR LINE
MONITORING?
STATIC VALUE
DYNAMIC VALUE
PREDICTIONS
Ampacity of a conductor is that maximum constant current which will meet the design,
security and safety criteria of a particular line on which the conductor is used.
Static rating is the simplest thermal rating system based on “ampacity Tables” provided by the
conductor manufacturer or calculated based on worst weather case. Using such tables, the “normal” or „continuous”
thermal rating of each conductor is specified for certain weather conditions and conductor parameters.
Conservative approach based on worst weather case.
Real-time monitoring – many different technologies.
Some technologies more effective during system normal
operation and other during system contingency.
Real added value for monitoring systems.
Key issues related to wind predictions in the OHL corridor
in so different terrains.
Global error margin for real-time rating acceptable for operators should be ± 10%.
Conditions for conservative thermal ratings:
1) Wind speed: 0,6 m / s perpendicular wind, 2) Ambient temperature 30 - 350 C, 3) Solar radiation 900-1000 W/m2 ; 4) Conductor absorptivity 0.5 – 0.6
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From CIGRE brochure 299 “Guide for selection of weather parameters for
bare overhead conductor ratings”:
• The average temperature of a line section will not exceed the maximum
design temperature by more than 10 °C, even under exceptional situations, and will provide a confidence level of at least 99% that the conductor temperature will be less than the design temperature when the line current equals the line rating.
• The highest local conductor temperature will not exceed the maximum design temperature by more than 20 °C when the line current equals the line rating. • Because ratings based on probabilistic clearances require consideration of other criteria than weather parameters (load probabilities, traffic under the lines etc.) their application is not included in this document. • This and other related documents discuss sag and tension calculations only in a general manner. The document recognizes that maintaining adequate
clearances is usually the primary objective of line ratings and that conservatism in sag calculations can mitigate the consequences of too optimistic rating assumptions. Yet, such combination may not be applicable in all circumstances.
• For ensuring adequate clearances, it is recommended that the transmission owner verifies their actual line clearances at appropriate intervals.
GOOD TO KNOW
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Static rating
2m/s
1m/s
0.6m/s
Static rating
STATIC RATING
Source: from CIGRE JWG C1-B2 - 19
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TECHNOLOGIES FOR THERMAL OHL MONITORING
-Ampacimon (vibration)
Conductor surface temperature
DONUT
Load cell (Tensor)
Surface Acoustic Waves (SAW),
Weather sta.
Source: from CIGRE TB 498
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1. TECHNOLOGY BASED ON WEATHER STATIONS
Weather station in ROW
Indirect Method
Calculating in-span Conductor temperature from a weather station. (CIGRE Bros. 207)
RTM system
The purpose of real-time monitoring is to determine, in real-time, the position of the conductor in space
conductor replica (SHAW technologies)
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2. TECHNOLOGY BASED ON TENSOR CELLS
RTM system
SOURCE: CIGRE TB 498
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3. TECHNOLOGY BASED ON CONDUCTOR TEMPERATURE
RTM system
SOURCE: CIGRE TB 498, from 2012
DONUT device clamped on conductor of OHL
Other type of conductor temperature is fiber optic measurement inside conductor. (4)
Temperature on surface of conductor
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5. TECHNOLOGY BASED ON SAG MONITORING DEVICE
RTM system
SOURCE: CIGRE TB 498, from 2012
camera target
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6. TECHNOLOGY BASED ON VIBRATION SENSOR
Fundamental
Frequency [Hz]
Sag [m]
0.1367 ± 4
10-4 16.40 ± 0.1
Principles behind Ampacimon
• Ampacimon detects low frequencies (accelerometers)
• The sag is determined via the main vibration mode
• Only the frequency is needed, not the amplitude
• No calibration is required • The accuracy of the measured sag depends on
the sampling frequency (approximately 2%) • Measurements are processed using the
Fourier transformations method
17 Kresimir Bakic, CIGRE Slovenia
Technology Use Where/how? How long?
Weather station wide No switch off 30 years
Load cell (Tensor) USA, EU Switch off line
On tower
20 years
Conductor surface temperature (Donut)
limited Switch off line On conductor in suitable span
20 years
Conductor inside temperature (Optical fiber)
limited Switch off line In conductor.
10 years
Sag measures (video, satellite imagery)
limited No switch off
Markers
10 years
Conductor vibration (Ampacimon)
Pilot
projects
Switch off line On conductor in suitable span
5 years
TECHNOLOGIES FOR THERMAL OHL MONITORING comparison
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TECHNOLOGY BASED ON DIFFERENTIAL GLOBAL
POSITIONING SATELLITE (DGPS)
Method for measure sag by DGPS. Capable of measuring sag to
accuracy of appr. 25 mm using commercially available GPS.
Method measures conductor to ground based on altitude information
obtained from GPS device.
Weakness of GPS: noise by radio signals, atmospheric conditions, etc.
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INFORMATION SYSTEM FOR OPERATORS BASED ON ANY SENSOR –
DEVELOPMENT IN ELES SLOVENIA
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An Attempt to develop innovative TECHNOLOGY
System based on Strain gauges
Measurements of fundamental
frequency and deformation
The measurement was carried out by sensors that were
attached to the legs of the towers, namely:
deformation gauges (resistance measuring gauges in
longitudinal and transverse direction) and also the
accelerometer and temperature gauges-tower.
DEVELOPMENT IN ELES, Slovenia, 2014
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An Attempt to develop strain gauges approch
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VISION ON OHL MONITORING AIDED BY SATELLITES
CONDUCTOR: SAG, TEMPERATURE, ICING
TOWERS: DEFORMATIONS
CORRIDORS: VEGETATION MANAGEMENT
PREDICTIONS – GROUND LEVEL WIND FLOW
RECOVERING SUPPORTS DURING LARGE
WEATHER STORMS, SPACE STORMS
23 Kresimir Bakic, CIGRE Slovenia
1 Development of sensor technologies as well as ICT has resulted in
the formation of the number of new monitoring technologies for
OVERHEAD power lines.
2. DLR is the cheapest approach to increase capacity, but decision
of technology needs very careful selection: method of data transfer
and the accuracy of the sensor.
3. New innovative methods as strain gauges and differential Global
Positioning Systems using satellites could be very promising
technologies for OHLs.
SOME CONCLUSIONS
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• Using National Weather Service forecast?
• Or to develop own tool?
1. Persistence models and combination -(models are in class of easy predictions models - plain predictor)
2. Statistical approaches -(time-series analyses, ARIMA, wavelet,...)
3. Data mining approaches (ANN) - Next generation of wind forecasting technology (Regime
switching space-time algorithms)
Approaches to predictive rating methods
-0,2
0
0,2
0,4
0,6
0,8
1
1,2
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76
Lag
ACF
-0,5
0
0,5
1
1,5
1 11 21 31 41 51 61 71 81 91 101 111 121 131 141 151 161 171
Lag
ACF
Bericevo (Wind speed prediction: Feedforward network wih 45 inputs,10 in the hidden layer
and 1 output)
0
1
2
3
4
5
6
7
Time (22.01.06 00:00 -28.01.06 23:55 )
Win
d s
pe
ed
(m
/c)
Real
Prediction
Podlog (Wind speed prediction: Feedforward network wih
52 inputs,20 in the hidden layer and 1 output)
0
1
2
3
4
5
6
Time (22.01.06 00:00 -28.01.06 23:55 )
Win
d s
peed m
/cReal
Prediction
Autocorrelation function for wind speed
Predictions for wind speed for 4 hours – ANN method
Comparison between real and predicted values
for wind speed in two different S/S
– 45 input neurons, 10 hide, 1 output – 52 input neurons, 20 hide, 1 output
S/S 1 S/S 2
Evaluation of flexible line capacity
Present approach: - Fixed or seasonal OHL rating,
- DLR using monitoring systems
without predictions.
Future approach:
- Use of a new technology (ICT, protection
schemes) and new mathematical
modeling for predictions will enables
dynamic evaluation of line capacity
and flexible line capacity for trade,
But take care: Maybe new type of HTLS conductors
can offer you better flexibility for
same cost or even cheaper.