Smart Grid: Definition and Concept

Smart Grid is define as a modern grid that enables bidirectional flow of energy and uses two-way cyber-secure information and communication technologies in an integrated fashion across electricity generation, transmission, substations, distribution and consumption to achieve a system that is clean, safe, secure, reliable, resilient, efficient, and sustainable. This description covers the entire spectrum of the energy system from the generation to the end points of consumption of the electricity. It co-ordinate the needs and capabilities of all generators, grid operators, end-users and electricity market stakeholders to operate all parts of the system as efficiently as possible. In order to realize this new grid paradigm, National Institute of Standards and Technology (NIST) provided a conceptual model based on the different roles involved in the SG as shown in Figure.

This conceptual model divides the SG into seven domains. The brief descriptions of the domains are given as:

Customers: They are end users of electricity that may also generate, store, and manage the use of energy.

Markets: The markets are where grid assets are bought and sold. The operators and participants of electricity market exchange price while operators trying to balance supply & demand within the power system.

Service Providers: The organizations providing services to electrical customers and utilities. This domain support the business processes of power system to enhance customer services. These business processes are billing and customer account management, monitoring and controlling of energy use and energy generation, etc.

Operations: The managers of this domain manages the movement of electricity. Supervise network topology, connectivity and loading conditions, including circuit breaker and switch states, and control equipment status. Perform real time data analysis, system efficiency and reliability analysis, faults analysis (Fault location, identification, isolation and restoration) etc.

Bulk Generation: This domain consists generators of electricity that generates power in bulk quantities (more than 300 MW). May also store energy for later distribution.

Transmission: The carriers of bulk electricity over long distances. May also store and generate electricity. A transmission network is typically operated by a Independent System Operator (such as PGCIL) whose primary responsibility is to maintain stability on the electric grid by balancing energy generation with energy demand across the transmission network.

Distribution: The distributors of electricity to and from customers. May also store and generate electricity.

In contrast Smart Grid from a technical view point is divides into three major systems: smart infrastructure, smart management and smart protection systems.

1.	Smart infrastructure system: The smart infrastructure system is the energy, information, and communication infrastructure underlying the SG. It supports two-way flow of electricity and information. We further divide this smart infrastructure into three subsystems: the smart energy subsystem, the smart information subsystem, and the smart communication subsystem.
2.	Smart management system: The smart management system is the subsystem in SG that provides advanced management and control services and functionalities. The smart management system takes advantage of the smart infrastructure to pursue various advanced management objectives.
	i. i. The smart energy subsystem is responsible for advanced electricity generation, delivery, and consumption. ii. The smart information subsystem is responsible for advanced information metering, monitoring, and management in the context of the SG. iii. The smart communication subsystem is responsible for communication connectivity and information transmission among systems, devices, and applications in the context of the SG.
3.	Smart protection system: The smart protection system is the subsystem in SG that provides advanced grid reliability analysis, failure protection, and security and privacy protection services. By taking advantage of the smart infrastructure, the SG must not only realize a smarter management system, but also provide a smarter protection system which can more effectively and efficiently support failure protection mechanisms, address cyber security issues, and preserve privacy.