CN-122017364-A - Dynamic test method for thermoelectric synergistic stress of aramid fiber-synthetic ester insulating material

CN122017364ACN 122017364 ACN122017364 ACN 122017364ACN-122017364-A

Abstract

The invention discloses a dynamic test method for thermoelectric synergistic stress of an aramid-synthetic ester insulating material, and belongs to the technical field of electric insulating material test. The method comprises the steps of sample preparation, baseline measurement, steady state judgment, low field scanning, middle field reciprocating circulation, short-time high field pulse sensitive detection, long-time high temperature constant field aging and comparison restoration which are sequentially carried out. The system applies and couples the multi-mode electric stress and the thermal stress of low field, middle field, high field pulse, constant field aging and the like in a wide temperature and wide electric field range, and ensures that the sample reaches a steady state before testing in each stage strictly according to the temperature difference and parameter change rate criteria. The invention can comprehensively and dynamically represent the evolution rule of the dielectric property of the material under the complex electric-thermal synergistic effect, sensitively identify early damage caused by transient impact and accumulated degradation under cyclic stress, and quantitatively distinguish reversible and irreversible changes in the aging process, thereby providing more accurate experimental basis closer to actual operation conditions for material reliability evaluation and life prediction.

Inventors

FAN XIAOZHOU
BI HANWEN
WANG HAITAO
Han hongze
WANG JUNJIE
DONG HE

Assignees

华北电力大学（保定）

Dates

Publication Date: 20260512
Application Date: 20260126

Claims (10)

1. A method for dynamically testing thermal-electric cooperative stress of an aramid-synthetic ester insulating material is characterized by comprising the following steps in sequence: (1) Preparing an aramid fiber-synthetic ester insulating material sample, cleaning, drying and carrying out environmental balance treatment on the sample, and measuring and recording the effective thickness of the sample and the effective area of an electrode; (2) A baseline measurement step, in which dielectric performance test is carried out on the sample under the condition of no external electric field under the preset baseline temperature condition, and initial dielectric constant, dielectric loss factor and conductivity are obtained as baseline data; (3) A steady state judging step of monitoring the temperature of different positions of the sample and the dielectric property parameter to be tested after the target temperature and/or the target electric field intensity are/is applied, and judging that the sample reaches a steady state when the temperature difference of the different positions of the sample is not more than a preset threshold value and the change rate of the dielectric property parameter to be tested in continuous preset time is less than the preset threshold value; (4) A low-field scanning test step, namely applying a low-intensity electric field which is gradually increased from zero to the sample at a target temperature under the condition that the sample reaches a steady state, and collecting a corresponding dielectric constant, a dielectric loss factor and conductivity after the sample reaches the steady state again under the intensity of each electric field; (5) At least one reciprocating electric field cycle of gradually increasing the electric field strength from zero to medium electric field strength and then falling back to zero electric field is applied to the sample at the target temperature, and dielectric performance parameters are acquired in the cycle process or at a cycle node; (6) The short-time high-field pulse sensitive detection step comprises the steps of enabling a sample to be under the conditions of constant temperature and constant background electric field and reach a steady state, applying short-time high-field pulse to the sample at least once, and measuring dielectric performance parameters respectively at different time points before pulse application and after pulse application; (7) A long-time high-temperature constant-field aging test step, namely applying a constant electric field to a sample under the high-temperature condition higher than the baseline temperature and continuously presetting aging time, and collecting dielectric performance parameters at a plurality of aging time nodes; (8) And a recovery comparison step, namely after the long-time high-temperature constant field aging test is completed, placing the sample under a low-temperature condition lower than the aging temperature and/or a no-electric field condition for recovery treatment, measuring dielectric performance parameters again, and comparing and analyzing the baseline data and the aged data.
2. The method according to claim 1, wherein the electric field strength applied in the steps (4), (5), (6), (7) is continuously adjustable in the range of 0 kV/mm to 25 kV/mm with an adjustment accuracy of not more than 0.1 kV/mm.
3. The method of claim 1, wherein the baseline temperature, target temperature, and high temperature conditions range from 20 ℃ to 190 ℃ and the sample temperature is controlled to fluctuate by no more than ± 0.5 ℃ during testing.
4. The method according to claim 1, wherein in the steady state determination step (3), the preset threshold value includes a temperature difference between different positions of the sample of not more than 0.5 ℃ and a change rate of the dielectric property parameter to be measured in 10 consecutive minutes of less than 0.1%, and the dielectric property parameter to be measured is a dielectric constant or a dielectric loss tangent.
5. The method of claim 1, wherein in the low field scan test step (4), the upper limit of the low intensity electric field is no higher than 5 kV/mm.
6. The method of claim 1, wherein in the middle field reciprocating cycle test step (5), the middle electric field strength is not higher than 15 kV/mm, and the number of reciprocating electric field cycles is not less than 5.
7. The method according to claim 1, wherein in the short-time high-field pulse sensitivity detection step (6), the peak electric field intensity of the short-time high-field pulse is not more than 90% of the short-time allowable electric field intensity of the material under the corresponding temperature condition, and the pulse duration is in the order of milliseconds to seconds.
8. The method of claim 1, wherein the predetermined aging time is not less than 24 hours in the long-term high temperature constant field aging test step (7).
9. The method of any one of claims 1 to 8, wherein the dielectric performance parameters collected in each step include at least one or more of dielectric constant, dielectric loss tangent, and electrical conductivity.
10. Use of the test method according to any one of claims 1 to 9 for evaluating the performance stability and the risk of failure of an aramid-synthetic ester insulating material, characterized in that the performance evolution trend, the damage reversibility and the risk of potential failure of the material under the action of thermo-electric co-stress are determined by comparing the dielectric performance parameters obtained in the baseline measurement step (2), the short-time high-field pulse sensitivity detection step (6), the long-time high-temperature constant-field aging test step (7) and the restoration comparison step (8).

Description

Dynamic test method for thermoelectric synergistic stress of aramid fiber-synthetic ester insulating material Technical Field The invention belongs to the technical field of electric insulation material testing, and particularly relates to a dynamic testing method for thermoelectric synergistic stress of an aramid fiber-synthetic ester insulation material. Background With the continuous development of high-voltage, high-capacity and high-reliability electrical equipment, electric transformers, high-temperature motors, power electronic equipment and new energy electrical systems have put more stringent requirements on the comprehensive performance of insulating materials under high electric field strength, high operating temperature and long-term service conditions. The insulating material often bears the coupling effect of electric stress and thermal stress at the same time in the actual operation process, and the evolution rule of the dielectric property of the insulating material is directly related to the safety, reliability and service life of equipment. Particularly, under the severe working conditions of high temperature, high field and long-term operation, a series of complex processes such as polarization, carrier migration, interface charge accumulation, chemical structure change and the like can occur in the insulating material, and the processes are mutually coupled and dynamically evolved, so that irreversible degradation of the material performance can be finally caused, and serious faults such as partial discharge, insulation breakdown and the like can be even caused. The aramid fiber reinforced insulating material is widely applied to the field of high-temperature electrical insulation due to excellent heat resistance, mechanical strength and electrical insulation property. In recent years, along with the continuous expansion of the application of synthetic ester insulating media in high-temperature and high-environmental-protection electrical equipment, an aramid-synthetic ester composite insulating system gradually becomes an important development direction of a high-temperature insulating system. The composite insulating material is immersed in a synthetic ester medium for a long time in actual operation, and is simultaneously subjected to higher working temperature and electric field intensity, and dielectric parameters such as dielectric constant, dielectric loss factor, conductivity and the like of the composite insulating material can dynamically change with time, even irreversibly deteriorate, so that the failure risks such as partial discharge, insulation breakdown and the like are induced. Therefore, the dielectric property evolution behavior of the material under the action of the thermal-electrical cooperative stress is accurately represented, and the material has important engineering significance for evaluating the long-term operation reliability, optimizing the material formula and designing the insulation structure. However, the prior art methods of testing dielectric properties of insulating materials have focused on static or quasi-static testing under single stress conditions, such as measuring dielectric constants, dielectric loss factors, or conducting short-time testing at lower electric field strengths at room temperature or under single temperature conditions. Although a heating condition is introduced or the electric field strength is improved in part of the research, only a simple combination of constant temperature and constant electric field is generally adopted, the test time is short, and complex working conditions such as electric field fluctuation, temperature circulation, transient overvoltage and the like experienced by the material in actual operation are not considered, so that the performance evolution behavior of the material under the long-term high-temperature and high-field operation condition is difficult to truly reflect. In addition, most of the existing test methods focus on measurement of steady-state parameters, and lack systematic characterization of the dynamic change process of dielectric properties under the synergistic effect of electric heat. In actual operation, the insulating material may not only experience long-time steady-state electrothermal stress, but also may suffer transient high electric field impact or electric field fluctuation, and the influence of such transient stress on dielectric properties is often difficult to capture by the existing method, so that the identification capability of early degradation or potential failure risk of the material is insufficient. On the other hand, when dielectric property test is performed under the conditions of a wide temperature range and a wide field intensity range, the problems of uneven temperature distribution in a sample, starting measurement when parameters do not reach a thermal steady state and the like are common due to the influences of factors such as material heat conduction c