CN-122017396-A - Synchronous heating and voltage tolerance testing method for hybrid cable transition joint

CN122017396ACN 122017396 ACN122017396 ACN 122017396ACN-122017396-A

Abstract

The application discloses a synchronous heating and voltage tolerance test method of a hybrid cable transition joint, which relates to the technical field of high-voltage submarine cables and comprises the following steps of S1, test system initialization and sample installation, sample preparation, sensor deployment and equipment connection, S2, double-cable differential heating control, XLPE section heating, oil filling section heating and temperature synchronous judgment, S3, coupling voltage loading and circulation test, S4, evaluation test after heat circulation, operation sequence of operation impact test, lightning impact test and power frequency voltage test for a cable system with Um more than or equal to 300kV, and S5, report generation, wherein an output report comprises original monitoring data, a key parameter comparison table and failure mode analysis. The application solves the problem that the prior standard can not verify the electrical performance of two cables under different temperature working conditions at the same time, and ensures the reliability of the transition joint in long-term operation.

Inventors

LIAO JIANPING
HUANG XIAOWEI
HUANG ZHONGKANG
WANG JIANYING
GAO FAN
CHEN YUFEI
LIU ZHIFENG
Dai Yurun
HOU MINGCHUN
WEI XIAOXING
XIAO XIANG
LIU QINGSONG
Xu yongye
LV JINZHUANG

Assignees

中国南方电网有限责任公司超高压输电公司电力科研院

Dates

Publication Date: 20260512
Application Date: 20260108

Claims (10)

1. The synchronous heating and voltage tolerance testing method for the hybrid cable transition joint is characterized by comprising the following steps of: S1, initializing a test system and installing a sample, wherein the test system comprises sample preparation, sensor deployment and equipment connection; s2, differential heating control of double cables, wherein the differential heating control comprises XLPE section heating, oil filling section heating and temperature synchronous judgment; S3, coupling voltage loading and cyclic testing, wherein the coupling voltage loading and cyclic testing comprises initial voltage application, a heating stage, a cooling stage, cyclic control, failure diagnosis and automatic protection; S4, performing evaluation test after thermal cycling, namely for a cable system with the Um more than or equal to 300kV, simultaneously executing an operation impulse test, a lightning impulse voltage test and a subsequent power frequency voltage test, wherein the operation sequence comprises the operation impulse test, the lightning impulse test and the power frequency voltage test; S5, generating a report, wherein the output report comprises original monitoring data, a key parameter comparison table and failure mode analysis.
2. The synchronous heating and voltage tolerance test method for the hybrid cable transition joint according to claim 1 is characterized in that in the step S1, the preparation of the test article comprises (1) connecting an XLPE cable and an oil-filled cable through the transition joint, and reserving free cable spaces with the length of more than or equal to 5m on two sides of the transition joint; the sensor deployment comprises (1) an XLPE section, an oil filling section, a pressure sensor, a sensor module and a sensor module, wherein the XLPE section is used for embedding an optical fiber temperature sensor in a conductor and installing a high-frequency CT partial discharge sensor; the equipment connection comprises (1) connecting the output end of the high-voltage power supply with the transition joint conductor through a shielding cable, (2) connecting the power supply of the heating belt with the oil filling section, and (3) connecting all sensor signal wires into the central control cabinet.
3. The method for simultaneous heating and voltage endurance testing of a hybrid cable transition joint as claimed in claim 1, wherein in step S2, the XLPE section heating includes applying a conductor alternating current, and then adjusting by PID algorithm to raise the insulating layer temperature to 90 ± 5K at a rate of 5 ℃/min or less; the heating of the oil filling section comprises the steps of starting a carbon fiber heating belt, and controlling the surface temperature to 70 ℃ plus or minus 5K through infrared feedback to avoid the insulation local overheating of the oil paper; the temperature synchronous judgment comprises the steps of calculating the temperature difference delta T of the double cables in real time, and judging that the temperature is stable when the delta T is less than or equal to 5K and is maintained for more than or equal to 30 minutes.
4. A method of simultaneous heating and voltage tolerance testing of a hybrid cable transition joint according to claim 3, wherein in step S2, the XLPE section heating heats the cable by a combination of conductor current heating and external heating.
5. The method for simultaneous heating and voltage tolerance testing of a hybrid cable transition joint according to claim 1, wherein in step S3, the initial voltage is applied by boosting to 2U 0 power frequency voltage at a rate of 1kV/S after temperature stabilization; The heating stage is to heat for 8 hours, maintain 2U 0 voltage, and monitor the following tests synchronously: The method comprises the steps of (1) partial discharge PD less than or equal to 5pC, (2) temperature gradient, namely XLPE oil filling interface delta T less than or equal to 15K, (3) oil pressure fluctuation delta P less than or equal to 5%, and if delta T is more than 10K and PD is more than 5pC, failing to pass the test; the cooling stage comprises (1) cooling for 16 hours, naturally cooling to ambient temperature, reducing the pressure to 1.5U 0 during the cooling, and continuously monitoring; The circulation control is that the heating and cooling circulation is repeated for 20 times, and key information such as PD phase distribution diagram, infrared thermal image diagram and the like is recorded after each circulation; The failure diagnosis and automatic protection comprise multi-parameter association early warning, triggering conditions and protection actions of the multi-parameter association early warning, namely (1) PD >10pC lasting for 1 second, immediately cutting off high-voltage power supply and recording fault phase, (2) DeltaT >15K lasting for 10 minutes, stopping heating and starting forced cooling, and (3) oil pressure DeltaP >10%, closing an oil way valve and giving an audible and visual alarm.
6. The method according to claim 1, wherein in step S4, when performing the operation impact test, the cable is heated by the thermal cycle voltage test until the cable reaches a stable temperature, which is 0K to 10K higher than the highest conductor temperature in normal operation, and the operation impact test is performed after the temperatures are maintained within the temperature limit for at least 2 hours, and the transition joint is allowed to withstand 10 positive polarity and 10 negative polarity voltage impacts without malfunction.
7. The method for simultaneous heating and voltage withstand test of a hybrid cable transition joint according to claim 6, wherein in step S4, when a lightning impulse voltage test and a subsequent power frequency voltage test are performed, after the above 10 positive polarity and 10 negative polarity voltage impulse cycle tests are completed, a lightning impulse test is performed in an evaluation stage to verify the insulation strength after a long-term thermo-electric cycle; And then heating according to a thermal cycle voltage test mode until the cable conductor reaches a stable temperature which is 0K to 10K higher than the highest conductor temperature in normal operation, and carrying out a lightning impulse test after the temperatures are maintained within the temperature limit for at least 2 hours, wherein 10 lightning impulse waves are respectively applied to positive and negative polarities, and no breakdown or flashover occurs.
8. The method for simultaneous heating and voltage withstand testing of a hybrid cable transition joint according to claim 7, wherein after the lightning impulse test is completed, the transition joint is verified to still withstand a short-time overvoltage condition of 2 times of phase voltage after long-term thermal-electric cycle, 2U 0 power frequency withstand voltage is applied for 15 minutes, no flashover or breakdown occurs, i.e. 2U 0 power frequency voltage is applied immediately after 20 times of thermal cycle and lightning impulse test are completed.
9. The method according to claim 8, wherein in step S4, an anatomic inspection is performed, i.e. disassembling the transition joint, and inspecting the transition joint, if necessary.
10. The method for synchronously heating and testing voltage tolerance of the hybrid cable transition joint according to claim 9 is characterized by further comprising detection of stress cone displacement and SEM interface carbonization, wherein the stress cone displacement is less than or equal to 0.5mm, and the SEM interface carbonization is required to detect whether XLPE oil interfaces are carbonized or not.

Description

Synchronous heating and voltage tolerance testing method for hybrid cable transition joint Technical Field The application relates to the technical field of high-voltage submarine cables, in particular to a synchronous heating and voltage tolerance testing method of a hybrid cable transition joint. Background The existing oil filled cable is mainly used for large core power transmission projects, such as airports, large power plants, straddling strait rivers and other scenes, is a key life line for guaranteeing regional power grid safety, but the full life cycle management technology of submarine cable accessories is limited by foreign countries for a long time and faces three core pain points, namely, firstly, import dependence leads to high operation and maintenance cost and insufficient timeliness, repair work is difficult to advance after cable faults, so that a system is forced to be degraded to be in single-loop connection operation, secondly, the existing cable repair technology in China cannot adapt to heterogeneous connection of 500kV crosslinked polyethylene cables and oil filled cables, the failure risk of an insulating medium interface is prominent, thirdly, high-value submarine cable assets face major loss hidden dangers, and the power supply reliability of the system falls to a critical threshold. In this context, a high-pressure crosslinked polyethylene-oil filled submarine cable transition joint manufacturing technology was developed, but related heterogeneous cable couplings currently lack related evaluation test methods, which are specifically expressed as follows: (1) Traditional cable test standards (such as IEC60840, IEEE 48) are designed for only a single cable type and cannot simulate the actual conditions of a hybrid cable system. (2) The temperature characteristics of the oil-filled cable (up to 70 ℃) and the XLPE cable (up to 90 ℃) are greatly different, and the temperature rise requirements of the oil-filled cable and the XLPE cable cannot be synchronously met by the existing heating cycle test. (3) The voltage application mode is single in the heating process, and the synergistic ageing effect of the two insulating materials is not considered. (4) The related testing method is lack, and the problem of double-cable temperature cooperative control is not solved only by conductor current heating. (5) The heating cycle test in the IEC 6041-1 standard is only applicable to oil filled cables, not covering the high temperature withstand requirements of XLPE cables. Disclosure of Invention The application aims to provide a synchronous heating and voltage tolerance test method for an XLPE-oil filled cable transition joint, which aims to solve the problem that the prior standards (such as GB/T9326 and IEC 60141-1) cannot simultaneously verify the electrical performances of two cables under different temperature working conditions, thereby ensuring the reliability of the transition joint in long-term operation. The synchronous heating and voltage tolerance testing method for the hybrid cable transition joint provided by the application adopts the following technical scheme: A synchronous heating and voltage tolerance test method for a hybrid cable transition joint comprises the following steps: S1, initializing a test system and installing a sample, wherein the test system comprises sample preparation, sensor deployment and equipment connection; s2, differential heating control of double cables, wherein the differential heating control comprises XLPE section heating, oil filling section heating and temperature synchronous judgment; S3, coupling voltage loading and cyclic testing, wherein the coupling voltage loading and cyclic testing comprises initial voltage application, a heating stage, a cooling stage, cyclic control, failure diagnosis and automatic protection; S4, performing evaluation test after thermal cycling, namely for a cable system with the Um more than or equal to 300kV, simultaneously executing an operation impulse test, a lightning impulse voltage test and a subsequent power frequency voltage test, wherein the operation sequence comprises the operation impulse test, the lightning impulse test and the power frequency voltage test; S5, generating a report, wherein the output report comprises original monitoring data, a key parameter comparison table and failure mode analysis. Further, in the step S1, the preparation of the sample comprises (1) connecting the XLPE cable with the oil-filled cable through a transition joint, and reserving free cable spaces with the length more than or equal to 5m at two sides of the transition joint; the sensor deployment comprises (1) an XLPE section, an oil filling section, a pressure sensor, a sensor module and a sensor module, wherein the XLPE section is used for embedding an optical fiber temperature sensor in a conductor and installing a high-frequency CT partial discharge sensor; The equipment connection comprises (1) connection of the outp