Trending functions for predicting the health of electric power assets

Patent metadata

Field	Value
Publication number	US-11067639-B2
Application number	US-201816143811-A
Country	US
Kind code	B2
Filing date	Sep 27, 2018
Priority date	Nov 3, 2017
Publication date	Jul 20, 2021
Grant date	Jul 20, 2021

Abstract

A method for determining a dynamic rating for a conductive path includes using a sensor to measure a value for a load parameter and selecting a heating process associated with the load parameter. A rated temperature change is changed by removing temperature changes due to a heating process other than the selected heating process to produce an impaired rated temperature change. A thermal load percentage is determined from the impaired rated temperature change. The thermal load percentage and the measured value are then used to determine the dynamic rating for the load parameter. A method also includes measuring a temperature rise, a current, and a voltage on the conductive path multiple times. Using at least two basis functions and the multiple measured temperature rises, currents and voltages, the values for at least two variables are determined. Trends in each variable are determined to determine a condition of electric equipment.

First claim

What is claimed is:

1. A method for determining a dynamic rating for a load parameter along a conductive path, the method comprising:
using a sensor to measure a value for the load parameter;
selecting a heating process associated with the load parameter;
modifying a rated temperature change for the conductive path by removing temperature changes due to a heating process other than the selected heating process to produce an impaired rated temperature change;
determining a thermal load percentage as a ratio of a temperature change due to the selected heating process over the impaired rated temperature change; and
using the thermal load percentage and the measured value for the load parameter to dynamically determine the dynamic rating for the load parameter.

2. The method of claim 1 wherein determining the thermal load percentage further comprises determining the temperature change due to the selected heating process by subtracting a temperature change due to the heating process other than the selected heating process from a measured temperature change.

3. The method of claim 2 wherein the measured temperature change is measured by measuring an ambient temperature, measuring a temperature of the conductive path and subtracting the measured ambient temperature from the measured temperature of the conductive path.

4. The method of claim 3 wherein measuring the ambient temperature comprises making a plurality of temperature measurements of at least one conductive path under different load conditions and taking a lowest measured temperature from the plurality of temperature measurements as the measured ambient temperature.

5. The method of claim 1 wherein determining the dynamic rating for the load parameter comprises performing an inverse of a function on the thermal load percentage to form a load parameter percentage and dividing the measured value by the load parameter percentage to obtain the dynamic rating for the load parameter.

6. The method of claim 5 wherein performing an inverse of a function comprises taking a square root of the thermal load percentage.

7. The method of claim 5 wherein performing an inverse of a function comprises performing an inverse that is different from a square root.

8. The method of claim 1 wherein the load parameter comprises a current on the conductive path.

9. The method of claim 8 wherein removing temperature changes due to a heating process other than the selected heating process comprises removing temperature changes due to conductance through an insulator.

10. The method of claim 9 wherein removing temperature changes due to a heating process other than the selected heating process further comprises removing temperature changes due to partial discharge.

11. The method of claim 8 wherein removing temperature changes due to a heating process other than the selected heating process comprises removing temperature changes due to partial discharge.

12. The method of claim 1 wherein the load parameter comprises a voltage across an insulator.

13. The method of claim 12 wherein removing temperature changes due to a heating process other than the selected heating process comprises removing temperature changes due to ohmic current through the conductive path.

14. The method of claim 13 further comprising further modifying a rated temperature change for the conductive path by removing temperature changes due to partial discharge.

15. The method of claim 12 wherein using the thermal load percentage and the measured value to dynamically determine the dynamic rating for the load parameter comprises performing an inverse of a function on the thermal load percentage to form a load parameter percentage and dividing the measured value by the load parameter percentage to obtain a result and selecting the smaller of the result and a partial discharge inception voltage as the dynamic rating for the load parameter.

16. The method of claim 1 wherein removing temperature changes due to a heating process other than the selected heating process comprises applying a second load parameter to a basis function to produce a basis function result and multiplying the basis function result by a state variable.

17. The method of claim 16 wherein the basis function comprises:
I 2 (1+ c ( T A +ΔT ))/( a+bΔT/T A )
where I is current on the conductive path, T A is an ambient temperature, ΔT is a difference between a temperature of the conductive path and the ambient temperature, and a, b and c are model parameters that account for nonlinearity of the basis function.

18. The method of claim 16 wherein the basis function comprises:
V 2 (1+ dH )(1+ c ( T A +ΔT ))/( a+bΔT/T A )
where V is the voltage on the conductive path, T A is an ambient temperature, ΔT is a difference between a temperature of the conductive path and the ambient temperature, a, b, c and d are model parameters that account for nonlinearity of the basis function, and H is the relative humidity.

19. The method of claim 16 wherein the basis function comprises:
( a *PD c +b*SD d ) V /( e+fΔT/T A )
where PD is an externally measured partial discharge intensity, SD is an externally measured corona discharge intensity, V is a voltage on the conductive path, T A is an ambient temperature, ΔT is a difference between a temperature of the conductive path and the ambient temperature and a, b, c, d, e are parameters of the basis function.

20. The method of claim 16 wherein the basis function comprises:
fV<Q><N>
where f is the frequency of voltage V on the conductive path, <Q> is the peak charge associated with partial discharge events, and <N> is a repetition number representing a number of partial discharge events per cycle of voltage V.

Assignees

• Rosemount Inc

Inventors

• Andle Jeffrey C
• Cunneen Thomas M
• Lane David

Classifications

• H02J2103/30

  Simulating, planning, modelling, reliability check or computer assisted design [CAD] of electric power networks · CPC title

• H02J2105/12

  supplying households or buildings · CPC title

• H02J3/14

  by switching loads on to, or off from, the networks, e.g. progressively balanced loading · CPC title

• Y02B70/3225

  Demand response systems, e.g. load shedding, peak shaving · CPC title

• G01R31/62

  Testing of transformers · CPC title