In this memo,Explain the purpose and difference between dielectric strength and insulation resistance tests as clearly as possible I will try to do so.
Both tests are used to determine the insulation performance of electrical products and components, but the contents of the dielectric strength test and the insulation resistance test are different. We will note the differences and our thoughts on them here.
- Difference between dielectric strength test and insulation resistance test
- dielectric strength test
- insulation resistance test
- Purpose of dielectric strength testing
- Is it called dielectric strength or dielectric breakdown voltage?
- Why Insulation Withstand Voltage Tests?
- What does the dielectric strength test (withstand voltage test) measure?
- Where can I check the contents of the dielectric strength test (withstand voltage test) (Reference: electromagnetic brake)
- Purpose of Insulation Resistance Testing
- Insulation performance of low-voltage electric circuits [Electric Facilities Technical Standards, Article 58].
- Low-voltage, high-voltage, and special high-voltage classifications
- Insulation resistance with respect to the rated measuring voltage of the insulation resistance tester
- Which comes first, the insulation resistance test or the dielectric strength test?
Difference between dielectric strength test and insulation resistance test
dielectric strength test
Apply the AC or DC voltage specified for the voltage used,Test to detect insulation defects by whether they cause dielectric breakdown(looking at the strength of the insulation)
insulation resistance test
DC voltage specified for the working voltage is applied,Detects insulation defects by measuring resistance
Below are notes with further details.
Purpose of dielectric strength testing
Dielectric strength testing is also called withstand voltage testing. This is a test to confirm whether or not an electrical product (component) has sufficient dielectric strength against the voltage used (i.e., whether or not dielectric breakdown will occur).
Is it called dielectric strength or dielectric breakdown voltage?
Although it is sometimes seen that "dielectric strength" is called "dielectric withstanding voltage," it is generally better to use "dielectric strength" or "dielectric withstanding voltage" since both the Japan Institute of Electrical Engineers and JIS refer to them as "dielectric strength" or "dielectric withstanding voltage.
Why Insulation Withstand Voltage Tests?
All electrical products and components must protect users from accidents such as electric shock and fire, and insulation resistance testing (withstand voltage testing) is used to prevent such accidents.
What does the dielectric strength test (withstand voltage test) measure?
Electrical products and components are basically composed of conductors (parts that conduct electricity) and insulation (parts that prevent the passage of electricity), but as a general method of testing dielectric strength,Applying the specified voltage for the voltage handled by the product (AC power supply, DC power supply) for the specified time The test is performed by a test engineer. If no breakdown occurs, the insulation is considered to have sufficient dielectric strength. Breakdown is measured by the rapid increase in current when voltage is applied to an insulator, and if current flows, the insulation is broken.
Where can I check the contents of the dielectric strength test (withstand voltage test) (Reference: electromagnetic brake)
The test voltage is defined by the standard of the electrical product (component).
For example.For electromagnetic brakes, JISB1404-2 [Electromagnetic clutches and brakes - Part 2: Test methods]. The contents are as follows
| Dielectric strength test (1 minute test) | |
| Rated voltage | Test voltage |
| 60V or less | 1000V AC |
| More than 60 and less than 220V | AC 1500V |
| Dielectric strength test (1 sec. test) | |
| Rated voltage | Test voltage |
| 60V or less | AC 1200V |
| More than 60 and less than 220V | AC 1800V |
Such as. The dielectric strength test of an electromagnetic brake in the example can be converted to a test by adding 1.2 times the test voltage for 1 second at 1.2 times the test voltage for 1 minute when testing numerous products. This alsoStandardized for each electrical product Please check with us.
RELATED:Links for those who want to buy or search for JIS standard books now.
Purpose of Insulation Resistance Testing
Insulation resistance tests are described in JIS for each electrical product, including the contents of the test and the resistance value to be guaranteed. Insulation resistance tests are also,Resistance is measured by applying a DC voltage specified for the voltage at which electrical products and components are handled. I will do so.
Reference: If they are not mentioned (not in the standard), please refer to Article 58 of the Technical Standard for Electrical Equipment and Facilities.
Insulation performance of low-voltage electric circuits [Electric Facilities Technical Standards, Article 58].
To determine whether the insulation resistance of an electrical circuit is good or bad, use the values listed in Article 58 of the Electrical Equipment Standards. These values must be greater than or equal to these values.
| Classification of operating voltage of electric circuits | Insulation Resistance | |
| 300V or less | When ground voltage is 150V or less | 0.1MΩ min. |
| Other cases | 0.2MΩ min. | |
| More than 300V | 0.4MΩ min. | |
*What is a power line...where electricity is connected under normal conditions of use.
*Ground-to-ground voltage is the difference between the voltage on the ground and the voltage on one side.
Low-voltage, high-voltage, and special high-voltage classifications
The "low voltage" in the table above is not limited to dielectric strength and insulation resistance tests, but you may see low voltage, high voltage, etc. when selecting testing equipment. The types of those voltages are as follows.
low voltage
Low voltage DC (750V or less) Low voltage AC (600V or less)
high voltage
High-voltage direct current (more than 750 V and less than 7000 V) High-voltage alternating current (more than 600 V and less than 7000 V)
extra-high pressure
More than 7000V
Insulation resistance with respect to the rated measuring voltage of the insulation resistance tester
An insulation resistance tester is used to measure insulation resistance.The rated measuring voltage (voltage to be applied) set by the insulation resistance tester should be selected according to the object to be measured, The insulation resistance tester has the following ranges
Reference: From the website of Hioki Electric Co.
The effective maximum scale value in parentheses in the following list is the JIS C 1302 standard. For example, HIOKI ELECTRIC has a lineup of resistance meters that satisfy the JIS standard and have a high effective maximum scale.
| Rated measurement
Voltage [V] |
effective maximum
Scale value [MΩ] |
Valid measurement
Range [MΩ] |
examples showing the use (of a word) | |
| General electrical equipment | Electrical equipment and circuits | |||
| 25 | 20 (10) | 0.02-10 | Insulation measurement at safe voltage | － |
| 50 | 20 (10) | 0.1-50 | Insulation of equipment for telephone lines | － |
| 100/125 | (20) | Insulation measurement of control equipment | Low-voltage circuits and equipment of 100 V class or less | |
| 250 | (50) | Insulation measurement of control equipment | Low-voltage circuits and equipment of 200 V class or less | |
| 500 | (100) | Circuit under 300V
Instrument Insulation Measurement |
Low-voltage circuits and equipment of 400 V class or less | |
| 500 | (1000) | 1-500 | Circuit under 300V
Instrument Insulation Measurement |
|
| 1000 | (2000) | 2-1000 | Circuit with more than 300V
Equipment insulation measurements |
Equipment that uses high voltage |
Which comes first, the insulation resistance test or the dielectric strength test?
The insulation resistance test is generally conducted first, since it is used to verify that it is possible to apply the test voltage before conducting the dielectric strength test. (Some product standards do not require an insulation resistance test.)
That's it.