Method for measuring trap parameters in XLPE cable based on polarizing-depolarizing current test

Abstract

The invention discloses a method for measuring trap parameters in an XLPE cable based on a polarizing-depolarizing current test. In the method, firstly, detrapping current is extracted from the polarizing current, then, staged linear fitting is executed for the detrapping current, moreover, fitting parameters A<m>. Tau<m> and Tau<m> are used to represent trap parameters, such as trap charge density and trap depth, in the XLPE current, and consequently, trap charge density and charge accumulation conditions of the XLPE cable insulation are reflected. The method provided by the invention can guarantee accuracy and effectiveness of trap parameter measurement; moreover, in the method, staged linear fitting is executed for the detrapping current, fitting effect is excellent, various interference signals are eliminated, thus, accuracy of trap parameter measurement is improved further; moreover, the method is based on a PDC nondestructive test method, has no high requirement on test apparatuses, is simple to operate, has no damage to cable insulation, has very high practicability in the aspect of acquiring XLPE cable trap characteristics, and is suitable for being generalized and used insuch field.

Description

technical field [0001] The invention belongs to the technical field of high voltage and insulation, and relates to a method for measuring traps in XLPE cables, in particular to a method for measuring the charge density and depth of traps in XLPE cables based on polarization-depolarization current testing. Background technique [0002] With the increasingly large power transmission system in our country, the application of HVDC cross-linked polyethylene (XLPE) cables is becoming more and more extensive. However, as the voltage level and service life of XLPE cables continue to increase, they will age under the action of electricity, heat, and mechanical stress, and at the same time, microstructural changes will occur, such as traps. Carriers trapped by traps in the medium form space charges. The accumulation of space charges will cause distortion of the electric field distribution, further accelerate the aging of insulating materials, and even cause insulation breakdown. [...

AI Technical Summary

Problems solved by technology

Trapping current refers to the current generated by the escape of carriers (charges) in the trap. The mainstream methods for measuring the trapping current include thermal stimulation current method (TSDC) and isothermal relaxation current method (IRC): (1) IRC test method test The isothermal relaxation current of the cable, and analyze the characteristics of the traps in the cable according to the measured isothermal relaxation current, but the actual isothermal relaxation current test results include dipole relaxation current and space charge detachment current components, which cannot be done. Therefore, it is difficult to guarantee the validity of the trap parameter measurement results; (2) The TSDC test method obtains the correlation of the carriers (charges) by observing the process changes of the carriers (charges) from the low-temperature imbalance state to the high-temperature thermal equilibrium state. Trap parameters, but the temperature of the sample needs to be adjusted in a large range during the measurement process, and the test system is relatively complicated, and it is difficult to apply to the actual cable size

[0004] It can be seen that there is still a lack of methods that can effectively measure the space charge detachment current, and then analyze the trap depth and space charge accumulation in XLPE cable insulation materials.

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