ASTMD149美标标准固体绝缘材料电压击穿的实验方法

ASTMD149

美标标准固体绝缘材料电压击穿的实验方法

Standard Test Method for Dielectric Breakdown Voltage and Dielectric

Strength of Solid Electrical Insulating Materials at Commercial Power

Frequencies

固体电绝缘材料在工业用电频率下的 电压击穿和介电强度的实验

方法

1. Scope*

1.1 This test method covers procedures for the determination

of dielectric

strength of solid insulating materials at

commercial power frequencies, under

specified conditions.2,3

1.2 Unless otherwise specified, the tests shall be made at 60Hz. However, this

test method is suitable for use at anyfrequency from 25 to 800 Hz. At

frequencies above 800 Hz,dielectric heating is a potential problem.

1.3 This test method is intended to be used in conjunction with any ASTM

standard or other document that refers to this test method. References to this

document need to specify the particular options to be used (see 5.5).

1.4 It is suitable for use at various temperatures, and in any suitable gaseous

or liquid surrounding medium.

1.5 This test method is not intended for measuring the dielectric strength of

materials that are fluid under the conditions of test.

1.6 This test method is not intended for use in determining intrinsic dielectric

strength,direct-voltage dielectric strength,or thermal failure under electrical

stress (see Test MethodD3151).

1.7 This test method is most commonly used to determine the dielectric

breakdown voltage through the thickness of a test specimen (puncture). It is

also suitable for use to determine dielectric breakdown voltage along the

interface between a solid specimen and a gaseous or liquid surrounding

medium (flashover). With the addition of instructions modifying Section 12, this

test method is also suitable for use for proof testing.

1.8 This test method is similar to IEC Publication 243-1. All procedures in this

method are included in IEC 243-1. Differences between this method and IEC

243-1 are largely editorial.

1.9

This standard does not purport to address all of the safety concerns, if any,

associated with its use. It is the responsibility of the user of this standard to

establish appropriate safety and health practices and determine the

applicability of regulatory limitations prior to use.

Specific hazardstatements

are given in Section 7. Also see 6.4.1.

ASTMD149

美标 标准固体绝缘材料电压击穿的实验方法

(

三

)

3.1 Definitions:

3.1.1dielectric breakdown voltage (electric breakdown voltage), n

—

the

potential

difference

at

which

dielectric

failureoccurs

under prescribed

conditions in an electrical insulatingmaterial located between two

electrodes. (See also

Appendix

X1

.)

3.1.1.1 Discussion

—

The term

dielectric breakdown voltage

is sometimes

shortened to “breakdown voltage.”

3.1.2dielectric failure (under test), n

—

an event that is evidenced by

an increase in conductance in the dielectric under test limiting the

electric field that can be sustained.

3.1.3dielectric strength, n

—

the voltage gradient at which dielectric

failure of the insulating material occurs under specific conditions of

test.

3.1.4 electric strength, n

—

see dielectric strength.

3.1.4.1 Discussion

—Internationally, “electric strength” is used

almost universally.

3.1.5flashover, n

—

a disruptive electrical discharge at the surface of

electrical

insulation

or

in

the

surrounding

medium,

which

may or

may

not

cause permanent damage to the insulation.

3.1.6 For definitions of other terms relating to solid insulating

materials, refer to Terminology

D1711

.

ASTMD149

美标标准固体绝缘材料电压击穿的实验方法

(

四

)

4. Summary of Test Method

4.2 Most commonly, the test voltage is applied using simple test electrodes on

opposite faces of specimens. The options for the specimens are that they be

molded or cast, or cut from flat sheet or plate. Other electrode and specimen

configurations are also suitable for use to accommodate the geometry of the

sample material, or to simulate a specific application for which the material is

being evaluated.

4.1 Alternating voltage at a commercial power frequency (60 Hz, unless

otherwise specified) is applied to a test specimen. The voltage is

increased from zero or

from a level

well below the

breakdown voltage, in

one

of

three

prescribed

methods

of

voltage

application,

until

dielectric

failure of the test specimen occurs.

5. Significance and Use

5.1 The dielectric strength of an electrical insulating material is a

property of interest

for

any application

where an electrical field will

be present. In many cases the dielectric strength of a material will be

the determining factor in the design of the apparatus in which it is to

be used.

5.2 Tests made as specified herein are suitable for use to provide part of the

information needed for determining suitability of a material for a given

application; and also, for detecting changes or deviations from normal

characteristics

resulting from processing variables, aging conditions, or other

manufacturing or environmental situations. This test method is useful for

process control, acceptance or research testing.

5.3 Results obtained by this test method can seldom be used directly to determine

the dielectric behavior of a material in an actual application. In most cases it is

necessary that these results be evaluated by comparison with results obtained

from other functional tests or from tests on other materials, or both, in order to

estimate their significance for a particular material.

5.4 Three methods for voltage application are specified in Section

12

:

Method A, Short-Time Test; Method B, Step-by- Step Test; and Method C,

Slow Rate-of-Rise Test. Method A is the most commonly-used test for

quality-control tests. However,the longer-time tests, Methods B and C,

which usually will give lower test results, will potentially give more

meaningful

results

when

different

materials

are

being

compared

with

each

other.

If

a

test

set

with

motor- driven

voltage

control

is

available,

the

slow

rate-of-rise

test

is

simpler

and

preferable

to

the

step-by-step

test.

The results obtained from Methods B and C are comparable to each other.

5.5 Documents specifying the use of this test method shall also specify:

5.5.1 Method of voltage application,

5.5.2 Voltage rate-of-rise, if slow rate-of-rise method is specified,

5.5.3 Specimen selection, preparation, and conditioning,

5.5.4 Surrounding medium and temperature during test,

5.5.5 Electrodes,

5.5.6 Wherever possible, the failure criterion of the currentsensing

element, and

5.5.7 Any desired deviations from the recommended procedures as given.

5.6 If any of the requirements listed in

5.5

are missing from the

specifying

document,

then

the

recommendations

for

the

several

variables

shall be followed.

5.7 Unless the items listed in

5.5

are specified, tests made with such

inadequate

reference

to

this

test

method

are

not

in

conformance

with

this

test

method.

If

the

items

listed

in

5.5

are

not

closely

controlled

during

the

test,

it

is

possible

that

the

precisions

stated

in

15.2

and

15.3

will

not be obtained.

5.8

Variations

in

the

failure

criteria

(current

setting

and

response

time)

of the current sensing element significantly affect the test results.

5.9

Appendix

X1

.

contains

a

more

complete

discussion

of

the

significance

of dielectric strength tests.

ASTMD149