1、BRITISH STANDARD BS 7923:2004 Electric cables Internal gas-pressure cables and accessories for alternating voltages up to and including 275 kV (U m= 300 kV) Requirements and test methods (Implementation of HD 634) ICS 29.060.20 BS 7923:2004 This British Standard was published under the authority of
2、the Standards Policy and Strategy Committee on 4 August 2004 BSI 4 August 2004 The following BSI references relate to the work on this British Standard: Committee reference GEL/20/16 Draft for comment 95/215973 DC ISBN 0 580 38567 1 Committees responsible for this British Standard The preparation of
3、 this British Standard was entrusted by Technical Committee GEL/20, Electric cables, to Subcommittee GEL/20/16, Medium/high voltage cables, upon which the following bodies were represented: British Approvals Service for Cables British Cables Association British Plastics Federation Energy Networks As
4、sociations ERA Technology Ltd. Co-opted members Amendments issued since publication Amd. No. Date CommentsBS 7923:2004 BSI 4 August 2004 i Contents Page Foreword ii 1S c o p e 1 2 Normative references 1 3T e r m s a n d d e f i n i t i o n s 1 4 Voltage designation 1 5 Characteristics 2 6 Test categ
5、ories, frequency and conditions 3 7 Routine tests on cables 4 8 Sample tests on cables 5 9 Routine tests on accessories 7 10 Sample tests on accessories 8 11 Type tests on cables and accessories 8 12 Non-electrical type tests on cables 15 13 Non-electrical type tests on accessories 18 14 Tests after
6、 installation 20 Bibliography 25 Table 1 Tan measurement requirements 5 Table 2 High voltage test values 5 Table 3 Diameter of the test cylinder 6 Table 4 Waveshape 13 Table 5 Voltage levels 13 Table 6 Lightning impulse test voltage levels 14 Table 7 Impulse voltage level requirements 19 Table 8 Tes
7、t voltages for salt fog test 19 Table 9 High voltage test levels 20BS 7923:2004 ii BSI 4 August 2004 Foreword This British Standard has been prepared by Subcommittee GEL/20/16. It implements the nationally applicable parts of Harmonization Document HD 634 published by the European Committee for Elec
8、trotechnical Standardization (CENELEC), in accordance with the decision of the CENELEC Technical Board. BS 7923 applies to internal gas-pressure cables and accessories for alternating voltages up to and including 275 kV (U m= 300 kV). It has been assumed in the preparation of this British Standard t
9、hat the execution of its provisions will be entrusted to appropriately qualified and experienced people, for whose use it has been produced. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a B
10、ritish Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 25 and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued. B
11、S 7923:2004 BSI 4 August 2004 1 1 Scope This British Standard specifies tests and requirements for radial-field impregnated-paper-insulated cables and accessories in which, during normal operation, a gas pressure exceeding 1.2 MPa (12 bar) gauge is applied internally, i.e. with the gas in direct con
12、tact with the insulation. It also specifies tests for cables and accessories intended for use in systems with a nominal voltage not exceeding 275 kV between phases. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references,
13、 only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. BS 228:1994, Specification for short-pitch transmission precision roller chains and chain wheels. BS 4727-2:Group 08, Glossary of electrotechnical, power, teleco
14、mmunication, electronics, lighting and colour terms Part 2: Terms particular to power engineering Group 08: Electric cables. IEC 60060-1, High-voltage testing techniques Part 1: General definitions and test requirements. 1) IEC 60228:1978, Conductors of insulated cables. 2) IEC 60229:1982, Tests on
15、cable oversheaths which have a special protective function and are applied by extrusion. IEC 60230, Impulse tests on cables and their accessories. 3) IEC 60507:1991, Artificial pollution tests for high-voltage insulators to be used on a.c. systems. IEC/TS 60859, Cable connections for gas-insulated m
16、etal-enclosed switchgear for rated voltages of 72,5 kV and above Fluid-filled and extruded insulation cables Fluid-filled and dry type cable-terminations. 3 Terms and definitions For the purposes of this British Standard the definitions given in BS 4727-2:Group 08 and the following apply. 3.1 rated
17、voltage U 0 nominal power-frequency voltage between any conductor and armour or earth for which the cable and its accessories are suitable 3.2 rated voltage U nominal power-frequency voltage between phase conductors for which the cable and its accessories are suitable 3.3 maximum voltage U m maximum
18、 sustained voltage between phase conductors for which the cable and its accessories are suitable 3.4 peak voltage U p peak value of the impulse withstand voltage for which the cable and its accessories are suitable 4 Voltage designation Cables and accessories shall be designated by the rated voltage
19、 between conductor and screen U 0and by the rated voltage between conductors U, both in kilovolts, e.g. 76/132 kV. NOTE See IEC 60183. 1) Published by BSI as BS 923-1. 2) Published by BSI as BS 6360. 3) Implemented by CENELEC as HD 48.BS 7923:2004 2 BSI 4 August 2004 5 Characteristics For the purpos
20、e of carrying out and recording the tests described in this British Standard, the following characteristics shall be known or declared for each cable tested: a) rated voltage U 0 , in kilovolts (kV); b) lightning impulse withstand voltage U p , in kilovolts (kV); NOTE 1 The lightning impulse withsta
21、nd voltage U pspecified above for each particular cable should be selected in accordance with IEC 60071-1. c) type of conductor, material, nominal cross-sectional area of the conductors in square millimetres (mm 2 ), and conductor resistance (for conductor resistances, see 7.2); d) conductor resista
22、nce, if the nominal cross-sectional area is not in accordance with the values given in IEC 60228; e) number of cores; f) capacitance between each conductor and screen, in microfarads per kilometre (4F/km); g) maximum permissible conductor temperature, in degrees Celsius (C), for continuous operation
23、 under the specified ambient and installation conditions; h) minimum and maximum permissible static fluid pressure, in kilopascals (kPa) or bars 4) ; i) type and material of the metallic sheath and the construction of the sheath reinforcement, if any; j) thermal resistance between conductor(s) and m
24、etallic sheath, in kelvin metres per watt (K m/W); NOTE 2 The thermal resistance should be calculated using the formulae given in IEC 60287-2-1. k) cable design stress, in kilovolts per millimetre (kV/mm); l) maximum design pressures of accessories, in kilopascals (kPa) (see Clause 9); m) type of co
25、nductor screen (with or without carbon-black paper); n) specified minimum thickness of insulation, nominal thickness of the metallic sheath and anti- corrosion covering, in millimetres (mm); o) nominal outside diameter of the cable and conductor, in millimetres (mm); p) type and material of the corr
26、osion-resistant covering over the metallic sheath; q) cable thermal resistance. The following additional characteristics shall be stated by the manufacturer when requested by the purchaser: 1) details of construction, e.g. shaped or circular conductor, screened or unscreened conductor, types of join
27、t and sealing end, etc.; 2) insulation thickness of the cable, in millimetres (mm), and maximum voltage gradient in the cable insulation at U 0 , in kilovolts per millimetre (kV/mm), neglecting any stranding effect; 3) maximum current rating, in amperes (A), under the specified installation and oper
28、ating conditions; 4) estimated effective (a.c.) resistance, in ohms per kilometre (7/km), of the cable at the maximum operating temperature and under the specified installation conditions; 5) estimated inductance, in henrys per kilometre (H/km), per phase of the completed cable under the specified i
29、nstallation conditions. 4) 1 bar = 10 5 N/m 2= 10 5Pa.BS 7923:2004 BSI 4 August 2004 3 6 Test categories, frequency and conditions 6.1 Categories of tests NOTE Test classified as sample or routine might be required as part of any type approval scheme. 6.1.1 Routine tests Tests made on all production
30、 cable lengths and accessories to demonstrate their integrity. 6.1.2 Sample tests Test made on samples of completed cable or accessories, or components taken from a completed cable or accessory, adequate to verify whether the finished product meets the design specifications. 6.1.3 Type tests Test re
31、quired to be made before supplying a type of cable or accessory covered by this standard on a general commercial basis in order to demonstrate satisfactory performance characteristics to meet the intended application. These tests are of such a nature that, after they have been made, they need not be
32、 repeated unless changes are made in the cable materials, design or type of manufacturing process, which might change the performance characteristics. 6.1.4 Tests after installation Tests intended to demonstrate the integrity of the cable and its accessories after installation and before use. 6.2 Fr
33、equency of tests 6.2.1 Frequency of measurements of dimensions This test shall be carried out on each drum length. 6.2.2 Frequency of bend tests Provided that the total length of cable supplied to the purchaser under a single contact exceeds 50 drums of one type of cable, the test shall be carried o
34、ut on 2 % of drum lengths. 6.3 Test conditions 6.3.1 Ambient temperature Unless otherwise specified in the details for the particular test, tests shall be made at an ambient temperature of (20 15) C. 6.3.2 Frequency of waveform of power frequency test voltage The frequency of the alternating test vo
35、ltages shall be in the range 49 Hz to 61 Hz. The waveform shall be substantially sinusoidal. NOTE The test voltage values quoted are r.m.s. values. 6.3.3 Waveform of impulse test voltage In accordance with IEC 60230, the impulse wave shall have a virtual front time between 14s and 54s and a nominal
36、time to half the peak value between 404s and 604s. In other respects the impulse wave shall be in accordance with IEC 60060-1.BS 7923:2004 4 BSI 4 August 2004 7 Routine tests on cables 7.1 General 7.1.1 The tests specified in 7.2, 7.3, 7.4, 7.5 and 7.6 shall be carried out as routine tests (see 6.1.
37、1) on all completed cables under a single contract. 7.1.2 For the tests specified in 7.3, 7.4 and 7.4, the cables shall be suitably terminated and the tests shall be carried out at atmospheric pressure, except for not-fully-impregnated insulation, for which either atmospheric pressure or an internal
38、 gas pressure not exceeding 200 kPa (2.0 bar) shall be used. 7.2 Conductor resistance test 7.2.1 Procedure The d.c. resistance of conductors in the finished cable shall be measured. The measured value of resistance shall be corrected to a temperature of 20 C and a length of 1 km. The correction for
39、temperature and length shall be made in accordance with IEC 60228. The cable shall be maintained at a reasonably constant temperature for at least 12 h before the test. If there is any doubt as to whether the conductor temperature is the same as the ambient temperature, this period shall be extended
40、 to 24 h. 7.2.2 Requirements 7.2.2.1 The measured value of resistance for 3-core cables (with a nominal cross-sectional area not exceeding 400 mm 2 ) and for single core cables (with a nominal cross-sectional area not exceeding 2 000 mm 2 ), when corrected, shall not exceed the value specified for c
41、lass 2 conductors in columns 8 and 9 (for copper conductors) or column 10 (for aluminium conductors) of IEC 60228:1978, Table II. 7.2.2.2 For cables with a nominal cross-sectional area greater than those specified in 7.2.2.1 or not included in IEC 60228:1978, Table II, the d.c. resistance shall meet
42、 the value stated by the manufacturer. 7.3 Capacitance test 7.3.1 Procedure The capacitance shall be measured at power frequency by means of an a.c. bridge. 7.3.2 Requirement The capacitance of each core shall be not greater than 8 % above the declared value see Clause 5f). 7.4 Tan measurement test
43、7.4.1 Procedure The tan measurement of the insulation shall be made at ambient temperature between each conductor and core screen, employing the following power-frequency test voltages. a) For cables with fully-impregnated insulation, the test voltage shall be increased from 0.25U 0to U 0in steps of
44、 0.25U 0 . The tan at 0.5U 0shall not exceed 0.005 and the increase in tan between 0.25U 0and U 0shall be not more than 0.001 per step of 0.25U 0 , the total increase between 0.25U 0and U 0being not greater than 0.002. b) For cables having not-fully-impregnated insulation, the test voltage shall be
45、increased from 0.25U 0to 0.5U 0 . The tan at 0.25U 0shall not exceed 0.005 and the increase in tan between 0.25U 0and 0.5U 0shall not exceed 0.001. If the measurements are made at a temperature below 20 C, the results shall be corrected to 20 C, either by subtracting from the measured value 2 % of t
46、his value per degree Celsius (C) of the difference between the test temperature and 20 C, or by the use of a correction curve appropriate to the insulation if agreement on such a curve has been reached between the purchaser and the manufacturer. No correction shall be made if the test temperature is
47、 20 C or higher.BS 7923:2004 BSI 4 August 2004 5 7.4.2 Requirement The tan and the tan difference shall not exceed the appropriate values given in Table 1, or the declared values, whichever are the lower. Table 1 Tan measurement requirements 7.5 High-voltage test 7.5.1 Procedure The high-voltage tes
48、t shall be made at ambient temperature, and the test voltage, which shall be either a.c. or d.c., shall be applied for 15 min between each conductor and core screen. The voltage shall be gradually increased to the specified value. The value of the test voltage shall be as follows. a) If an a.c. test
49、 voltage is used, the value of the test voltage shall be as specified in Table 2. NOTE The a.c. test may be made in conjunction with the measurement of tan (see 7.4). b) If a d.c. test voltage is used, the value of the test voltage shall be: 1) for fully-impregnated cables, 5U 0 ; 2) for not-fully-impregnated cables, 4U 0 . Table 2 High voltage test values 7.5.2 Requirement No breakdown of the insulation shall occur. 7.6 Test on oversheath When th
