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This Is How We Perform Electrical Safety Tests on Generator Sets at Inmesol

At Inmesol, ensuring the safety of our generator sets is paramount. That is why we carry out several verification tests during the final stage of manufacture. As we are dealing with machines which generate electrical energy, the electrical safety checks have particular relevance in the process.

At Inmesol, ensuring the safety of our generator sets is paramount. That is why we carry out several verification tests during the final stage of manufacture. As we are dealing with machines which generate electrical energy, the electrical safety checks have particular relevance in the process.

As well as load tests–checking the generator sets supply the power they are designed for–each generator set is subjected to an exhaustive protocol of tests. These include checking the thermal-magnetic and differential electrical protection works properly and verifying the potential equalisation and electrical insulation. The latter tests are essential to ensure that the equipment offers the necessary safety mechanisms in the event of a power supply or bypass. Here at Inmesol, we perform these tests in the order described below:

1º. Potential equalisation protection verification trials

These tests comply with Section 18.2 of the standard EN 60204-1: Safety of machinery – Electrical equipment of machines. They allow us to check that all the metal components to which the user has access are connected to the main earthing protection terminal, thereby forming a proper potential equalisation network so that if there is a bypass or leak while the machine is being used, the electrical protections ensure that the current comes from the earthed installation.

Taking measurements between the different metal parts on the generator set
Taking measurements between the different metal parts on the generator set canopy and the main protection terminal.

Fundamentally, this trial must check that there is very low electrical resistance between the main potential equalisation protection terminal and the metal parts to which the user has access. To check this, and given the characteristics of our generator sets, we usually apply a trial current of at least 25 A, so we use a power source which supplies up to 24 V of alternating current.

We measure the resistance between the main protection terminal and the points on the genset with which the user may come into contact during the machine’s operation, noting the values, which generally oscillate between 8 and 36 m Ω. Although the resistances are extremely low and the regulation establishes determined limits, if we obtain a value which significantly differs from those stipulated, we rectify the earthing interconnection, as the difference tells us that there is no continuity in this part. This revision is carried out exhaustively to confirm continuity in all the pieces.

Reading of the resistance between the generator set’s main protection terminal
Reading of the resistance between the generator set’s main protection terminal and the right-hand canopy.

2º. Electrical insulation trials

 These tests are performed in accordance with Section 18.3 of the abovementioned standard EN 60204-1 and they serve to check that the insulation between the active parts of the generator set (those subjected to voltage) and the non-active parts (with metal accessible to the user) is sufficiently effective.

The verification process consists of measuring the resistance between the active parts in the genset and the main earthed protection terminal by applying a power source of 500 Vdc. (All the non-active metal parts in the genset are already connected with potential equalisation to the main earthing protection terminal.)

A 500 V direct current is applied using a digital multimeter.
A 500 V direct current is applied using a digital multimeter.

For these trials, the regulation does establish a minimum resistance value of 1 MΩ, even though the tests carried out give values of several dozen MΩ or GΩ. In the latest tests performed at Inmesol, for example, the resistance value was 12.2 GΩ, indicating that the insulation is indeed very high.