1、 GUIDE FOR ESTABLISHING STABILITY OF VOLUME RESISTIVITY FOR SEMICONDUCTING POLYMERIC COMPONENTS OF POWER CALBES ICEA T-25-425-2015 2015 by INSULATED CABLE ENGINEERS ASSOCIATION, INC. ICEA T-25-425-2015 Insulated Cable Engineers Assoc., Publication No. T-25-425-Revised 2015 Guide For Establishing Sta
2、bility Of Volume Resistivity For Semiconducting Polymeric Components Of Power Cables Published by Insulated Cable Engineers Association, Inc. Approved September 16, 2015 by Insulated Cable Engineers Association, Inc. Copyright 2015 by the Insulated Cable Engineers Association. All rights including
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5、ation, Inc. (ICEA) standards and guideline publications, of which the document contained herein is one, are developed through a voluntary consensus standards development process. This process brings together persons who have an interest in the topic covered by this publication. While ICEA administer
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10、o someone else. Anyone using this document should rely on his or her own independent judgement or, as appropriate, seek the advice of a competent professional in determining the exercise of reasonable care in any given circumstances. Information and other standards on the topic covered by this publi
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12、ducts, designs, or installations for safety or health purposes. Any certification or other statement of compliance with any health or safety-related information in this document shall not be attributable to ICEA and is solely the responsibility of the certifier or maker of the statement. ICEA T-25-4
13、25-2015 Page i Copyright 2015 by the Insulated Cable Engineers Association, Incorporated. CONTENTS Page Foreword ii Scope iii Section 1 Samples 1 1.1 Samples . 1 Section 2 Specimens 1 2.1 Stress control layer (conductor shield) . 1 2.2 Insulation Shield Polymeric . 1 2.3 Semiconducting Jacket . 1 Se
14、ction 3 Electrodes . 1 3.1 High Degree of Accuracy 1 3.2 Lesser Degree of Accuracy . 2 Section 4 Test Equipment . 2 Section 5 Test Procedure 2 Section 6 Demonstration of Stability of Volume Resistivity . 3 ICEA T-25-425-2015 Page ii Copyright 2015 by the Insulated Cable Engineers Association, Incorp
15、orated. Foreword ICEA publications are adopted in the public interest and are designed to eliminate misunderstanding between the manufacturer and user and to assist the user in selecting and obtaining proper products for his particular need. Existence of an ICEA publication does not in any respect p
16、reclude the manufacture or use of products not conforming to the publication. The user of this publication is cautioned to observe any health or safety regulations and rules relative to the manufacture and use of cable covered by this document. T-25-425 was revised and approved by ICEA in September
17、16, 2015. Suggestions for improvements in this publication are welcome, and should be sent to ICEA at the address below. Insulated Cable Engineers Association, Inc. ICEA T-25-425-2015 Page iii Copyright 2015 by the Insulated Cable Engineers Association, Incorporated. Scope This guide applies to test
18、ing of extruded semiconducting polymeric components of power cable with extruded insulation. It describes a method of demonstrating the stability over a period of time of the volume resistivity (calculated from longitudinal resistance) of these components at temperatures up to the emergency operatin
19、g temperature of the cable. ICEA T-25-425-2015 Page iv Copyright 2015 by the Insulated Cable Engineers Association, Incorporated. ICEA T-25-425-2015 Page 1 Copyright 2015 by the Insulated Cable Engineers Association, Incorporated. Section 1 Samples 1.1 SAMPLES Representative samples shall be obtaine
20、d from lengths of completed extruded dielectric power cable with extruded shields. From these samples, test specimens shall be prepared for application of electrodes. Section 2 Specimens Longitudinal resistance samples shall be a minimum of 5.0 inches (127 mm) long. 2.1 STRESS CONTROL LAYER (CONDUCT
21、OR SHIELD) Test specimens shall be prepared by cutting a sample in half longitudinally and removing the conductor. One of the halves shall have electrodes applied and be tested as described below. The other half may be discarded. The coverings over the insulation may or may not be removed depending
22、upon the method used to attach external connections to the electrodes as described in 3.0. 2.2 INSULATION SHIELD POLYMERIC Test specimens shall be prepared by removing from a sample all coverings and metals (including those embedded in the polymer) over the semiconducting polymeric shield. 2.3 SEMIC
23、ONDUCTING JACKET Test specimens shall be prepared by making a longitudinal cut through the jacket then removing the jacket from the sample. Section 3 Electrodes Electrodes for longitudinal resistance specimens shall be applied as follows. 3.1 HIGH DEGREE OF ACCURACY When a high degree of accuracy is
24、 required four electrodes shall be applied with separation specified in 3.1.1 to an exposed surface of the semiconducting component. The electrode shall be painted using a conductive paint (silver or similar) and a suitable paint brush, e.g., an artists type with a brush not larger than 1/8” (3mm).
25、After the paint has been allowed to dry for at least one hour at room temperature, external connections shall be attached to each of the electrodes. Copper wires wrapped around the electrodes make suitable leads for the insulation shield specimens. Wires may also be used for stress control layer spe
26、cimens, if the insulation shield is removed and electrodes applied as a ring to the stress control layer and the insulation. ICEA T-25-425-2015 Page 2 Copyright 2015 by the Insulated Cable Engineers Association, Incorporated. 3.1.1 Electrode Spacing Two of the electrodes shall be placed at least 2”
27、(50.8 mm) apart and be used for potential measurements. The other two electrodes shall be used for passage of current and one of these shall be placed at least 1” (25.4 mm) beyond each potential electrode. 3.2 LESSER DEGREE OF ACCURACY When a high degree of accuracy is not required only two electrod
28、es shall be applied with separation specified in 3.1.1 and spaced at least 2” (50.8 mm) apart may be used for potential measurements and passage of current. External connections shall be applied to each of the electrodes as in 3.1.1 or an alligator clip or equivalent may be used to connect leads to
29、the electrodes on stress control layer and jacket specimens. Section 4 Test Equipment A suitable instrument (e.g., Wheatstone or Kelvin Bridge) or instruments (e.g., voltmeter and ammeter) for determining resistance and a source of 60 Hz ac or dc voltage. The energy released in the semiconducting co
30、mponent shall not exceed 100 milli-watts. A convection-type forced-draft, circulating air oven, capable of maintaining any constant ( 1 C) temperature up to 140 C. A recorder for measuring oven temperature continuously Section 5 Test Procedure Connect the two outer electrodes (current) in series wit
31、h the current source and an ammeter or the current leads of a bridge. Connect the two inner electrodes (potential) to potentiometer leads of a bridge or to a voltmeter. The dc or 60 Hz ac resistance of the semiconducting component between the electrodes shall be determined at room temperature. The s
32、pecimen shall next be placed in an oven preheated to the temperature ( 1 C) specified in Table 1 and the resistance determined after 24 hours and 14 days and at 14 day intervals thereafter for a minimum of 42 days. The oven temperature shall be recorded continuously. Note: it may be necessary to rep
33、aint the electrodes and tighten the wire leads after each reduction in oven temperature. When stability has been demonstrated by the calculation of 6.0, the oven temperature shall be reduced in 20 C increments every 24 hours and resistance determined at each 20 C lower temperature, with the final me
34、asurement being made at room temperature. Each resistance determination shall be converted to volume resistivity by the following formula using dimensions from the cable samples. ICEA T-25-425-2015 Page 3 Copyright 2015 by the Insulated Cable Engineers Association, Incorporated. L)dD(kRP10022=Where:
35、 P = Volume resistivity (rho) in ohm-meters. R = Measured resistance in ohms. D = Diameter over the semiconducting component in inches. d = Diameter under the semiconducting component in inches. L = Distance between potential electrodes in inches. k = 1 for a conductor stress control component and 2
36、 for an insulation shield component or a conducting jacket. Note: When dimensions are expressed in millimeters, include a 25.4 multiplying conversion factor in the denominator of the formula. Section 6 Demonstration of Stability of Volume Resistivity A semiconducting component demonstrates stability
37、 of volume resistivity whenever the following equation is satisfied. Rho shall also remain less than the maximum value specified in the applicable standard during the entire testing period, including the reduction in oven temperature to room temperature. n)n()n()n(PLog.PLogPLogPLog10421028101410330
38、+oror 34228142n)n()n()n(PPPP Where: Pn = Volume Resistivity Calculated at the n-th day, when n 42. P(n-14) P(n-28) = Volume Resistivity calculated at intervals of 14, 28, and 42 days prior to Pn P(n-42) respectively. When the total duration of the test is 42 days, the 24 hour reading shall be used f
39、or P(n-42). The requirement for resistivity stability may be satisfied at 42 days or at the end of any 14 day incremental period thereafter. ICEA T-25-425-2015 Page 4 Copyright 2015 by the Insulated Cable Engineers Association, Incorporated. Table I Test Temperatures Oven Temperature (C ) Cables Rat
40、ed 5 Thru 46 kV Cables Rated 46 kV For 75 C Rated Cables* For 90 C Rated Cables* For 105 C Rated Cables* 105C Emergency Rated Cables* 130C Emergency Rated Cables* Semiconducting Jackets 80 110 120 80 110 Insulation Shield 85 110 125 90 110 Stress Control Shield 90 130 140 105 130 *Note these ratings apply to cable designs, not materials.
