Pulse Circuit Fault Current Injection for DC Grid Selectivity
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Solution Overview
Problem
In DC voltage power supply grids, the selectivity of protective devices is compromised during overcurrent events, leading to unintended deactivation of non-faulty electrical devices, as the principle of selectivity is not reliably ensured due to the time required to detect and respond to faults, particularly in systems with varying electrical capacitance and inductance.
Innovation Solution
A pulse circuit is connected to the electrical lines to discharge a predefined electrical charge quantity when a voltage dip occurs, allowing for the reliable deactivation of the faulty device connection without affecting other devices, thereby improving selectivity by providing a pre-defined charge quantity based on the overcurrent and discharge time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protective devices deactivate faulty device connections during overcurrent events, then fault isolation is achieved, but operational readiness of other devices deteriorates due to voltage dips
Solution Approach 1:
The pulse circuit implements beforehand cushioning by pre-calculating and injecting a charge quantity q = I_overcurrent × U_supply × t_discharge that compensates for the voltage dip caused by faulty device deactivation. This cushioning current ensures that other electrical devices maintain adequate power supply during the fault isolation process, preventing operational disruption and maintaining productivity while achieving reliable fault isolation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution significantly enhances selectivity in power supply grids with DC voltage, reducing the undesired deactivation of non-faulty devices and ensuring operational readiness of other electrical devices, while maintaining a low implementation effort.
Implementation Method 1
a pulse circuit for discharging a pre-definable electrical charge quantity with at least one capacitor, which is designed to discharge the electrical charge quantity when a voltage dip of the supply voltage occurs
Data Source
AI summary
Electrical devices are connected to a DC voltage power supply grid being connected to a power source and having a supply voltage. Protection devices protect the electrical devices against an unintentional overcurrent sensed by a sensor unit. The protection devices disconnect the electrical devices from the DC voltage power supply grid when an overcurrent is detected. A pulse circuit having a capacitor with a semiconductor switching element connected in series with the capacitor is connected to respective inputs of the protection devices and supplies an amount of electric charge when a voltage dip occurs, wherein the amount of supplied electric charge is determined based on the detected overcurrent and a predetermined time period.