Three-Winding Transformer Voltage Regulation in Local Substations
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Solution Overview
Problem
The increasing integration of decentralized energy sources and electric vehicles in low-voltage networks leads to voltage fluctuations and load changes, which existing technologies struggle to manage effectively, particularly due to the inflexibility and high costs associated with expanding the grid or using controllable transformers and low-voltage linear regulators.
Innovation Solution
A local network station equipped with a three-winding transformer, which includes a high-voltage winding and two low-voltage windings, allows for selective voltage regulation by dividing supply lines into groups with and without decentralized energy sources, using a controllable second low-voltage winding to adjust voltage levels independently of the first, thereby maintaining voltage within specified limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the low-voltage network is expanded by increasing cable cross-section or adding transformers, then voltage stability is improved, but cost and complexity increase significantly
Solution Approach 1:
The low-voltage network is segmented into multiple independently controllable sections, each with its own regulating transformer. This allows localized voltage control without requiring comprehensive network expansion, reducing overall system complexity while maintaining voltage stability in each segment.
Solution Approach 2:
Regulating transformers with adjustable transformation ratios are deployed to dynamically adapt voltage levels according to real-time load conditions and decentralized energy generation, providing flexible voltage control without permanent network infrastructure expansion.
2Reliability
If controllable transformers are used to regulate voltage, then voltage stability is improved, but all supply lines are regulated uniformly which causes voltage drops in lines with only loads
Solution Approach 1:
The network is divided into separate controllable zones with individual regulating transformers, allowing selective regulation of specific supply lines based on their characteristics (whether they have decentralized energy sources or only loads), avoiding uniform regulation problems.
Solution Approach 2:
Each supply line or zone receives customized voltage regulation tailored to its specific characteristics - lines with decentralized energy sources receive different regulation than lines with only loads, optimizing performance for each local condition rather than applying a one-size-fits-all approach.
3Adaptability or versatility
If low-voltage linear regulators are deployed at consumer connections, then selective voltage control is achieved, but system complexity and cost increase significantly
Solution Approach 1:
Regulating transformers are deployed as intermediary devices at strategic network points rather than at every consumer connection. These intermediaries provide selective voltage control for groups of consumers, achieving adaptability without the complexity of widespread individual regulator deployment.
Solution Approach 2:
Multiple consumers or supply lines are grouped together and served by shared regulating transformers, combining control functions to reduce the total number of regulatory devices needed while maintaining selective control capability across different network zones.
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 enables flexible and selective voltage management, reducing voltage fluctuations and load changes without the need for extensive network expansion, maintaining voltage stability within ±10% limits while being cost-effective and adaptable to existing infrastructure.
Implementation Method 1
a three-winding transformer (8) with a high-voltage winding (14) for connection to the medium-voltage switchgear (9) and with two low-voltage windings (15, 16)
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Local substation for the low-voltage network for voltage transformation from medium voltage to low voltage and for supplying connected consumers (4) in the low-voltage network (200), comprising a medium-voltage connection (2), a medium-voltage switchgear (9), a low-voltage distribution panel (10) with a plurality of low-voltage feeders (5) connected to a supply line (3) in the low-voltage network (200), wherein at least one consumer (4) is connected to each supply line (3). The local substation (1) further comprises a measuring unit (21) for measuring the voltage and current of the low voltage and a three-winding transformer (8) as well as an adjusting device (20) for adjusting the ratio of the medium voltage to the low voltage. The low-voltage distribution panel (10) has two busbars (11, 12), each of which is connected to a low-voltage winding (15, 16) of the three-winding transformer (8).The adjusting device (20) can adjust the ratio of medium voltage to low voltage at the second busbar (12) such that the voltage remains within a predetermined range. At least one supply line (3) is connected to the second busbar (12), to which an external power source (7) is connected for feeding power into the low-voltage network (200).