The leakage current test

Do I feel safe?

Am I doing everything correctly?

You will know this for sure in a few minutes.

Safety tests are mandatory and are part of every final inspection of your electrical product.
Learn the most important facts about the leakage current test concisely.
We explain the WHY?, WHERE? and HOW?
And if you want to learn more, you can download even more detailed information for free at the end of this page!

The INSULATION ?

As with the insulation resistance and high voltage test, the leakage current test also revolves around the quality and safety of the insulation.

The leakage current test takes place during the real operation of the electrical device. For this purpose, the electrical device is connected to operating voltage and tested to see if an excessive leakage current flows through the insulation to the housing. It is therefore a combination of a safety and function test.

The WHY?

Safe insulation is the central protective measure to ensure electrical safety. It ensures that the operator cannot touch live conductors and that no short circuit can occur between the conductors or to the equipment housing. Because if it were to occur, touching the housing could cause a life-threatening current to flow through the operator. Of course, the protective earth conductor should ensure that this does not happen. But in the worst case, it could also be defective. And it would only be an avoidance of the effect, not the cause.

To ensure all of this, the insulation must function perfectly! And this must be proven and documented by you through a leakage current test before the electrical product is delivered.

This test is not mandatory for all electrical devices. However, it may well be required for the certification of the electrical device in the type test. If it is required during manufacturing, it is a routine test. This means that every single electrical product you place on the market absolutely requires a leakage current test.

The HOW?

Since the insulation has "something to do with voltage", the test is carried out with an increased nominal voltage. The increase is typically +6%, +10%, or +15%. Justification: since the mains voltage at the end customer's site could later be increased by up to +10%, this should be simulated accordingly during the test. The electrical product is therefore in an operating state with overvoltage.
This approach has the advantage that, during the ongoing test, as many components of the electrical product as possible are temporarily or permanently energized.
The test is also often referred to as the "warm leakage current test". Logically, there is also the "cold leakage current test". In this case, the electrical product is consequently not operated. The test severity is lower here.

The objective is to measure the current flowing through the insulation under a wide range of fault conditions, as this current serves as the evaluation criterion for the insulation. It must never exceed a predefined maximum current throughout the entire test duration.
The upper limit for the leakage current can vary depending on the product and different regions/continents. Therefore, operators must refer to the test parameters specified in the applicable standard for the respective product and region.

Current measurement is not merely a simple measurement performed with a multimeter!
Instead, the operator is simulated using various RC networks (resistor-capacitor networks), which are defined in the relevant standards for different potential fault conditions.

The Test is performed under various fault conditions automatically simulated by the tester.
During this process, the leakage current in the protective earth conductor of the electrical device is measured.

If there are housing parts on the electrical product that are not connected to the protective earth conductor, the test is performed using a test probe.

For 25 years, complex tests have therefore consistently been performed automatically and freely programmable at any desired test points using the SCHLEICH-typical matrix:

Given this wide range of requirements, it is naturally ideal to use a test device that covers as many worldwide standards as possible.
This is our strength.

The LEAKAGE CURRENT up to 1 MHz?

Increasingly, modern electrical products feature built-in electronic components. Switching power supplies are very frequently employed for internal voltage supply. These can generate pulse-like leakage currents with very high frequency components up to 1 MHz. To effectively test these, the leakage current measurement technology must necessarily be designed to operate up to 1 MHz.

The effort involved is not insignificant.
SCHLEICH provides the 1 MHz leakage current test, including factory calibration or DAkkS calibration! The frequency response of the measurement circuit is also documented as part of this process.

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– Dipl. Ing. Martin Lahrmann

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