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GB/T 31838 consists of the following parts, under the general title Solid Insulating Materials — Dielectric and Resistive Properties: Solid Insulating Materials — Dielectric and Resistive Properties:
— Part 1: General
— Part 2: Resistive Properties (DC Methods) — Volume Resistance and Volume Resistivity;
— Part 3: Resistive Properties (DC Methods) — Surface Resistance and Surface Resistivity;
— Part 4: Resistive Properties (DC Methods) — Insulation Resistance.
This part is Part 2 of GB/T 31838.
This part is drafted in accordance with the rules given in the GB/T 1.1-2009
This part replaces GB/T 1410-2006 Methods of Test for Volume Resistivity and Surface Resistivity of Solid Electrical Insulating Materials, and the following technical deviations have been made with respect to the GB/T 1410-2006 (the previous edition):
— modification of the Normative References (see Clause 2; Clause 2 of Edition 2006);
— deletion of the terms of “surface resistance”, “surface resistivity” and “electrodes” (see 3.3, 3.4 and 3.5 of Edition 2006);
— addition of the term of “stray current” (see 3.3);
— combination of the “Power Supply”, “Accuracy”, “Guarding”, “Test Specimens”, “Electrode Material”, “Specimen Handling”, “Conditioning” into “Method of Test” (see Clause 5; Clause 5, 6.2, 6.3, Clause 7 to Clause 10 of Edition 2006);
— combination of the “Measuring Methods”, “Test Procedure”, “Volume resistivity” into “Test Procedure” (see Clause 6; 6.1, Clause 11, 12.1 of Edition 2006);
— deletion of the “Surface resistance” and “Surface resistivity” (see 11.2 and 12.2 of Edition 2006);
— modification of the “Reproducibility” (see Clause 8; 12.3 of Edition 2006) .
— deletion of the Annexes A, B and C (Annexes A, B and C of Edition 2006);
This part is identical with International Standard IEC 62631-3-1:2016 Dielectric and Resistive Properties of Solid Insulating Materials — Part 3-1: Determination of Resistive Properties (DC methods) — Volume Resistance and Volume Resistivity — General Method.
The Chinese documents consistent and corresponding with the normative international documents in this part are as follows:
— GB/T 1981.2-2009 Varnishes Used for Electrical Insulation — Part 2: Methods of Test (IEC 60464-2:2001 and Amendment 1:2006, MOD);
— GB/T 1981.3-2009 Varnishes Used for Electrical Insulation — Part 3: Specifications for Hot Curing Impregnating Varnishes (IEC 60464-3-2:2001, IDT);
— GB/T 2411-2008 Plastics and Ebonite — Determination of Indentation Hardness by Means of a Durometer (Shore Hardness) (ISO 868:2003, IDT);
— GB/T 5132.1-2009 Industrial Rigid Round Laminated Tubes and Rods Based on Thermosetting Resins for Electrical Purposes — Part 1: General Requirements (IEC 61212-1:2006, IDT);
— GB/T 5132.2-2009 Industrial Rigid Round Laminated Tubes and Rods Based on Thermosetting Resins for Electrical Purposes — Part 2: Methods of Test (IEC 61212-2:2006, IDT);
— GB/T 5132.5-2009 Industrial Rigid Round Laminated Tubes and Rods Based on Thermosetting Resins for Electrical Purposes — Part 5: Round Laminated Moulded Rods (IEC 61212-3-3:2006, IDT);
— GB/T 6554-2003 Resin Based Reactive Compounds Used for Electrical Insulation — Part 2: Methods of Test — Methods for Coating Powders for Electrical Purposes (IEC 60455-2-2:1984, MOD);
— GB/T 10580-2015 Standard Conditions for Use Prior to and During the Testing of Solid Electrical Insulating Materials (IEC 60212:2010, IDT);
— GB/T 15022.1-2009 Resin Based Reactive Compounds Used for Electrical Insulation — Part 1: Definitions and General Requirements (IEC 60455-1:1998, IDT);
— GB/T 15022.2-2017 Resin Based Reactive Compounds Used for Electrical Insulation — Part 2: Methods of Test (IEC 60455-2:2015, NEQ);
— GB/T 15022.3-2011 Resin Based Reactive Compounds Used for Electrical Insulation — Part 3: Unfilled Epoxy Resinous Compounds (IEC 60455-3-1:2003, IDT);
— GB/T 15022.4-2009 Resin Based Reactive Compounds Used for Electrical Insulation — Part 4: Unsaturated Polyester Based Impregnating Resins (IEC 60455-3-5:2006, MOD);
— GB/T 15022.5-2011 Resin Based Reactive Compounds Used for Electrical Insulation — Part 5: Quartz Filled Epoxy Resinous Compounds (IEC 60455-3-2:2003, MOD).
For the purposes of this part, the following editorial changes have also been made:
— change of the standard name to Solid Insulating Materials — Dielectric and Resistive Properties — Part 2: Resistive Properties (DC Methods) — Volume Resistance and Volume Resistivity.
This standard was proposed by China Electrical Equipment Industrial Association.
This standard is under the jurisdiction of SAC/TC 301 (National Technical Committee 301 on Evaluation and Qualification of Electrical Insulating Material and Systems of Standardization Administration of China).
The previous editions of this part are as follows:
— GB/T 1410-2006
Solid Insulating Materials — Dielectric and Resistive Properties — Part 2: Resistive Properties (DC Methods) — Volume Resistance and Volume Resistivity
1 Scope
This part of GB/T 31838 specifies a method of test for the determination of volume resistance and volume resistivity of electrical insulation materials by applying a DC voltage.
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
IEC 60212 Standard Conditions for Use Prior to and During the Testing of Solid Electrical Insulating Materials
IEC 60455 (all parts) Resin Based Reactive Compounds Used for Electrical Insulation
IEC 60464 (all parts) Varnishes Used for Electrical Insulation
IEC 61212 (all parts) Industrial Rigid Round Laminated Tubes and Rods Based on Thermosetting Resins for Electrical Purposes
ISO 868 Plastics and Ebonite — Determination of Indentation Hardness by Means of a Durometer (Shore Hardness)
3 Terms and Definitions
For the purposes of this document, the following terms and definitions apply.
3.1
volume resistance
the quotient of a direct voltage applied between two electrodes placed on two faces (opposite) of a specimen, and the steady-state current between the electrodes
Note: Volume resistance is expressed in the unit of Ω.
3.2
volume resistivity
the quotient of a d.c. electric field strength and the steady-state current density within an insulating material. In practice it is taken as the volume resistance reduced to a cubical unit volume
Note 1: According to IEC 60050-121, “conductivity” is defined as “scalar or tensor quantity, the product of which by the electric field strength in a medium is equal to the electric current density” and “resistivity” as “the inverse of the conductivity when this inverse exists”. Measured in this way, the volume resistivity is an average of the resistivity over possible heterogeneities in the volume incorporated in the measurement; it includes the effect of possible polarization phenomena at the electrodes.
Note 2: For insulating materials, the volume resistivity is usually determined by means of measuring electrodes arranged on a sheet of the material.
Note 3: Volume resistivity is expressed in the unit of Ωm.
3.3
stray current
leakage current in the earth or in metallic structures buried in the ground and resulting from their intended or unintended earthing
4 Significance
Insulating materials are used in general to electrically isolate components of an electrical system from each other and from earth. Solid insulating material may also provide mechanical support. For these purposes it is generally desirable to have the insulation resistance as high as possible, consistent with acceptable mechanical, chemical and heat resistance properties. Volume resistance is a part of the insulating resistance.
Volume resistivity can be used as an aid in the choice of an insulating material for a specific application. The change in resistivity with temperature and humidity may be great and has to be known when designing for operation conditions.
When a direct voltage is applied between electrodes in contact with a specimen, the current through it decreases asymptotically towards a steady-state value. The decrease of current with time may be due to dielectric polarization and the sweep of mobile ions to the electrodes. For materials having volume resistivity less than about 1010 Ωm the steady state is generally reached within 1 min and the resistance is determined after this time of electrification. For materials with higher volume resistivity the current may continue decreasing for several minutes, hours, days or even weeks. For such materials, therefore, longer electrification times may be necessary.
Note: For very high electric field strengths different behaviour can occur.
5 Method of Test
5.1 General
This general method describes common values for general measurements. If a method for a specific type of material is described in this standard, the specific method shall be used.
The measurement of volume resistance (and volume resistivity respectively) shall be carried out carefully and taking into account the electric properties of the measuring circuit as well as the specific electric properties of the material.
To carry out the test, in most cases the use of high voltages is necessary. Care shall be taken to prevent electric shock.
Polarization effects can influence the measurement. Therefore it is not acceptable to achieve the measured resistance twice in two consecutive experiments without a sufficient space of time in-between.
Note: For materials with volume resistance of not more than 1012Ω a period of 1 h after voltage application might be sufficient.
5.2 Power supply and voltage
A source of very steady direct voltage is required. This may be provided either by batteries or by rectified and stabilized power supply. The degree of stability required is such that the change in current due to any change in voltage is negligible compared with the current to be measured.
Note 1: The ripple of the voltage source is important. A typical value for 100 V is < 5×10-5 peak to peak.
Commonly specified test voltages to be applied to the complete specimen are 10 V, 100 V, 500 V, 1 000 V, and 10 000 V. If not otherwise stipulated, a voltage of 100 V is to be used.
Note 2: In air, below 340 V no partial discharges will occur. Partial discharge can lead to erroneous measurements of the resistance when a specific inception voltage is exceeded.
Foreword II
1 Scope
2 Normative References
3 Terms and Definitions
4 Significance
5 Method of Test
6 Test Procedure
7 Test Report
8 Repeatability and Reproducibility
Bibliography
