1 Scope
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
Foreword III
1 Scope
2 Normative References
3 Terms and Definitions
4 General Test Requirements
4.1 Test Methods
4.2 Arrangement of the Insulator for the Test
4.3 Requirements for the Test Circuit
5 Salt Fog Method
5.1 Salt Solution
5.2 Spraying System
5.3 Conditions Before Starting the Test
5.4 Preconditioning Process
5.5 Withstand Test
5.6 Acceptance Criteria for the Withstand Test
6 Solid Layer Method
6.1 Composition of the Contaminating Suspension
6.2 Main Characteristics of the Inert Material
6.3 Application of the Pollution Layer
6.4 Determination of the Degree of Pollution of the Test Insulator
6.5 Test Procedure
6.6 Withstand Test and Acceptance Criteria
7 Withstand Characteristic of Insulators
7.1 Determination of the Withstand Characteristics of Insulators
7.2 Determination of the Maximum Withstand Degree of Pollution at a Given Test Voltage
7.3 Determination of the Maximum Withstand Voltage at a Given Degree of Pollution
7.4 Determination of the 50% Withstand Voltage at a Given Degree of Pollution
Annex A (Informative) Method for Checking the Uniformity of the Layer
Annex B (Informative) Additional Recommendations Concerning the Solid Layer Method Procedures
B.1 Drying of the Pollution Layer
B.2 Checking the Wetting Action of the Fog
B.3 Fog Input to the Test Chamber
B.4 Duration of the Withstand Test
B.5 Evaluation of the Reference Salt Deposit Density (SD)
Annex C (Informative) Information to Check Equipment for Artificial Pollution Tests
Annex D (Informative) Introduction of IEC/TR 61245:1993
Annex E (Informative) Technical Differences between IEC/TR 61245:1993 and This Standard and Their Reasons
Annex F (Informative) Comparison Table of Clause Numbers between IEC/TR 61245:1993 and This Standard
Figure 1 Ripple Amplitude and Actual Mean Voltage, Measured on a Resistive Load Absorbing 100 mA
Figure 2 Voltage Drop and Voltage Overshoot and Leakage Current
Figure 3 Typical Construction of Fog Spray Nozzle
Figure 4 Test Layout for Inclined Insulators
Figure A.1 Arrangement of the Probe Electrodes
Figure A.2 Circuit Diagram of the Meter
Figure B.1 Determination of Layer Conductance and Evaluation of Its Rise Time TC = t2 – t1
Table 1 Salt-fog Method: Correspondence between the Value of Salinity, Volume Conductivity and Density of the Solution at a Temperature of 20℃
Table 2 Correspondence between the Solution Temperature θ and the Factor b
Table 3 Approximate Correspondence between SD and σ20 for Kaolin Compositions
Table 4 Main Characteristics of Kaolin Used in the Solid Layer Suspension
