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BSI 21/30443331 DC:2021 Edition

BSI 21/30443331 DC:2021 Edition

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BS IEC 61442. Test methods for accessories for power cables with rated voltages from 6 kV (Um = 7,2 kV) up to 30 kV (Um = 36 kV)

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BSI 2021 35
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PDF Pages PDF Title
3 20/1976/CD
COMMITTEE DRAFT (CD)
Project number:
IEC 61442 ED3
Date of circulation:
Closing date for comments:
2021-09-10
2021-12-03
Supersedes documents:
20/1975/RR
IEC TC 20 : Electric cables
Secretariat:
Secretary:
Germany
Mr Walter Winkelbauer
Of interest to the following committees:
Proposed horizontal standard:
Other TC/SCs are requested to indicate their interest, if any, in this CD to the secretary.
Functions concerned:
EMC
Environment
Quality assurance
Safety
This document is still under study and subject to change. It should not be used for reference purposes.
Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to provide supporting documentation.
Title:
Test methods for accessories for power cables with rated voltages from 6 kV (Um = 7,2 kV) up to 30 kV (Um = 36 kV)
Note from TC/SC officers:
HORIZONTAL_STD
FUNCTION_EMC
FUNCTION_ENV
FUNCTION_QUA
FUNCTION_SAFETY
4 CONTENTS
FOREWORD 6
1 Scope 8
2 Normative references 8
3 Test installations and conditions 9
4 AC voltage tests 9
4.1 Dry test for all accessories 9
4.1.1 Installation 9
4.1.2 Method 9
4.2 Wet test for outdoor terminations 9
4.2.1 Installation 9
4.2.2 Method 10
4.3 Test in water for stop ends 10
4.3.1 Installation 10
4.3.2 Method 10
5 DC voltage tests 10
5.1 Installation 10
5.2 Method 10
6 Impulse voltage tests 10
6.1 Installation 10
6.2 Method 10
6.3 Test at elevated temperature 10
7 Partial discharge test 11
7.1 Method 11
7.2 Test at elevated temperature 11
8 Tests at elevated temperature 11
8.1 Installation and connection 11
8.2 Measurement of temperature 11
8.2.1 Cable conductor temperature 11
8.2.2 Thermocouple position 12
9 Heating cycles voltage test 15
9.1 Installation and method 15
9.2 Test in air 15
9.3 Test in water 15
9.4 Immersion test for outdoor terminations 16
9.4.1 Installation 16
9.4.2 Method 16
10 Thermal short-circuit test (screen) 16
10.1 Installation 16
10.2 Method 16
11 Thermal short-circuit test (conductor) 17
11.1 Installation 17
11.2 Method 17
12 Dynamic short-circuit test 18
12.1 Installation 18
12.2 Method 18
5 13 Humidity and salt fog tests 18
13.1 Apparatus 18
13.2 Installation 19
13.3 Method 19
14 Impact test at ambient temperature 19
15 Screen resistance measurement 21
15.1 Installation 21
15.2 Method 21
16 Screen leakage current measurement 21
16.1 Installation 21
16.2 Method 21
17 Screen fault current initiation test 22
17.1 Installation 22
17.2 Method 23
17.2.1 Solidly earthed system 23
17.2.2 Unearthed or impedance earthed system 23
18 Operating force test 24
18.1 Installation 24
18.2 Method 24
19 Operating eye test 24
19.1 Installation 24
19.2 Method 24
20 Capacitive test point performance 25
20.1 Installation 25
20.2 Test method 25
Annex A (informative) Determination of the cable conductor temperature 26
A.1 Purpose 26
A.2 Calibration of the test cable conductor temperature 26
A.2.1 Installation of cable and thermocouples 26
A.2.2 Method 27
A.3 Heating for accessory test 28
A.3.1 Method 1: Test based on measurement of ambient temperature 28
A.3.2 Method 2: Test based on measurement of the external surface temperature 29
A.3.3 Method 3: Test using a control cable 30
Annex B (informative) Details of the test chamber and spray equipment for humidity and salt fog tests 32
B.1 Test chamber 32
B.2 Spray equipment for humidity and salt fog tests 32
B.3 High voltage transformers 33
Bibliography 34
Figure 1 – Terminations tested in air 12
Figure 2 – Joints tested in air 12
Figure 3 – Separable connectors tested in air 13
Figure 4 – Joints tested under water 13
Figure 5 – Separable connectors tested under water 14
6 Figure 6 – Outdoor terminations tested under water 14
Figure 7 – Heating cycle 15
Figure 8 – Typical impact test apparatus for joints 20
Figure 9 – Test arrangement for the screen leakage current measurement 22
Figure 10 – Test arrangement for screen fault current initiation test 23
Figure A.1 – Reference cable 27
Figure A.2 – Arrangement of the thermocouples 27
Figure A.3 – Current/temperatures curves 29
7 INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
TEST METHODS FOR ACCESSORIES
FOR POWER CABLES WITH RATED VOLTAGES
FROM 6 kV (Um = 7,2 kV) UP TO 30 kV (Um = 36 kV)
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work. International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international consensus of opinion on the relevant subjects since each technical committee has representation from all interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications transparently to the maximum extent possible in their national and regional publications. Any divergence between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and members of its technical committees and IEC National Committees for any personal injury, property damage or other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61442 has been prepared by IEC technical committee 20: Electric cables.
This second edition of IEC 61442 cancels and replaces the first edition of IEC 61442, published in 1997, and constitutes a technical revision.
Significant technical changes with respect to the previous edition are as follows:
a) 3.6 – the option to start tests immediately has been included
b) 4.3.2 & 9.3 – details of Insulation resistance testing added
c) 10.1 – inclusion to allow testing of accessories with external earthing devices.
d) 10.2 – short circuit duration and maximum kA levels added
e) 10.2 – temperature measurement not required if time between short circuits >1hr.
8 The text of this standard is based on the following documents:
FDIS
Report on voting
xxxxx
xxxxxx
Full information on the voting for the approval of this standard can be found in the report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until the maintenance result date indicated on the IEC web site under “http://webstore.iec.ch” in the data related to the specific publication. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
9 TEST METHODS FOR ACCESSORIES
FOR POWER CABLES WITH RATED VOLTAGES
FROM 6 kV (Um = 7,2 kV) UP TO 30 kV (Um = 36 kV)
1 Scope
This International Standard specifies the test methods to be used for type testing accessories for power cables with rated voltage from 3,6/6 (7,2) kV up to 18/30 (36) kV. Test methods are specified for accessories for extruded and paper insulated cables according to IEC 60502-2 and IEC 60055-1 respectively.
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 amendments) applies.
IEC 60055-1: Paper-insulated metal-sheathed cables for rated voltages up to 18/30 kV (with copper or aluminium conductors and excluding gas-pressure and oil-filled cables) – Part 1: Tests on cables and their accessories
IEC 60060-1:2010, High-voltage test techniques – Part 1: General definitions and test requirements
IEC 60230:2018, Impulse tests on cables and their accessories
IEC 60270:2000+A1:2005, High-voltage test techniques – Partial discharge measurements
IEC 60502-2, 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 2: Cables for rated voltages from 6 kV (Um = 7,2 kV) up to 30 kV (Um = 36 kV)
IEC 60811-401:2012, Common test methods for insulating and sheathing materials of electric and optical cables – Part 1: Methods for general application – Section Two: Thermal ageing methods
IEC 60885-3:2015, Electrical test methods for electric cables – Part 3: partial discharge tests
IEC 60986:2000+A1:2008, Short-circuit temperature limits of electric cables with rated voltages from 6 kV (Um = 7,2 kV) up to 30 kV (Um = 36 kV)
IEC 61238-1-3:2018, Compression and mechanical connectors for power cables for rated voltages up to 30 kV (Um = 36 kV) – Part 1: Test methods and requirements
IEC 60507:2013, Artificial pollution tests on high-voltage ceramic and glass insulators to be used on a.c. systems
IEC 60949:1988+A1:2008, Calculation of thermally permissible short-circuit currents, taking into account non-adiabatic heating effects
10 3 Test installations and conditions
3.1 The test methods described in this standard are intended to be used for type tests.
3.2 Test arrangements and the number of test samples are given in the relevant standard.
3.3 The test conditions are specified in Clauses 4 to 20 of this standard. When they are not, they shall be as specified in the relevant standards.
3.4 Unless otherwise stated, the testing parameters and the requirements are given in the relevant standard.
3.5 For transition joints (either extruded insulation to extruded insulation or extruded insulation to paper insulation), the testing parameters (voltage and conductor temperature) are those for the lower rated cable.
3.6  The tests can be started immediately after installation of accessories on the cable test loops, unless otherwise specified by the manufacturer.. The time interval shall be recorded in the test report.
3.7 Cable screens, and armour if any, shall be bonded and earthed at one end only to prevent circulating currents.
3.8 All parts of an accessory which are normally earthed shall be connected to the cable screen. Any supporting metalwork shall also be earthed.
3.9 Ambient temperature shall be (20 ± 15) °C.
3.10 Tap water shall be used for all tests in water.
4 AC voltage tests
4.1 Dry test for all accessories
4.1.1 Installation
The set(s) of accessories shall be erected with all associated metalwork and fittings. The accessories shall be clean and dry before applying the test voltage.
4.1.2 Method
Unless otherwise specified, the test shall be made at ambient temperature, and the procedure for voltage application shall be as specified in Section 5 of IEC 60060-1:2010.
4.2 Wet test for outdoor terminations
4.2.1 Installation
The terminations shall be erected in a vertical position, unless they are to be specifically installed in another orientation, with the relative spacing as under service conditions and according to manufacturer’s instructions.
11 4.2.2 Method
Unless otherwise specified, the wet test method is as described in 9.1 of IEC 60060-1:2010, and shall be carried out at ambient temperature.
4.3 Test in water for stop ends
4.3.1 Installation
The stop ends shall be installed in a water tank of such dimensions as to have a height of water of 1,00 m over their top surface, unless otherwise specified. The water shall be at ambient temperature.
4.3.2 Method
Unless otherwise specified, the procedure for voltage application shall be as specified in IEC 60060-1:2010.
After the AC voltage withstand, the insulation resistance shall be measured between the screen and water. The D.C. test voltage shall be in the range of 100 V to 1 000 V and shall be applied for a sufficient time to reach reasonably steady measurement, but in any case, not less than 1 min and not more than 5 min.
5 DC voltage tests
5.1 Installation
The set(s) of accessories shall be erected with all associated metalwork and fittings. The accessories shall be clean and dry before applying the test voltage.
5.2 Method
A voltage of negative polarity shall be applied to the cable conductor.
The test shall be made at ambient temperature and the procedure for voltage application shall be as specified in Section 4 of IEC 60060-1:2010.
6 Impulse voltage tests
6.1 Installation
For preparation of the test installation, involving metal enclosures and terminal boxes, reference shall be made to the relevant standard.
In the case of three-core accessories (such as three single-core terminations in an enclosure), one phase shall be tested at a time, with the other two phases earthed.
6.2 Method
The test shall be conducted according to the procedure given in IEC 60230:2018 (Clause 3 and following).
6.3 Test at elevated temperature
Installation and the measurement of temperature are given in Clause 8 of this standard.
The cable conductor shall be heated and stabilized for at least 2 h at a temperature of
12 – 5 K to 10 K above the maximum cable conductor temperature in normal operation for extruded insulation cables,
– 0 K to 5 K above the maximum cable conductor temperature in normal operation for paper insulated cables,
before and during the impulse test.
7 Partial discharge test
This test is only required for accessories for extruded insulation single-core cables and three-core cables with individually semi-conducting screened cores. It is not required for accessories incorporating paper insulated cables.
7.1 Method
The test shall be conducted in accordance with IEC 60270:2000+A1:2005and IEC 60885-3
The partial discharge shall be measured at the test voltage given in the relevant standard.
7.2 Test at elevated temperature
Installation and measurement of temperature are given in Clause 8 of this standard.
The cable conductor shall be heated and stabilized for at least 2 h at a temperature of 5 K to 10 K above the maximum cable conductor temperature in normal operation, before and during the partial discharge test.
8 Tests at elevated temperature
8.1 Installation and connection
The accessories shall be erected, supported where necessary and provided with connections to permit heating current to be circulated.
Where terminations or separable connectors are to be tested, the connection between either lugs or bushings shall have an electrical cross-section equivalent to that of the cable conductor.
Where branch joints are to be tested, only the main cable shall carry the heating current.
Three-core accessories may be connected for either single-phase or three-phase heating current. Single-phase or three-phase voltage in accordance with requirements shall be superimposed on the heating current. In the case of a magnetic covering, a three-phase heating current shall be applied.
Accessories for belted cables shall be subjected to three-phase voltage.
8.2 Measurement of temperature
8.2.1 Cable conductor temperature
It is recommended that one of the methods described in Annex A is used to determine the actual conductor temperature.
13 8.2.2 Thermocouple position
If method 2 of Annex A is used to determine the conductor temperature, two thermocouples shall be attached to the cable sheath as shown in Figures 1 to 6.
Figure 1 – Terminations tested in air
Figure 2 – Joints tested in air
14 Figure 3 – Separable connectors tested in air
Figure 4 – Joints tested under water
NOTE The height of the water is as indicated, unless otherwise specified.
15 Figure 5 – Separable connectors tested under water
NOTE The height of the water is as indicated, unless otherwise specified.
Figure 6 – Outdoor terminations tested under water
16 9 Heating cycles voltage test
9.1 Installation and method
The arrangement for tests in air or water shall be as given in Clause 8 of this standard.
Measurement of temperature is also given in Clause 8.
Each heating cycle in air or water shall be of at least 8 h duration with at least 2 h at a steady temperature:
– 5 K to 10 K above the maximum cable conductor temperature in normal operation for cables with extruded insulation;
– 0 K to 5 K above the maximum cable conductor temperature in normal operation for paper insulated cables,
followed by at least 3 h of natural cooling to within 10 K of ambient temperature (see Figure 7).
Figure 7 – Heating cycle
9.2 Test in air
The test assembly shall be subjected to the required number of heating cycles, energized at the voltage given in the relevant standard.
9.3 Test in water
For heat cycling in water, joints or separable connectors shall be installed in a vessel so as to have a height of water 1,00 m above the top surface of all accessories under test, unless otherwise specified. The water shall be at ambient temperature.
17 For accessories used with non-longitudinally water-blocked cable designs, the heating cycles voltage test under water shall be performed with oversheath damage. Expose the core(s) of one polymeric insulated cable at the entry to the accessory by removing an annulus of the oversheath, together with any bedding or filling material, of at least 50 mm length, at a point which will be within the water and between 50 mm and 150 mm from the exterior of the accessory.
The exposure of the core(s) shall be made on the side with the shorter length between oversheath cut and connectors.
NOTE The oversheath damage requirement does not apply to longitudinally water-blocked cable designs.
The test under water is not required for joints with a continuous metallic covering plumbed/ welded to the cable metallic sheath.
The test assembly shall be subjected to the required number of thermal cycles, energized at the voltage given in the relevant standard.
After testing, the insulation resistance shall be measured between the conductor and metallic screen/sheath and the screen to water. The DC. test voltage shall be in the range of 100 V to 1 000 V and shall be applied for a sufficient time to reach reasonably steady measurement, but in any case, not less than 1 min and not more than 5 min.
9.4 Immersion test for outdoor terminations
9.4.1 Installation
All the terminations of a the test loop shall be immersed in water at ambient temperature with a height of water 0,03 m above every part of the terminations. The test loop shall be installed upside down in a water tank at ambient temperature, in such a way that the terminations are fully immersed in water, including the end of the sealing element (see Figure 6).
9.4.2 Method
The test loop shall be subjected to 10 cycles under the conditions given in 9.1. The test loop shall not be energized.
10 Thermal short-circuit test (screen)
This test is only required for accessories that are equipped with a connection to, or adaptor for, the metallic screen of the cable.
10.1 Installation
The test loop shall consist of cable with accessories. The screen connections at both ends of the test loop shall be disconnected from earth and connected to a short-circuit generator. Accessories equipped with external earthing devices shall have these connections included in the short circuit test
10.2 Method
The current (Isc) and duration (t) of the short-circuit current shall be (1 ±0.5) s with a maximum current of 25kA. If the required short-circuit current, to achieve the required temperature, exceeds this value a longer duration ≤5 s with a current between 25 kA and 45 kA shall be used.
18 Installation and the measurement of conductor temperature are given in Clause 8. The cable conductor shall be heated and stabilized for at least 2 h at a temperature of
– 5 K to 10 K above the maximum cable conductor temperature in normal operation for cables with extruded insulation;
– 0 K to 5 K above the maximum cable conductor temperature in normal operation for paper insulated cables,
before carrying out the short-circuit test.
Before and after the short-circuits, the temperature of the screen shall be measured using thermocouples or any other suitable means. Measurement of the screen temperature is not necessary, if the time between the two short-circuits is longer than 1 hour.
Two short-circuits, corresponding to the current and time requirements agreed, shall then be applied to the screen. Between the two short-circuits, the cable screen shall be allowed to cool to a temperature less than 10 K above its temperature prior to the first short-circuit.
If the current is not constant during the short-circuit, it is recommended to determine the r.m.s value of the short-circuit current using Annex D of IEC 61238-1-3.
11 Thermal short-circuit test (conductor)
11.1 Installation
The test loop shall consist of cable with accessories.
Three-core accessories shall be tested with one end of the cable loop connected to the short-circuit generator and the other to a short-circuiting bar as described in the relevant standard. Alternatively, the three cores may be connected in series and tested as single-core accessories.
11.2 Method
The test shall be carried out on the test loop at ambient temperature.
Two short-circuits shall be applied using either a.c. or d.c. to raise the conductor temperature to the maximum permissible short-circuit temperature of the cable (sc) within 5 s. Between the two short-circuits, the test loop shall be allowed to cool to a temperature less than 10 K above its temperature prior to the first short-circuit (i). An alternative method to avoid having to measure the conductor temperature prior to the second short-circuit is to ensure that the test sample has cooled for >3 hours.
The maximum permissible short-circuit temperature of the cable conductor is given in IEC 60949:1988+A1:2008.
The following formulae from IEC 60949: 1988+A1:2008 shall be used:
For aluminium conductors I2t = 2,19 ( 104 ( S2 ( In
For copper conductors I2t = 5,11 ( 104 ( S2 ( In
19 where
I is the r.m.s value of short-circuit current (A);
t is the duration (s);
S is the conductor cross-sectional area (mm2);
sc is the permissible short-circuit conductor temperature (°C);
i is the conductor temperature at start of test (°C);
ln is the loge.
If the current is not constant during the short-circuit, it is recommended to determine the r.m.s value of the short-circuit current using Annex D of IEC 61238-1-3.
12 Dynamic short-circuit test
This test is a three-phase test required for single-core cable accessories designed for initial peak currents larger than 80 kA and for three-core cable accessories designed for initial peak currents larger than 63 kA.
12.1 Installation
The test loop shall consist of either three single-core cables or a three-core cable with accessories.
One end of the test cable loop shall be connected to the short-circuit generator and the other to a short-circuiting bar, as described in the relevant standard.
For terminations, separable connectors and joints, the cable and accessories clamping method and the spacing between the accessories shall be as recommended by the manufacturer and shall be recorded in the test report. In addition, single-core cable joints shall be tested in a trefoil configuration.
12.2 Method
The short-circuit current shall be applied for a minimum of 10 ms to ensure that the initial peak current, as specified in the relevant standard, is reached.
The waveform shall be recorded.
NOTE In practice, clearance times of the order of 60 ms may be expected. Exceeding this time may cause thermal problems with the cable or accessory.
13 Humidity and salt fog tests
13.1 Apparatus
A single- or three-phase a.c. voltage source is required. The maximum voltage drop at the high voltage side of the source shall be less than 5 % at 250 mA leakage current during the test.
A humidity test chamber shall be used equipped with spray nozzles or other form of humidifier capable of discharging atomized water at a rate of (0,4 ± 0,1) l/h/m3 volume. Throughout the test duration, the spray water conductivity shall be (70 ± 10) mS/m for humidity tests and (1 600 ± 200) mS/m for salt fog tests. The chamber shall be designed such that no water drips directly on the accessories during the test.
Guidance is given in Annex B on the test chamber and on the spray equipment.
20 13.2 Installation
The test accessories shall be installed in the humidity chamber with the accessories having the same orientation and relative spacing as installed in service, and according to manufacturer’s instructions.
Three unscreened separable connectors or three shrouded terminations shall be mounted in a test terminal box and subjected to a three-phase voltage.
Three-core terminations shall also be subjected to a three-phase voltage.
The phase(s) of the transformer shall be protected with an automatic tripping device, connected to the current measuring source, set to de-energize the circuit when a leakage current of (1,0 ± 0,1) A r.m.s flows in the high-voltage circuit for a period between 50 ms and 250 ms.
13.3 Method
The humidity chamber during the tests shall be at ambient temperature.
The duration and the voltage of the tests are given in the relevant standard.
Up to 5 % of the testing duration shall be permitted in breaks. Cleaning of the accessories or any other form of similar interference shall not be permitted during the test.
The accessories shall be photographed in colour in at least two opposite directions before commencement and after completion of the test. Photographs shall clearly show the condition of the leakage path.
The condition of the samples shall be noted at the end of the test.
The test results shall record the occurrence of any flashover, a description and photographs of the condition of the accessories, particularly any tracking, erosion or mechanical damage.
14 Impact test at ambient temperature
The test shall be carried out on joints only.
Prior to impacting, the insulation resistance shall be measured between the conductor and metallic screen/sheath. The d.c. test voltage shall be in the range of 100 V to 1 000 V and shall be applied for a sufficient time to reach reasonably steady measurement, but in any case, not less than 1 min and not more than 5 min.
NOTE If more than one joint is included in the loop, provision should be made for the insulation resistance of each joint to be measured separately.
The joint shall be placed on a hard base, e.g. a concrete slab or floor, and solidly supported in a box filled with sand up to the horizontal centre line of the accessory (see Figure 8).
21 A wedge shaped steel block of 4.00 (±0.05)kg having a 90(±1)° angle with a 2(±0.4) mm radius impacting edge shall be dropped freely from a height of 1,0(±0.01) m onto the joint so that the impacting edge is horizontal and at right angles to the axis of the joint. There shall be one impact at each end of the joint and one impact at a position over the conductor connectors. The impact at the end of the joint shall be at the oversheath cut in the case of an extruded insulation cable and at the metallic sheath cut in the case of a metallic sheathed cable.
After the impact test, the joint shall be immersed in water at ambient temperature with a height of water 1,00  m over the top surface of the joint for a minimum of 3 h. The insulation resistance shall then again be measured as specified above between the conductor and the metallic screen/sheath and between the metallic screen/sheath (if insulated) and the water.
Details of visible effects and position of the impacts on the joint shall be recorded by photographs in the test report.
Dimensions in millimetres
Figure 8 – Typical impact test apparatus for joints
22 15 Screen resistance measurement
The purpose of this test is to ensure that if a separable connector is touched by hand when it is in service, no electrical shock is experienced.
This test shall be carried out on separable connectors without a metallic housing or with a removable metallic housing. The metallic housing shall be removed prior to the test.
This test is not required for separable connectors which can only be used in service with the metallic housing in position.
15.1 Installation
The test shall be carried out on a separable connector which does not need to be installed on either a cable or a mating bushing. Silver painted or wraparound electrodes shall be installed at each end of the separable connector.
15.2 Method
The screen resistance of the separable connector shall be measured at ambient temperature between the two electrodes. The power dissipation of the test circuit shall not exceed 100 mW.
The sample shall then be subjected to thermal ageing in an air oven at (120 ± 2) °C for 168 h under the conditions described in 8.1 of IEC 60811-1-2.
The separable connector screen resistance at ambient temperature shall be measured again as above.
16 Screen leakage current measurement
The purpose of this test is to ensure that if a separable connector is touched by hand when it is in service, no electrical shock is experienced.
This test is required for separable connectors without a metallic housing or with a removable metallic housing. The metallic housing shall be removed prior to the test.
This test is not required for separable connectors which can only be used in service with the metallic housing in position.
16.1 Installation
A separable connector shall be installed on a length of cable and connected to its mating bushing.
16.2 Method
The test shall be carried out at ambient temperature.
A metal foil of 50 mm ( 50 mm, shall be fixed without any air gap to the outer screen of the separable connector as far as possible from the earthing points:
23 – in the case of separable connectors with an earthed metal flange (see Figure 9a), the metal foil shall be placed mid-way between the metal flange and the earth bond of the cable screen;
– in the case of separable connectors without a metal flange (see Figure 9b), the metal foil shall be placed at the end of the separable connector opposite to the earth bond of the cable screen.
In both cases, the metal foil shall be earthed through a milliammeter and a resistance of 2 000 (, as shown in Figure 9.
The leakage current shall be measured with an a.c. test voltage of Um applied between conductor and earth.
Figure 9 – Test arrangement for the screen leakage current measurement
17 Screen fault current initiation test
The purpose of this test is,
a) in the case of a solidly earthed system or resistance earthed system, in which the first earth fault is cleared,
to demonstrate the ability of the separable connector screen to initiate a fault to earth which produces sufficient current to operate the circuit protection, should its insulation fail;
b) in the case of an unearthed or impedance earthed system, in which the first earth fault is held,
to demonstrate the ability of the separable connector screen to initiate and sustain a fault current to earth, should its insulation fail.
The test is applicable only to screened separable connectors, and shall be carried out with the connectors installed as in service.
This test is required for separable connectors without a metallic housing or with a removable metallic housing. The metallic housing shall be removed prior to the test.
This test is not required for separable connectors which can only be used in service with the metallic housing in position.
17.1 Installation
A separable connector shall be assembled on a cable in accordance with the manufacturer’s instructions. All parts of the separable connector which are normally earthed shall be connected to the cable screen, including the bushing screen.
24 For testing separable connectors used in solidly earthed systems, the faulting rod shall be of erosion resistant metal, approximately 10 mm in diameter and threaded at one end to engage the accessory metal connector through a drilled hole. The rod shall be in contact with the inner and outer screens and shall not protrude beyond the outer screen surface, as shown in Figure 10.
For separable connectors used in unearthed systems or impedance earthed systems, the faulting rod shall be replaced by a copper wire of approximately 0,2 mm diameter. The wire shall be in contact with the inner and outer screens and shall not protrude beyond the outer screen surface, as shown in Figure 10.
17.2 Method
17.2.1 Solidly earthed system
The test shall be carried out at ambient temperature.
The circuit shall be adjusted to impose the separable connector phase-to-earth voltage U0 on the test specimen and a short-circuit current of 10 kA r.m.s. The test specimen shall be subjected to two tests that cause initiation of a fault current arc to earth, each operation having a minimum current flow duration of 0,2 s. Between the two tests, the test sample shall be allowed to cool to a temperature less than 10 K above its temperature prior to the first test.
Figure 10 – Test arrangement for screen fault current initiation test
17.2.2 Unearthed or impedance earthed system
The test shall be carried out at ambient temperature.
The circuit shall be adjusted to impose the separable connector phase-to-earth voltage U0 on the test specimen and a short-circuit current of at least 10 A.
The current for the short-circuit test shall be agreed upon between the manufacturer and the customer, taking into account the actual short-circuit conditions of the network.
The test voltage and current shall be recorded continuously during the entire period. The sequence of the test shall be as follows:
25 a) voltage switched on for 1 s;
b) voltage switched off for 2 min;
c) voltage switched on for 2 min;
d) voltage switched off for 2 min;
e) voltage switched on for 1 min;
f) voltage switched off.
18 Operating force test
This test is only required for screened separable connectors equipped with a sliding contact.
18.1 Installation
A separable connector shall be assembled in accordance with the manufacturer’s instructions and connected to its mating bushing, using the lubricant supplied by the manufacturer.
18.2 Method
The separable connector assembly shall be conditioned at (–20 ± 2) °C for at least 12 h. The test shall be carried out within 5 min after removal from the conditioning chamber. The separable connector shall be clamped by means of a suitable tool which allows operation along the axis of the separable connector and mating bushing interface.
A force shall be gradually applied to the separable connector in the axial direction. The force to open and close the separable connector/bushing interface shall be measured.
19 Operating eye test
This test is only required for screened separable connectors equipped with a sliding contact.
19.1 Installation
A separable connector shall be assembled on a cable loop in accordance with the manufacturer’s instructions and connected to its mating bushing, using the lubricant supplied by the manufacturer. The separable connector shall be mechanically clamped along the interface.
19.2 Method
The test shall be carried out at ambient temperature.
A tensile force shall be gradually applied to the operating eye with a suitable tool in the direction of the bushing axis up to the specified force and maintained for the specified time as given in the relevant standard.
A rotational torque shall then be gradually applied, up to the specified value given in the relevant standard, using a suitable tool first in a clockwise direction and then in an anticlockwise direction.
26 20 Capacitive test point performance
This test is only required for screened separable connectors.
20.1 Installation
A separable connector shall be installed on a cable and the outer screen earthed in accordance with the manufacturer’s instructions. The separable connector need not be connected to its mating bushing. It is recommended that the length of cable used be as short as possible.
20.2 Test method
Since the capacitances to be measured are very small, the use of a differential bridge is recommended in order to eliminate the influence of stray capacitances.
The following capacitances shall be measured at ambient temperature:
– Ctc: capacitance between the test point and the cable conductor;
– Cte: capacitance between the test point and the earth.
27 Annex A (informative)Determination of the cable conductor temperature
A.1 Purpose
For some of the accessory tests, it is necessary to raise the cable conductor to a given temperature, typically 5 K to 10 K above the maximum temperature in normal operation, while the cable is energized, either at power frequency or under impulse conditions. It is therefore not possible to have access to the conductor to enable direct measurement of temperature.
In addition, the conductor temperature should be maintained within a restricted range (5 K), whereas the ambient temperature may vary over a wider range.
Thus, it is necessary to carry out a preliminary calibration on the test cable to determine the actual conductor temperature during the accessory tests, allowing for the permitted variation in ambient temperature.
Guidance is given hereafter on commonly used methods.
A.2 Calibration of the test cable conductor temperature
The purpose of the calibration is to determine the conductor temperature by direct measurement for a given current, within the temperature range required for the test.
The cable used for calibration should be identical to that to be used for the accessory test.
A.2.1 Installation of cable and thermocouples
The calibration should be performed on a minimum cable length of 2 m, the thermocouples being installed at 0,5 m from the cable ends, as shown in Figure A.1.
At each place, two thermocouples should be attached: one on the conductor (a), and one on the external surface (b), as shown in Figure A.2.
NOTE The thermocouples (b) on the external surface are only necessary if method A.3.2 is used.
It is recommended that the thermocouples are attached to the conductor by mechanical means since they may move due to vibrations of the cable conductor during heating.
If the actual test loop includes several individual cable lengths installed close to each other, these lengths will be subjected to thermal proximity effect. The calibration should therefore be carried out taking account of the actual test arrangement, measurements being performed on the hottest cable length (usually the middle length).
28 Figure A.1 – Reference cable
Figure A.2 – Arrangement of the thermocouples
NOTE: optionally the thermocouple could be welded to the copper tape at (a)
A.2.2 Method
The calibration should be carried out in a draught free situation at a temperature between 5 °C and 35 °C.
Temperature recorders should be used to measure the conductor, sheath and ambient temperatures.
The cable should be heated until the conductor temperatures a1 and a2, indicated by thermocouples (a) at positions 1 and 2 of Figure A.1, have stabilized and reached the temperatures given below:
– between 5 K and 10 K above the maximum conductor temperature of the cable in normal operation, as given in the relevant standard for extruded insulation cables;
– between 0 K and 5 K above the maximum conductor temperature of the cable in normal operation, as given in the relevant standard for paper insulated cables.
It is considered that stabilization has been reached if the conductor temperatures, a1 and a2, do not show any variation larger than 2 K within a 2 h period.
29 When stabilization has been reached, the following should be noted:
– conductor temperature (cond =
– sheath temperature (sheath.c =
– ambient temperature (amb.c
– heating current lcal
A.3 Heating for accessory test
R20 is the resistance per unit length of conductor at 20 °C (see IEC 60228);
20 is the temperature coefficient of resistance at 20 °C (see IEC 60228);
T is the thermal resistance between the conductor and the surrounding medium (including T4, the thermal resistance of air);
T´ is the thermal resistance between the conductor and the external surface of cable (excluding T4, the thermal resistance of air).
NOTE According to IEC 60287: T´ = T1 + nT2 + nT3.
where
n = 1 for single-core cables;
n = 3 for three-core cables;
T = T´ + nT4.
amb.t is the ambient temperature during accessory test;
sheath.t is the temperature of external surface during accessory test;
Itest is the current during accessory test.
A.3.1 Method 1: Test based on measurement of ambient temperature
Assuming that dielectric, metallic sheath and armour losses are negligible:
– during cable calibration:
cond – amb.c = R20 ( I2cal [1 + 20 (cond – 20)]T (1)
– during accessory test:
cond – amb.t = R20 ( I2test [1 + 20 (cond – 20)]T (2)
(it is assumed that T, and particularly T4, have not changed).
Combining (1) and (2) gives:
Itest = Ical (3)
30 A.3.2 Method 2: Test based on measurement of the external surface temperature
– during cable calibration:
cond – sheath.c = R20 ( I2cal [1 + 20 (cond – 20)]T´ (4)
– during accessory test:
cond – sheath.t = R20 ( I2test [1 + 20 (cond – 20)]T´ (5)
Combining (4) and (5) gives:
Itest = Ical (6)
It should be noted that Equation (4) allows the determination of the internal thermal resistance T´ of the cable from readings of temperature and current.
Equation (5) can be written in the form:
(cond = (7)
It is therefore possible to transpose this formula in the form of a chart, as shown in Figure A.3, giving (cond from (sheath.t readings, for various values of the heating current Itest 1, Itest 2,….
The use of such a chart is advisable if the test is not automatically controlled.
Figure A.3 – Current/temperatures curves
31 A.3.3 Method 3: Test using a control cable
In this method, a control cable identical to the cable used for the test is heated with the same current as the test loop. This cable is not energized and therefore thermocouples can be fitted to the conductor as recommended in A.2.1 above.
The test arrangement should be such that
– the control cable should carry the same current as the test loop at any time,
– it should be installed in such a way that mutual heating effects are taken into account throughout the test.
– for test in water, the control cable remains in air in draught free situation
The thermocouples should be mounted on the external surface of the test loop at the positions given in figure A.1, in the same way as the thermocouples are mounted on or under the surface of the control cable.
NOTE The temperature measured with the thermocouples on the oversheath of the energized test loop and of the control cable, are used to check whether the oversheath of both test loops has the same temperature.
The temperature measured with the thermocouple fitted to the conductor of the control loop may be considered as representative for the conductor temperature of the energized test loop.
All thermocouples should be connected to a temperature recorder to enable temperature monitoring. The heating current of each test loop should be recorded to prove that the two currents are of the same value throughout the duration of the test. The difference between the heating currents should be kept within (1 %.
The heating current is adjusted so that the conductor temperature is kept within the specified limits.
33 Annex B (informative)Details of the test chamber and spray equipment for humidity and salt fog tests
B.1 Test chamber
The dimensions of the test chamber should be adequate to contain the number of accessories being tested simultaneously, having due regard to the size of the accessory, the test voltage, safety clearances and stray electric fields, and the ratio of chamber volume to number of spray producing nozzles.
It should be constructed from corrosion resistant, waterproof materials. Temporary structures may be used. All high voltage bushings and support insulators should be mounted on earthed supports to ensure that an electric field does not exist along the surface of the chamber. The chamber should incorporate observation ports.
When the voltage supply (three-phase or single-phase, as appropriate) is introduced into the chamber through suitable bushings, such bushings should be well spaced to avoid interaction between adjacent phases. The length of the bushings within the test chamber should be designed with a long creepage length and deep undercuts in the skirt design to resist flashover.
A drain should be provided to conduct water out and away from the test chamber. The chamber should be so designed so as to prevent corrosion products or other contamination from dripping on the accessories during the test. The test chamber may be ventilated to prevent a build-up of pressure inside, but any such ventilation should not allow a significant amount of vapour or fog to escape to the atmosphere.
For the humidity and salt fog tests, means should be provided for measuring the rate of flow of solution into the atomizing sprays.
B.2 Spray equipment for humidity and salt fog tests
Humidity and salt fog tests may be conducted using the air nozzle spraying system described in IEC 60507. The equipment should be designed to run continuously for the duration of the test.
The nozzles should be set to blow fog into the test chamber. The fog should not be blown directly on the accessories but should fill the test chamber and circulate freely among the accessories by the action of fog/air currents. At least 80 % of the water ejected by the nozzles should be atomized into droplets not greater than 10 m in diameter.
Alternatively, proprietary equipment is available for atomizing water and salt solution, which may be more convenient for the manufacturer conducting the tests. Use of such equipment should not be discouraged, but it is a pre-requisite that the manufacturer produces information showing that his equipment has the capacity to fill the test chamber adequately with the correct size of atomized water droplets.
34 B.3 High voltage transformers
For three-phase testing, a three-phase or three single-phase transformers should be used to energize the accessories under test. Single-phase transformers should be star-connected with the neutral point earthed. The voltage in the test circuit should remain stable and practically unaffected by varying leakage currents. The output voltage may be controlled by varying the low voltage supply to the transformers, and it should be possible to measure or calibrate the output voltage.
35 Bibliography
IEC 60228, Conductors of insulated cables
IEC 60287 (all parts), Electric cables – Calculation of the current rating
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