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1、BRITISH STANDARD BS 7816-3: 1998 IEC 61244-3: 1998 Long-term radiation ageing in polymers Part 3: Procedures for in-service monitoring of low-voltage cable materials ICS 29.035.20 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:03:00 GMT+00:00 2006, Uncontrol
2、led Copy, (c) BSI BS 7816-3:1998 This British Standard, having been prepared under the direction of the Electrotechnical Sector Board, was published under the authority of the Standards Board and comes into effect on 15 July 1998 BSI 05-1999 ISBN 0 580 30035 8 National foreword This Part of BS 7816
3、reproduces verbatim IEC 61244-3:1998 and implements it as the UK national standard. NOTEIEC 61244-3:1998 is a Technical Report type 2, issued as a “prospective standard for provisional application”. It is not to be regarded as an “International Standard”. A review will be carried out not later than
4、three years after its publication, with the options of its extension for a further three years, or conversion to an International Standard, or withdrawal. The UK participation in its preparation was entrusted by Technical Committee GEL/15, Insulating materials, to Subcommittee GEL/15/5, Methods of t
5、est, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promul
6、gate them in the UK. A list of organizations represented on this subcommittee can be obtained on request to its secretary. From 1 January 1997, all IEC publications have the number 60000 added to the old number. For instance, IEC 27-1 has been renumbered as IEC 60027-1. For a period of time during t
7、he change over from one numbering system to the other, publications may contain identifiers from both systems. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section enti
8、tled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Complia
9、nce with a British 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, the CEI IEC title page, pages ii to iv, pages 1 to 30 and a back cover. This standard has been updated (see copyright
10、date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No.DateComments Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:03:00 GMT+00:00 2006, Uncontrolle
11、d Copy, (c) BSI BS 7816-3:1998 BSI 05-1999i Contents Page National forewordInside front cover Text of CEI IEC 61244-31 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:03:00 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ii blank Licensed Copy: London South Bank U
12、niversity, London South Bank University, Fri Dec 08 12:03:00 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:03:00 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7816-3:1998 ii BSI 05-1999 Contents Page Introduction1
13、1Scope1 2Requirements of a monitoring technique1 3Techniques available1 3.1Local tests without sampling2 3.1.1Indenter2 3.1.2Sonic velocity3 3.1.3Near infrared reflectance3 3.1.4Torque tester4 3.2Local tests with microsampling4 3.2.1Infrared spectroscopy (IR)4 3.2.2Oxidation induction time (OIT)5 3.
14、2.3Plasticizer content5 3.2.4Density6 3.3Global tests with spatial resolution6 3.3.1Time domain reflectometry (TDR)6 3.3.2Partial discharge (PD)7 3.4Global tests without spatial resolution7 3.4.1Time domain spectrometry (TDS)7 3.4.2Dielectric loss7 3.4.3Pass/fail tests8 3.5Paced tests8 4Summary9 Ann
15、ex A (informative) Bibliography29 Figure 1 Cross-section of the indenter 111 Figure 2 Effect of jacket temperature on indenter modulus of EPR/CSPE after thermal ageing 412 Figure 3 Results with indenter on EPR/CSPE cable13 Figure 4 Results with indenter on kerite KR cable14 Figure 5 Schematic diagra
16、m showing the operating principles of the sonic velocity meter 615 Figure 6 Sonic velocity test results16 Figure 7 Variation in IR absorbance with wavelength for PVC material and the use of first derivative to eliminate baseline shifts 617 Figure 8 Correlation of first derivative of IR absorbance at
17、 1 640 nm to 1 650 nm and elongation at break for thermal ageing of PVC at 110 C 618 Figure 9 Schematic diagram of prototype device for torque measurement of cables 818 Figure 10 Elongation at break versus torque value for flame-retardant PVC cables thermally aged at 158 C 819 Figure 11 Elongation a
18、t break versus torque value for PVC cables exposed to sequential radiation ageing to 0,5 MGy and thermal ageing at 120 C 819 Figure 12 Elongation at break versus torque value for PVC cables thermally aged at 120 C 820 Figure 13 Carbonyl absorbance as a function of the radiation dose for XLPE 1120 Fi
19、gure 14 Carbonyl absorbance as a function of thermal ageing for XLPE 1021 Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:03:00 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7816-3:1998 BSI 05-1999iii Page Figure 15 Correlation between elongation at break and
20、 oxidation induction time for unfilled XLPE insulation thermally aged at 130 C 921 Figure 16 Correlation between elongation at break and oxidation induction time for EPR insulation thermally aged at 140 C 922 Figure 17 Correlation between elongation at break and plasticizer content for PVC insulatio
21、n thermally aged at 120 C 922 Figure 18 Correlation between elongation at break and density for radiation-aged cable insulation 1523 Figure 19 Correlation between elongation at break and density for radiation-aged cable jackets 1523 Figure 20 Density profiles through the thickness of unaged and radi
22、ation-aged XLPE 1524 Figure 21 Time domain signature files for a lighting circuit with switches on and off, showing location of first switch24 Figure 22 Schematic representation of a partial discharge signal propagating in a shielded cable and the signals recorded by the detection instrument 1925 Fi
23、gure 23 Spatial distribution of discharge pulses along a cable length (unshielded) containing a known defect at 6,1 m 2025 Figure 24 Schematic diagram of the measuring set-up for time domain spectrometry 1926 Figure 25 Time domain spectrometry measurements on thermally aged EPDM/CSPE cables 1926 Fig
24、ure 26 Effect of cable temperature on a tan versus frequency spectrum of an EVA cable 2327 Figure 27 Effect of radiation dose rate on the tan versus frequency spectrum of XLPE insulation 2327 Figure 28 Effect of radiation ageing on the tan versus frequency spectrum of a PVC insulated cable 2328 Figu
25、re 29 Correlation between tan at specific frequencies and elongation at break for PVC cables 2328 Table 1 Summary of currently available techniques for cable condition monitoring10 Table 2 Current status of the most developed monitoring techniques11 Licensed Copy: London South Bank University, Londo
26、n South Bank University, Fri Dec 08 12:03:00 GMT+00:00 2006, Uncontrolled Copy, (c) BSI iv blank Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:03:00 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7816-3:1998 BSI 05-19991 Introduction Polymers are widely used
27、 as electrical insulating materials (e.g. in cables for control, instrumentation and power) in environments in which they are exposed to radiation. In such applications, these materials may well be required to survive the full working life of the plant, which may be more than 40 years, and accident
28、conditions at the end of working life. Although considerable data are available on the behaviour of polymeric insulating materials under irradiation, there is still some uncertainty on the effects of long-term low dose rate irradiation, such as would be experienced by cables. There is therefore a re
29、quirement for techniques for monitoring the state of degradation of cable materials in situ throughout the lifetime of the plant. Suitable cable monitoring techniques would also be important to surveillance programmes in support of plant life extension and licence renewal. Although this report is pr
30、imarily aimed at cable condition monitoring in nuclear power plants, it can also be applied to other polymeric components. Many of the techniques are equally applicable to thermal-only ageing of polymeric components in conventional power plants. 1 Scope This technical report summarizes the main cabl
31、e monitoring techniques which are currently being assessed worldwide. These techniques are primarily aimed at monitoring degradation of low-voltage cables. Most of the methods are at the development stage and require in-plant evaluation before they could be recommended as standard techniques. The ad
32、vantages and disadvantages of each method, and its current state of development, are outlined in the following sections. There are two aspects of cable monitoring that need to be taken into account techniques suitable for ageing evaluation and techniques suitable for monitoring faults in cables. The
33、 methods discussed may, in some cases, be more suitable for monitoring faults than for evaluating the degree of degradation of the cable materials. 2 Requirements of a monitoring technique There is a range of requirements which the ideal cable monitoring technique would need to satisfy. In practice,
34、 no one technique will satisfy all of the requirements and a range of techniques is likely to be needed. In each case, baseline data (i.e. data on unaged material of the same formulation and manufacturer) are needed to make full use of the techniques. The ideal monitoring technique would have the fo
35、llowing attributes: non-destructive; capable of use during normal operation; not require disconnection of equipment; related to an identifiable degradation criterion; applicable to a wide range of cable materials and configuration; applicable at accessible locations; capable of identifying hot-spots
36、; reproducible and capable of compensating for environmental conditions (temperature, humidity); less expensive to implement than periodic cable replacement; readily available reference data. 3 Techniques available There is a wide range of possible techniques being considered for cable monitoring. A
37、 few are already in use in-plant, others are only at the laboratory evaluation stage. The methods can be grouped together under generic types, as follows. Local tests without sampling indenter sonic velocity near infrared reflectance torque testing Local tests with micro-sampling infrared oxidation
38、induction time (OIT) plasticizer content density Global tests with spatial resolution time domain reflectometry (TDR) partial discharge Global tests without spatial resolution dielectric loss time domain spectrometry (TDS) pass/fail tests dielectric strength, insulation resistance Paced tests elonga
39、tion at break Each of these types of test is described in more detail in the following subclauses. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 12:03:00 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7816-3:1998 2 BSI 05-1999 3.1 Local tests without sampling T
40、he term “local” refers to techniques which give information on the state of the cable at the measuring point only and are thus likely to miss defective spots. These methods can only be applied in man-accessible areas and are generally limited to tests of the cable jacket material except at terminati
41、ons where the insulation is exposed. Where the techniques have been cross-correlated with changes in elongation at break, these methods have a predictive capability. This type of test will provide immediate data in-plant on the state of the cable. Where the cable jacket is more likely to degrade tha
42、n the insulation (which is often true) the methods provide early warning of cable failure. Local bend tests by manipulation of the cable by hand can give qualitative information when carried out by experienced personnel. 3.1.1 Indenter The indenter is a portable device developed by the Franklin Inst
43、itute which measures a property related to the modulus of elasticity of cable jacket and insulation materials 1 21). A schematic diagram of the indenter is shown in Figure 1. An instrumented probe of known shape is driven against the outside of the cable at a fixed velocity (12,7 mm/min) and the slo
44、pe of the force versus distance is obtained over a force range of 2 N to 9 N. The probe shape used is the same as that used in the ASTM standard for hardness testing 3, i.e. a truncated cone, but with an end area equal to half that of the ASTM cone. The indenter modulus values measured with the port
45、able indenter have to be corrected for temperature to obtain comparable data sets when used in-plant. The amount of temperature compensation required varies with the ageing of the cable material 4, see Figure 2. Practical tests of the unit in nuclear power plants have shown that the indenter can be
46、successfully used in situ to test cables in trays, panels and junction boxes, provided that about 7,5 cm of exposed cable are accessible 4. In accelerated ageing tests, good correlation has been obtained between modulus measurements and elongation at break for polyvinyl chloride (PVC) jacketed cable
47、s, chlorosulphonated polyethylene (CSPE) and a range of elastomers 4 5 6. Examples are shown in Figure 3 and Figure 4 for an ethylene propylene (EPR)/CSPE cable and for an EPR based cable (kerite FR) respectively. The indenter does not appear to be suitable for use with polyolefins and radiation age
48、d PVC because their modulus changes very little with ageing. More recent indenter data indicates that the method may be usable with these materials with a modified technique 7. Limitations: By its very nature, the indenter can only measure the properties of the cable material over a limited area in
49、the vicinity of the probe. The indenter modulus values obtained can show a marked variation if the jacket thickness is variable, increasing as the thickness decreases. The construction of the cable, for example the presence of armouring or shielding, is also likely to affect the modulus value. Because of this, extensive baseline data would be required to cover the range of cable m