Short-circuit power and short-circuit resistance

Short-circuit power is the theoretical current that will run in the event of a short circuit if the protection has not yet intervened. This theoretical short-circuit current at the point of the voltage junction depends on the impedance of the voltage source (power-supply transformer, generator, etc.).

The short-circuit power can be calculated, but this can be difficult because not all data on the electrical installation is available in many cases. The standard value lies between 6 kA and 60 kA. However, as much as 150 kA must be taken into account for a voltage junction in a substation close to the power-supply transformer.

Click here to read the whitepaper about short-circuit power and short-circuit resistance.

Safe Voltage Tap

Securing a voltage tap is an important part of ensuring a safe connection. When selecting a fuse, the short-circuit power must be taken into account.

A standard glass fuse can often only sustain a short-circuit capacity of up to 700 A. In the event of a short circuit caused by a glass fuse in a sub-fuse box, there is a high risk of an electric arc.

Click here to read the whitepaper about a safe voltage tap.

Current and voltage measurements

To gain insight into energy currents and energy quality it is important to measure both the current and the voltage.

The current is measured per phase of a field. This can be the supply field or the outgoing fields. Depending on the type of electrical installation and the meter used, the voltage is measured at one point in the installation. After all, the current on the supply field and the outgoing fields is different, but, under normal circumstances, the voltage is the same. However, in case the loss of voltage on an outgoing field has to be detected as well, it is necessary to measure the voltage on all outgoing fields.

Click here to read the whitepaper about current and voltage measurements.

Measurements Category

Determining the short-circuit power of an electrical installation can be difficult. To gain a clear understanding of the necessary short-circuit resistance and components in a certain installation, measurement categories are defined.

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Transient overvoltage

There are various causes for overvoltage in an electrical installation. The most common transient overvoltage is caused by lightning or switching events in the grid.

This means that components in the CAT IV area must be able to withstand a higher overvoltage than those in the CAT II area.

Click here to read more about the impulse withstand voltage levels prescribed in NEN 1010.

Burden of a Current Transformer

A current transformer converts a high primary current with a secondary winding around a magnetizable core to a lower secondary current. A current transformer is passive, therefore no external power supply is connected, and what is secondary connected forms a load for the current transformer. In short, the connecting wires and the connected meter form the load of the current transformer. In technical terms this is called load in VA. This load is of influence on the accuracy of the current transformer.

In the design of the current transformer, internal losses and the external load of the current transformer are taken into account. The current transformer acts as a power source.

Click here to read the whitepaper about the Burden of a Current Transformer.