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GB/T 12706.1-2020 (GB/T12706.1-2020)

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GB/T 12706.1-2020English910 Add to Cart 0--3 minutes. Auto-delivery. Power cables with extruded insulation and their accessories for rated voltages from 1 kV (Um=1.2 kV) up to 35 kV (Um=40.5 kV) -- Part 1: Cables for rated voltage of 1 kV (Um=1.2 kV) and 3 kV (Um=3.6 kV) Valid


GB/T 12706.1-2020: PDF in English (GBT 12706.1-2020)
GB/T 12706.1-2020
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 29.060.20
K 13
Replacing GB/T 12706.1-2008
Power Cables with Extruded Insulation and Their Accessories
for Rated Voltages from 1 kV (Um = 1.2 kV) up to 35 kV (Um =
40.5 kV) - Part 1: Cables for Rated Voltage of 1 kV (Um = 1.2 kV)
and 3 kV (Um = 3.6 kV)
[IEC 60502-1:2004, Power Cables with Extruded Insulation and Their Accessories for
Rated Voltages from 1 kV (Um = 1.2 kV) up to 30 kV (Um = 36 kV) - Part 1: Cables for
Rated Voltage of 1 kV (Um = 1.2 kV) and 3 kV (Um = 3.6 kV), MOD]
ISSUED ON: MARCH 31, 2020
IMPLEMENTED ON: OCTOBER 1, 2020
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of
China.
Table of Contents
Foreword ... 4 
1 Scope ... 11 
2 Normative References ... 11 
3 Terms and Definitions ... 14 
4 Voltage Marking and Materials ... 15 
5 Conductors... 18 
6 Insulation ... 18 
7 Cores, Inner Coverings and Fillers of Multi-core Cables ... 21 
8 Metallic Layers for Single-core or Multi-core Cables ... 24 
9 Metallic Screen ... 24 
10 Concentric Conductor ... 25 
11 Lead Sheath ... 26 
12 Metallic Armor ... 26 
13 Over-sheath ... 30 
14 Test Conditions ... 32 
15 Routine Tests ... 32 
16 Sample Tests ... 34 
17 Electrical Type Tests ... 41 
18 Non-electrical Type Tests ... 44 
19 Electrical Tests after Installation ... 53 
20 Supplementary Clauses for Cable Products ... 53 
Appendix A (normative) Fictitious Calculation Method for Determination of
Dimensions of Protective Coverings ... 61 
Appendix B (normative) Rounding-off of Numerical Values ... 69 
Appendix C (normative) Measurement and Calculation of Overlap Rate and
Clearance Rate ... 72 
Appendix D (normative) Determination of Hardness of HEPR Insulations ... 73 
Appendix E (normative) Supplementary Clauses for Cable Products ... 76 
Bibliography ... 82 
Power Cables with Extruded Insulation and Their
Accessories for Rated Voltages from 1 kV (Um = 1.2
kV) up to 35 kV (Um = 40.5 kV) - Part 1: Cables for
Rated Voltage of 1 kV (Um = 1.2 kV) and 3 kV (Um = 3.6
kV)
1 Scope
This Part of GB/T 12706 specifies the structure, dimensions and test requirements for
power cables with extruded insulation for rated voltage of 1 kV (Um = 1.2 kV) and 3 kV
(Um = 3.6 kV).
This Part is applicable to power cables with extruded insulation for rated voltage of 1
kV (Um = 1.2 kV) and 3 kV (Um = 3.6 kV) for fixed installations in distribution networks
or industrial units.
This Part is inapplicable to cables with special installation and service conditions, such
as: cables for overhead networks, the mining industry, nuclear power plants (inside
and around the containment area), submarine purposes or shipboard application.
2 Normative References
The following documents are indispensable to the application of this document. In
terms of references with a specified date, only versions with a specified date are
applicable to this document. In terms of references without a specified date, the latest
version (including all the modifications) is applicable to this document.
GB/T 156 Standard Voltages (GB/T 156-2017, IEC 60038:2009, MOD)
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 (IEC 60811-1-1:2001, IDT)
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 (IEC 60811-1-2:1985, IDT)
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
of Limiting Values
GB/T 11017.2-2014 Power Cables with Cross-lined Polyethylene Insulation and Their
Accessories for Rated Voltage of 110 kV (Um = 126 kV) - Part 2: Power Cables
GB/T 11091 Copper Strips for Cables
GB/T 12706.2 Power Cables with Extruded Insulation and Their Accessories for Rated
Voltages from 1 kV (Um = 1.2 kV) up to 35 kV (Um = 40.5 kV) - Part 2: Cables for Rated
Voltages from 6 kV (Um = 7.2 kV) up to 30 kV (Um = 36 kV) (GB/T 12706.2-2020, IEC
60502-2:2014, MOD)
GB/T 16927.1 High-voltage Test Techniques - Part 1: General Definitions and Test
Requirements (GB/T 16927.1-2011, IEC 60060-1:2010, MOD)
GB/T 17650.1 Test on Gases Evolved during Combustion of Materials from Cables -
Part 1: Determination of the Amount of Halogen Acid Gas (GB/T 17650.1-1998, IEC
60754-1:1994, IDT)
GB/T 17650.2 Test on Gases Evolved during Combustion of Materials from Cables -
Part 2: Determination of Degree of Acidity of Gases by Measuring pH and Conductivity
(GB/T 17650.2-1998, IEC 60754-2:1991, IDT)
GB/T 18380.11 Tests on Electric and Optical Fiber Cables under Fire Conditions - Part
11: Test for Vertical Flame Propagation for a Single Insulated Wire or Cable - Apparatus
(GB/T 18380.11-2008, IEC 60332-1-1:2004, IDT)
GB/T 18380.12 Test on Electric and Optical Fiber Cables under Fire Conditions - Part
12: Test for Vertical Flame Propagation for a Single Insulated Wire or Cable -
Procedure for 1 kW Pre-mixed Flame (GB/T 18380.12-2008, IEC 60332-1-2:2004, IDT)
GB/T 18380.13 Tests on Electric and Optical Fiber Cables under Fire Conditions - Part
13: Test for Vertical Flame Propagation for a Single Insulated Wire or Cable -
Procedure for Determination of Flaming Droplets / Particles (GB/T 18380.13-2008, IEC
60332-1-3:2004, IDT)
GB/T 18380.33 Tests on Electric and Optical Fiber Cables under Fire Conditions - Part
33: Test for Vertical Flame Spread of Vertically-mounted Bunched Wires or Cables -
Category A (GB/T 18380.33-2008, IEC 60332-3-22:2000, IDT)
GB/T 18380.34 Tests on Electric and Optical Fiber Cables under Fire Conditions - Part
34: Test for Vertical Flame Spread of Vertically-mounted Bunched Wires or Cables -
Category B (GB/T 18380.34-2008, IEC 60332-3-23:2000, IDT)
GB/T 18380.35 Tests on Electric and Optical Fiber Cables under Fire Conditions - Part
35: Test for Vertical Flame Spread of Vertically-mounted Bunched Wires or Cables -
Category C (GB/T 18380.35-2008, IEC 60332-3-24:2000, IDT)
Routine tests are tests carried out by the manufacturer on all the manufacturing lengths
of finished cables to check whether all the cables meet the specified requirements.
3.2.2 Sample tests
Sample tests are tests carried out by the manufacturer on finished cable specimens or
some parts taken from finished cables at a specified frequency to check whether the
cables meet the specified requirements.
3.2.3 Type tests
Type tests are tests carried out before the supply of a type of cables included in this
Part in accordance with general commercial principles, to prove that the cables have
satisfactory performance to satisfy the expected conditions of use.
NOTE: the characteristic of the tests is that unless changes of cable materials or design
or manufacturing process might alter the characteristics of the cables, it is
unnecessary to re-conduct the tests.
3.2.4 Electrical tests after installation
Electrical tests after installation are tests carried out after installation to prove that the
installed cables and their accessories are in good condition.
4 Voltage Marking and Materials
4.1 Rated Voltage
In this Part, the rated voltage of the cables U0/U(Um) is 0.6/1(1.2) kV and 1.8/3(3.6)kV.
NOTE: the above-mentioned voltage representation method is suitable, even though other
representation methods are used in some countries, for example, 1.7/3 kV or
1.9/3.3 kV, instead of 1.8/3 kV.
In the voltage representation of the cables U0/U(Um):
---U0: the rated power frequency voltage between conductor and earth or metallic
screen for the design of the cables;
---U: the rated power frequency voltage between conductors for the design of the
cables;
---Um: the maximum value of the “highest system voltage” that the equipment can
withstand (see GB/T 156).
The rated voltage of the cables shall be suitable for the operating conditions of the
system, where the cables are located. In order to facilitate the selection of cables, the
For cables with rated voltage of 0.6/1 kV, the insulated core or cable core can be
covered with a collective metallic layer.
NOTE: whether a cable uses metallic layer depends on relevant specifications and
installation requirements, so as to avoid the danger of mechanical damage or
direct electrical contact.
7.3.2 Cables with a collective metallic layer (see Chapter 8)
There shall be an inner covering outside the cable core. The inner coverings and fillers
shall comply with the stipulations of 7.2 and shall be non-hydroscopic materials.
If the thickness of a single layer of the used metallic tape does not exceed 0.3 mm,
then, the metallic tape may also be directly lapped outside the cable core, omitting the
inner covering. This type of cable shall comply with the requirements of special bending
test specified in 18.19.
7.3.3 Cables without a collective metallic layer (see Chapter 8)
As long as the outer shape of the cable remains circular, and there is no adhesion
between the cable core and the sheath, the inner covering may be omitted.
Under the circumstance where the thermoplastic sheath covers a circular cable core
of 10 mm2 and below, the over-sheath may be embedded in the gap of the cable core.
If an inner covering is used, then, its thickness does not have to comply with the
stipulations of 7.2.3 or 7.2.4.
7.4 Cables with Rated Voltage of 1.8/3 kV
7.4.1 General rules
For cables with rated voltage of 1.8/3 kV, there shall be a split-phase or collective
metallic layer.
7.4.2 Cables with a collective metallic layer (see Chapter 8)
There shall be an inner covering outside the cable core. The inner coverings and fillers
shall comply with the stipulations of 7.2 and shall be non-hydroscopic materials.
7.4.3 Cables with a split-phase metallic layer (see Chapter 9)
The metallic layers of the various insulated cores shall be in contact with each other.
For cables with an additional collective metallic layer (see Chapter 8), when the metal
material is the same as the material of the split-phase coated metallic layer, then, there
shall be an inner covering outside the cable core. The inner coverings and fillers shall
comply with the stipulations of 7.2 and shall be non-hydroscopic materials.
9.2.1 The resistance of copper wire screen in the metallic screen, when applicable,
shall comply with the stipulations of GB/T 3956. The nominal cross-sectional area of
the copper wire screen shall be determined in accordance with the fault current
capacity.
9.2.2 The copper wire screen shall be composed of a sparsely wound soft copper wire.
The surface may be tightly tied with reversely lapped copper wire or copper tape. The
average gap between adjacent copper wires shall not be greater than 4 mm. The
definition and calculation of the average gap between adjacent copper wires are shown
in 6.5.2 of GB/T 11017.2-2014.
9.2.3 The copper tape screen shall be composed of an overlapped soft copper tape.
The nominal overlap rate between the overlapped copper tapes is 15%, and the
minimum overlap rate shall not be smaller than 5%. When the supply-side and the
demand-side reaches a consensus through negotiation, other structures may also be
adopted.
The soft copper tapes, as the raw material of the screen, shall be copper tapes that
comply with the stipulations of GB/T 11091.
The nominal thickness of the copper tapes is:
---For single-core cables: ≥ 0.12 mm;
---For multi-core cables: ≥ 0.10 mm.
The minimum thickness of the copper tapes shall not be smaller than 90% of the
nominal value.
10 Concentric Conductor
10.1 Structure
The gap of the concentric conductors shall comply with the stipulations of 9.2.2.
When selecting structures and materials of the concentric conductor, special
consideration shall be given to the possibility of corrosion, not only for mechanical
safety, but also for electrical safety.
10.2 Requirements
The dimensions, physical properties and resistance requirements of the concentric
conductors shall comply with the stipulations of 9.2.
10.3 Application
If a concentric conductor structure is adopted, the inner covering of multi-core cables
wire (non-magnetic), copper wire or tinned copper wire, aluminum wire or aluminum
alloy wire.
The metallic tape shall be galvanized steel tape, stainless steel tape (non-magnetic),
aluminum tape or aluminum alloy tape.
Under the circumstance where the armored steel wire is required to satisfy the
minimum electrical conductivity, sufficient copper wires or tinned copper wires are
allowed in the armor layer, so as to ensure that the requirement is satisfied.
When selecting materials of the armor, especially when the armor is used as a screen,
special consideration shall be given to the possibility of corrosion, not only for
mechanical safety, but also for electrical safety.
Except for special structures, the single-core cable armor used for the AC circuit shall
be made of non-magnetic materials.
NOTE: even if the magnetic armor of a single-core cable used in the AC circuit adopts a
special structure, the current carrying capacity of the cable will still be significantly
reduced.
12.3 Application of Armor
12.3.1 Single-core cables
Under the armor layer of the single-core cables, there shall be an extruded or lapped
inner covering, and the thickness shall comply with the stipulations of 7.2.3 or 7.2.4.
12.3.2 Multi-core cables
When the multi-core cables need to be armored, the armor shall be covered on the
inner covering that complies with the stipulations of 7.2. When metallic tapes are used
to directly lap the armor, see 7.3.2 for the stipulations.
12.3.3 Separation sheath
When the material of the metallic layer under the armor is different from the armor, an
extruded sheath of a type of material specified in 13.2 shall be used to separate them.
The separation sheath shall withstand the spark test specified in GB/T 3048.10.
The separation sheath of halogen-free cable (halogen-free flame-retardant ST8) shall
comply with the stipulations of Table 5.
When the lead sheathed cable requires armoring, a lapped bedding may be adopted
and shall comply with the stipulations of 12.3.4.
If a separation sheath is used under the armor layer, it may replace the inner covering
metal wire armor, and the deviation of the steel tape shall comply with the stipulations
of 16.7.3.
When thick round metal wire armor is used, and when the calculated value of the
nominal thickness of the separation sheath or the inner covering under the armor is
smaller than 2.0 mm, the nominal thickness of the separation sheath or the inner
covering shall be 2.0 mm.
12.7 Double Metal Tape Armor
When the metal tape armor and the lapped inner covering that complies with the
stipulations of 7.2 are used, the inner covering shall be reinforced with a lapped
bedding. If the thickness of the armored metal tape is 0.2 mm, then, the total thickness
of the inner covering and the additional lapped bedding shall comply with the nominal
value of 7.2, plus 0.5 mm; if the thickness of the armored metal tape is greater than
0.2 mm, then, the total thickness of the inner covering and the additional lapped
bedding shall comply with the nominal value of 7.2, plus 0.8 mm.
The measured value of the total thickness of the lapped inner covering and the
additional lapped bedding shall not be smaller than 80% of the specified value, minus
0.2 mm.
The metal tape armor shall be spirally lapped in two layers, so that the middle part of
the outer layer of metal tape is roughly above the gap of the inner layer of metal tape;
the gap rate of each layer of metal tape shall not be greater than 50%.
13 Over-sheath
13.1 Overview
All cables shall have an over-sheath.
Generally speaking, the over-sheath is black, but in accordance with the agreement
between the manufacturer and the purchaser, colors other than black may also be
used, so as to adapt to the specific environment, to which, the cables are applied.
The over-sheath of the cables covered on the armor, metallic screen or concentric
conductor shall go through the spark test specified in GB/T 3048.10.
13.2 Materials
The over-sheath shall be made of thermoplastic materials (polyvinyl chloride,
polyethylene or halogen-free flame retardant material) or elastomer materials
(chloroprene rubber, chloro-sulfonated polyethylene or similar polymers).
If it is required that in the event of a fire, the cables shall be able to prevent the spread
of flame, generate less smoke and release no halogen gas, then, halogen-free flame-
14 Test Conditions
14.1 Ambient Temperature
Unless it is otherwise specified, tests shall be carried out at the ambient temperature
of (20 ± 15) °C.
14.2 Frequency and Waveform of Power Frequency Test Voltage
The frequency of the power frequency test voltage shall be 49 Hz ~ 61 Hz; the
waveform is basically a sine wave, and the quoted values are effective values.
14.3 Waveform of Impulse Test Voltages
In accordance with GB/T 3048.13, the impulse waveform shall have an effective
wavefront time of 1 μs ~ 5 μs, and a nominal half-peak time of 40 μs ~ 60 μs. The other
aspects shall comply with GB/T 16927.1.
15 Routine Tests
15.1 Overview
Generally speaking, routine tests shall be carried out on the manufacturing length of
each cable (see 3.2.1). In accordance with the quality control agreement reached
between the purchaser and the manufacturer, the number of test cables may be
reduced.
The routine tests required in this Part are:
a) Conductor resistance measurement (see 15.2);
b) Voltage test (see 15.3).
15.2 Conductor Resistance
All conductors of each cable length in the routine tests shall be measured, including
concentric conductors.
Finished cables or specimens removed from finished cables shall be stored for at least
12 h in a test room maintained at an appropriate temperature. If it is doubtful whether
the conductor temperature is consistent with the room temperature, then, the cables
shall be stored in the test room for 24 h, then, be measured. Another method may also
be selected, which is to immerse the conductor specimen in a temperature-controllable
liquid tank for at least 1 h, then, measure the resistance.
The measured value of resistance shall be corrected, in accordance with the formula
The measurement shall be carried out on a 50 mm long sheath specimen taken from
finished cables. The specimen shall be cut open along the axial direction and carefully
flattened. After the specimen is wiped clean, the measurement shall be carried out
along the circumference of the sheath and not less than 10 mm away from the edge of
the flattened specimen. Enough measurements shall be carried out to ensure that the
minimum thickness is measured.
16.6.3 Ring method
A micrometer with a flat probe and a spherical probe, or a micrometer with a flat probe
and a rectangular flat probe with a length of 2.4 mm and a width of 0.8 mm shall be
used for measurement. During measurement, the spherical probe or rectangular probe
shall be placed inside the sheath ring. The accuracy of the micrometer shall be ± 0.01
mm.
The measurement shall be performed on an annular sheath carefully cut from the
sample. Enough points shall be measured along the circumference to ensure that the
minimum thickness is measured.
16.7 Measurement of Armor Metal Wires and Metal Tapes
16.7.1 Measurement of metal wires
A micrometer with two flat probes with an accuracy of ± 0.01 mm shall be used to
measure the diameter of round metal wires and the thickness of flat metal wires. For
the round metal wires, respectively conduct the measurement once at two positions at
right angles to each other on the same cross-section; take the average value of the
two measurements as the diameter of the metal wires.
16.7.2 Measurement of metal tapes
A micrometer with two flat probes with a diameter of 5 mm and an accuracy of ± 0.01
mm shall be used for the measurement. For metal tapes with a width of 40 mm and
below, the thickness shall be measured at the center of the width; for wider tapes, the
thickness shall be measured at a distance of 20 mm from each edge; take the average
value as the thickness of the metal tapes.
16.7.3 Requirements
The dimensions of armor metal wires and metal tapes shall not fall below the nominal
values provided in 12.5 by more than:
---Round metal wires: 5%;
---Flat metal wires: 8%;
---Metal tapes: 10%.
16.12 Measurement of Total Thickness of Lapped Inner Coverings and / or
Lapped Beddings
16.12.1 Procedures
Remove the lapping tape from the sample. After flattening it, measure the thickness of
the central part. When multiple tapes are overlapped, each tape shall be respectively
tested.
Use the pointer-type thickness gauge specified in GB/T 2951.11-2008 to maintain
under a pressure of (0.07 ± 0.01) mPa for 20 s, then, immediately conduct the test.
The upper and lower measuring planes of the thickness gauge are flat, in which, the
diameter of the circular upper presser foot is (5.0 ± 0.1) mm; the diameter of the lower
measuring plane is not less than 5.0 mm. Take the average value of 5 tests as the
measurement result.
For single-tape overlapping, the measured value of total thickness is the measured
value of the thickness of a tape. For multi-tape overlapping, the measured value of
total thickness is the sum of the average measured values of the thickness of each
tape.
16.12.2 Requirements
The measured value of the thickness of the lapped inner coverings shall not be smaller
than 80% of the nominal value, minus 0.2 mm.
When double metal tape armor is adopted, the total thickness of the lapped inner
coverings and the additional lapped beddings shall comply with the stipulations of 12.7.
17 Electrical Type Tests
17.1 Overview
Take a specimen with a length of 10 m ~ 15 m from finished cables. The following tests
shall be successively carried out:
a) Insulation resistance measurement at ambient temperature (see 17.2);
b) Insulation resistance measurement at the maximum conductor temperature
during normal operation (see 17.3);
c) Voltage test for 4 h (see 17.4).
The cables with rated voltage 1.8/3(3.6) kV shall receive the impulse voltage test. The
test shall be carried out on another 10 m ~ 15 m long specimen taken from finished
cables (see 17.5).
values specified in Table 16.
17.4 Voltage Test for 4 H
17.4.1 Procedures
Before the test, the insulated core used for the cable test shall be immersed in the
water at ambient temperature for at least 1 h.
Between the water and the conductor, apply a power frequency voltage of 4U0; the
voltage shall gradually increase and continue for 4 h.
17.4.2 Requirements
The insulation shall manifest no breakdown.
17.5 Impulse Voltage Test on Cables with Rated Voltage 1.8/3(3.6) kV
17.5.1 Procedures
The test shall be carried out on cables whose conductor temperature is 5 °C ~ 10 °C
higher than the maximum conductor temperature during normal operation.
In accordance with the steps specified in GB/T 3048.13, apply the impulse voltage,
with a peak value of 40 kV.
For the multi-core cables without split-phase screen, each time, the impulse voltage
shall be successively applied between each phase conductor and the earth, and the
other conductors shall be connected together and earthed.
17.5.2 Requirements
The insulated core of each cable shall not break down after withstanding the positive
and negative impulse voltage respectively for 10 times.
18 Non-electrical Type Tests
18.1 Overview
In this Part, the non-electrical type test items are shown in Table 17.
18.2 Measurement of Insulation Thickness
18.2.1 Sampling
From each insulated core, respectively take 1 specimen.
For cables with more than three cores and conductors of equal nominal cross-section,
but so far there has not been enough information to suggest that these
requirements must be compulsorily reached, unless the manufacturer and the
purchase reach an agreement.
18.5.3 Pre-treatment and mechanical tests
In accordance with the stipulations of 9.1 in GB/T 2951.11-2008, conduct pre-treatment
and the tests of mechanical properties.
18.5.4 Requirements
The test results of the test piece before and after the ageing shall comply with the
stipulations of Table 18.
18.6 Test of Mechanical Properties of Non-metallic Sheaths before and
after Ageing
18.6.1 Sampling
In accordance with the stipulations of 9.2 in GB/T 2951.11-2008, conduct sampling and
prepare for test pieces.
18.6.2 Ageing treatment
Under the conditions specified in Table 19, in accordance with the stipulations of 8.1 in
GB/T 2951.12-2008, perform the ageing treatment.
18.6.3 Pre-treatment and mechanical tests
In accordance with the stipulations of 9.2 in GB/T 2951.11-2008, conduct pre-treatment
and the tests of mechanical properties.
18.6.4 Requirements
The test results of the test piece before and after the ageing shall comply with the
stipulations of Table 19.
18.7 Additional Ageing Test on Pieces of Finished Cables
18.7.1 Overview
The purpose of this test is to check whether there is a trend of degradation when the
cable insulation and non-metallic sheath are in contact with other cable components in
the cable during operation.
This test is applicable to any type of cables.
18.7.2 Sampling
......
 
(Above excerpt was released on 2021-05-22, modified on 2021-06-07, translated/reviewed by: Wayne Zheng et al.)
Source: https://www.chinesestandard.net/PDF.aspx/GBT12706.1-2020