EN 50395-2005 低压电缆的电气试验方法

EUROPEAN STANDARD

EN 50395

NORME EUROPéENNE EUROP?ISCHE NORM

August 2005

CENELEC

European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europ?isches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

? 2005 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 50395:2005 E

ICS 29.060.20 Partly supersedes HD 21.2 S3:1997 + A1:2002 &

HD 22.2 S3:1997 + A1:2002

English version

Electrical test methods for low voltage energy cables

Méthodes d'essais électriques

pour les cables d'énergie basse tension

Elektrische Prüfverfahren

für Niederspannungskabel und -leitungen

This European Standard was approved by CENELEC on 2005-07-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

EN 50395:2005 – 2 –

Foreword

This European Standard was prepared by the Technical Committee CENELEC TC 20, Electric cables. In accordance with the decision of TC 20 at its Setubal meeting (June 2004), the text of the draft was submitted to the formal vote. It was approved by CENELEC as EN 50395 on 2005-07-01.

This European Standard, together with EN 50396:2005, supersedes HD 21.2 S3:1997 + A1:2002 and HD 22.2 S3:1997 + A1:2002. The following dates were fixed: –

latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement

(dop)

2006-07-01 – latest date by which the national standards conflicting with the EN have to be withdrawn

(dow)

2008-07-01

__________

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– 3 – EN 50395:2005

Contents

Page Introduction (5)

1Scope (5)

2Normative references (5)

3General requirements (6)

3.1Pre-conditioning (6)

3.2Test temperature (6)

3.3Test voltage (6)

3.4Test values (6)

4Definitions (6)

5Electrical d.c. resistance of conductor (6)

6Voltage test on completed cable (6)

7Voltage test on cores in water (7)

7.1Test sample (7)

7.2Procedure (7)

7.3Requirement (7)

8Insulation resistance test (7)

8.1Insulation resistance for cables having maximum conductor temperatures

not exceeding 90 °C (7)

8.1.1Test sample (7)

8.1.2Procedure (8)

8.1.3Requirement (8)

8.2Insulation resistance for cables with maximum conductor temperatures

exceeding 90 °C (8)

8.2.1Test sample (8)

8.2.2Procedure (8)

8.2.3Requirement (8)

9Long term resistance of insulation to d.c (9)

9.1Test sample (9)

9.2Procedure (9)

9.3Requirement (10)

10Check for the absence of faults in insulation (10)

10.1General (10)

10.2Spark test (10)

10.2.1Procedure (10)

10.2.2Requirement (10)

10.3Voltage test (10)

10.3.1Procedure................................................................................................................10--` ` , , ` , , ` , ` ` ` , , , ` , ` , ` ` ` ` ` ` ` , , ` -` -` , , ` , , ` , ` , , ` ---

EN 50395:2005 – 4 –

10.3.2 Requirement (10)

11 Surface resistance of sheath (11)

11.1 Test samples........................................................................................................................11 11.2 Procedure.............................................................................................................................11 11.3 Requirement. (11)

12 Transfer impedance......................................................................................................................11 Annex A. (12)

A.1 Basic formula........................................................................................................................12 A.2 Rounding..............................................................................................................................12 A.3

Examples of calculation (12)

Annex B (informative) Source of electrical test methods in EN 50395.............................................13 Bibliography..........................................................................................................................................14 Figure 1 – Positioning of electrodes (9)

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– 5 – EN 50395:2005 Introduction

EN 50395 contains the electrical test methods that are used for harmonized low voltage energy cables. These electrical test methods include all those previously contained in HD 21 and HD 22. Annex B gives a comparison between the original location of each test method and its place in this new European Standard.

The content of EN 50395 is not, and will not be, restricted only to test methods for cables to HD 21 and HD 22. Other test methods for harmonized LV cables may be included. Furthermore, the use of test methods in EN 50395 for cables outside HD 21 and HD 22 is not prohibited, but it is strongly recommended that expert advice be taken before such use, or before any proposal for incorporation into another standard.

1 Scope

EN 50395 contains electrical test methods required for the testing of harmonized low voltage energy cables, especially those rated at up to and including 450/750 V.

NOTE 1 A description of the origin of these test methods and the background to this European Standard is given in the Introduction and in Annex B.

The particular cable standard dictates the tests which need to be performed on the relevant cable type. It also specifies whether the specific test is a type test (T), a sample test (S) or a routine test (R) for the particular cable type.

NOTE 2 T, S and R are defined in the relevant cable standard.

The requirements to be met during or after the test are specified for the particular cable type in the relevant cable standard. However, some test requirements are obvious and universal, such as the fact that no breakdown shall occur during voltage tests, and these are stated in the particular test method.

Test methods for use specifically in utility power cables are not covered by this European Standard. They can be found in HD 605.

Test methods for use specifically in communications cables are the responsibility of the Technical Committee CENELEC TC 46X, Communication cables. At present such test methods are given in EN 50289 series.

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.

EN 50289-1-6 2002 Communication cables – Specifications for test methods -

Part 1-6: Electrical test methods – Electromagnetic performance

EN 50356 2002 Method for spark testing of cables

EN 60228 2005 Conductors of insulated cables

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EN 50395:2005 – 6 –

3 General requirements

3.1 Pre-conditioning

All the tests shall be carried out not less than 16 h after the extrusion or cross-linking, if any, of the insulating or sheathing compounds.

3.2 Test temperature

Unless otherwise specified, tests shall be made at an ambient temperature of (20 ± 15) °C.

3.3 Test voltage

Unless otherwise specified in the individual clause of this European Standard or in the product standard, the test voltage shall be a.c. of approximately sine-wave form and of frequency between 49 Hz and 61 Hz. The ratio of peak value to r.m.s. value shall be equal to √2 with a tolerance of ± 7 %. The values quoted are r.m.s. values.

3.4 Test values

Full test conditions (such as temperatures, durations, etc.) and full test requirements are not specified in this European Standard; it is intended that they should be specified by the standard dealing with the relevant type of cable.

Any test requirements which are given in this European Standard may be modified by the relevant cable standard to suit the needs of a particular type of cable.

4 Definitions

For the purposes of this document, the following terms and definitions apply.

4.1

median value

when several test results have been obtained and ordered in an increasing or decreasing succession, the median value is the middle value if the number of available values is odd, and is the mean of the two middle values if the number is even

5 Electrical d.c. resistance of conductor

The test shall be carried out in accordance with Annex A of EN 60228.

6 Voltage test on completed cable

If the cable has no metallic layer, a sample of the cable as manufactured shall be immersed in water. The length of the sample, the temperature of the water and the period of immersion shall be as specified in the cable standard. A voltage shall be applied between conductor(s) and groups of conductors in such a way that the insulation on each core is tested against all adjacent cores and the water.

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– 7 – EN 50395:2005 If the cable has a metallic layer, a sample of the cable shall be taken of the length specified in the cable standard. A voltage shall be applied between conductor(s) and groups of conductors in such a way that the insulation on each core is tested against all adjacent cores and the metallic layer, which shall be earthed.

If the cable has a metallic strain-bearing member, this shall be connected to the water or to the metallic layer, as appropriate.

In each case, the voltage and the duration of its application shall be as specified in the cable standard. The voltage shall be increased gradually on each occasion to the specified value.

No breakdown of the insulation shall occur during the test.

7 Voltage test on cores in water

The test applies to sheathed cables, braided cables and flat unsheathed cords.

NOTE For 1-core unsheathed cables, the test in Clause 6 generally applies, in which case this test on cores is not required.

7.1 Test sample

Prepare a sample of cable 5 m long, by carefully removing, without damaging the cores, the sheath or the overall braid and any other covering or filling from a length of completed cable.

In the case of flat unsheathed cord, make a cut in the insulation between the cores, and separate the cores by hand for a length of 2 m.

7.2 Procedure

Immerse the sample in water at the temperature, and for the period, specified in the cable standard. Ensure that the ends of the cores protrude above the water by a distance sufficient to prevent excessive surface leakage when the test voltage is applied. Apply a voltage, of the magnitude specified in the cable standard, between the conductors and the water for the time specified in the cable standard.

7.3 Requirement

No breakdown of the insulation shall occur during the test.

8 Insulation resistance test

8.1

I nsulation resistance for cables having maximum conductor temperatures not

exceeding 90 °C

sample

8.1.1 Test

Make the test on a sample of cable 5 m long, previously submitted to the test specified in Clause 7 or, in the case of 1-core unsheathed cable, to the test described in Clause 6.

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EN 50395:2005 – 8 –

8.1.2 Procedure

Immerse the sample in water previously heated to the temperature specified in the cable standard, with a length of about 250 mm at each end of the sample projecting above the water, for the period of time specified in the cable standard.

Apply a d.c. voltage of between 80 V and 500 V between each conductor and the water.

Measure the insulation resistance of each core 1 min after application of the voltage. Use this value to calculate the insulation resistance of a 1 km length of each core.

8.1.3 Requirement

None of the resulting values shall be below the minimum insulation resistance value specified in the cable standard.

8.2 Insulation resistance for cables with maximum conductor temperatures

exceeding 90 °C

NOTE Further basic information on this test method may be obtained from HD 429, Clause 6 “Test pieces for the volume resistivity measurement”.

8.2.1 Test

sample

Make the test on the same sample of cable used for the voltage test in Clause 7 or, in the case of 1-core unsheathed cable, to the test described in Clause 6.

8.2.2 Procedure

Cut a test piece 1,40 m long from the cable or core to be tested. Cover this test piece with a semi-conducting layer, and over this layer apply a metal braid or a metal tape in such a way as to obtain an active measuring length of 1,0 m.

At both ends of the active measuring length, leaving a gap 1 mm wide, apply a protective wire binding of approximately 5 mm length (see Figure 1).

Wind the test piece to form a ring with a diameter of approximately 15D but at least 0,20 m (D = nominal outer diameter of insulation).

Maintain the test piece in an air oven for at least 2 h at the test temperature specified in the relevant cable standard, leaving a clearance between the sample and the walls of the air oven of at least 50 mm.

After the conditioning period a d.c. voltage between 80 V and 500 V shall be applied between the conductor and the screen (semi-conducting layer and metal braid/metal tape including the protective wire binding), the sample still being kept in the air oven.

The insulation resistance shall be measured 1 min after application of the voltage and this value shall be used to calculate the insulation resistance of a 1 km length of cable.

8.2.3 Requirement

None of the resulting values shall be below the minimum insulation resistance value specified in the cable standard.

NOTE Annex A shows the calculation method for minimum insulation resistance.

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– 9 – EN 50395:2005

Key

1 guard electrode (protective wire binding)

2 screen electrode

Figure 1 – Positioning of electrodes

9 Long term resistance of insulation to d.c.

9.1 Test sample

Carry out the test on a sample of cable of 5 m length from which all coverings have been removed. The cores of flat unsheathed cords shall not be separated.

For cables having up to five cores, each core shall be tested. For multicore cables having more than five cores, one core of each colour in the cable shall be tested, and where the number of colours is less than 5, duplicate coloured cores shall be tested as necessary to bring the number of cores tested up to a minimum of 5.

Take care to avoid damage to the core(s) during removal of the coverings.

9.2 Procedure

Immerse the sample, for the period and at the temperature given in the relevant cable standard, in an aqueous solution of sodium chloride having a concentration of 10 g/l, with a length of about 250 mm at each end of the sample projecting above the solution. Connect the negative pole of a 220 V d.c. supply to the conductor(s) of the sample and the positive pole to a copper electrode immersed in the solution for the time given in the relevant cable standard. --` ` , , ` , , ` , ` ` ` , , , ` , ` , ` ` ` ` ` ` ` , , ` -` -` , , ` , , ` , ` , , ` ---

EN 50395:2005 – 10 –

9.3 Requirement

No breakdown of the insulation shall occur during the test and, after the test, the exterior of the insulation shall show no sign of damage.

NOTE Discoloration of the insulation should be ignored.

10 Check for the absence of faults in insulation

10.1 General

Test all cable that is in the final stage of manufacture, whether it is in delivery lengths or in manufacturing lengths prior to being cut into delivery lengths.

Test single core cables, whether sheathed or unsheathed, by the spark test in accordance with 10.2. Test all other cables, including sheathed flat cables, by the voltage test in accordance with 10.3.

The requirements of 3.1 of this European Standard do not apply when the check for absence of faults is carried out as a Routine (R) test.

10.2 Spark test

10.2.1 Procedure

Carry out the test according to EN 50356, except that the option to use a pulsed waveform high

voltage source is not permitted.

10.2.2 Requirement

No faults shall be detected during the test.

10.3 Voltage test

10.3.1 Procedure

With the cable in the dry state and at ambient temperature apply a voltage of the magnitude given in the relevant cable standard, supplied either from an a.c. source or from a d.c. source, between each conductor and all the other conductors and, if any, the metallic layer connected to earth.

Increase the voltage gradually and maintain it at the full value for the duration given in the relevant cable standard.

10.3.2 Requirement

No breakdown of the insulation shall occur during the test. --` ` , , ` , , ` , ` ` ` , , , ` , ` , ` ` ` ` ` ` ` , , ` -` -` , , ` , , ` , ` , , ` ---

– 11 – EN 50395:2005 11 Surface resistance of sheath

11.1 Test samples

Carry out the test on three samples of completed cable, each about 250 mm in length.

11.2 Procedure

Clean the sheath of each of the samples with industrial methylated spirit, and apply to each sample two electrodes, consisting of wire helices of copper wire of between 0,2 mm and 0,6 mm diameter, at a distance of (100 ± 2) mm from each other. After the wire has been applied, clean the surface of the sheath again thoroughly between the electrodes.

Condition the samples with electrodes attached in a conditioning chamber at a temperature of (20 ± 2) °C and a relative humidity of (65 ± 5) % for 24 h.

Immediately after removal from the conditioning chamber, apply a d.c. voltage of between 100 V and 500 V between the electrodes, and measure the resistance after 1 min.

Multiply the measured resistance of each sample, in ohms, by a/100, where a is the circumference of the sheath of the sample, in millimetres. Record the median of the three values so obtained as the surface resistance of the sheath.

11.3 Requirement

The median of the three values so obtained shall be not lower than the value in the cable standard.

12 Transfer impedance

The test shall be carried out in accordance with EN 50289-1-6, clause 6.

NOTE EN 50289-1-6 is maintained by the Technical Committee CENELEC TC 46X, Communication cables.

C O M

EN 50395:2005 – 12 –

Annex A (informative)

Calculation of minimum insulation resistance

A.1 Basic formula

The general basic formula is:

=?d D R log .10..0367,08ρ

where:

R =

insulation resistance in M ?.km

ρ = volume resistivity in ?.m

d = th

e diameter o

f the bare conductor as given in EN 60719 Table 1 (class 1 and class 2 conductors) or Table 2 (class 5 and class 6 conductors)

D = d + twice the specified mean value of the thickness of the insulation and any mandatory separator between conductor and insulation.

NOTE For cables with PVC insulation, the volume resistivity of the insulation compounds at the operating temperature of the cable is assumed to be 10+8?.m. Thus the general formula reduces to:

km .M log 0,0367. = ?

d D R

A.2 Rounding

As the requirement in cable standards is for a minimum value the calculated value of R should be rounded down to two significant figures.

A.3 Examples of calculation

HD 21.3 S3, Table 1, H07V-R

Conductor cross-section

Insulation thickness

Conductor diameter (d ) Overall diameter R R (rounded)

mm2 mm mm mm M ?.km M ?.km 1,5 35 50

0,7 1,2 1,4

1,45 7,0 8,2

2,85 9,4 11,0

0,010 77 0,004 699 0,004 682

0,010 0,004 6 0,004 6

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W

W

W

.C

E S – 13 – EN 50395:2005

Annex B (informative)

Source of electrical test methods in EN 50395

Source (subclause number) Test HD 21.2 S3

HD 22.2 S3

Clause in EN 50395

Electrical resistance of conductor 2.1 2.1 5 Voltage test on completed cable

2.2 2.2 6 Voltage test on cores 2.3 2.3 7 Insulation resistance

2.4

2.4

8

Long term resistance of insulation to d.c. 2.5 2.5 9 Test to check

absence of faults on insulation

2.6 2.6 10

Transfer impedance (Screening efficiency) 2.7 - 12 Surface resistance of sheath

2.8 2.7 11

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EN 50395:2005 – 14 –

Bibliography

The following documents are referred to in the text for information. HD 21.2 S3:1997

Cables of rated voltages up to and including 450/750 V and having thermoplastic insulation - Part 2: Test methods

HD 22.2 S3:1997

Cables of rated voltages up to and including 450/750 V and having cross-linked insulation - Part 2: Test methods

HD 429 Methods of test for volume resistivity and surface resistivity of solid electrical insulating materials (IEC 60093) HD 605

Electric cables - Additional test methods

EN 50289 Series

Communication cables - Specifications for test methods

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