IEC 61395:1998 pdf download – overhead electrical conductors – Creep test procedures for stranded conductors

IEC 61395:1998 pdf download – overhead electrical conductors – Creep test procedures for stranded conductors.
IEC 61395 is pnmarlly applicable to non’interrupted creep.testing of stranded conductors for overhead lines such as those specified by IEC 61089. Procedures for interpreting the results are also included.
The object of the test is principally to calculate creep lot any purpose and to compare creep of different conductors.
The requirement of this standard aims ai an accuracy of 1 %. However, it should be recognized that due to variations occurring In the manufacturing process, the creep obtained In the test is not a precise value for all conductors of the type tested.
2 NormatIve reference
The following normative document contains provisions which, through reference In this text. constitute provisions of this International Standard. At the time of publication, the edition indicated wag valid. All normative documents are subject to revision, and parties to agreements made on this International Standard are encouraged to investigate the possibility of applying the most recent edition of the normative document indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.
IEC 61089:1991 Round wire concentric lay overhead electrical stranded conductors
3 Definitions
For the purpose of this International Standard. the following definitions apply.
3.1
sample length
total length of the conductor between the end fittings
3.2
gauge length
distance of the conductor over which the creep is measured
3.3
test temperature
mean temperature taken at the three pre-specified positions along the gauge length or. when more than three measuring positions are used, the mean temperature taken at equal distances along the gauge length
6.1 Temperature variations
Conductor temperature variation along the gauge length shall be less than 2,0 C. Conductor temperature variation during the test shall be less than ±2.0 C. It as important to ensure that greater deviations than those stated above do not take place. A means of continuously monitoring the air or conductor temperature is recommended.
6.2 Accuracy of temperature measuring devices
The accuracy of the equipment used for temperature measurements shall be within ±0,5 C. The accuracy of the temperature measuring device used on the gauge length shall be clearly stated in the test report. The method used for temperature control and measurement shall also be fully documented.
6.3 Temperature compensation
Temperature variations shall be compensated. either by using a thermal reference with the same coefficient of thermal expansion as the sample, called reference bars in figure 1, or by using a thermocouple reference. In the latter case. the strain variation is calculated and subtracted from the elongation measurements Three temperature measuring devices are used, the accuracy of which shall be within 0,5 C. It shall be clearly understood that the temperature compensahon is to reduce the scatter In the measurement arising from the length change of the conductor sample due to thermal elongation only. The effect of temperature change on the creep rate cannot be compensated.
7 Load
7.1 Test load
The accuracy of the iest ioad shall be within ±1 % or 120 N whichever is ffie greater. Load cells shall be used during the test.
7.2 Strain measurement
The accuracy and the set up of the strain measuring device shall be sufficient to determine the conductor sample strain to the nearest 5 x lO. The measurin9 devices may be of any suitable type such as micrometer dial gauges, low voltage displacement transducers or optical systems. Uncontrolled rotation during the test, especially of long samples may take place and shall be avoided or compensated for.
8 Test procedure
The sample prepared in accordance with the procedure described In clause 5 shall be placed in the creep test machine. Some machines may require a preload in order to attach the strain measuring devices. In such cases a preload of up to 2 % of the rated lensile strength of the conductor may be allowed. Prolonged period at preload shall be avoided in order not to influence the shape of the creep curve. Usually not more than 5 mm at preload can be accepled.