Overhead Power Line Ampacity Calculation via Sag Monitoring
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for determining the thermal power line rating are limited by the need for detailed conductor and meteorological data, and often rely on uncertain models, making them inefficient and prone to errors in real-time and forecasted ampacity calculations.
Innovation Solution
A method that uses sensor outputs for sag and effective wind speed, along with actual load current, to calculate power line ampacity without requiring conductor data, focusing on the relationship between sag and current flow to determine ampacity, with a watchdog for regular checks on deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing methods use detailed conductor and meteorological data with thermal models to determine power line rating, then the calculation comprehensiveness is improved, but the reliability deteriorates due to uncertain models and data
Solution Approach 1:
The patent extracts and removes the uncertain thermal models and detailed conductor/meteorological data requirements from the ampacity calculation process. Instead of using complex thermal models that require extensive input data, the invention directly uses sensor measurements of sag, wind speed, and temperature to calculate ampacity, eliminating the source of model uncertainty while maintaining calculation comprehensiveness
Solution Approach 2:
The patent introduces sensor measurements as an intermediary between environmental conditions and ampacity calculation. Rather than directly modeling the complex thermal processes, the invention uses measured sag, wind speed, and temperature as intermediate parameters that directly correlate with conductor behavior, providing a more reliable basis for calculation
2Measurement precision
If existing methods require detailed conductor data and meteorological data for ampacity calculation, then the theoretical accuracy is improved, but the ease of operation deteriorates due to data collection requirements
Solution Approach 1:
The patent implements self-service by using sensors that automatically measure sag, wind speed, and temperature directly at the power line location. The system serves itself by collecting necessary data through onboard sensors rather than requiring external data collection efforts, thereby maintaining theoretical accuracy while dramatically improving ease of operation
Solution Approach 2:
The patent creates a universal solution where a single sensor system performs multiple functions: measuring sag, wind speed, and temperature simultaneously. This multi-functional approach eliminates the need for separate data collection systems for each parameter, reducing operational complexity while maintaining comprehensive measurement capability
3Adaptability or versatility
If existing methods use ruling span concept with thermal equations and state change equations, then the model completeness is improved, but the device complexity increases due to multiple data requirements
Solution Approach 1:
The patent extracts the essential measurement requirements from the complex ruling span concept and thermal equations, keeping only the critical sensor measurements needed for accurate ampacity calculation. By removing the complexity of implementing full thermal models and state change equations, the system maintains model completeness for practical purposes while reducing device complexity
Solution Approach 2:
Instead of using complex thermal models to predict conductor behavior from environmental data, the patent inverts the approach by directly measuring conductor sag and using that measurement as the primary input for ampacity calculation. This inversion simplifies the system by making the measurement process the foundation rather than the consequence of complex modeling
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for accurate and efficient determination of power line ampacity in real-time and forecasted scenarios, reducing reliance on uncertain data and models, and providing a more reliable maximum allowable current rating.
Implementation Method 1
Measurement of the sag of power line spans between successive supports to determine whether the sag is greater than a maximum value has become a mandatory requirement in some countries. U.S. Patent No. 8,184,015 discloses a device and method for continuously monitoring the sag on a power line span. This method allows the determination of mechanical dynamic properties of the power lines just by sensing mechanical vibrations in a frequency range from 0 to some tens of Hertz.
Implementation Method 2
The ampacity calculation is also based on the ruling span concept which allows to replace a full multi-span section by one equivalent so-called 'ruling span' which is theoretically giving access to all individual span behaviors but many hypotheses lie behind that theory. Thus, all existing models so far usually use the ruling span concept coupled with the state change equation (Kissling et al, ibid., page 546) and thermal equations including meteorological data, conductor data, sagging conditions, etc.
Implementation Method 3
Power line rating (i.e. ampacity) can be dynamically estimated using smart sensors. The so-called dynamic line rating is nowadays considered with great interest in everyday operation of power networks all around the world. Forecasted values of ampacity are also used in day-ahead network management as well in several days ahead network market approach
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The present invention relates to a method for measuring the power line thermal rating or maximum allowable current rating of an overhead power line with respect to a suspended/anchored cable span (2), comprising at least the following steps of: monitoring a motion of at least one point P of said suspended/anchored cable span (2) over a time interval; monitoring actual line current I, in A, over said time interval; determining an actual sag of said suspended/anchored cable, as a variable of actual line current; measuring or determining the effective wind speed of said suspended/anchored cable span (2) over said time interval; determining a sag reserve DF, in m, for thermal rating, which is the distance between the actual sag and a maximum allowable sag; determining the rate of change, tan(a), in m/A2, of the actual sag versus the square of the line current for the effective wind speed; and determining the power line thermal rating of the overhead power line, or ampacity, linked to a corresponding safety clearance, at measured or determined effective wind speed, by adding the square of actual current I to the ratio of the sag reserve DF by the sag rate of change, tan(a), at the effective wind speed, and taking the square root of that addition, i.e. (formula I) wherein ampacity is in amperes.