Regulating Transformer Tap Switching for Low-Voltage Loss Reduction
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Solution Overview
Problem
Regulating transformers in electrical energy grids face inefficiencies and component wear due to frequent switching operations and inrush currents when disconnecting renewable energy sources like PV farms from the grid, leading to energy losses and potential damage.
Innovation Solution
A method and system utilizing a regulating transformer with dual on-load tap changers and a take-off lead, where the second on-load tap changer is actuated to minimize voltage on the low-voltage side during non-energy feeding states, and a switching element is used to manage current commutation, reducing wear and losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If circuit breakers are used to disconnect PV farms from the grid at night, then energy losses from idle distribution transformers and cable runs are avoided, but the circuit breaker wears out quickly due to frequent switching operations and inrush currents damage the windings and components of distribution transformers
Solution Approach 1:
The patent introduces a regulating transformer with an on-load tap changer as an intermediary device between the PV farm and the distribution grid. This mediator enables smooth transition and disconnection without requiring circuit breaker switching, thereby avoiding the wear and inrush current problems while still achieving energy loss reduction.
Solution Approach 2:
The on-load tap changer is configured to switch to a neutral point connection before complete disconnection occurs. This preliminary action prepares the system for smooth transition by gradually reducing voltage and current, preventing sudden inrush currents that would otherwise damage components during disconnection.
2Loss of energy
If circuit breakers are used to disconnect PV farms from the grid at night, then energy losses from idle distribution transformers and cable runs are avoided, but frequent switching operations cause quick wear of the circuit breaker
Solution Approach 1:
The regulating transformer serves as a mediator that handles the disconnection function without requiring circuit breaker intervention. The on-load tap changer gradually adjusts the connection state, enabling the system to avoid frequent circuit breaker switching operations and extend their service life.
Solution Approach 2:
By switching the on-load tap changer to a neutral point connection in advance of complete disconnection, the system prepares for transition smoothly. This preliminary action reduces the frequency and intensity of required circuit breaker operations, thereby extending circuit breaker durability.
3Loss of energy
If the second on-load tap changer is actuated to minimize voltage on the low-voltage side during non-energy feeding states, then energy losses are reduced, but additional control complexity is introduced
Solution Approach 1:
The patent combines the voltage minimization function with the existing on-load tap changer mechanism that is already used for voltage regulation during energy feeding states. By merging these functions into a single control system, the patent reduces control complexity while still achieving energy loss reduction during non-feeding states.
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 approach minimizes energy losses and reduces wear on components by optimizing voltage transitions and current management during idle states of renewable energy sources, enhancing the operational efficiency and longevity of grid equipment.
Implementation Method 1
Regulating transformers are variable transformers that change the transmission ratio between their high-voltage side, e.g. a transmission grid operating at 380 kV, and their low-voltage side, e.g. a medium-voltage grid operating at 30 kV
Implementation Method 2
known regulating transformers are equipped, on their high-voltage side, with an on-load tap changer which is designed to switch between winding taps of a tap winding of the transformer without interruption
Data Source
AI summary
A method operates a regulating transformer for coupling two electrical energy grids using a system. The system includes: the regulating transformer having a first tap winding on a high-voltage side and a second tap winding on a low-voltage side; a first on-load tap changer that switches between winding taps of the first tap winding; a second on-load tap changer that switches between winding taps of the second tap winding; and a take-off lead connected to the low-voltage side. The method includes: detecting a first signal indicating an imminent transition from a first operating state to a second operating state on the low-voltage side, and actuating the second on-load tap changer such that the second on-load tap changer is switched from a first operating position to a second operating position, in which voltage present on the take-off lead assumes a minimum value.