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GB/T 31489.1-2015 English PDF (GBT31489.1-2015)

GB/T 31489.1-2015 English PDF (GBT31489.1-2015)

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GB/T 31489.1-2015: D.C. extruded cable systems for power transmission at a rated voltage up to and including 500 kV -- Part 1: Test methods and requirements

This Part of GB/T 31489 specifies the test methods and requirements for D.C. extruded cable systems for power transmission at a rated voltage up to and including 500 kV (including DC land cables, DC submarine cables and their accessories). This Part applies to XLPE insulated DC power cables of 500 kV and below installed on land and on the seabed. It also applies to land cable accessories such as connectors and terminals for land cables, as well as submarine cable and #39;s factory joints (soft joints), repair joints, transition joints and terminals between submarine DC cables and land DC cables, and other submarine cable accessories.
GB/T 31489.1-2015
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 29.060.20
K 13
D.C. extruded cable systems for power transmission at a
rated voltage up to and including 500 kV - Part 1: Test
methods and requirements
ISSUED ON: MAY 15, 2015
IMPLEMENTED ON: DECEMBER 01, 2015
Issued by: General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China;
Standardization Administration of the People's Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 6
4 Test voltage, cable design thermal parameters and test conditions ... 8 5 Development test ... 12
6 Type test ... 12
7 Prequalification test ... 32
8 Routine test ... 35
9 Sample test... 37
10 Tests after installation ... 41
Annex A (normative) Test method for electrical conductivity of cable insulation ... 42 Annex B (normative) Test method for cable insulation space charge ... 44 D.C. extruded cable systems for power transmission at a
rated voltage up to and including 500 kV - Part 1: Test
methods and requirements
1 Scope
This Part of GB/T 31489 specifies the test methods and requirements for D.C. extruded cable systems for power transmission at a rated voltage up to and including 500 kV (including DC land cables, DC submarine cables and their accessories).
This Part applies to XLPE insulated DC power cables of 500 kV and below installed on land and on the seabed. It also applies to land cable accessories such as connectors and terminals for land cables, as well as submarine cable's factory joints (soft joints), repair joints, transition joints and terminals between submarine DC cables and land DC cables, and other submarine cable accessories.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. GB/T 2951.11-2008, Common test methods for insulating and sheathing materials of electric and optical cables - Part 11: Methods for general application - Measurement of thickness and overall dimensions - Tests for determining the mechanical properties
GB/T 2951.12-2008, Common test methods for insulating and sheathing materials of electric and optical cables - Part 12: Methods for general application - Thermal ageing methods
GB/T 2951.13-2008, Common test methods for insulating and sheathing materials of electric and optical cables - Part 13: Methods for general application - Measurement for determining the density - Water absorption tests - Shrinkage test GB/T 2951.14-2008, Common test methods for insulating and sheathing materials of electric and optical cables - Part 14: Methods for general application - Test at low temperature
GB/T 2951.21-2008, Common test methods for insulating and sheathing materials IEC 60840:2011, Power cables with extruded insulation and their accessories for rated voltages above 30 kV (Um=36 kV) up to 150 kV (Um=170 kV) - Test methods and requirements
IEC 62067:2006, Power cables with extruded insulation and their accessories for rated voltages above 150 kV (Um=170 kV) up to 500 kV (Um=550 kV) - Test methods and requirements
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply. 3.1 line commutated converters (LCC)
The voltage polarity of the cable system changes when the power flow is reversed. It is used for high-voltage direct current transmission system.
3.2 voltage source converters (VSC)
The voltage polarity of the cable system does not change when the power flow is reversed. It is used for high-voltage direct current transmission system. 3.3 transmission cable
HVDC cables in unipolar or bipolar HVDC transmission systems.
3.4 return cable
LV/MV DC cables for return flow in unipolar HVDC transmission systems. It can be used for full-line connection between converter stations. It can also be used for partial connection between converter stations and electrode stations.
3.5 extrusion length
Length of continuous extruded insulated core (including insulating and semiconducting layers). It excludes the scrapped portion of extrusion start and end segment cuts. 3.6 manufacturing length
The extrusion length of the complete cable (or the length of the cable after cutting off the scrap) including all components except the semiconducting layer.
3.7 delivery length
The length of cable after one or more manufacturing lengths have been joined with factory joints.
NOTE: The delivery length for submarine cables is usually the shipping length. For land cables it is the complete cable length on the cable reel.
3.8 factory joint
A joint between extrusion length/manufacturing length under controlled factory conditions.
3.9 repair joint
A joint between two complete cables.
3.10 field joint
A joint that is field installed between two complete cables of an existing cable system. 3.11 transition joint
A joint between two cables that are extruded insulation but differ in design (for example, conductor cross-section or structure).
3.12 development tests
Tests performed during cable system development.
3.13 type tests
Tests on a type of cable system prior to supply on normal commercial principles, so as to prove that the cable system has satisfactory performance in accordance with the requirements of the intended use.
NOTE: Unless changes in the material, manufacturing process, and electrical stress design level of the cable or accessory may change its performance characteristics, once the test is successfully passed, it does not need to be repeated.
3.14 prequalification test
Tests on a type of cable system prior to supply on normal commercial principles, so as to prove that the cable system has satisfactory long-term performance.
NOTE 1: Unless the material, manufacturing process and electrical stress design level of the cable system are substantially changed, the prequalification test only needs to be carried out once. NOTE 2: Substantial changes are defined as changes that adversely affect the cable system. If the manufacturer declares that certain changes do not constitute substantial changes, detailed examples including test verification are required.
3.15 routine tests
Tests carried out by the manufacturer on all manufactured lengths or attachments of NOTE: If the polarity reversal cannot be achieved within 2min, the time for the polarity reversal can be agreed upon by both parties.
4.3.7 Superimposed impulse voltage test (S/IMP)
Before the first impulse voltage is applied to the test object, the test object shall be heated until the temperature of the conductor is not lower than Tc,max and the internal temperature difference of the insulation is not lower than ??Tmax for at least 10 h. And the test object has been subjected to U0 (corresponding polarity) for at least 10 h. Maintain DC voltage. Superimpose the impulse voltage on the test object for 10 consecutive times. Then apply a DC voltage U0 of opposite polarity to the test object under the same temperature conditions for at least 10 h. Maintain DC voltage. Superimpose the impulse voltage on the test object for 10 consecutive times. The interval between each impact shall not be less than 2min. Impulse voltage waveform shall comply with the provisions of GB/T 3048.13-2007.
5 Development test
The manufacturer shall complete all analytical and development tests prior to prequalification test. A development test shall at least include the following: a) Evaluation of materials and processes used, typically including resistivity evaluation, breakdown level and space charge measurements;
b) Distribution of electrical stresses within the insulation of cable systems under typical installation and loading conditions;
c) Long-term stability assessment, including factory experiments to evaluate the impact of various parameters on long-term performance, such as electrical stress, temperature, environmental conditions;
d) Sensitivity to electrical stress distribution to expected changes in cable size, material composition and process conditions (extrusion, post-extrusion handling). 6 Type test
6.1 Scope of type test approval
Type tests are also valid for other cable systems within the scope of this Standard if the following conditions are met:
a) The design, material, manufacturing process and operating conditions of the cable system are basically the same.
b) The operating voltage U0, UP1, UP2, S and UP2, O (URC, AC and URC, DC if it is a return cable) is not higher than the tested cable system.
c) The mechanical stress applied by the mechanical pretreatment is not higher than that of the tested cable system.
d) The maximum operating temperature Tc,max of the conductor is not higher than the tested cable system.
e) The maximum temperature difference ??Tmax of the insulation layer is not higher than the tested cable system.
f) The cross-sectional area of the conductor is not larger than the tested cable system. g) The calculated value of the average field strength of the insulation (rated voltage divided by the average thickness of the insulation) is not greater than the tested cable system.
h) The Laplace electric field intensity at the cable conductor shield and insulation shield calculated with the nominal size is not greater than that of the tested cable system.
i) For cable systems that pass the LCC type test, as long as they pass the ??UP2,S superimposed operating impulse voltage according to the provisions of 6.4.5.3, the scope of approval can cover the VSC system, and vice versa.
Non-electrical type tests are not required for cables of all conductor cross-sections and all voltage classes unless different materials and different manufacturing processes are used (see 6.3). However, when the material outside the shielded core is different from the tested cable system, the compatibility aging test of the finished cable section shall be added, so as to verify the compatibility of the material.
6.2 Test object
All components (cables and accessories) of the cable system shall be type tested. Each component can be tested in different test loops. These test loops shall contain all relevant components of the cable system.
The test objects included in the typical test loop of the electrical type test are shown in Figure 2. Accessory test objects shall include 0.5 m cables per side. Measure from cable locations where no disassembly or disassembly has occurred due to mounting accessories. The continuous cable length between the accessories in the test loop shall not be less than 5 m. The length of continuous cable included in the test loop shall not be less than 10 m.
Cable test objects shall include features that cause discontinuous connections in the cable, such as metal connections between metal layers.
Specimens of land cables or submarine cables shall be mechanically pretreated before insulating layer and protrusions greater than 0.125 mm into the semiconducting shielding layer.
6.3.5 Combustion test
If the land cable adopts ST2 sheath, and the manufacturer declares that the design of the cable meets the requirements of the combustion test, then the combustion test shall be carried out on the finished cable specimen according to the provisions of GB/T 18380.12-2008, which shall meet the requirements.
6.3.6 Scraping test of non-metallic outer sheath
For land cable specimens after bending test in 6.4.3.1, the non-metallic outer sheath shall be subjected to scraping test according to JB/T 10696.6-2007 and GB/T 2952.1- 2008, which shall meet the corresponding requirements.
6.3.7 Corrosion extension test (only applicable to aluminum sleeve)
For land cable specimens after bending test in 6.4.3.1, the aluminum sleeve shall be subjected to corrosion expansion test according to JB/T 10696.5-2007 and GB/T 2952.1-2008, which shall meet the requirements.
6.3.8 Water penetration test
6.3.8.1 Water penetration test for land cables
When the land cable has a water-blocking structure, the water penetration test shall be carried out. This test is applicable to the following cable constructions: a) The barrier that can prevent water penetration longitudinally along the gap between the outer surface of the insulation shield and the impermeable barrier; b) The barrier that can prevent water penetration along the longitudinal direction of the conductor.
The test device, sampling, test method and requirements shall comply with the provisions of Annex I in GB/T 11017.1-2014.
6.3.8.2 Water penetration test for submarine cables
6.3.8.2.1 Overview
When the submarine cable has a water-blocking structure, the water penetration test shall be carried out. Submarine cables shall be subjected to conductor water penetration test, metal sheath water penetration test and factory joint radial water penetration test, respectively.
The conductor water penetration test is to simulate the failure of the submarine cable in the maximum water depth area, resulting in water intrusion from the conductor and water penetration along the length direction. Cable specimens shall be subjected to pretreatment as close to real installation conditions as possible. That is, specimens shall be subjected to tensile bending test and thermal cycling test before the specimens are immersed in water. Thermal cycle test is not required for immersion test. Because the cable line will be out of service in the event of such a fault. The manufacturer shall declare the maximum water penetration distance (d1) of the cable conductor after the 10-day water penetration test of the submarine cable.
The water penetration test under the metal sheath is to simulate the water penetration under the metal sheath caused by the damage of the submarine cable in the nearshore area. At this time, the effect of external water pressure on the cable does not increase the water resistance under the metal sheath. The pretreatment of cable specimens shall be as close as possible to the real cable installation. That is, cables need not be subjected to a tensile bending test but shall be subjected to thermal cycling, so as to make the specimen subjected to radial expansion prior to the water penetration test. This thermal cycling causes the radial expansion of the cable to be much more severe than the external water pressure on the cable in shallow seas. Since cable damage in this case does not cause the cable to withdraw from service, thermal cycling shall be performed during the test. External pressure will not compress the metal sleeve. Therefore, it is appropriate to set the test pressure at 0.3 MPa for the lead sleeve currently designed. If other test pressures are used, the manufacturer shall provide reasons. The manufacturer shall declare the maximum water penetration distance (d2) under the metal sheath of the submarine cable allowed.
External hydrostatic test of factory joints and repair joints is to verify the performance of joints against radial water penetration at the maximum water depth. The submarine cable specimen shall be as close as possible to the installation condition. That is, before the test, the specimen shall be subjected to a tensile test or a tensile bending test (depending on its structure) and a thermal cycle test, so as to make the specimen subjected proper tension and radial expansion.
Unless otherwise specified by the user, the water for the water penetration test shall be tap water or brine with seawater salinity in the sea area where the submarine cable is used. In case of dispute, it is recommended to use brine with an average salinity of China's coastal waters with a mass ratio of (31??2)?€? [(31??2)g/kg].
6.3.8.2.2 Conductor water penetration test
6.3.8.2.2.1 Specimen preparation and pretreatment
Specimens shall be taken from cables that have been subjected to the mechanical test of 6.4.3.2. The specimen length shall be at least d1(1+33%) m. The test may be performed on finished cables or on insulated cores.
The specimen shall be subjected to at least three 24h load cycles to ensure moderate thermal expansion of the cable. In this load cycle, the conductor temperature shall wound during manufacture or laying. It is not applicable to the situation where the submarine cable is only wound on the cable reel or coiled in the turntable. Submarine cables are subjected to torsion during winding operation. Therefore, after the winding test, the structure of the submarine cable shall be inspected for damage. The winding test is to be carried out on submarine cables of suitable length capable of forming at least 8 full turns. At least 2 factory joints shall be installed in the middle of the submarine cable test section. The minimum distance between the ends of 2 factory joints shall be 2 full turns of the submarine cable.
The shape of the coil shall be the same as when the submarine cable is manufactured or transported. The manufacturer shall specify the minimum radius of the coil and the direction of the coil. The test shall be carried out on the smallest circular winding radius. Before starting to wind up, a mark line parallel to the axis of the submarine cable shall be marked on the submarine cable, so as to check whether the submarine cable is evenly twisted during the winding operation.
The distance between the height of the pay-off frame and the uppermost submarine cable in the circle shall not exceed the actual winding operation height of the submarine cable, for example, the height of pay-off frame during fabrication, take-up and lay-up. Submarine cables shall be coiled according to the minimum bend radius specified by the manufacturer. Both ends of the submarine cable shall be clamped, so as to prevent the cable from rotating during the test.
After winding, the submarine cable shall be wound onto the cable reel again. The number of such winding cycles shall be the same as the number of windings expected for the cable during manufacture, winding and laying.
During the winding operation, the twisting of the submarine cable shall be substantially uniform, as assessed by the pre-applied marking line. The sample is taken from the middle of the test section of the submarine cable, which shall include 1 factory joint. Carry out visual inspection.
The following damages shall not occur after the winding test:
a) Damage to cable insulation, metal sheath and outer sheath;
b) Permanent deformation of the conductor or armor.
If a tension bending test is subsequently performed, visual inspection may be performed after the tension bending test.
6.4.3.2.2 Tension bending test
6.4.3.2.2.1 Test requirements
NOTE: The 48h load cycle uses positive polarity voltage. For accessories, this condition is considered to be the most severe condition.
6.4.5 Superimposed impulse voltage test
6.4.5.1 Overview
The DC superimposed impulse voltage test shall be carried out on the test object that has passed the load cycle according to the requirements of 4.3.7.
6.4.5.2 Impulse voltage test for superimposed operation (cable system operated by LCC)
The test subject shall be subjected to:
- Under positive polarity U0, superimpose negative polarity operating impulse voltage UP2,0 for 10 consecutive times;
- Under negative polarity U0, superimpose positive polarity operating impulse voltage UP2,0 continuously f...

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