THE CLIENT
A subway substation in a large metropolis.
THE NEED
The need was to limit the short-circuit current to 8kA for 100ms for the UPS intended for emergency services. This was because the power line would have a short-circuit current of around 30kA, with the risk of compromising the integrity of the backup system and the continuity of power supply in critical conditions.
OUR SOLUTION
To overcome this critical issue, it was necessary to install a limiting reactor capable of increasing the impedance of the circuit and limiting fault currents to values compatible with the characteristics of the UPS.
Unlike ferromagnetic core reactors, which are subject to magnetic saturation during current peaks, air reactors maintain their inductive value even under heavy stress. This is possible because the magnetic permeability of air does not vary with current, ensuring a stable and predictable response even in the event of a short circuit.
The reactance supplied was custom designed by Ortea, with the support of advanced magnetic simulations using finite element analysis (FEM). This approach made it possible to:
- Study the distribution of the magnetic field inside the IP31 metal cabinet.
- Minimise mutual inductances between the three phases.
- Reduce additional localised losses.
- Optimise the distance between the coils.
- Ensure reliable and safe performance even under the most severe fault conditions.
The reactance was installed in an IP31 cabinet weighing approximately 200 kg and measuring 600 x 900 x 2100 mm, perfectly integrated into the technical environment of the substation.