Short circuit calculations: calculating and simulating occurrence of short circuit currents
In addition to simulations of aspects such as harmonic distortion and rapid voltage variations, HyTEPS also performs short circuit calculations. These calculations allow HyTEPS to provide a clear insight into currents that occur in the event of a short circuit. In this way, problems and risks can be prevented. To carry out short circuit calculations, we rely on professional software packages and the academic knowledge (and experience) of our engineers.
In part, the safety of an electrical installation depends on its resistance to short circuit currents. In the event of a short circuit, an excessive current will result in overheating of electrical components and an electromagnetic force between the conductors. This, in turn, may lead to powerful explosions that could potentially destroy components and endanger people. A toxic copper emulsion will also be released. For this reason, it is vital that electrical installations are resistant to occurring short circuit currents. Short circuit calculations provide insight into the short circuit resistance of an installation and components and the dangers for anyone working around or with the installation.
Simulating installations and making short circuit calculations are of the utmost importance to ensuring safety is guaranteed in all situations. This applies to low-voltage and medium-voltage installations, to installations with one transformer or more than 200, and to normal and emergency operation.
A short circuit current depends on the impedance of the network and the power supply, emergency generator(s) and engines. For this reason, short circuit calculations are based on the following situations:
1) Power supply
2) Emergency power
Short circuit calculations during installation design
When designing an electrical installation, short circuit calculations are a prerequisite. By calculating the short circuit currents that might possibly occur, you can assess whether components in an installation are sufficiently short circuit-proof. For example, switching and distribution devices are built with a specific thermal and dynamic short circuit resistance. This short circuit resistance must be specified for each distribution device. Often, there is a maximum peak value and an effective short circuit current carried by the rail system for one second. However, the protection will cut off the occurring short circuit current much faster and recalculation can take place.
Circuit breakers also limit any short circuit current that they can switch off. This value is indicated on the circuit breaker. You should check whether circuit breakers have (inadvertently) been placed at a point in the installation where the short circuit current is exceeded. Short circuit calculations provide insight into components’ short circuit resistance.
Short circuit resistance of existing installations
In existing installations, it is important to find out whether the installation and components are still short circuit resistant by carrying out short circuit calculations. Over the years, a great deal may have changed in electricity grids, installations and components. These changes may have affected the short circuit resistance. Installations protected from problems and the risk of short circuit currents during the implementation phase may now conceal hidden dangers. It is also important to gain insight into the short circuit resistance of the current installation and the influence intended changes have on this; ensuring installation safety has the highest priority. Short circuit calculations provide the necessary tools for this.
Maximum and minimum short circuit currents
In addition to the maximum value of a short circuit current that may occur, the minimum short circuit current that may occur must also be taken into account. Even when closing at the end of a line or at the end of an installation, the short circuit current must still be sufficient to ensure that the protection is activated in time. The duration of this may depend on the purpose of the protection. In the case of a closure between a phase and a metal device, there an earth fault current will occur. This can cause a fault voltage to be applied to the metal frames. This fault voltage should normally be disconnected in 0.4 seconds. The protective measure takes care of automatic disconnection of the power supply in the event of a fault in the installation. This is taken into account in the short circuit calculations that HyTEPS performs.
Safety guarantee by short circuit calculations
Simulating installations and producing short circuit calculations are essential to guaranteeing safety in all situations. Even in emergency power situations, in which an installation is powered by one or more generators, an adequately functioning safety concept is necessary. The short circuit current that occurs changes significantly in the case of generators that run in parallel with the public grid or in situations in which these need to power the installation autonomously. It is very important to monitor the short circuit currents by means of short circuit calculations.
Arc energy is the cause of most electrical damage
Most electrical injuries and deaths are the result of burns caused by an electric arc that may occur during closure. The electric arc not only threatens the safety of employees, but also causes an operational shutdown. Short circuit calculations can also be used to calculate the occurring arc energy and implement measures for this problem.
Example: Arc flash - Worst case scenario
HyTEPS is an expert in short circuit calculations
By using professional software packages and our engineers' significant electro technical knowledge, we can carry out these vital short circuit calculations for you. This provides you with a good overview of the installation, the proper functioning of the protections and an answer to the question whether the installation has been properly designed, for normal as well as emergency operation!