The insulation test

Do I feel safe?

Am I doing everything right?

With safety , you safety in just a few minutes.

Safety tests are mandatory and are part of every final inspection of your electrical product.
Learn the most important facts about insulation resistance testing in a nutshell.
We explain the WHY, WHERE, HOW, and also the WHEN NOT!
And if you want to learn more, you can download more detailed information at the bottom of this page for free!

The WHY?

Safe insulation is the key protective measure for ensuring electrical safety. It ensures that the operator touch operator live conductors and that no short circuit can occur between the conductors or to the housing of the equipment. If this were to happen, a life-threatening current could operator through the operator when they touch the housing. Of course, the protective earth conductor ensure that this does not happen. But in the worst case, it could also be defective. And it would only be avoiding the effect, not the cause.

to ensure all this, the insulation must function perfectly! And you must prove and document this by performing an insulation resistance test before delivering the electrical product.

The insulation resistance test is an individual test. This means that every item, i.e. every single electrical product you place on the market, must undergo an insulation resistance test.

The WO?

Now it gets a little more complicated than, for example, with the protective earth conductor. Basically, there must be good insulation between live conductors or between these and housing parts. Typically, the electrical conductors are insulated against dangerous contact, i.e., they are covered with an insulating material. However, this protective cover must be removed at the latest when the electrical conductor is connected to other electrical components. At these points, insulation is ensured by a safe distance. This involves safety distances through air and creepage distances.

In addition, live conductors can also be insulated from each other using casting compounds, insulating films, or solid materials, for example.
When is which type of insulation used?
This always depends on the design of the electrical product and the type of requirements, such as high temperatures or mechanical stress, etc.

It is certainly understandable that insulation in a light fixture, an iron, an electric motor a high-voltage insulator in a power plant has very different requirements and designs.
This diversity therefore results in quite complex electrical insulation structures on a case-by-case basis.

The HOW?

Since the insulation has "something to do with voltage, voltagethe test is performed with a defined test voltage level. This can be device under test to the device under test in a ramp-shaped increase or directly at full level.

The aim is insulation resistance measurement the current measurement then insulation resistance the insulation resistance , as this is the evaluation criterion for insulation. It must be equal to or greater than a specified minimum resistance.
The lower limit of insulation resistance may be defined differently from product to product and in different regions/continents. Therefore, you must test parameters refer to the standard applicable to the product and region for the test parameters .

insulation resistance is often measured insulation resistance between all conductors involved in the electrical product. These can be groups of conductors, individual conductors, and, of course, the housing or housing parts. It quickly becomes apparent that, depending on the complexity of the electrical product, the test run and must run at a wide variety of locations.
This could be done by scanning the test points with a test probe – an approach that can quickly prove to be time-consuming and costly.
For this reason, complex tests have been carried out automatically and freely programmable at any test points using the SCHLEICH matrix for 25 years:

SCHLEICH switch flexibly in 2- and 4-wire technology. The 4-wire technology is particularly important in automated systems and plants. It guarantees reliable contact control of the TEST VOLTAGE thus process reliability.

With such a wide range of requirements, it is of course ideal to use a testing device that covers as many of the global standards as possible.
That is our strength.

The test duration?

Does insulation always consist of insulation resistance a capacitor? Why a capacitor? It wasn't even installed? ...

Insulation measurement always takes place between electrical conductors and/or housing parts. In abstract terms, these two components form two metal surfaces that are a certain distance apart. The insulation is between them. And this structure corresponds to a capacitor. As a result, the entire insulation structure also behaves similarly to a capacitor.
After applying the TEST VOLTAGE, the capacitor will naturally charge first. Only when the capacitor is charged insulation resistance the current insulation resistance through the insulation resistance .

It is clear that, due to physical conditions, insulation resistance measurement cannot be performed within tenths of a second in many cases. The tester could do so, but the device under test not yet ready.

Complex structures such as electric motors, windings in general, and long cables/underground cables still exhibit polarization effects. Discussing this phenomenon in detail would go beyond the scope of this article, but you can read about it in the free download.

When not?

Insulation resistance testing is generally always required, unless a high voltage test is high voltage test as an alternative.
The high voltage test even more intensive and reliably detects insulation weaknesses. However, it also has a decisive disadvantage, as the precise measurement insulation resistance in MΩ or GΩ is not possible with high voltage AC. The niO rating is therefore based on excessive leakage current insufficient insulation resistance in the case of high voltage!

Standards often specify the use of both test methods.
The insulation resistance test with 500 V DC for very precise insulation resistance determination and the high voltage test AC and typically 1500 V or 1800 V TEST VOLTAGE 100 mA short-circuit current and 500 VA power.
Further information on high voltage test in our next know-how newsletter or at SCHLEICH .

All clear? Want more details?

Our mission – knowledge, knowledge, knowledge ... Those who have a sound technical and normative understanding of testing methods will get the most out of their testing equipment.
– Dipl. Ing. Martin Lahrmann

Yes—keep me informed. I want maximum safety our customers, our company, and myself.

Please send me further detailed information from the SCHLEICH.