Tap Changer Impedance Switching for High-Voltage Fault Current Limiting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-voltage transformers with tap changers experience excessive short-circuit currents during faults, leading to significant damage and safety hazards due to the inability to effectively curb or minimize fault consequences within the existing technology's response time.
Innovation Solution
Incorporating an impedance unit between each selector and load changeover switch in the tap changer, which can be switched between low and high impedance states, limiting short-circuit currents by altering the current path impedance in response to faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional protection systems (e.g., differential protection) are used, then the transformer is disconnected from the grid after a delay of at least 40 ms, but significant damage has already occurred during this time
Solution Approach 1:
The impedance unit is pre-positioned in the current path between the selector and load changeover switch, ready to activate immediately upon fault detection. This preliminary placement allows the system to respond instantaneously without waiting for circuit breaker operation, effectively preventing damage before it occurs.
Solution Approach 2:
The impedance unit acts as an intermediary element inserted between the selector and load changeover switch. When activated, it provides high impedance to limit short-circuit currents, serving as a protective mediator that prevents direct fault current flow while the main circuit breaker operates.
2Reliability
If the impedance unit is activated during normal operation, then short-circuit currents are limited, but the impedance unit must be switched between low and high impedance states
Solution Approach 1:
The impedance unit is positioned locally at a specific point in the circuit path between the selector and load changeover switch, rather than throughout the entire system. This localized placement allows for targeted impedance control only where needed, minimizing overall system complexity while providing effective fault protection.
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 impedance unit effectively reduces short-circuit currents, preventing damage to the transformer and allowing for timely disconnection from the grid, thereby mitigating the risks associated with faults in high-voltage transformer systems.
Implementation Method 1
an impedance unit is arranged between each selector and each load changeover switch, the impedance of which is able to be switched between a low impedance and a high impedance
Data Source
AI summary
A device for connecting to a high-voltage grid carrying an AC voltage and having a plurality of phases, includes an active part having at least one phase connection for connecting to a phase of the high-voltage grid, at least one step winding connected downstream of one of the phase connections and having a plurality of taps, a tap changer having, for each step winding, a selector for currentlessly switching over from a current to a desired tap of the step winding, and a load changeover switch connected downstream of the selector in series for commutating the current from the current to the desired tap, for avoiding a high short-circuit current in the step winding or in the tap changer. An impedance unit, having an impedance to be switched between a low impedance and a high impedance, is disposed between each selector and each load changeover switch.