Question

in power system operation and control
there are three major subsystems are
1/Data acquisition
2/security monitoring
3/energy economy

explain in short answer these three

Answer 1

The functions of a typical control center can be grouped into three distinct groups resulting in the three subsystems:

(a) the data acquisition and processing subsystem,

The objective of the data acquisition and processing subsystem is to obtain an accurate (as much as possible) estimate of the operating state of the system. This is achieved with a large number of Remote Terminal Units (RTU) and associated communication network. The system is known as SCADA (Supervisory Control And Data Acquisition).The remote terminal units collect analog measurements (i.e. voltage magnitude, power flows, etc.) and status variables (i.e. status of breakers, switches, etc.) and transmit this data to the computers of the energy management system via the communication network. There, the topology of the network is formed (network configurator) and the state of the system is constructed (on-line power flow or state estimation). The results are displayed in whatever user interface media exist at the energy management system, i.e. computer monitors, mimic boards, projection systems, etc..

The Data Acquisition and Processing Subsystem comprises a set of software which process the data collected by the SCADA system. This data is utilized in two ways. Status data (circuit breaker status, interrupt switch status, transformer tap setting, etc.) are utilized to form the system configuration and model. The software which uses the status data for the purpose of computing the system configuration and model is known as system network configurator. Typically, this software is executed only when a change in status data occurs. All other data (analog measurements) is utilized to compute the best (in some sense) estimate of the operating state of the system. Two approaches are used in practice: (1) use of an on-line power flow, or (2) use of a state estimator.

(b) the energy management/automatic generation control subsystem,

This subsystem manages the energy generation, controls the frequency and the power transactions (net interchange) of the system, and optimizes the operation of the system. There is a hierarchical structure within this system. An example of functions within each level is provided below:

Level 1: Load Forecasting

Unit Commitment

Economy Purchases

Level 2: Economic Dispatch

Economic Interchange Evaluation

Optimal Power Flow

Transfer Capability

Level 3: Automatic Generation Control

- Frequency Control

- Power Transaction (Interchange) Control

- Inadvertent Power Flow Control

The economic importance of the energy management system is enormous. Because of the fact that the power system tries to supply a changing electric load characterized with uncertainty, many long and medium term scheduling functions are driven by parameters which possess considerable uncertainty. Thus probabilistic approaches are typically used for level 1 functions. Level 2 and 3 functions are deterministic using the results of level 1 functions as directives.

(c) the security monitoring and control subsystem.

Security of an electric power system is loosely defined as the ability of the system to withstand major disturbances without losing synchronism. The security of the system is a very complex concept. Experience accumulated over the years indicates that the security of the system can be only insured by continuous monitoring and control of the system. Security control comprises the integration of a number of automated and manual control operations, such as:

* Automatic generation control,

* Economic dispatch,

* Generation rescheduling,

* Voltage control,

* Coordination with neighboring utilities, and

* Load control.

The integration of all these functions is incorporated in the security monitoring and control subsystem. A hierarchical control scheme is typically employed. The functions of this subsystem can be grouped into two classes: (1) Security monitoring, and (2) Security controls.