Transformer Differential Protection at Low Grid-Side Voltage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional longitudinal differential protection methods for transformers are insufficiently sensitive when the grid-side voltage is low, particularly in series transformers under light load conditions, leading to reduced detection of minor internal faults due to low short-circuit currents.
Innovation Solution
A modified longitudinal differential protection method that calculates a corrected parameter for the transformer using an adjustment coefficient based on the transformer's voltage and electrical parameters, enhancing sensitivity by adjusting the calculation of secondary-rated currents to better detect malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional secondary rated current calculation method is used, then the protection method is simple to implement, but the sensitivity of fault detection is insufficient when grid-side voltage is low
Solution Approach 1:
The patent changes the parameter used for sensitivity compensation from a complex multi-parameter calculation to a single voltage parameter. By using the ratio of actual grid-side voltage to rated voltage as the compensation factor, the method maintains high sensitivity while simplifying the calculation process and reducing computational complexity.
Solution Approach 2:
The patent segments the protection method into two distinct parts: the conventional secondary rated current calculation and the voltage-based sensitivity compensation. This segmentation allows the complex sensitivity compensation to be applied as a separate, manageable step that can be independently optimized and implemented.
2Reliability
If conventional calculation method is used, then the calculation process is straightforward, but the differential current is too small to detect minor internal faults under light load conditions
Solution Approach 1:
The patent introduces a voltage-based compensation parameter that directly scales the differential current calculation. This single-parameter approach maintains calculation efficiency while significantly improving the reliability of minor internal fault detection by compensating for the low differential current produced during light load operations.
3Measurement precision
If traditional fault judgment method is used, then the method is easy to implement, but the sensitivity is insufficient when transformer operates at low voltage
Solution Approach 1:
The patent changes the judgment parameter by introducing a voltage compensation factor that adjusts the differential current threshold based on actual operating voltage. This maintains ease of implementation by building upon the traditional method while improving sensitivity through a simple voltage ratio calculation that can be easily integrated into existing protection schemes.
Data Source
AI summary
A longitudinal differential protection method for a transformer comprises: calculating a corrected parameter of a transformer according to a voltage and electrical parameters of the transformer, wherein the electrical parameters of the transformer comprise a rated capacity of the transformer, and the corrected parameter of the transformer comprise a capacity of the transformer.