A model predictive approach to protect power systems against cascading blackouts

A robust optimization approach for protecting power systems against cascading blackouts

This paper approaches the topic of protection system reliability from an economic point of view by 1) designing an optimal modern protective relay based on a prescribed level of reliability subject to economic constraints and 2) determining optimal routine test intervals by balancing the cost of routine tests and losses due to relay failure. This paper proposes a method that enables the designer to optimally select hardware and software components of a digital protective relay to gain the highest possible overall reliability with a restricted budget. This design can be viewed as a reliability and redundancy allocation problem for which a new easy-to-implement algorithm is proposed. In contrast to the existing literature that views the problem of routine test interval optimization solely from a reliability viewpoint, this paper proposes an optimization procedure for determining optimal test intervals. The optimization objective function consists of three terms: cost of routine tests, losses due to relay unresponsiveness, and losses due to relay maloperation. The value of the objective function is calculated based on a new, simple, and comprehensive Markov model. Illustrative numerical examples clarify the application of the proposed methods and demonstrate their effectiveness in achieving an optimum for both cases.

Design and Routine Test Optimization of Modern Protection Systems With Reliability and Economic Constraints

A cyber attack on an ICS must begin at an ICS element, and influence some of the other elements. For this reason, we begin the discussion of ICS security by introducing the basic components of ICSs, their functions, variety, and ways in which they connect and interact to produce the intended effects.

Components of Industrial Control Systems

Distribution systems continue to grow and becoming more complex with increasing operational challenges such as protection miscoordination. Initially, conventional methods were favoured to solve overcurrent relay coordination problems; however, the implementation of these methods is time-consuming. Therefore, recent studies have adopted the utilisation of particle swarm optimization and genetic algorithms to solve overcurrent relay coordination problems and maximise system selectivity and operational speed. Particle swarm optimization and genetic algorithms are evolutionary algorithms that at times suffer from premature convergence due to poor selection of control parameters. Consequently, this paper presents a comprehensive sensitivity analysis to evaluate the effect of the discrete control parameters on particle swarm optimizer and genetic algorithms performance, alternatively on the behaviour of overcurrent relays. Optimization algorithms aim to minimise overcurrent relay time multiplier settings and accomplish optimal protection coordination. The findings indicate that particle swarm optimization is more sensitive to inertia weight and swarm size while the number of iterations has minimal effect. The results also depict that 30% crossover, 2% mutation, and smaller population size yield faster convergence rate and optimise fitness function, which improves genetic algorithms performance. Sensitivity analysis results are verified by comparing the performance of particle swarm optimization with the genetic algorithms which show the former parameter setting outperforms the latter. The relay operational speed is reduced by 15% for particle swarm optimization and system selectivity is maximised. The optimal protection coordination achieved using particle swarm optimization showed superiority of the algorithm, its ability to circumvent premature convergence, consistency, and efficiency.

https://ieeexplore.ieee.org/ielx7/6287639/9668973/09672123.pdf

Effects of Particle Swarm Optimization and Genetic Algorithm Control Parameters on Overcurrent Relay Selectivity and Speed

lant operators, electricians, field technicians and engineers will gain a practical understanding of the role and workings of power system protection systems from this work. An understanding of power systems and their optimized management will increase plant efficiency and performance as well as increasing safety levels. This book provides both the underpinning knowledge and basic calculations needed to understand, specify, use and maintain power protection systems, and the practical techniques required on a daily basis.After studying this book you will have an excellent knowledge of the principles of protection. You will also have a better understanding of the possible problems likely to arise in day-to-day work with power protection systems.Key areas of knowledge and expertise developed will include:

 Fundamentals of electrical power protection and applications
 Different fault types
 Perform simple fault and design calculations
 Practical knowledge of protection system components
 Apply relay settings
 Improve the safety of your site with the knowledge gained

Practical Power System Protection

This chapter presents a simple calculation of short-circuit currents. For general practical purposes for operators, electricians, and men-in-the field, it is possible to achieve a good approximation of three-phase short-circuit currents using some very simple methods. These simple methods are used to decide the equipment short-circuit ratings and relay setting calculations in standard power distribution systems, which normally have limited power sources and interconnections. Even a complex system can be grouped into convenient parts, and calculations can be made groupwise depending upon the location of the fault. Vectors are a most useful tool in electrical engineering and are necessary for analyzing AC system components, such as voltage, current, and power, that tend to vary in line with the variation in the system voltage being generated. In any distribution, the power source is a generator and it is a common practice to use transformers to distribute the power at the required voltages. A fault can occur immediately after the generator or the transformer, and depending upon the location, the fault current could vary. Only the source impedance limits the fault current, whereas in the second case the transformer impedance is an important factor that decides the fault current.

Simple calculation of short-circuit currents

This chapter presents the faults, their types, and effects. It is not practical to design and build electrical equipment or networks to eliminate the possibility of failure in service. It is therefore an everyday fact that different types of faults occur in electrical systems, however infrequently, and at random locations. Faults can be broadly classified into two main areas: active and passive. The solid fault occurs as a result of an immediate complete breakdown of insulation as would happen if, say, a pick struck an underground cable bridging conductors, or if the cable was dug up by a bulldozer. In mining, a rockfall could crush a cable, as might a shuttle car. In these circumstances, the fault current would be very high resulting in an electrical explosion. Transient faults are the faults that do not damage the insulation permanently and allow the circuit to be safely re-energized after a short period of time. A typical example would be an insulator flashover following a lightning strike, which would be successfully cleared on opening the circuit breaker. Transient faults occur mainly on outdoor equipment where air is the main insulating medium. Permanent faults, as the name implies, are the result of permanent damage to the insulation. In this case, the equipment has to be repaired and must not be recharged before repair/restoration.

Faults, types and effects

This chapter reviews some of the fundamental points for the design engineer to watch for in planning the application of IDMTL OCEF protection to medium-voltage switchboards and networks. It also explains the protection design parameters on medium- and low-voltage networks. There are numerous installations where the performance of the current transformers has been overlooked or misunderstood. The most widely mistaken error has undoubtedly been the choice of CT ratio, which is invariably selected on the basis of full-load current without due regard to performance under fault conditions. The voltage developed across the CT secondary shall be sufficient to drive the transformed current through its own internal impedance plus the impedance of the relay and any other equipment to which it is connected. A number of instances arise where the load current demands high-ratio line current transformers, and the neutral current has been limited to a low value by the use of a remote high-impedance neutral earthing device for safety reasons.

Ramesh Balakrishnan

Papers

Practical Power System Protection

Simple calculation of short-circuit currents

Faults, types and effects

Coordination by time grading