Repeated applications of voltage will sometimes result in failure at lower voltages sometimes unmeasurably low , usually with additional damage at the breakdown area. A number of different physical arrangements of voltage source, measuring equipment, baths or ovens, and electrodes are possible, but it is essential that 1 all gates or doors providing access to spaces in which there are electrically energized parts be interlocked to shut off the voltage source when opened; 2 clearances are sufficiently large that the? Breakdown is when an electrical burn-through punctures the sample, or decomposition occurs in the specimen. In many cases it is speci? When making a direct comparison of results from two or more laboratories, evaluate the precision between the laboratories.
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When resurfacing, do not change the transition between the electrode face and any speci? The initial voltage shall be reached as speci?
If tests are to be made at other than room temperature, the bath must be provided wstm a means for heating or cooling the liquid, and with a means to ensure uniform temperature. The transformer, its voltage source, and the associated controls shall have the following capabilities: Breakdown is when an electrical burn-through punctures the sample, or decomposition occurs in the specimen.
ASTM D149 - DIELECTRIC STRENGTH TESTING SERVICES
After the initial step, the time required to raise the voltage to the d49 step shall be counted as part of the time at the succeeding step. References to this document need to specify the particular options to be used see 5. Since the dielectric strength is so dependent ast, thickness it is meaningless to report dielectric strength data for a material without stating the thickness of the test specimens used.
This is often necessary for specimens that have not been dried and impregnated with oil, as well as for those which have been prepared in accordance with Practice D, for example.
ASTM D - National Technical Systems
Each of these three methods has the same basic set-up, which consists of the test specimen placed between two electrodes in air or oil. D — 09 9. 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.
The results obtained from Methods B and C are comparable to each other. This is to be expected because the thermal breakdown mechanism is time-dependent and the discharge mechanism is usually time-dependent, although in some cases the latter mechanism may cause rapid failure by producing critically high local?
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.
These procedures are the short-time method, the slow rate-of-rise asstm and the step-by-step method. Make the setting high enough that transients, such as partial discharges, will not trip the breaker but not so high that excessive burning of the specimen, with resultant electrode damage, will occur on breakdown.
When making high-voltage tests, particularly in compressed gas or in oil, it is possible that the energy released at breakdown will be sufficient to result in?
E Refer to the appropriate standard for the proper gap settings. If the control is set too high, the circuit will not respond when breakdown occurs; if set too low, it is possible that it will respond to leakage currents, capacitive currents, or partial discharge corona currents or, when the sensing element is located in the primary, to the step-up transformer magnetizing current. AC Voltage is applied to the electrodes at a frequency of 60 Hz and the voltage is slowly increased until it burns through the center of the panel.
This standard has been approved for use by agencies of the Department of Defense. The breakdown mechanisms usually operate in combination rather than singly. If the items listed in 5.
Dielectric Strength ASTM D, IEC
If breakdown repeatedly occurs at a value greater than 2. Due to copyright restrictions, we are not able to provide copies of standards.
Standard Test Method f For the most common test, the short-time method, voltage is applied across the two electrodes and raised from zero to dielectric breakdown at a uniform rate. However, this test method is suitable for use at any frequency from 25 to Hz.
Link to Active This link will always route to the current Active version of the standard. In many cases the dielectric strength of a material c149 be the determining factor in the design of the apparatus in which it is to be used. Since the electrode separation can be?
Precision and Bias Last previous edition approved in as D — 97a 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.