Protective conductor resistance test devices

Typically, electrical products are connected to the power grid via power cords with a power plug or connection terminals. The protective conductor test is therefore carried out between the PE of the mains plug or the PEconnection clamp and all associated metallic housing parts of the electrical product.

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

The protective conductor test detects these faults.

• Interrupted protective earth conductors
• Protective earth conductors with excessively high resistance, poor contact resistance
• Intermittent connections or poor terminal points of the protective earth conductor

How is the protective earth conductor tested?

The protective conductor test is performed in most cases based on the measured ohmic resistance. Alternatively, the voltage drop across the protective earth conductor can also be measured.

To determine the resistance or voltage drop, a high minimum Test current must flow through the protective earth conductor, depending on the test standard. The test device adjusts 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 earth conductor to 'Burn away' any weak connections. However, with typical test times of one second, this is usually not achieved in reality, as heating the contact to the point of burning away is hardly possible within this time.

For precise protective conductor tests, the four-wire technology (also called Kelvin measurement, 4L or 4W) is extremely important. Only with this is it reliably possible to precisely measure small resistances in the mΩ-space. The test device therefore determines the voltage drop across the protective earth conductor using four-wire technology and calculates the protective conductor resistance based on Ohm's Law.

The "good/bad" criteria.

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

Protective conductor test with AC or DC?

The Test current is alternating current in most cases. However, in some applications, for example with long coiled Connection leads, direct current can also be advantageous.

This is how the protective conductor test is run.

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

Our test devices are all designed according to the "KISS principle". Following the motto: »Keep It Simple and Smart«. This principle serves as a guiding theme for all SCHLEICH products!

A manual Test is performed with a protective earth conductor test tip. For this, the operator guides the test tip manually from test point to test point. Despite the manual process, the Test can be perfectly documented. A typical application here is the inspection of electrical products, control cabinets, and machines according to the Machinery Directive EN60204.

For the requirements of production facilities, semi- or fully automated protective conductor test devices or protective conductor test systems provide suitable solutions. For this purpose, the test devices are equipped with a relay switch-over field (relay matrix). These automatically switch the Test currents to the desired test points.

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

The requirements for a standard protective conductor test device.

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

SCHLEICH protective conductor test devices are based on over 30 years of experience. From the beginning, the measurement technology was not analog but always designed digitally. Fundamentally, the latest technologies are always applied.

This is how you find the right protective conductor test device.

The number of protective conductor test devices available on the market is large, and the quantity of configurable features is overwhelming.

If you only wish to run protective conductor tests with AC or DC on your device under test, a single test device is highly recommended. It contains only the "protective conductor resistance" test method.

If the device under test also requires a more comprehensive safety and function check, we recommend our combination test devices/multifunction testers. With these, various test methods such as protective conductor, insulation, and high voltage test can be conveniently combined in one test device. The fully automatic test method switch-over built-in to the test device ensures that no measurement leads need to be manually re-terminaled on the device under test during the Test.

Furthermore, the combination of safety tests and extensive function tests is also frequently found. For the function test, the test device additionally supplies the device under test with electrical operating voltage to also check the electrical operating characteristics.

Thanks to the intuitive and convenient operation of SCHLEICH protective conductor resistance test devices, every Test is performed quickly, precisely, and cost-effectively.