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Dedication
To my treasures, Roxana and Linda
Preface
This book discusses the application and the improved performance of overcurrent relays to highly dynamic power systems. Advanced solutions such as new adaptive relay designs and new coordination methods are used to solve application problems in electrical networks. This book presents the functional alternatives that allow the relay to be viewed as an active element of the electrical network, modifying the functional structure by incorporating dynamic adjustments according to the quasidynamic state of electrical networks and presenting the formulation of a new relay coordination method.
The operating structure of electrical networks has been modified in recent decades with the interconnection of highly intermittent generation. The application of protection systems presents a challenge for the detection of faults and security, avoiding false operation. Current-based protection is the most widely used in electrical systems, offering phase and ground protection in all voltage networks. Due to its functional simplicity, it is the most affected by highly dynamic operating conditions. The functional improvement of these relays is urgent and highly impactful, incorporating the information available from other locations of the relay to tune in to the current operating conditions of the electrical network.
Current protection systems are functionally passive, with predefined settings that are not adjusted to the dynamic conditions of the electrical network. The use of communication channels has been very favorable to help improve protection performance, either speeding up its operation or avoiding false triggers. Nevertheless, the use of standardized time curves and fixed settings does not always represent the best solution for the diversity of coordination problems of the electrical networks.
The active relay presented in this proposal is conceived as an element that is subject to adaptive adjustment according to the dynamic operating conditions of the electrical network and with optimization strategies for coordination. The implementation of proposed systems for setting and online coordination is aimed at improving the relay operation. Also, the use of nonstandardized time curves offers a wide range of applications that allow to improve coordination. Through it, it is possible to obtain a new coordination method, where the setting of each overcurrent relay is stand-alone, improving operation times and reducing coordination violations.
Because the protection zone of the overcurrent relay is highly dynamic under highly intermittent conditions, there may be protection zones without adequate sensitivity. This has repercussions in undetected faults and in operating times, which, in many cases, impact on the quality of voltage in the electrical networks, triggering a low-voltage load and increasing the operational technical losses of the electrical network. Adaptable schemes that seek protection retuning will manage to monitor and guarantee more sensitive protection zones, reducing fault release times for a better quality of supply. The requirements for the conformation of these monitoring systems of protection zones and the dynamic adjustment of relays are presented.
Finally, the laboratory platform necessary for the functional evaluation of an overcurrent relay is presented. Expensive laboratory and simulation equipment requirements are avoided. It is possible by means of modest equipment to carry out the operational validation of overcurrent relays subject to various operating conditions.
Arturo Conde Enrquez
Nomenclature
A(I) dynamic nonlinear function
A, p, B time curve constants
ACO ant colony optimization
AS adjustable setting
BESS battery storage systems
CC conventional time curves
CIGRs converter interfaced generation resources
CT current transformer
CTI coordination time interval
Cx chromosome
DE differential algorithms
DER distributed energy resources
DG distributed generation
DOCR directional overcurrent relay
GA genetic algorithms
Gk accumulated value of the integrator
GWO gray wolf optimization
H(Ik) relay functions to represent the dynamic disk displacement
HIF high impedance fault
IpickupAdp adaptive load current
Iload load current
Ipickup pickup current of relay
Ipickup_max maximum load current
Iprimary multiple of current
Ireset reset current
Isc short circuit current
IWO invasive weed optimization
J(Ik) relay functions to represent the tap position
kop operation sample
MG microgrid
MOGWO multiobjective gray wolf optimizer
NCC nonconventional time curves
OCR overcurrent relay
OF objective function
PS population size
PSM plug setting multiplier