875 / 2022-06-29 22:01:49

Improved Setting and Analytical Methods for Step-Stress Test to get DC electrical life model of XLPE cable and its application

step–stress test,DC cables,cross-linked polyethylene,life model

Purpose/Aim

The inverse power electrical life model (IPM) and its parameter n are important bases for cable insulation design and pre-qualification test voltage selection. The step-stress test has the advantages of short time and high efficiency, and is more suitable for obtaining the IPM. In our pervious studies, a complex method, which requires a lot of computation and is difficult to apply in engineering, for setting the step-stress test has been proposed. The aim of this paper is to propose a simplified test setting method to meet the cable engineering.

Experimental/Modeling methods

In this paper, by analyzing the aging mechanism and the cumulative damage of cross-linked polyethylene (XLPE) cable, the method for setting the step-stress test is simplified; A data analysis method based on cumulative damage is also presented, which includes the extraction of IPM from data and the evaluation of the accuracy and significance of extracted results. According to the proposed method, the DC step-stress tests are designed and carried out on new and aged XLPE cables, and oil-water terminals with advantages of low cost and uniform DC field are used the tests. The IPM of these cables are extracting from the test data, and the accuracy and significance of results are evaluated.

Results/discussion

The results show the n value of IPM are 15.25 and 16 for new cables, and is 6.73 for aged cable. The n value of aged cable is smaller that that recommended by CIGRE TB 496. The results are comparable to those obtained by constant-stress test, which confirms the validity of the proposed method.

Conclusions

An improved setting and analytical method for step-stress test is proposed to get IPM parameters of XLPE cable, and the validity of the proposed method is confirmed.

Purpose/Aim

The inverse power electrical life model (IPM) and its parameter n are important bases for cable insulation design and pre-qualification test voltage selection. The step-stress test has the advantages of short time and high efficiency, and is more suitable for obtaining the IPM. In our pervious studies, a complex method, which requires a lot of computation and is difficult to apply in engineering, for setting the step-stress test has been proposed. The aim of this paper is to propose a simplified test setting method to meet the cable engineering.

Experimental/Modeling methods

In this paper, by analyzing the aging mechanism and the cumulative damage of cross-linked polyethylene (XLPE) cable, the method for setting the step-stress test is simplified; A data analysis method based on cumulative damage is also presented, which includes the extraction of IPM from data and the evaluation of the accuracy and significance of extracted results. According to the proposed method, the DC step-stress tests are designed and carried out on new and aged XLPE cables, and oil-water terminals with advantages of low cost and uniform DC field are used the tests. The IPM of these cables are extracting from the test data, and the accuracy and significance of results are evaluated.

Results/discussion

The results show the n value of IPM are 15.25 and 16 for new cables, and is 6.73 for aged cable. The n value of aged cable is smaller that that recommended by CIGRE TB 496. The results are comparable to those obtained by constant-stress test, which confirms the validity of the proposed method.

Conclusions

An improved setting and analytical method for step-stress test is proposed to get IPM parameters of XLPE cable, and the validity of the proposed method is confirmed.