Power Device Surge Malfunction Prevention
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Solution Overview
Problem
Protecting devices in electric power systems malfunction when exposed to surge signals, such as lightning or switching surges, as they incorrectly interpret these signals as normal power flow, leading to improper relay functions and potential system breakdowns.
Innovation Solution
A power device that processes analog signals from the electric power system, converts them into digital signals, calculates slopes based on sampled data, and determines whether the signal is a surge signal by checking for changes in slope signs, thereby controlling the operation of protecting devices to prevent malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the protecting relay performs relaying function on all detected signals, then the relay responds quickly to faults, but the relay malfunctions when surge signals are introduced
Solution Approach 1:
The patent applies preliminary action by calculating slopes from sampled data points before making the relaying decision. The controller computes slopes between consecutive sampled values (S1=(V2-V1)/(t2-t1), S2=(V3-V2)/(t3-t2), etc.) and checks for sign changes in advance. This preliminary slope analysis filters out surge signals that cause inconsistent slope directions, preventing the relay from malfunctioning while maintaining quick response to genuine faults.
2Measurement precision
If the relay detects current over a larger correction range, then the relay detects faults more accurately, but the relay becomes more susceptible to surge signals
Solution Approach 1:
The patent introduces slope calculation as an intermediary mechanism between signal detection and relaying decision. The slope analysis acts as a mediator that evaluates the rate of change and direction of the detected signal. By checking whether consecutive slopes have consistent signs, the system distinguishes between genuine fault signals (which produce consistent slope directions) and surge signals (which produce inconsistent slope directions), thereby protecting the relay from surge interference while maintaining detection accuracy.
Data Source
AI summary
The protecting relay may include: an input conversion unit configured to receive the analog signal and sample the analog signal according to a pre-set sampling period; a multiplexer configured to selectively output any one of a plurality of signals output from the input conversion unit; a programmable gain amplifier (PGA) configured to set different gain values according to signals output from the multiplexer, and amplify a signal output from the multiplexer with a pre-set gain value; an analog-to-digital converter (ADC) configured to convert an analog signal output from the PGA into a digital signal; and a controller configured to determine whether the analog signal received through the input conversion unit includes a surge signal based on the plurality of sampled data which have been converted into the digital signal, and determine whether to perform a relay function based on the determination results.