Synchronous Machine Reactance for Electrical Network Disruption Protection
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Solution Overview
Problem
Existing protection systems for local electrical networks connected to external urban or industrial networks fail to adequately manage disruptions, leading to voltage drops and overcurrents that can shut down local power sources and users, especially when 'green' energy sources like photovoltaic panels and wind turbines cannot supply sufficient current peaks during network disconnections.
Innovation Solution
A protection system that includes a synchronous machine with low subtransient reactance connected to the local network via a network choke and a local choke between the local power source and the synchronous machine, which limits current injection into the external network and current supply from local sources, maintaining voltage and preventing overcurrents during external network failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If local power sources (photovoltaic panels, wind turbines) are connected to the external network via semiconductor inverters, then green energy can be injected into the external network, but during external network disruptions the inverters cannot supply sufficient current peaks causing voltage drops and shutdown of local users and sources
Solution Approach 1:
A synchronous machine with low subtransient reactance is introduced as an intermediary between the local power sources and the external network. This synchronous machine acts as a buffer that can rapidly respond to network disruptions by providing high current peaks during the disconnection period, thereby maintaining voltage stability and preventing shutdown of local users and power sources while allowing green energy injection during normal operation
2Object-affected harmful factors
If circuit breakers are opened quickly (less than 100 milliseconds) to isolate the local network from external network disruptions, then local users can be protected from external disruptions, but the local power sources must supply considerable power to both local users and external network users during the opening time causing overcurrents and shutdown
Solution Approach 1:
The synchronous machine serves as a mediator that absorbs the shock of network disconnection. Its low subtransient reactance allows it to rapidly pick up load and provide high current peaks during the circuit breaker opening period, preventing the local power sources from having to supply excessive current to both local and external network users simultaneously
Solution Approach 2:
The synchronous machine's subtransient reactance is specifically designed to be low (5-15% of nominal reactance), which fundamentally changes its electrical characteristics during transient conditions. This parameter change enables the machine to supply high current peaks rapidly during network disruptions without causing overcurrents to the local power sources
3Ease of operation
If synchronous machines with high subtransient reactance (12-20%) are used in protection systems, then the systems can operate normally, but during external network disruptions they cannot supply sufficient current peaks causing voltage drops and shutdown of local systems
Solution Approach 1:
The synchronous machine is specifically designed with low subtransient reactance (5-15% of nominal reactance) which fundamentally changes its transient response characteristics. This parameter change enables the machine to supply high current peaks rapidly during network disruptions while still maintaining normal operation during steady-state conditions
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
The system ensures continuity and quality of power to local users by limiting voltage drops and preventing overcurrents, allowing local power sources to supply users during external network disruptions without shutting down, and enabling efficient use of 'green' energy sources.
Implementation Method 1
A protection system that includes a synchronous machine with low subtransient reactance connected to the local network via a network choke and a local choke between the local power source and the synchronous machine, which limits current injection into the external network and current supply from local sources, maintaining voltage and preventing overcurrents during external network failures
Data Source
AI summary
Protection system for limiting the impact of disruptions of an external urban or industrial electrical network on a local electrical network of a site which is connected to the external network and which includes at least one local electric power source, referred to as “local source” connected to the local network and capable of injecting the surplus electric power into the external network, with the protection system including a synchronous machine connected to the local network which is itself connected to the external network by way of a choke, referred to as “network choke.” The protection system includes at least a local choke which is associated with the local source and which is connected to the local network between this local source and the synchronous machine.