Schleich Test Technologies

Everything you always wanted to know about the protective conductor test.

The protective conductor test, also known worldwide as the PE test or GB test ( G round  bond ), is one of the most important test methods of all.

Why is the protective conductor test so important?

Devices with  protection class I  have a high degree of danger. Therefore, the protective conductor test required by the standards is absolutely necessary here.

In an electrical device with protection class I, the protective conductor is used to avoid dangerous contact voltages on the metallic housing parts of the device. The protective conductor on these products must therefore function with absolute reliability. It connects the metallic housing parts to earth.
In the case of a defective electrical device with an insulation fault, the upstream residual current circuit breaker (FI) will not trip if the protective conductor is interrupted. The defective electrical device would therefore pose the greatest risk. That is why the protective conductor test can be found in almost all test regulations (e.g. VDE, EN, IEC, UL ...).

Where is the test object tested?

Electrical products are typically connected to the mains via mains cables with mains plugs or connection terminals.
The protective conductor test is therefore carried out between the PE of the mains plug or the PE connection terminal and all metal housing parts of the electrical product connected to it.

If several metal housing parts are connected to the protective conductor in an electrical device, the safe function of the protective conductor must be verified individually on each housing part. If protective conductor connections are no longer accessible on the fully assembled electrical device, these protective conductor connections must be tested during production in intermediate tests.

What errors does the protective conductor test reveal?

• Broken protective conductor
• Protective conductor too high resistance, poor contact resistance
• Loose contacts or bad terminal points of the protective conductor

How is the protective conductor checked?

In most cases, the protective conductor is tested on the basis of the measured  ohmic resistance . Alternatively, the voltage drop
across the protective conductor can also be measured.

Depending on the test standard, a high minimum test current must flow through the protective conductor to determine the resistance or the voltage drop. The test device sets the level of the test current according to the specification and regulates it to a constant value.

The high test current is intended to simulate a load on the protective conductor in order to "burn away" any weak transitions that may be present. With typical test times of one second, however, this usually does not succeed in reality, since it is hardly possible for the contact to heat up to the point of burning off in this time.

The  four-wire technique  (also called Kelvin measurement, 4L or 4W) is extremely important for precise protective conductor tests. This is the only way   to reliably measure small resistances in the mΩ range . The tester uses four-wire technology to determine the voltage drop across the protective conductor and calculates the protective conductor resistance based on Ohm's law.

What are the “good/bad” criteria?

Upper limit values ​​for the ohmic resistance or the voltage drop are defined in standards. These limit values ​​must not be exceeded under any circumstances.

Protective conductor test with AC or DC?

In most cases, the test current is alternating current. In some applications, for example with long, coiled connecting cables, direct current can also be advantageous.

How is the protective conductor test carried out?

Whether manual, semi-automatic or fully automatic: with protective conductor test devices from SCHLEICH, every test task can be carried out quickly and efficiently.

Our testing devices are all designed according to the "KISS principle". So according to the motto:  " Keep It Simple and Smart " . The principle is the leitmotif for all SCHLEICH products!

A manual test is carried out with a protective conductor test probe. To do this, the operator guides the test probe by hand from test point to test point. Despite the manual process, the test can be perfectly documented. A typical application here is the testing of electrical products, control cabinets and machines according to the Machinery Directive EN60204.

Partially or fully automated protective conductor testing devices or protective conductor testing machines are available for the requirements of production companies. For this purpose, the test devices are equipped with a relay switch panel (relay matrix). These automatically switch the test currents to the desired test points.

Depending on the application, test systems of this type have up to 1,000 test connections.

Requirements for a standard protective conductor test device?

Many national and international standards require  test currents between 10 and 30 A. These test currents can be specified in stages in the test device. In addition, SCHLEICH also supplies protective conductor test devices from  1 A to 500 A AC/DC  test current.

SCHLEICH protective conductor test devices are based on more than 30 years of experience. From the beginning, the measurement technology was not analogue, but always digital. In principle, the latest technologies are always used.

How do you find the right protective conductor tester?

The number of protective conductor testers available on the market is large and the number of configurable features is overwhelming.

If you only want to carry out protective conductor tests with AC or DC on your test object, you are well advised to use a single test device. It only contains a single test method, namely the protective conductor test.

If the test object also requires a more comprehensive safety and function check, we recommend our combination test devices/multifunction testers. This means that various test methods such as protective conductor, insulation and high-voltage tests can be conveniently combined in one test device. The test method switching integrated in the test device ensures that no measuring lines on the test object have to be reconnected manually during the test.
In addition, there is often a combination of safety tests and extensive functional tests. For the function test, the test device also supplies the test object with electrical operating voltage in order to also check the electrical operating properties.

Thanks to the intuitive and convenient operation of our protective conductor testers, each test is quick, precise and cost-effective.

The SCHLEICH product portfolio

• Test currents from 1 to 500 A AC or DC
• Electronically and automatically regulated test current
• Standardized interfaces such as RS 232, Ethernet/LAN, USB for PC communication
• 24 V digital I/O for PLC communication
• Expandable to Industrial Ethernet and fieldbus systems for PLC communication
• Almost unlimited storage space for test plans and test results
• All parameters determined via the software
• Test probes of various designs with/without integrated start button and indicator light

In addition, we are happy to plan, design and produce individually tailored solutions for you:

• Combination tests/Multifunction tests
• Testing machines/testing systems with a small to complex relay matrix
• Complete testing workstations
• Production lines with transfer systems
• EOL jobs
• large plants

When selecting your protective conductor test device, also pay attention to the "soft skills" of the provider. We offer all the necessary accessories and support you throughout the entire service life of your protective conductor test device:

• Professional advice with technical know-how
• Careful initial start-up
• Regular certified calibration
• After-sales support from our service team
• Service on the phone, via remote maintenance or on site
• Tailored training

SCHLEICH - the world's only provider of protective conductor test devices that has already been awarded the "TOP100 Innovator" seal of quality four times.