IEC 60331-21:1999 pdf download – Tests for electric cables under fire conditions -Circuit integrity – Part 21: Procedures and requirements -Cables of rated voltage up to and including 0,6/1,o kV

IEC 60331-21:1999 pdf download – Tests for electric cables under fire conditions -Circuit integrity – Part 21: Procedures and requirements -Cables of rated voltage up to and including 0,6/1,o kV.
This part of IEC 60331 specifies the lest procedure and gives the performance requirement. including a recommended flame application time, for cables of rated voltage up to and including 0.611,0 kV required to maintain circuit integrity when subjected to fire under specified conditions,
It describes the means of sample preparation, continuity checking arrangements, electrical testing procedure, method of burning the cables and gives requirements for evaluating test results,
It is intended to cover low voltage power cables, and control cables with a rated voltage.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this part of IEC 60331 For dated references, subsequent amendments 10, or revisions of, any of these publications do not apply. However, parties to agreements based on this part of lEG 60331 are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of IEC and ISO maintain registers of currently valid International Standards
lEG 60269-3-1:1 994, Low-voltage fuses — Part 3-1: Supplementary requirements for fuses for use by unskilled persons (fuses mainly for household and similar applications) — Sections I to/V
IEC 60331•11 :1999. Tests for electric cables under lire conditions — Circuit lntegnty — Part 11:
Apparatus — F,re alone at a flame temperature of at least 750 C
IEC Guide 104:1997, The preparation of safety publications and the use of basic safety publications and group safety publications
3 DefInition
For the purpose of this part of IEC 60331, the following definition applies.
3.1
circuit integrity
ability to continue to operate in the designated manner whilst subjected to a specified flame source for a specified period of time
4 Sample preparation
A sample of the completed cable approximately I 200 mm long shall have approximately 100mm of sheath or outer coverings removed at each end.
At each end of the cable, each cOnduCtOr shall be suitably prepared for electrical connections, and the exposed conductors shall be spread apart to avoid contact with each other,
5 Continuity checking arrangements
During the test a current for continuity checking is passed through all conductors of the cable and this shall be provided by a three-phase star connected or single-phase transformer(s) of sufficient capacity to maintain the test voltage up to the maximum leakage current allowable.
This current is achieved by connecting, at the other end of the sample, a suitable load and an Indicating device (e.g. lamp) to each conductor. or group of conductors.
NOTE — A current o4 0,25 A at the test voltage, throu9h each Conductor OF QFOUP of conductors, has been found to be suitable.
6 Test procedure
6.1 The test procedure defined In this clause shall be carried out using the apparatus detailed in 1EC6033I-1l.
6.2 Fuses used in the test procedure shall be type DII complying with IEC 60269-3-1. Alternatively, a circuit-breaker with equivalent characteristics may be used.
Where a circuit-breaker is used, its equivalent characteristics shall be demonstrated by reference to the characteristic curve shown In annex A.
The fuse shall be the reference method in the case of dispute
6.3 Mount the sample in the clamp and supports. Adjust the burner to the correct position relative to the sample. as defined by the values of x and y arising from the verification procedure (see IEC 60331.11).
6.4 At the transformer end of the sample, earth the neutral conductor and any protective conductors. Any metal screens, drain wire or metallic layer shall be interconnected and earthed, Connect the transformer(s) to the conductors, excluding any conductor which is specifically identified as intended for use as a neutral or a protective conductor, as shown in the circuit diagram in figure 1. Where a metallic sheath, armour or screen acts as a neutral or protective conductor, it shall be connected, as shown in the circuit diagram in figure 1, as for a neutral or protective conductor.
For single., twin- or three-phase cables, connect each phase conductor to a separate phase of the transformer(s) output with a 2 A fuse or circuit-breaker with equivalent characteristics in each phase.