Protective Relay Fault Detection Using Dynamic Quotient Ranges
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Solution Overview
Problem
Existing protective relays using delta filters lack flexibility in determining fault criteria for one-phase, two-phase, and three-phase faults, with conventional methods being rigid and not allowing for differentiated criteria.
Innovation Solution
A protective relay system that processes signal values from a power system to determine whether a single-phase, two-phase, or three-phase fault has occurred by removing frequency components and calculating a quotient within predetermined ranges, allowing for flexible fault determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional protective relays use fixed fault determination criteria, then the device complexity is reduced, but the adaptability to different fault types (single-phase, two-phase, three-phase faults) deteriorates
Solution Approach 1:
The patent implements dynamic fault determination by calculating a quotient value that varies based on the specific fault condition. The system dynamically adjusts the fault type identification by comparing the quotient against predetermined ranges, allowing the relay to adapt its determination criteria based on the actual fault scenario rather than using fixed thresholds for all fault types.
Solution Approach 2:
The patent changes the parameter used for fault determination from fixed criteria to a calculated quotient parameter. By removing frequency components and computing the quotient of processed signals, the system transforms the fault detection approach into one that uses variable parameters adapted to different fault types, enabling flexible determination without requiring separate fixed criteria for each fault scenario.
2Measurement precision
If protective relays remove frequency components from signal values, then the measurement precision of fault detection is improved, but the loss of information about the original signal characteristics increases
Solution Approach 1:
The patent extracts and removes the frequency component from the signal values using delta filters. This extraction process separates the frequency-related information from the magnitude information, allowing the system to eliminate the frequency component while retaining the essential fault detection capabilities in the remaining signal characteristics.
Solution Approach 2:
The patent introduces processed signals as an intermediary between the original signal values and the fault determination. By creating this intermediate representation that has frequency components removed, the system achieves precise fault detection without directly losing access to the original signal characteristics, as the processed signals serve as a mediator that preserves essential fault information.
Data Source
AI summary
The present invention is directed to a protective relay for providing protective control to a power system carrying three-phase power. The protective relay performs a faulted phase detection method wherein signal values representative of electrical properties of the power carried by the power system are received and are processed to produce processed signals, respectively. The processed signals have components of the signal values removed that are the same frequency as the nominal operating frequency of the power system. The process signal values are added to produce a sum, which is then divided by a predetermined number to yield a quotient. A determination is made whether the quotient falls within one of a plurality of predetermined ranges. This determination is used to determine whether the power system has a single-phase fault, a two-phase fault, or a three-phase fault.