Distribution grids
POWERSAVE ensures safe and stable grid operation in distribution grids.
The devices monitor lines, transformers and busbars and react reliably to overloads, short circuits or earth faults. Thanks to the modular platform and integrated communications, all protective functions can be easily adapted to the grid structure.
The nondirectional and directed overcurrent time protection (UMZ) with ground fault detection enables precise fault localization and fast disconnection of faulty grid sections.
This increases the security of supply and simplifies reconnection after power-system faults.
Distribution grids – interaction scheme
The single-pole interaction scheme clearly shows the protection and control functions in transmission networks.
The proven principle of evaluating the total zero sequence current IE and displacement voltage UNE in the 50 Hz range enables reliable fault detection. The intermediate angle is taken into account and, depending on the device type, the capacitive charging power QEcap can also be used as a triggering criterion.
In isolated networks with earth fault currents in the range of 80…150…(300) A and in compensated networks, the zero sequence current often has to be provided by a balanced tie-bar group or a cable conversion transformer.
Sine and cosine circuits are precisely analyzed with wattmetric detection. SAVE technology calculates the active and reactive components of the earth current (P0 and Q0) in the frequency range up to 1000 Hz. This method offers increased stability in earth fault detection and avoids false detections.
In compensated systems, the earth fault current can be so small that the fault arc extinguishes immediately. As soon as the line phase voltage of the faulty phase-to-phase conductor exceeds a critical value again, re-ignition begins. This process repeats itself as long as the fault has not been rectified and is identified as an intermittent earth fault.
The problem is that the recharging current in the two healthy conductors flows in the opposite direction to the displacement voltage UNE. As a result, the active current (IWE/PE) and reactive current (ICE/QE) continuously change sign, which can lead to inaccurate direction detection.
SAVE technology solves this problem by evaluating the zero sequence energy E0. The actual fault direction can be reliably determined via the averaged power in the forward direction.
Our protection solutions combine precision, reliability and simple integration – for maximum grid stability.
Contact us and find out how NSE can make your distribution grid safer and more efficient.
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