Proper Setting of Underfrequency Load Shedding Relays in Industrial Plants :
Introduction
Remarkable Considerations For Load Shedding Design
Case Study
Proposed Algorithm For Designing Load Shedding Scheme
Implemented in simulation software of power system
2. Underfrequency Relay Setting of the Generator
3. Rate of Change of Frequency (ROCOF)
Conclusion
A. Finding Severe Contingencies
Effectiveness proposed algorithm confirmed by transient stability simulations.
B. Load Shedding Scheme: results of impelementation proposed algorithm
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
1. Severe Contigencies by the Transient Stability Simulation
4. Shedding Magnitude of Loads (Load Blocks) Arranged
Proposed new algorithm : to suggest an effective load shedding scheme again severe frequency decay conditions.
B. Setting of Load Shedding Steps
2. Transient Stability Module
3. Sorts obtained contingencies in previous stages according to minimum frequencies
1. Calculate rate of change of frequency setting 
2. Amount of load
3. Optimal combination from "search space"
4. Update "contingencies list"
C. Simulation Results: scenario of frequency decay verifies proper load shedding performances in frequency decline
A. Description: Bandar-Abbas refinery plant as case study
Recognized the proper mathematical models of the power system components and the parameters
Predetermined values set according to the load and generator limitations.
Prevent tripping of the generation units by the corresponding underfrequency protective relays.
Addition the frequency values
Shed the loads quickly enough for severe frequency declines
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
1. Algorithm requires data other than ordinary data