The National Grid Dispatching (NGD) department is responsible for preserving the stability and security of Iran’s national grid, ensuring the continued supply of the required electricity for consumers and optimal operation of Iran's power system based on electricity market regulations through planning, monitoring and managing the generation and transmission network.

The mission objectives and expectations on reliability level and performance quality of operational planning and control of the bulk power system, implies a multi discipline organization and with very diversified skills and expertise. The complex nature of tasks and high level of expectations on safety, security and reliability as well as economy of operations requires that the following domains to be covered by operational planning and control procedures and process:

• Bulk Power System Reliability management (Risk Management);
• Information and Communication Technology
• Execution of outcome/results of trade in electricity market (day-ahead-market)

Inherent dynamic nature of bulk electric power system and probable system states (Fig. 1), from operations point of view, justifies the necessity for adaptation of a suitable “Functional Model”, (Fig. 2). The “Functional Model” reflects the continuous and recursive nature of processes in operational planning and control.

Based on this “Functional Model”, activities and processes can be categorized as:

• Proactive
• Preventative, and
• Reactive

The overall goals are to ensure:

• Balanced Generation-Demand supply under normal conditions (Frequency control)
• Adequate reserve capacity (generation and transmission) to meet changes in load demand, availability of generation capacity, etc.
• Preserving system stability under normal and emergency conditions
• Acceptable voltage levels throughout the transmission network
• Integrity of the power system, following any credible event/disturbance (risk management)

From time domain perspective, operational planning and control processes are divided into:

• Pre-dispatch or Scheduling processes/activities
• Monitoring and Control (on-line real-time dispatching) processes/activities

For efficient and dependable execution of processes and functions related to, and with direct or indirect impact on quality, National Grid Dispatching (NGD) department relies on services provided by high quality, well trained and experienced engineers. These engineers perform their assigned tasks and duties in the following functional areas:

• Operational Planning and Scheduling (forecasting, generation scheduling, maintenance planning, etc.)
• System Modeling and Reliability Evaluation (identification of power system limitations and stability margins – Creating Guidelines for both scheduling and dispatch activities)
• Power System Monitoring and Control (On-Line, Real-Time Control Processes and Functions)
• Engineering and Supervision (engineering and support services to ensure reliability, availability and functionality of SCADA/EMS facilities, dedicated telemetering and telecommunication services at National Load Dispatch Center)

These duties are performed in three categories that are detailed in the following:

• Continuously evaluating the stability and security of Iran's national grid
• Analyzing the bottlenecks of the national grid and issuing special operating instructions in order to support the operating and security assessment of the grid
• Modeling the equipment of the national grid in order to use in state estimation process and all of the security assessment studies
• Designing special protection schemes (SPSs) including different types of frequency and voltage load shedding and generation rejection schemes and supervision on their implementation in order to increase the level of power system reliability
• Short term load forecasting (i.e. daily and weekly) considering the evaluation of effective parameters on energy consumption
• Providing daily generation scheduling based on the data analyzing of power plant units, cross-border transactions, load forecasting, the security constraints of the national grid and coordination with electricity market
• Scheduling planned maintenance of the national grid considering the security constraints
• Supporting and providing the required basis to perform online studies including the security assessment of the national grid, generation and maintenance scheduling and proposing the preventive and corrective control actions to preserve the stability and security of the national grid

• National grid monitoring and dispatching according to “Operations Procedures” and supervision on the accurate application of these procedures
• Evaluating the real-time operating point of the national grid regarding to the security and reliability level and implementing the required control actions in order to preserve the normal operational condition
• Controlling the grid in Emergencies & Disturbances, and restoring it to the normal operational condition
• Balancing active power generation and consumption based on the unit commitment schedule in electricity market, as well as frequency controlling of the national grid and the connected cross-border grids
• Balancing reactive power generation and consumption in different areas of the national grid as well as voltage controlling
• Real-time monitoring and controlling of the spinning and non-spinning reserves
• Coordinating, assessing and executing maintenance programs in real-time operation
• Providing and updating restoration plans

• Engineering and support services to ensure reliability, availability and functionality of SCADA/EMS facilities, dedicated telemetering and telecommunication services at National Load Dispatch Center
• Supporting the National Dispatching required communication, software and hardware
• Implementing functional instruments and its amendments in case of providing required reports on internet network, intranet, energy balance unit, and national System Control Center (SCC)
• Managing the operation, repair & maintenance of the national grid monitoring and dispatching centers' installations (including substations, supplying required electricity for vital facilities, emergency electricity diesel system, UPS, and ventilation systems,…)

The “GRID CODES” and “Operations Procedures” assign the final responsibility and the needed authority for safe, secure and reliable management, as well as efficient and economic utilization of electric power generation resources and operation of transmission network infrastructure to NGD department. The area of jurisdiction also includes monitoring and control of cross-border power exchanges via transmission lines, interconnecting transmission network of Iran with neighboring countries.

In addition to highly trained, skilled and experienced man power, National Grid Dispatching (NGD) department makes extensive use of dedicated telecommunication infrastructure, developed and operated within the electric power industry, with primary purpose of providing necessary services for Monitoring and Control (Dispatching) functions.

The SCADA/EMS facility at national System Control center (SCC), and Area Operating Centers (AOC) in nine regions in electric power transmission network, provide NGD with necessary hardware and software tools and applications to perform its tasks and discharge its responsibilities through a decentralized hierarchy of “Monitoring and Control” (Command and Control) procedures (Fig. 3).

There are plans for upgrading and replacement of the existing SCADA/EMS facility in the System Control Center with a state-of-art technology, employing advanced functionalities and capabilities. The overall architecture of the new SCADA/EMS/WAMS and the two concurrently active control centers (national System Control Centers (SCC) and Backup System Control Centers (BSCC)) is based on a centralized approach to monitoring and control procedures.

In normal condition, some parts of the dispatching activities are performed in BSCC based on the previous coordination with SCC. A backup operation starts in BSCC whenever the dispatching activities cannot be fulfilled in SCC due to any reasons.

In the near future, professional training courses for all of the country’s dispatchers are held in the Backup Dispatching that two buildings (i.e. Training and Guest House buildings) are founded for this purpose in the Backup Dispatching.