What is selectivity?
Selectivity is the practice of dividing an installation by introducing circuit breakers, so that any part eliminated in the event of a defect will be as small as possible. In other words, the overcurrent protection of the sub-distribution system is activated earlier than the overcurrent protection of the main distribution device. Earth fault protection also has selectivity. Selectivity is a NEN1010 requirement for the earth fault protection as well as the overcurrent protection. This is to guarantee the safety in the installation.
Why is selectivity so important?
HyTEPS provides validation, simulation and calculations for selectivity
HyTEPS can use simulations to help ensure business processes continuity by validating current selectivity and setting the right requirements for future installations. HyTEPS always provides customization and can, therefore, potentially make discoveries that are usually not taken into account, such as long cables with a high impedance. HyTEPS offers you years of knowledge and experience, and an extra pair of – objective – eyes.
Selectivity: sometimes regulations are not enough
A short circuit at the end of a long cable, resulting from the cable impedance, causes a lower short-circuit current than at the beginning of the cable. It is, therefore, possible that the short-circuit current in the event of a short-circuit at the end of the cable is too low to trigger the short-circuit protection. This is life threatening and causes greater damage than necessary. Elements in the circuit can melt and the arc energy increases. This elevates the risks of long-term arcs. HyTEPS can help you detect and prevent situations such as this.
Selectivity and Power Quality
At first sight, Power Quality and selectivity may appear to have little to do with each other. However, the way in which problems are solved sometimes affects selectivity. For example, when a larger circuit breaker or earth leakage breaker is installed to solve the problem of inrush currents being too high. The tripping of the machine can also be caused by harmonic currents or unbalance.
Selectivity and weak nets such as ships and yachts
At sea, safety and reliability are of the utmost importance. Properly functioning selectivity can be vital in offshore applications. As a result, selectivity is described in detail in DNVGL guidelines.
Selectivity and stand-alone operation
Incorrect selectivity can cause generators to fail with a relatively small error. This can be catastrophic and cause a wave of failure within weak networks. If your installation is running in stand-alone operation, it is extra vulnerable to influences from within, where a selectivity flaw can be the last straw.
Some cases
Wij verzorgen al jarenlang simulaties op het gebied van Power Quality. Onze engineers brengen het probleem in kaart en HyTEPS levert de best passende oplossing. Onze relaties bevinden zich in een breed scala aan sectoren waaronder industrie, ziekenhuizen en offshore. Enkele van onze cases hebben wij voor u uitgewerkt. Klik op de case en lees meer over de uitdaging, onze oplossing en de resultaten.
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