Rejuvenation of retired power cables by heat treatment

Xie, Yunxiang; Liu, Gang; Zhao, Yifeng; Li, Licheng; Ohki, Yoshimichi

doi:10.1109/tdei.2018.007783

Cited by 19 publications

(13 citation statements)

References 4 publications

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“…Three cables were used in this study; two of them were retired cables with a service year of 15 and 30 years, and the other cable was a spare cable. They came from different manufacturers and differed from the cables used in [12]. The two retired cables were in good condition when they were out of service because of the movement of the cable transmission line.…”

Section: Experimental Setting and Sample Preparation A Cable Desmentioning

confidence: 99%

“…Based on the melting curves measured in the first heating phase, the crystallinity and melting range are calculated by using the following two equations [12], [20],…”

Section: A Annealing Effect On Thermal Performancementioning

confidence: 99%

“…Many studies on retired cables that operated for decades have revealed a phenomenon in which many retired cables maintain better thermal and electrical properties than new cables [9], [10], because the cables have gone through an annealing process during cable operation with elevated temperatures promoted molecular chain movement and favor the emergence and growth of new crystals and the rearrangement of the crystal-amorphous region [9]- [11]. In our previous research, thermal annealing was performed on XLPE sheets peeled from retired cables at the temperatures around 90 • C; the results showed that the thermal and electrical properties were significantly enhanced by the heat treatment, and 95 • C exhibits the best results [12], [13]. These studies provide the possibility that the XLPE from retired cables could be rejuvenated.…”

Section: Introductionmentioning

confidence: 99%

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Rejuvenation of Retired Power Cables by Heat Treatment: Experimental Simulation in Lab

et al. 2020

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In this work, heat treatment was performed on three retired 110 kV AC cables with service years of 0, 15 and 30, and the effects on the thermal and electrical performance of the cable insulation were investigated. First, each cable with a length approximately of 5 m was prepared and cut into five equal segments. Four segments of each cable were annealed at a temperature of 90, 95, 100, or 105 • C by building a small circuit to simulate cable operation. Then, a section at the middle of each segment was cut out, and the insulation layer was peeled away. The peeled-off layers from the inner, middle and outer positions were selected as the test samples. Subsequently, Fourier transform infrared spectrometry (FTIR), and differential scanning calorimetry (DSC) were performed, and the DC conduction current and dielectric breakdown strength were measured. The best thermal properties of the highest melting point, crystallinity, and smallest melting range were found when the cables were annealed at 100, 105, and 105 • C for the inner, middle, and outer positions, respectively. The highest dielectric breakdown strength and lowest electrical conductivity were found at temperatures of 95 or 100 • C for the inner and middle positions, respectively, and at 105 • C for the outer position. The FTIR results showed that thermal annealing for hundreds of hours did not adversely affect the molecular chains. It is found that this type of heat treatment could be a feasible method to rejuvenate retired cables, and a conservative temperature of 95 • C is regarded as the optimum annealing temperature. INDEX TERMS Cable, DSC, melting point, crystallinity, electrical conductivity, dielectric breakdown strength.

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Section: Experimental Setting and Sample Preparation A Cable Desmentioning

confidence: 99%

“…Based on the melting curves measured in the first heating phase, the crystallinity and melting range are calculated by using the following two equations [12], [20],…”

Section: A Annealing Effect On Thermal Performancementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Rejuvenation of Retired Power Cables by Heat Treatment: Experimental Simulation in Lab

et al. 2020

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“…XLPE is a high-molecular polymer with crystal and amorphous phase, which is subjected mostly to the thermal effect because the crystal structure of XLPE is prone to be affected by the melting and 2 of 22 cooling process [5]. It is well evidenced that long-term thermal effect can change the morphology of the insulation distinctly and lead to degradation on the insulation [6,7]. In fact, the influence of thermal effect on polymers is a complicated process and the insulation properties can be improved in some certain situations [8].…”

Section: Introductionmentioning

confidence: 99%

Thermal Effect of Different Laying Modes on Cross-Linked Polyethylene (XLPE) Insulation and a New Estimation on Cable Ampacity

et al. 2019

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This paper verifies the fluctuation on thermal parameters and ampacity of the high-voltage cross-linked polyethylene (XLPE) cables with different insulation conditions and describes the results of a thermal aging experiment on the XLPE insulation with different operating years in different laying modes guided by Comsol Multiphysics modeling software. The thermal parameters of the cables applied on the models are detected by thermal parameter detection control platform and differential scanning calorimetry (DSC) measurement to assure the effectivity of the simulation. Several diagnostic measurements including Fourier infrared spectroscopy (FTIR), DSC, X-ray diffraction (XRD), and breakdown field strength were conducted on the treated and untreated specimens in order to reveal the changes of properties and the relationship between the thermal effect and the cable ampacity. Moreover, a new estimation on cable ampacity from the perspective on XLPE insulation itself has been proposed in this paper, which is also a possible way to judge the insulation condition of the cable with specific aging degree in specific laying mode for a period of time.Energies 2019, 12, 2994 3 of 22 insulation endured the most severe electrical and thermal stresses. These obtained specimens were all cleaned by alcohol to remove the surface impurities.

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“…Large-scale OWFs use cables as the collector system. Thus, the loads of the cables cannot exceed the limit of the cable ampacity [5,6], and the cables should be insulated reliably [7,8]. Moreover, the safety of the tower terminal transformers needs to be carefully considered.…”

Section: Introductionmentioning

confidence: 99%

Study on Transient Overvoltage of Offshore Wind Farm Considering Different Electrical Characteristics of Vacuum Circuit Breaker

Zhou

Guo

Jiang

et al. 2019

JMSE

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For the study of transient overvoltage (TOV) in an offshore wind farm (OWF) collector system caused by switching off vacuum circuit breakers (VCBs), a simplified experimental platform of OWF medium-voltage (MV) cable collector system was established in this paper to conduct switching operation tests of VCB and obtain the characteristic parameters for VCB, especially dielectric strength parameters; also, the effectiveness of the VCB reignition model was verified. Then, PSCAD/EMTDC was used to construct the MV collector system of the OWF, and the effects of normal switching and fault switching on TOV amplitude, steepness, and the total number of reignition of the VCB were studied, respectively, with the experimental parameters and traditional parameters of dielectric strength of the VCB. The simulation results show that when the VCB is at the tower bottom, the overvoltage amplitude generated by the normal switching is the largest, which is 1.83 p.u., and the overvoltage steepness of the fault switching is the largest, up to 142 kV/μs. The overvoltage amplitude and steepness caused by switching off VCB at the tower bottom faultily with traditional parameters are about 2 and 1.5 times of the experimental parameters under the same operating condition.

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Rejuvenation of retired power cables by heat treatment

Cited by 19 publications

References 4 publications

Rejuvenation of Retired Power Cables by Heat Treatment: Experimental Simulation in Lab

Rejuvenation of Retired Power Cables by Heat Treatment: Experimental Simulation in Lab

Thermal Effect of Different Laying Modes on Cross-Linked Polyethylene (XLPE) Insulation and a New Estimation on Cable Ampacity

Study on Transient Overvoltage of Offshore Wind Farm Considering Different Electrical Characteristics of Vacuum Circuit Breaker

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