GB/T 18890.1-2015 PDF English
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GB/T 18890.1-2015: Power cables with cross-linked polyethylene insulation and their accessories for rated voltage of 220 kV (Um=252 kV) -- Part 1: Test methods and requirements
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GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 29.060.20
K 13
Replacing GB/Z 18890.1-2002
Power cables with cross-linked polyethylene insulation and
their accessories for rated voltage of 220 kV (Um=252 kV) --
Part 1.Test methods and requirements
(IEC 62067.2011, 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, MOD)
Issued on: OCTOBER 09, 2015
Implemented on: MAY 01, 2016
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... 5
2 Normative references... 5
3 Terms and definitions... 7
4 Voltage marking and materials... 8
5 Water blocking measures for cables... 10
6 Cable characteristics... 10
7 Accessory characteristics... 11
8 Test conditions... 12
9 Routine tests on primary insulation of cables and prefabricated accessories... 13
10 Sample test of cables... 15
11 Sampling test of accessories... 20
12 Type test of cable systems... 21
13 Prequalification test of cable system... 37
14 Type test of cables... 43
15 Type test of accessories... 43
16 Electrical test after installation... 43
Annex A (informative) Determination of cable conductor temperature... 44
Annex B (normative) Numerical rounding... 49
Annex C (informative) List of type tests, prequalification tests and extensions of
prequalification test for cable systems... 50
Annex D (normative) Measurement method of resistivity of semi-conductive shielding
... 52
Annex E (normative) Water permeability test... 55
Annex F (normative) Test of cable assemblies having longitudinally wrapped metal tape
or foil bonded to the outer sheath... 57
Annex G (normative) Test of outer protective layer of joints... 60
Annex H (normative) Protrusion test on interface between micropores, impurities and
semi-conductive shielding layer... 63
Annex I (informative) Structural changes between this Part and IEC 62067.2011... 65
Annex J (informative) Technical differences between this Part and IEC 62067.2011 and
their reasons... 66
Bibliography... 68
Power cables with cross-linked polyethylene insulation and
their accessories for rated voltage of 220 kV (Um=252 kV) --
Part 1.Test methods and requirements
1 Scope
This Part of GB/T 18890 specifies the test methods and requirements for fixedly-
installed power cables with cross-linked polyethylene insulation, cable bodies and their
accessories for rated voltage of 220 kV (Um=252 kV).
This Part applies to single-core cables and their accessories used under normal
installation and operating conditions. However, it does not apply to cables and their
accessories used under special conditions, such as submarine cables. For these special-
purpose cables and accessories, the tests in this standard may need to be modified or
special test conditions may need to be established.
This Part does not include transition joints for connecting cross-linked polyethylene
insulated cables and paper insulated cables.
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 (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 2951.14-2008, Common test methods for insulating and sheathing materials
of electric and optical cables -- Part 14.Methods for general application -- Test at
low temperature (IEC 60811-1-4.1985, IDT)
GB/T 2951.21-2008, Common test methods for insulating and sheathing materials
of electric and optical cables -- Part 21.Methods specific to elastomeric compounds
sheaths
IEC 60183, Guidance for the selection of high-voltage a.c. cable systems
IEC 60229.2007, Electric cables -- Tests on extruded over sheaths with a special
protective function
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 Definitions of dimensional values (thickness, cross-sectional area, etc.)
3.1.1 nominal value
A specified quantity and is often used in tables.
NOTE. In this Part, nominal values generally refer to values of quantities that have been verified
by measurement taking into account stated tolerances.
3.1.2 median value
Arrange several measured values in ascending (or descending) order. If the number of
values is odd, the middle value is the middle value. If the number of values is even, the
average of the two middle values is the middle value.
3.2 Definitions for relevant tests
3.2.1 routine test
A test carried out by the manufacturer on components (all manufactured lengths of cable
or all accessories) to check that they comply with specified requirements.
3.2.2 sample test
A test carried out by the manufacturer at a specified frequency on samples of finished
cables or components taken from finished cables or accessories to verify that the
finished cables or accessories meet the specified requirements.
3.2.3 type test
A test carried out before a cable system of the type covered by this Part is supplied on
a normal industrial basis to demonstrate that it has satisfactory performance under the
conditions of intended use.
NOTE. Once the type test is passed, it does not need to be repeated unless the material,
manufacturing process, structure or design electric field strength of the cable or accessories are
changed and such change may have an adverse effect on its performance.
3.2.4 prequalification test
A test carried out before a cable system of the type covered by this Part is supplied on
a normal industrial production basis to demonstrate that the complete cable system has
satisfactory long-term operating performance.
3.2.5 extension of prequalification test
A test in which before a cable system of a type covered by this Part is supplied on a
general industrial production basis, the system cables and accessories have each passed
a prequalification test to verify that the complete cable system has satisfactory long-
term operating performance.
3.2.6 electrical test after installation
A test performed on a cable system to prove its integrity after installation.
3.3 Other definitions
3.3.1 cable system
Cables fitted with various accessories, including components for use only with
terminals and connectors, to suppress the thermal-mechanical forces on the system.
3.3.2 nominal electrical stress
Electric field strength at U0 calculated based on nominal size.
4 Voltage marking and materials
4.1 Rated voltage
This Part uses the symbols U0, U and Um to indicate the rated voltage of cables and
accessories. The meanings of these symbols are given by IEC 60183.
4.2 Cable insulation materials
This standard applies to cables with cross-linked polyethylene (XLPE) insulation. Table
1 specifies the maximum operating temperature of XLPE insulated cable conductors
and the test conditions accordingly.
Table 1 -- Cross-linked polyethylene insulation compound for cables
Insulation mixture Maximum conductor temperature/℃
Cross-linked polyethylene (XLPE)
Normal operation Short circuit (maximum duration is 5 s)
5 Water blocking measures for cables
When the cable system is laid underground, in an underground passage prone to water
accumulation, or in water, it is recommended to use a radially impermeable barrier layer
to cover the cable.
NOTE. There is currently no radial water permeability test method.
To prevent the need to replace long lengths of cable once the cable is damaged and
water ingress occurs, longitudinal water-blocking measures can also be adopted.
The longitudinal water penetration test is given in 12.5.14.
6 Cable characteristics
For the purpose of carrying out and recording the tests on cable systems or cables
described in this standard, the cables shall be marked.
The following cable characteristics should be specified or stated.
a) Manufacturer's name, model, designation, date of manufacture or date code.
b) Rated voltage. the values of U0, U, and Um should be given (see 4.1 and 8.4).
c) Conductor type, material, and nominal cross-sectional area in square millimeters;
conductor construction; measures to reduce skin effect (if any) and their nature;
longitudinal water-blocking measures (if any) and their nature; if the nominal
cross-sectional area does not conform to GB/T 3956, the DC resistance of the
conductor converted to 1 km at 20°C.
d) Insulation material and nominal thickness (see 4.2). Table 3 gives the tanδ of
cross-linked polyethylene insulation.
e) Manufacturing process of the insulation system.
f) Water-blocking measures (if any) and their nature for the shielding layer.
g) Material and construction of the metal shield, such as the number and diameter of
the metal wires. The DC resistance of the metal shield should be stated. Material,
construction, and nominal thickness of the metal sheath, or the material,
construction, and nominal thickness of the longitudinally wrapped metal tape or
foil bonded to the outer sheath (if any).
h) Material and nominal thickness of the outer sheath.
i) Nominal conductor diameter (d).
j) Nominal outer diameter of the finished cable (D).
k) Nominal inner diameter of the insulation (dii) and calculated nominal outer
diameter (Dio).
l) Nominal capacitance per 1 km between the conductor and the metallic shield
and/or metallic sheath.
m) Calculated nominal electric field strength on the conductor shield (Ei) and
nominal electric field strength on the insulation shield (Eo).
7 Accessory characteristics
For the purpose of carrying out and recording the tests on cable systems or accessories
described in this standard, the accessories shall be marked.
The following characteristics should be identified or stated.
a) Cables used for accessory tests shall be correctly marked in accordance with
Chapter 6;
b) Conductor connection fittings used in accessories should be correctly marked.
- Installation process;
- Tools, dies, and necessary assembly equipment;
- Treatment of contact surfaces;
- Model, serial number, and other identification marks of the connecting fittings;
- Details of the type tests and approvals that the conductor connecting fittings
have undergone, where applicable.
c) Accessories used for testing should be correctly marked with.
- Manufacturer's name;
- Model, name, date of manufacture or date code;
- Rated voltage [see Section 6, item b)];
- Installation instructions (number and date).
8 Test conditions
8.1 Ambient temperature
Unless otherwise specified for a particular test, the test shall be carried out at an ambient
temperature of (20 ± 15)°C.
8.2 Frequency and waveform of power frequency test voltage
Unless otherwise specified in this standard, the frequency of the AC test voltage shall
be between 49 Hz ~ 61 Hz. The waveform shall be essentially sinusoidal. The voltage
value shall be expressed in root mean square (r.m.s.) terms.
8.3 Waveform of lightning impulse test voltage
According to GB/T 3048.13, the wavefront time of a standard lightning impulse voltage
wave should be 1 μs~5 μs. According to GB/T 16927.1, the half-wave peak time should
be (50±10) μs.
8.4 Relationship between test voltage and rated voltage
The test voltages specified in this standard are expressed as multiples of the rated
voltage U0.To determine the test voltage U0 value as 127 kV, the test voltage shall be
as specified in Table 4.
The test voltages in this standard are based on the assumption that the cables and
accessories are used in Class A systems as defined in IEC 60183.
8.5 Determination of cable conductor temperature
It is recommended that one of the test methods described in Annex A be used to
determine the actual temperature of the conductor.
9 Routine tests on primary insulation of cables and prefabricated
accessories
9.1 Overview
The following tests shall be carried out on each manufactured length of cable.
a) Partial discharge test (see 9.2);
b) Voltage test (see 9.3);
c) Electrical test on the outer sheath (see 9.4).
The order of these tests is left to the discretion of the manufacturer.
The main insulation of each prefabricated accessory shall be subjected to the partial
discharge test (see 9.2) and the voltage test (see 9.3). The test may be carried out
according to the following 1), 2) or 3) methods.
1) Test conducted on an accessory installed on the cable;
2) Test conducted on the main insulating component installed on an accessory
specifically designed for testing;
3) Test conducted using a simulated accessory device so that the electric field
strength experienced by the main insulating component replicates actual electric
field conditions.
In cases 2) and 3) above, the test voltage should be selected so that the electric field
strength produced is at least the same as the electric field strength produced in the
accessory product when the test voltage specified in 9.2 and 9.3 is applied to the
component.
NOTE. The primary insulation of prefabricated accessories includes components that are in direct
contact with the cable insulation and are essential and fundamental to controlling the electric field
distribution in the accessory, such as molded or precast prefabricated rubber insulation or epoxy
insulation with filler. They can be used alone or in combination to provide the necessary insulation
and shielding for the accessory.
9.2 Partial discharge test
Cable partial discharge tests should be conducted in accordance with GB/T 3048.12.
The detection sensitivity should be 10 pC or better. Accessory tests should follow the
same principles. The detection sensitivity should be 5 pC or better.
The test voltage shall be gradually increased to 1.75 U0 and maintained for 10 s, then
slowly decreased to 1.5 U0 (see Table 4, column 5).
At 1.5 U0, the test object shall have no detectable discharge exceeding the declared
sensitivity.
9.3 Voltage test
The voltage test should be carried out at ambient temperature using industrial frequency
AC voltage.
The test voltage shall be applied between the conductor and the metal shield and/or
metal sleeve, gradually increasing to 2.5 U0 (see Table 4), and then maintained for 30
min.
There should be no insulation breakdown.
9.4 Electrical test on outer sheath
The electrical test specified in Chapter 3 of IEC 60229.2007 shall be carried out. Apply
a DC voltage of 25 kV between the metal shield and/or metal sheath and the conductive
layer on the surface of the outer sheath with the metal sheath connected to the negative
pole for 1 min.
The outer sheath should not be punctured.
10 Sample test of cables
10.1 Overview
The following tests shall be carried out on a sample of cable representing the delivery
batch. For tests b) and g), the sample may be a whole reel of cable.
a) Conductor inspection (see 10.4);
b) Conductor resistance and metallic screen and/or metallic sheath resistance
measurement (see 10.5);
c) Insulation and outer sheath thickness measurement (see 10.6);
d) Metal sheath thickness measurement (see 10.7);
e) Diameter measurement, where required (see 10.8);
f) XLPE insulation thermal expansion test (see 10.9);
g) Capacitance measurement (see 10.10);
h) Lightning impulse voltage test (see 10.11);
i) Water penetration test, where applicable (see 10.12);
j) Testing of cable components with longitudinally wrapped metal tape or foil bonded
to the outer sheath (see 10.13).
10.2 Test frequency
The sample test items a) ~ g) and j) in 10.1 shall be conducted on one specimen taken
from each batch (production series) of cables of the same model and conductor cross-
sectional area, but shall not exceed 10% of the total number of cables in any contract.
Round to the nearest integer.
The sampling frequency for items h) ~ i) in 10.1 shall be in accordance with the agreed
quality control method. In the absence of such an agreement, contracts with cable
lengths between 4 km~20 km shall be subject to a single test. Contracts with cable
lengths exceeding 20 km shall be subject to a second test.
10.3 Retest
If a specimen from any cable fails any of the tests in 10.1, two more specimens shall be
taken from the same batch of cables and tested for the failed items. If both of the
additional cables pass the test, the remaining cables in the batch from which the two
specimens were taken shall be considered to meet the requirements. If any of the
additional cables fails the test, the entire batch of cables shall be considered to fail the
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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