**2. Standardization of the communication system brought by IEC 61850**

IEC 61850 standard was published in 2003 to cover the inter-substation communication and since that the standard has expanded and evolved. Nowadays it consist of around 35 parts covering many area of power system protection an automation. The later development has expanded its use intr-substations covering wider area in the grid including distributed generation and reaching up to the control center. IEC61850 cover all various aspects, which are common and related to the substation site e.g. SCD files that specify communication protocols, SAS configuration and conformity over the channel. While, grouping and organizing SAS parameters in applications level by means of syntax and semantics in IEDs they left for the software design engineers.

IEC 61850 developed based on the associated architectural construct "abstracting" data object definition and its services. The data structures (data objects along with the associated services) are abstracted in a way that severely independent from communication links. The data structure support all the aspect of the SAS based on the monitoring, controlling and protection functions along with their associated services in order to execute and facilitate the energy system operation. Therefore, data object can be mapping over any IEC 61850 defined protocol that can meet the best requirements need.

At this point, the major focusing of the IEC 61850 specification can be organized into three main issues;

Firstly, (data object model), SAS data object that associated with the available measurements, SAS functions (functional model) and IEDs name should be standardized in a way that provides to the IEDs a shared vocabulary that support the intended semantic meaning.

Secondly, abstract communication services interface (ACSI), accessing scheme to the available data can be defined as a services that specified in different standardizing ways over the assigned communication protocols.

Lastly, eXtendable Markup Language (XML) is selected to describe all the SAS data (data object models, configuration information and communication protocol) and organized in different SAS IEC 61850 extensions files. These files can be shared among all the SAS IEDs, networks and power system.

The scope of the first version of the IEC 61850 standard is composed of 10 major parts that together define the various aspects and the entire requirement that has to be fulfilled by SAS. The main drive is to achieve interoperability among the IEDs within the SAS. Where, the positive impact of the IEC 61850 standard in SAS operation cost it is clearly known in terms of increasing the power quality and reducing the outage response [12]. However, this goal requires paying attentions on how to implement the IEC 61850 standard in order to build, integrate and operate the SAS. While, rapidly transforming of the energy systems from analog to digital environment, which need huge amounts of real-time data to be shared based on their efficient operation. Therefore, IEC 61850 standard along with its uniqueness properties, that originated in hierarchy principle from the bottom to up which are dependent from the underlying operating technology. This will allow the Standard to operate over the stat-of-the-art technologies. The standard will cover all the electrical system aspects as well as the standard will provide a novel set of functionalities, which are not, exists within the legacy SAS operation. At this point and from the IEC 61850 implementation point view, the standard will be an enabler to upgrade and utilize the fullest functionality, where their operation and implementation are depend on sharing information among different LNs located on the same LD within an IED or different LDs located on different IEDs. Therefore, numerous of benefits will be achieved that included but not limited [13].

