CN-121994377-A - Quick positioning method for short-circuit point of thermocouple compensation wire

CN121994377ACN 121994377 ACN121994377 ACN 121994377ACN-121994377-A

Abstract

The invention belongs to the technical field of equipment fault diagnosis and provides a method for quickly positioning a short-circuit point of a thermocouple compensation wire, which comprises the steps of acquiring the compensated temperature of a cold end of a collecting end, the temperature of a thermocouple temperature measuring end and the short-circuit environmental temperature short-circuit after abnormal thermocouple output and elimination of faults of a thermocouple body and front-end equipment; modeling the short-circuit point as a new thermocouple junction formed by positive and negative electrode lead materials, establishing a temperature response model containing the temperature and lead resistance parameters, inverting and calculating the compensation lead resistance between the thermocouple and the short-circuit point based on the model, further calculating the physical distance between the short-circuit point and the thermocouple by combining the lead material parameters, and finally taking the thermocouple as a starting point, measuring the distance along a known laying path and initially calibrating the area where the short-circuit fault point is located. The invention does not need to disassemble the wire, is suitable for aviation and other closed systems, can realize rapid and nondestructive fault positioning, and remarkably improves maintenance efficiency.

Inventors

WANG BING
ZHAO YU
LI PENGHUI

Assignees

苏州长风航空电子有限公司

Dates

Publication Date: 20260508
Application Date: 20260128

Claims (10)

1. A method for rapidly positioning a short-circuit point of a thermocouple compensation wire is characterized by comprising the following steps: after the thermocouple output is abnormal and faults of a thermocouple body and front-end equipment are eliminated, acquiring the compensated temperature of the cold end of the acquisition end and the temperature of the temperature measuring end of the thermocouple, and acquiring the environment temperature of the short circuit part through an environment temperature sensor or a multipoint temperature measuring means; Modeling a compensation lead short joint as a new thermocouple junction formed by positive and negative lead materials, and establishing a temperature response model containing the compensated temperature of the cold end of the acquisition end, the temperature of the thermocouple temperature measuring end, the environment temperature of the short joint and lead resistance parameters based on thermoelectric effect; based on the temperature response model, combining the temperature after compensation of the cold end of the acquisition end and the temperature of the temperature measuring end of the thermocouple, and inversely calculating the compensation wire resistance between the thermocouple and the short-circuit point; calculating the physical distance from the short junction to the thermocouple according to the compensation wire resistance and the wire material parameters; and taking the thermocouple as a starting point, measuring the physical distance along the known laying path of the compensation wire, and preliminarily determining the area where the short circuit fault point is located.
2. The method for rapidly positioning a short-circuit point of a thermocouple compensation wire according to claim 1, wherein the temperature change of the acquisition end caused by disturbance is dynamically measured by applying local temperature disturbance to a suspected area of a compensation wire path, and an estimated value of the environmental temperature at the short-circuit point is updated in combination with a temperature response model.
3. The method for rapidly positioning the short-circuit point of the thermocouple compensation wire according to claim 2, wherein the local temperature disturbance is realized by a micro-heating plate, a hot air nozzle or a laser heat source, and the disturbance amplitude is controlled within a range of +/-5 ℃ to +/-20 ℃.
4. The method for rapidly positioning a short-circuit point of a thermocouple compensation wire according to claim 1, wherein the expression of the temperature response model is: ; Wherein T is the temperature after compensation of the cold end of the acquisition end, The temperature of the thermocouple temperature measuring end is measured; Is the ambient temperature at the position of short circuit, In the form of a thermocouple resistance, In order to short the contact resistance, The resistance of the compensating wire between the thermocouple and the short-circuit point is compensated.
5. The method for quickly positioning the short-circuit point of the thermocouple compensation wire according to claim 1, wherein the resistance of the compensation wire and the short-circuit contact resistance are subjected to joint inversion through temperature data under a plurality of groups of different working conditions.
6. The method for quickly positioning a short-circuit point of a thermocouple compensation wire according to claim 1, wherein the calculation formula of the physical distance from the short-circuit point to the thermocouple is as follows: ; Wherein, the For the resistivity of the wire material, And L is the physical distance from the short-circuit point to the thermocouple.
7. The method for quickly positioning a short-circuit point of a thermocouple compensation wire according to claim 1, further comprising: Applying secondary local temperature disturbance to the area where the short circuit fault point is located, and correcting the physical distance by adopting an iterative algorithm; and determining a short circuit fault point on the laying path of the compensation wire according to the corrected physical distance.
8. The method for quickly positioning a short-circuit point of a thermocouple compensation wire according to claim 7, wherein the iterative algorithm is newton-Lafson method or gradient descent method, and the iterative convergence threshold is set such that the positioning error is smaller than the set distance.
9. The method for quickly positioning the short-circuit point of the thermocouple compensation wire according to claim 1, further comprising the steps of identifying a short-circuit fault mode, and specifically comprising: Comparing the compensated temperature of the cold end of the acquisition end with the ambient temperature and the temperature of the thermocouple temperature measuring end; If the temperature of the cold end of the collecting end after compensation is close to the ambient temperature and does not change along with the temperature of the thermocouple temperature measuring end, judging that the cold end is in a complete short circuit fault; And if the temperature of the cold end of the acquisition end shows nonlinear drift after compensation, judging that the cold end of the acquisition end has high-resistance contact short circuit fault.
10. The method for rapidly positioning a short-circuit point of a thermocouple compensation wire according to claim 1, wherein the thermocouple is a K-type thermocouple, and the thermoelectric voltage and the temperature of the thermocouple are approximately in a linear relation in a working range.

Description

Quick positioning method for short-circuit point of thermocouple compensation wire Technical Field The invention belongs to the technical field of equipment fault diagnosis, and relates to a method for quickly positioning a short-circuit point of a thermocouple compensation wire, which is particularly suitable for quickly positioning a fault point when an undetachable thermocouple compensation wire of an aeroengine, a gas turbine or an industrial high-temperature measurement system is in positive and negative short-circuit. Background Thermocouples are often used for measuring the temperature of high-temperature media such as aeroengines, gas turbines or industrial high-temperature measurement systems, and the working principle of the thermocouples is based on the Seebeck effect, so that thermoelectric signals related to the temperature of the measured media are generated. In order to realize remote signal transmission and ensure temperature measurement accuracy, a lead wire with the same graduation number as the thermocouple is generally adopted to lead out the thermoelectric voltage to a data acquisition unit. The wires are permanently laid in the interior of the fuselage shell of the aircraft or in the nacelle sandwich during installation, and belong to a non-detachable or inaccessible wiring structure. In actual operation, if the thermocouple output is abnormal (such as low reading, drifting or distortion), and the thermocouple body, the wiring terminal and the collection equipment are not faulty through inspection, the cause of the abnormality may be short-circuited between the positive electrode and the negative electrode of the lead (such as caused by vibration abrasion, insulation aging or foreign matter extrusion). However, due to the closed installation state of the wires, the traditional fault diagnosis methods such as section-by-section disassembly and inspection, on-off test, resistance section measurement and the like cannot be implemented, or a great deal of manpower, working hours and shutdown cost are required, so that the maintenance efficiency and the attendance rate of the aircraft are seriously affected. Therefore, there is a need for a fault diagnosis method that does not require disassembly, can be remotely implemented, and can accurately locate the shorted region. Disclosure of Invention In order to solve the technical problem that in the prior art, wires of a thermocouple are laid in an aircraft fuselage shell and cannot be disassembled, so that after faults of a thermocouple body and front-end equipment are removed, effective, rapid and nondestructive positioning of short-circuit points of the wires are difficult to perform, the invention discloses a rapid positioning method for short-circuit points of compensation wires of the thermocouple, which comprises the following steps: S1, after thermocouple output is abnormal and faults of a thermocouple body and front-end equipment are removed, acquiring temperature after compensation of a cold end of an acquisition end and temperature of a thermocouple temperature measuring end, and acquiring the environment temperature of a short circuit position through an environment temperature sensor or a multi-point temperature measuring means; S2, modeling a compensation lead short joint as a new thermocouple junction formed by positive and negative lead materials, and establishing a temperature response model containing the compensated temperature of the cold end of the acquisition end, the temperature of the thermocouple temperature measuring end, the environment temperature of the short joint and lead resistance parameters based on a thermoelectric effect; s3, based on the temperature response model, combining the temperature after compensation of the cold end of the acquisition end and the temperature of the temperature measuring end of the thermocouple, and inversely calculating the resistance of the compensation wire between the thermocouple and the short-circuit point; s4, calculating the physical distance from the short junction to the thermocouple according to the compensation wire resistance and the wire material parameters; s5, taking the thermocouple as a starting point, measuring the physical distance along the known laying path of the compensation wire, and primarily determining the area where the short circuit fault point is located. Further, in step S1, local temperature disturbance is applied to the suspected area of the compensation wire path, the temperature change of the acquisition end caused by the disturbance is dynamically measured, and the estimated value of the environmental temperature at the short circuit is updated in combination with the temperature response model. Still further, the local temperature disturbance is realized by a micro-heating plate, a hot air nozzle or a laser heat source, and the disturbance amplitude is controlled within a range of +/-5 ℃ to +/-20 ℃. Further, in step S2, the expression of the temp