Data processing: generic control systems or specific application – Specific application – apparatus or process – Electrical power generation or distribution system
Reexamination Certificate
1999-03-04
2003-09-09
Picard, Leo (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Electrical power generation or distribution system
C700S286000, C700S292000, C700S299000
Reexamination Certificate
active
06618648
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control system for controlling a plant, such as an electric power system, a general industrial plant, a public plant and so on, in accordance with state quantities inputted from a plurality of equipment devices of the plant, which include a state quantity input device (input/output device), such as a transformer for instruments and an opening/closing device.
Moreover, the present invention relates to an electric power system protective control system for protectively controlling the electric power system.
Furthermore, the present invention relates to a method of protectively controlling the electric power system.
Still furthermore, the present invention relates to a storage medium storing a program code.
2. Description of the Prior Art
In a plant, such as an electric power system, for controlling state quantities, such as the electric quantities, which are changed as time elapses, a control system having a plurality of digital control apparatuses has widely been operated. The digital control apparatus recognizes a change state of each of a plurality of equipment devices constituting the plant and an abnormal state, such as an accident occurring in any one of the equipment devices, so that stabilizing control and system protective control are performed. In recent years, a high-performance electronic circuit including a high speed microprocessor or a large-capacity memory has been mounted on each digital control apparatus to improve the performance thereof.
As the digital control apparatus for constituting the control system, a variety of apparatuses have been developed to mainly correspond to the contents of the protective control of the electric power system. The control apparatuses are disposed at required locations in the electric power system. Specifically, as an example of the control apparatus, there is a digital relay for detecting an accident (a system accident) occurring in each of equipment devices (power-transmission lines, transformers and the like) of the electric power system so as to separate the accident portion therefrom thereby protecting the electric power system. Moreover, as another example of the control apparatus, there is a fault locator for accurately locating a location of an accident point (a faulty point) on, for example, a power-transmission line. Furthermore, as another example of the control apparatus, there is a system stabilizing relay for performing stabilizing control of the electric power system.
The structure and operation of a digital protective control apparatus (a digital relay) will now be described, which is an example of the digital control apparatus and which performs a protective relay operation for the electric power system.
FIG. 60
is a diagram showing the basic structure of a conventional multi-input digital relay. Referring to
FIG. 60
, a digital relay
1
is provided with an analog-digital converting unit
2
for taking a multiplicity of analog state quantities (electric quantities), such as electric currents and voltages, from an electric power system to be protectively controlled so as to convert the state quantities into digital state data. Moreover, the digital relay
1
is provided with a digital processing unit
3
for processing protective control operations in response to the digital state data digitized by the analog/digital converting unit
2
. The digital relay
1
also has an input/output interface (I/O)
4
for performing an interface process related to a data inputting/outputting operation with respect to the electric power system protective control devices (hereinafter simply called protective control devices, or external devices), such as breakers. The components (the analog-digital converting unit
2
, the digital processing unit
3
and the input/output interface
4
) of the digital relay
1
are mutually connected to one another through a bus
5
such that data communication is permitted.
The analog-digital converting unit
2
is provided with n analog filters
6
-
1
to
6
-n corresponding to the number of supplied electric quantities (A-
1
to A-n) for removing needless frequency components. Moreover, sample hold circuits
7
-
1
to
7
-n corresponding to the analog filters
6
-
1
to
6
-n are provided in the analog-digital converting unit
2
for performing sampling operation. In addition, a multiplexer
8
for selectively outputting and an A/D (analog/digital) converter
9
for performing A/D conversion are provided in the analog-digital converting unit
2
.
The digital processing unit
3
is provided with a computer circuit, that is, a CPU (central processing unit)
10
for processing protective control operations; a random access memory (RAM)
11
for temporarily storing electric quantity data and data processed by the CPU
10
; a read only memory (ROM)
12
for storing processing procedures (program codes) of the protective control including sequence software constituted by relay software modules; and a nonvolatile memory (EEPROM)
13
for rewritably storing setting values to operate respective relay software modules.
The digital relay
1
is provided with a display device
14
, such as an LED, connected to the bus
5
for displaying electric quantity data stored in the RAM
11
by the process of the CPU
10
and the operations of the protective control devices, such as the breakers.
In the thus-structured digital relay
1
, n electric quantities A-
1
to A-n in parallel taken from the electric power system are passed through the analog filters
6
-
1
to
6
-n so that unnecessary frequency components (a harmonic component except for the fundamental wave, DC component and so on) are removed. Then, the electric quantities are supplied to the sample hold circuits
7
-
1
to
7
-n so as to be sampled in predetermined time intervals (periods) as state values (instantaneous values).
The instantaneous values sampled by the sample hold circuits
7
-
1
to
7
-n are passed through the multiplexer
8
so as to sequentially and selectively be outputted from a single output terminal to the A/D converter
9
. The instantaneous values transmitted to the A/D converter
9
are converted thereby into digitized electric quantity data, so that the electric quantity data are sequentially outputted through the bus
5
to the digital processing unit
3
.
Electric quantity data sequentially outputting to the digital processing unit
3
are sequentially transmitted to the RAM
11
by a reading process of the CPU
10
in accordance with the protective control program (program code) stored in the ROM
12
so as to temporarily be stored in the RAM
11
. On the basis of the electric quantity data stored in the RAM
11
, the setting values of the protective relay software modules stored in the EEPROM
13
and contact information of the external devices, such as the breakers, taken through the input/output interface
4
, the CPU
10
performs the protective control operation processes (for example, a digital filtering process, an amplitude calculating process, an effective value calculating process, a phase difference calculating process and a process for judging the relay operation of the relay software modules according to the setting value and the like) in accordance with the protective control program stored in the ROM
12
.
Results of the protective control operation processes performed by the CPU
10
are outputted by a process of the CPU
10
to the protective control devices (external devices), such as the breakers, through the input/output interface
4
as a protective control operation command, such as a breaking command (a trip command) and a reset command. Thus, the operation for protecting the electric power system {a tripping operation or a reset operation (a contact opening/closing operation) and so on } is performed.
Electric quantity data stored in the RAM
11
are displayed by the display unit
14
by the displaying process of the CPU
10
.
Therefore, in the control system having the above-mentioned digital prote
Fuwa Yutaka
Hori Masao
Miyoshi Tetsuya
Sasaki Hideki
Sekiguchi Katsuhiko
Kabushiki Kaisha Toshiba
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Picard Leo
Rao Sheela S.
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