21-06-2012, 04:27 PM
Power System Operation and Control
Power System.pdf (Size: 1.18 MB / Downloads: 293)
Introduction
Power system operation and control are guided by the
endeavour of the utility to supply electric energy to the customer
in the most economic and secure way. This objective
is underlined by the fact that the electric energy system is a
coherent conductor-based system in which the load effects
the generation without delay. Energy storage can only be
realised in non-electrical form in dedicated power-stations,
so that each unit of power consumed must be generated
at the same time. It is therefore necessary to maintain all
the variables and characteristics designating the quality of
service, such as frequency, voltage level, waveform, etc.
Objectives and requirements
The often-cited objectives of economy and security have to
be considered in various time-scales and in different system
conditions in order to achieve a systematic approach to
power systems operation, particularly when computerbased
systems are involved. Before we go into details, it
should be noted that system operation as considered here
is a problem within the framework of a given power system.
Planning problems and problems of procuring the primary
energy are omitted.
System description
In describing an electric power system we must distinguish
the network (responsible for transmission and distribution)
and the generating stations, as well as the loads.
The network is amenable to description by topological
means such as graphs and incidence matrices as long as the
connection of two nodes, by a line or cable, is of importance.
Thereby it is implied that the connection is made by
a three-phase line which is itself described by differential
equations. This topological description is always inherent
and necessary. In routine work, however, it may not always
be obvious what the true background is. Hence it is worthwhile
to consider these topological means as a starting point.
Graphs and incidence matrices are equivalent and
describe the way in which nodes are connected. A graph is
a pictorial representation, whereas the incidence matrix is
a mathematical formulation which can be interpreted by a
computer.
Data acquisition and telemetering
Introduction
To be able to supervise and control a power system, the
network control engineer requires reliable and current
information concerning the state of the network. This he
obtains from the power flows, bus voltages, frequency, and
load levels, plus the position of circuit-breakers and isolators;
the source of these data being in the power stations
and substations of the network.
Substation equipment
The data-acquisition equipment in a substation is usually a
microprocessor-based RTU, equipped with both programmable
read-only memory (PROM) and random-access
memory (RAM). The data-acquisition program and the
transmission program are loaded into the PROM, which is
non-volatile (not corrupted during a power supply failure).
All the system modules are connected to the system bus (see
Figure 40.7) which is structured to facilitate data transfer
from the information source to its destination, under the
control of the program. The microprocessor function
is monitored by the watch-dog module.
Power System.pdf (Size: 1.18 MB / Downloads: 293)
Introduction
Power system operation and control are guided by the
endeavour of the utility to supply electric energy to the customer
in the most economic and secure way. This objective
is underlined by the fact that the electric energy system is a
coherent conductor-based system in which the load effects
the generation without delay. Energy storage can only be
realised in non-electrical form in dedicated power-stations,
so that each unit of power consumed must be generated
at the same time. It is therefore necessary to maintain all
the variables and characteristics designating the quality of
service, such as frequency, voltage level, waveform, etc.
Objectives and requirements
The often-cited objectives of economy and security have to
be considered in various time-scales and in different system
conditions in order to achieve a systematic approach to
power systems operation, particularly when computerbased
systems are involved. Before we go into details, it
should be noted that system operation as considered here
is a problem within the framework of a given power system.
Planning problems and problems of procuring the primary
energy are omitted.
System description
In describing an electric power system we must distinguish
the network (responsible for transmission and distribution)
and the generating stations, as well as the loads.
The network is amenable to description by topological
means such as graphs and incidence matrices as long as the
connection of two nodes, by a line or cable, is of importance.
Thereby it is implied that the connection is made by
a three-phase line which is itself described by differential
equations. This topological description is always inherent
and necessary. In routine work, however, it may not always
be obvious what the true background is. Hence it is worthwhile
to consider these topological means as a starting point.
Graphs and incidence matrices are equivalent and
describe the way in which nodes are connected. A graph is
a pictorial representation, whereas the incidence matrix is
a mathematical formulation which can be interpreted by a
computer.
Data acquisition and telemetering
Introduction
To be able to supervise and control a power system, the
network control engineer requires reliable and current
information concerning the state of the network. This he
obtains from the power flows, bus voltages, frequency, and
load levels, plus the position of circuit-breakers and isolators;
the source of these data being in the power stations
and substations of the network.
Substation equipment
The data-acquisition equipment in a substation is usually a
microprocessor-based RTU, equipped with both programmable
read-only memory (PROM) and random-access
memory (RAM). The data-acquisition program and the
transmission program are loaded into the PROM, which is
non-volatile (not corrupted during a power supply failure).
All the system modules are connected to the system bus (see
Figure 40.7) which is structured to facilitate data transfer
from the information source to its destination, under the
control of the program. The microprocessor function
is monitored by the watch-dog module.