This standard specifies procedures for artificial pollution tests applicable to d.c. overhead-line insulators, substation insulators and traction line insulators. It may also be applied to bushings with suitable precautions to avoid internal damage and to hollow insulators intended for use in other apparatus. In applying these procedures to apparatus incorporating hollow insulators, the relevant technical committees should consider their effect on the internal equipment and the special precautions which may be necessary.
This standard is applicable to the determination of the withstand characteristics of ceramic and glass insulators to be used outdoors and exposed to polluted atmospheres, on d.c. systems with voltages from ±1 000 V up to ±800 kV.
These tests are not directly applicable to insulators made of organic materials, to composite insulators, to greased insulators or to special types of insulators (insulators with semiconductive glaze or covered with any organic insulating material).
Note: For largest objects such as large wall bushings and transducers, a high spread of test results has been experienced.
2 Normative References
The following normative document contains provisions which, through reference in this text, constitute provisions of this standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent edition of the normative document indicated below. For undated references, the latest edition of the normative document referred to applies.
GB/T 16927.1-1997 Hign Voltsge Test Techniques — Part 1: General Test Requirements (eqv IEC 60060-1:1989)
3 Terms and Definitions
For the purposes of this standard, the following terms and definitions apply.
3.1
individual test
one single process consisting in applying to the object a specified test voltage, for a specified time or until flashover occurs, at a specified degree of pollution
3.2
actual mean voltage
Ua
mean value of the voltage at a given instant over a time interval ending at the instant considered and having a duration equal to that of one cycle of the alternating voltage supplying the rectifier
Note: When it is not possible to determine the cycle of the supply voltage, the time interval is 20 ms.
3.3
test voltage
Ut
actual mean voltage at the beginning of an individual test
3.4
ripple factor
ratio of the ripple amplitude to the actual mean voltage (Ur/Ua in Figure 1)
3.5
voltage drop
ΔUt
difference between the test voltage and the actual mean voltage (Figure 2)
3.6
relative voltage drop
ratio of the voltage drop Aut to the test voltage (ΔUt) usually expressed as a percentage
3.7
voltage overshoot
difference between the actual mean voltage and the test voltage (Figure 2)
3.8
relative voltage overshoot
ratio of the voltage overshoot to the test voltage Ut, usually expressed as a percentage
3.9
leakage current
current measured in series with the insulator surface at its earth end during a pollution test
3.10
highest leakage current during an individual test
highest leakage current value occurring during an individual test without flashover
3.11
short-circuit current
current delivered by the complete testing circuit, when the test object is energized at the test voltage and then short- circuited
