1、NEMA Standards PublicationNational Electrical Manufacturers AssociationNEMA WC 56-1986 (R2012)3.0 kHz Insulation Continuity Proof Testing of Wire and Cable Copyright 2013 by National Electrical Manufacturers Association NEMA WC 56-1986 (R1993, R2000, R2005, R2012) 3.0 kHz Insulation Continuity Proof
2、 Testing of Wire and Cable Published by: National Electrical Manufacturers Association 1300 North 17th Street Rosslyn, Virginia 22209 www.nema.org Copyright 2013 by the National Electrical Manufacturers Association. All rights including translation into other languages, reserved under the Universal
3、Copyright Convention, the Berne Convention for the Protection of Literary and Artistic Works, and the International and Pan American Copyright Conventions. WC 56-1986 (R1993, R2000, R2005, R2012) Page ii Copyright 2013 by National Electrical Manufacturers Association NOTICE AND DISCLAIMER The inform
4、ation in this publication was considered technically sound by the consensus of persons engaged in the development and approval of the document at the time it was developed. Consensus does not necessarily mean that there is unanimous agreement among every person participating in the development of th
5、is document. The National Electrical Manufacturers Association (NEMA) 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 volunteers and/or seeks out the views of
6、persons who have an interest in the topic covered by this publication. While NEMA administers the process and establishes rules to promote fairness in the development of consensus, it does not write the document and it does not independently test, evaluate, or verify the accuracy or completeness of
7、any information or the soundness of any judgments contained in its standards and guideline publications. NEMA disclaims liability for any personal injury, property, or other damages of any nature whatsoever, whether special, indirect, consequential, or compensatory, directly or indirectly resulting
8、from the publication, use of, application, or reliance on this document. NEMA disclaims and makes no guaranty or warranty, express or implied, as to the accuracy or completeness of any information published herein, and disclaims and makes no warranty that the information in this document will fulfil
9、l any of your particular purposes or needs. NEMA does not undertake to guarantee the performance of any individual manufacturer or sellers products or services by virtue of this standard or guide. In publishing and making this document available, NEMA is not undertaking to render professional or oth
10、er services for or on behalf of any person or entity, nor is NEMA undertaking to perform any duty owed by any person or entity to someone else. Anyone using this document should rely on his or her own independent judgment or, as appropriate, seek the advice of a competent professional in determining
11、 the exercise of reasonable care in any given circumstances. Information and other standards on the topic covered by this publication may be available from other sources, which the user may wish to consult for additional views or information not covered by this publication. NEMA has no power, nor do
12、es it undertake to police or enforce compliance with the contents of this document. NEMA does not certify, test, or inspect products, designs, or installations for safety or health purposes. Any certification or other statement of compliance with any health or safetyrelated information in this docum
13、ent shall not be attributable to NEMA and is solely the responsibility of the certifier or maker of the statement. WC 56-1986 (R1993, R2000, R2005, R2012) Page iii Copyright 2013 by National Electrical Manufacturers Association FOREWORD This standards publication has been prepared to delineate the b
14、asic requirements for spark testing apparatus utilizing a 3 kHz nominal frequency. It is intended as a substitute or an alternative to conventional spark testing at an industrial frequency. The use of an elevated frequency will allow a reduction in the electrode length while exposing the wire or cab
15、le to a suitable number of wave crests. Performance criteria have been included which will stipulate minimum sensitivities for the equipment. Underwriters Laboratories has recognized 3 kHz spark test for testing of wire or cable. The NEMA High Performance Wire and Cable Section prepared this test pr
16、ocedure. Comments or proposed revisions are welcomed and should be submitted to: Senior Technical Director, Operations National Electrical Manufacturers Association 1300 N. 17thStreet Rosslyn, VA 22209 At the time of the reaffirmation of this standard in 2012, the NEMA High Performance Wire and Cabl
17、e Section comprised the following member companies: AFC Cable Systems, Inc. a part of Atkore International New Bedford, MA Apical Division, Kaneka Texas Corporation Pasadena, TX Belden St. Louis, MO Cable USA LLC Naples, FL Champlain Cable Corporation Colchester, VT Coleman Cable, Inc. Waukegan, IL
18、Freeport-McMoRan Copper and Gold Phoenix, AZ General Cable Highland Heights, KY Harbour Industries LLC Shelburne, VT IWG High Performance Conductors Inman, SC Leoni Wire, Inc. Chicopee, MA Marmon Innovation and Technology Group Seymour, CT Prestolite Wire and Cable Southfield, MI Quirk Wire Company,
19、 Inc. West Brookfield, MA Radix Wire Company Euclid, OH RSCC Wire and Cable Group East Granby, CT Rubadue Wire Co., Inc. Greeley, CO Southwire Company Carrolton, GA TE Connectivity Ltd., a Tyco Electronics Corporation Menlo Park, CA The Monroe Cable Company, Inc. Middletown, NY The Okonite Company R
20、amsey, NJ WC 56-1986 (R1993, R2000, R2005, R2012) Page iv Copyright 2013 by National Electrical Manufacturers Association WC 56-1986 (R1993, R2000, R2005, R2012) Page v Copyright 2013 by National Electrical Manufacturers Association TABLE OF CONTENTS FOREWARDiii Section 1 TEST EQUIPMENT .2 1.1 ELECT
21、RODE2 1.1.1 Electrode Length2 1.1.2 Use of Electrode.2 1.2 VOLTAGE SHAPE.2 1.3 VOLTAGE FREQUENCY.2 1.4 VOLTMETER3 1.5 REGULATION 3 1.6 FAILURE DETECTION CIRCUIT 3 1.7 SAFETY OF EQUIPMENT AND SAFE USE OF EQUIPMENT.5 Section 2 TEST PROCEDURE. 6 2.1 SET-UP. 6 2.1.1 Voltage 6 2.1.1.1 Maximum Voltage. 6
22、2.1.2 Frequency 6 2.1.3 Line Speed6 2.1.3.1 Maximum.7 2.1.3.2 Minimum7 2.2 FAULT IDENTIFICATION 7 2.3 CALIBRATION AND CREST FACTOR7 2.4 VENTILATION OF WORK AREA 7 WC 56-1986 (R1993, R2000, R2005, R2012) Page 1 Copyright 2013 by National Electrical Manufacturers Association SCOPE This standard covers
23、 a general procedure for continuous voltage proof testing of wire and cable. It is intended to apply primarily to the final inspection of wire or cable for the purpose of finding and eliminating defects prior to shipment or before use. The method can also be used to eliminate defects at an early sta
24、ge of manufacturing, i.e., for wire or cable to be used in multiconductor cables or jacketed constructions. Because of possible damage in handling, damage caused by repeated testing, and variations in test parameters, comparison between producers and consumers test results are not significant. WC 56
25、-1986 (R1993, R2000, R2005, R2012) Page 2 Copyright 2013 by National Electrical Manufacturers Association Section 1 TEST EQUIPMENT 1.1 ELECTRODE The electrode shall be of a bead chain construction (see Figure 1-1) that will give intimate metallic contact with practically all of the wire insulation s
26、urface. The chain shall be suspended in a U or V-shaped trough having a width approximately 11/2 in. (38 mm) greater than the diameter of the larger size of wire that is tested. The chain shall have a length appreciably greater than the depth of the enclosure so that the beads will droop below the w
27、ire under test. The electrode shall consist of an array of 1/16 in. (1.59 mm) diameter stainless steel bead chains suspended approximately 0.08 in. (2.03 mm) apart, perpendicular to the wire line and spaced approximately 0.10 in. (2.54 mm) apart along the wire line. 1.1.1 Electrode Length The electr
28、ode length shall be chosen so that, at the speed being used, the wire shall be subjected to no less than a total of six positive and negative crests of the supply voltage (the equivalent of three complete cycles or more than 1200 positive or negative wave crests (600 complete cycles) at any given cr
29、oss section. 1.1.2 Use of Electrode Only one electrode shall be connected to the power supply transformer. The electrode shall be kept free of water and foreign matter; it shall be provided with an earth grounded metal screen or an equivalent guard to provide protection for the operating personnel.
30、Broken chains shall be replaced as required. 1.2 VOLTAGE SHAPE The applied voltage shall be essentially sinusoidal. The crest factor of the voltage shall be no less than 1.35 nor more than 1.48 under any load condition (see 2.3). 1.3 VOLTAGE FREQUENCY The frequency shall be 2.5 1.0 kHz under any loa
31、d condition. The most desirable frequency range is 3 0.5 kHz. There are wire and cable constructions that will cause the frequency to drop below 2.5 kHz. Under no conditions shall the frequency be allowed to go below 1.5 kHz. Line speeds should be adjusted at low frequencies. Use 2.1.3 to calculate
32、the speed. If equipment with multiple load or frequency settings is used, it shall contain a frequency meter or tripping device that will render the unit non-operational when the frequency does not fall within the specified range. WC 56-1986 (R1993, R2000, R2005, R2012) Page 3 Copyright 2013 by Nati
33、onal Electrical Manufacturers Association 1.4 VOLTMETER The voltmeter measuring the rms voltage shall be capable of operating accurately up to 4 kHz, shall be connected directly to the measuring circuit, and shall continually indicate the electrode potential. The full scale meter reading shall not b
34、e greater than 15 kV rms. The meter accuracy shall be such that, when the voltage is adjusted to any specified value by a calibrating voltmeter, the actual electrode value will be within 2 % of full scale. 1.5 REGULATION The maximum current which the equipment can deliver to a purely capacitive load
35、 shall be no less than 40.0 mA. The maximum current which can be delivered to purely resistive load shall be no greater than 4.0 mA. The voltage at the test electrode shall not change more than 5 % between no load and full load conditions when the load consists of a capacitance passing a current of
36、10.0 mA in parallel with a resistance passing a current of 1.0 mA. 1.6 FAILURE DETECTION CIRCUIT There shall be a fault indicating circuit which shall give a visible or audible indication of a dielectric failure. The system shall be sufficiently sensitive so that a fault is indicated at any voltage
37、above 2 kV when the electrode is arced to ground through a needle spark gap in series with a test network, for duration of 1 millisecond (see Figure 1-2). The spark gap shall consist of a metal plate and a needle point, and the distance between them shall be maintained at .010 in. .002 in. (.25 mm .
38、05 mm). A suitable type of needle is shown in Figure 1-3, or equivalent. The 50 pF capacitor shall be of the high voltage type (15 kV rms) with polyethylene insulation, or suitable equivalent. After a fault occurs, the equipment shall come back to full sensitivity and full potential within 40ms. Equ
39、ipment used for proof testing without stopping mechanism shall have a response time such that every segment of the wire will be subjected to the full test potential at full sensitivity and fault registering capability for at least three complete cycles. WC 56-1986 (R1993, R2000, R2005, R2012) Page 4
40、 Copyright 2013 by National Electrical Manufacturers Association Figure 1-1 TYPICAL BEAD CHAIN ARRANGEMENT *Note: All Dimensions in inches. 3/32”WC 56-1986 (R1993, R2000, R2005, R2012) Page 5 Copyright 2013 by National Electrical Manufacturers Association Figure 1-2 TYPICAL ARRANGEMENT FOR SENSITIVI
41、TY MEASUREMENT Figure 1-3 SUITABLE NEEDLE POINT There shall be no indication of a fault when the electrode is shorted to ground through a 2 M resistor at a voltage of 2 kV for a period of 2 s. 1.7 SAFETY OF EQUIPMENT AND SAFE USE OF EQUIPMENT Any equipment built or purchased for performance of this
42、test shall comply with applicable electrical safety codes, and shall be used in accordance with the manufacturers instructions for safe use. WC 56-1986 (R1993, R2000, R2005, R2012) Page 6 Copyright 2013 by National Electrical Manufacturers Association Section 2 TEST PROCEDURE 2.1 SET-UP The insulate
43、d wire or cable shall be threaded through the electrode head and the conductor grounded at one or both ends. With the electrode head energized to the specified voltage, the wire shall pass from the payoff spool through the electrode and on to the takeup spool. 2.1.1 Voltage The voltage shall be adju
44、sted with the wire or cable in the electrode. The equipment shall not be used if any noticeable voltage drop occurs when the wire starts moving through the electrode at any selected speed. 2.1.1.1 Maximum Voltage Loading of the equipment beyond its power supply capabilities may result in malfunction
45、ing or erroneous indications. The maximum allowable voltage may therefore have to be restricted due to capacitive loads. It may be calculated based on the minimum current necessary to trigger the detection circuit (40 mA per paragraph 1.5) divided by 2 F (where F is frequency) and the capacitance of
46、 the wire in the electrode. For purposes of this determination, the maximum allowable frequency of 3.5 kHz should be used, so that maximum voltage is determined as follows: CV6max)10(82.1 Where: V = Voltage in Volts (V) C = Capacity in Picofarads (pF) Modern high performance insulation systems may n
47、ot require any such determination for the resistive component to calculate the maximum allowable voltage; for lossy dielectrics, however, a maximum allowable voltage should also be calculated for the resistive component of the load current. 2.1.2 Frequency Equipment with multiple settings shall be a
48、djusted such that the test frequency will be 2.5 1.0 kHz. 2.1.3 Line Speed The rate of speed, as a function of electrode length, shall be controlled by the requirements of 1.1.1. 2.1.3.1 Maximum The maximum acceptable line speed in feet per minute (fpm) shall be determined as follows: fpm = 5/3 x Freq (Hz) x Electrode Length (in),
