Standby Power Supply Isolation Using Series Switching Elements
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Solution Overview
Problem
Standby power supply systems require ensuring safe disconnection from the superordinate power grid to prevent power feeding back into it, especially during maintenance, without using expensive contactors with priority control, which are not suitable for conventional installation boxes.
Innovation Solution
A standby power supply system utilizing two series-connected switching elements, where one is directly actuated by the superordinate power grid and the other by an island detector in the local power supply device, ensuring safe disconnection without priority control contactors, ensuring 'single-fault safety' by monitoring voltage and island situations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If contactors with priority control and checkback contacts are used to ensure safe disconnection, then safety of personnel is improved, but device cost and size increase
Solution Approach 1:
The patent divides the disconnection device into two separate switching elements (first and second switching elements) connected in series. Each switching element is controlled independently - the first by voltage detection from the superordinate grid and the second by the island detector. This segmentation allows using simple, inexpensive switching elements instead of complex priority control contactors, while maintaining safety through the series connection configuration.
2Reliability
If contactors with priority control are used to ensure safe disconnection, then reliability is improved, but ease of installation worsens due to incompatibility with conventional installation boxes
Solution Approach 1:
By segmenting the disconnection function into two independent switching elements with simple control mechanisms, the patent creates a system that fits within conventional installation boxes. The first switching element responds to voltage presence from the superordinate grid, while the second responds to island detection, together achieving safe disconnection without requiring specialized priority control contactors.
Solution Approach 2:
The switching elements are designed to operate autonomously based on their control inputs - the first switching element automatically opens when voltage is detected, and the second opens when an island situation is detected. This self-service operation eliminates the need for complex priority control logic and checkback contacts, making the system compatible with standard installation boxes.
3Device complexity
If two series-connected switching elements are used instead of priority control contactors, then device cost and size are reduced, but ensuring single-fault safety becomes more challenging
Solution Approach 1:
The patent segments the control mechanism into two independent pathways: voltage detection for the first switching element and island detection for the second switching element. This segmentation ensures that a single fault in one detection system or switching element does not compromise overall safety, as the other pathway remains functional. The series connection of switching elements further ensures that both must be closed for power flow, providing redundant safety.
Data Source
AI summary
The disclosure relates to a standby power supply system for connection to a superordinate power supply network and a local power distribution network, having a network isolation device for connecting the local power distribution network to the superordinate power supply network by means of at least two series-connected switching elements with respectively associated switching contacts and having a local power supply device with a separate-network detector for identifying a separation situation for the local power distribution network. A first of the two switching elements is connected to the superordinate power supply network and the second of the two switching elements is connected to the local power supply device. The disclosure furthermore relates to methods for isolating a local power distribution network from a superordinate power supply network.