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Proper Setting of Underfrequency Load Shedding Relays in Industrial Plants…
Proper Setting of Underfrequency Load Shedding Relays in Industrial Plants :
Introduction
Implemented in simulation software of power system
Transient stability analysis
: generators, governors, AVRs, excitation systems, loads, induction motors.
Algorithm
First part
: decrease system frequency significantly are detected.
Second part
: underfrequency load shedding relay steps are set
Proposed new algorithm
: to suggest an effective load shedding scheme again severe frequency decay conditions.
Remarkable Considerations For Load Shedding Design
2. Underfrequency Relay Setting of the Generator
Predetermined values set according to the load and generator limitations.
Prevent tripping of the generation units by the corresponding underfrequency protective relays.
3. Rate of Change of Frequency (ROCOF)
Addition the frequency values
Shed the loads quickly enough for severe frequency declines
1. Severe Contigencies by the Transient Stability Simulation
Recognized the proper mathematical models of the power system components and the parameters
4. Shedding Magnitude of Loads (Load Blocks) Arranged
Maintain frequency within acceptable range
Load have different priority levels in industrial power systems
: operate without power interruption to alleviate the production losses
Over load shedding
: investigate overfrequency condition and have proper load block section
Case Study
B. Load Shedding Scheme
: results of impelementation proposed algorithm
C. Simulation Results
: scenario of frequency decay verifies proper load shedding performances in frequency decline
A. Description
: Bandar-Abbas refinery plant as case study
Proposed Algorithm For Designing Load Shedding Scheme
A. Finding Severe Contingencies
2. Transient Stability Module
3. Sorts obtained contingencies in previous stages according to minimum frequencies
1. Algorithm requires data other than ordinary data
B. Setting of Load Shedding Steps
1. Calculate rate of change of frequency setting
2. Amount of load
3. Optimal combination from "search space"
4. Update "contingencies list"
Conclusion
Effectiveness proposed algorithm confirmed by transient stability simulations.
