FIELD OF INVENTION
The present invention generally relates to a historian system and method for
remote storage of long term realtime data from generating plants, like a hydro
power plant.
More particularly, the invention relates to a remote historian system for storage
of data collected from a distributed control system (DCS) to a geographically
separated remote location through microwave link. The data stored in the
remote location can then be retrieved and viewed in trend or log format at the
remote location.
BACKGROUND OF THE INVENTION
In a distributed control system (DCS), the input / output modules and the
controllers in the central control room process the data captured from various
sensors, actuators, and field devices in the generating plants for example, a
hydro power plant. The data is centrally stored in the storage mechanism in the
control room and this data is processed by human machine interface for
monitoring and decision-making on the performance of the total system.
A typical distributed control system has mainly the following components:-
field sensors, transmitters, actuators etc;
input / output module connected to the field elements for data acquisition;
controller unit for processing the acquired data and also for issuing the
commands for field operation,
HMI system for data display and control;
data storage unit and
plant network, which interconnects all the controllers and the HMI.
The input / output modules are connected to the field elements, and the Input
modules acquire data provided by the field elements. Commands issued through
the controller are sent to the output field elements through the output modules.
The logic to process the data is programmed in the controller and controller
issues monitoring and control instructions so as to implement the desired
functioning schedule of the plant. The controller processes the data available in
the Input module and take decisions based on the logic built in it. If the decision
is to output some values to a field device, then this is sent out through the
output module.
The real-time data acquired or sent out by the controller can be tagged for
storage in a server typically called as "Historian". This historian acts as a data
provider for all the functions that needs historical data. Presently this Historian is
placed along with other HMI machines in the computer room.
Some of the prior art systems use an extended local area network in the same
location. These systems thus cannot be used to make the historical data
displayable over a wide area.
There is therefore, a need for a system for remote storage of data from the
hydro power plant which can be used for analyzing the performance of the plant
/ machinery and also causes of trip that has occurred in the plant.
SUMMARY OF THE INVENTION
The main object of the present invention is to provide a remote historian system
adaptable to large power plants for storage and retrieval of historical plant data
at a remote location through microwave link, which is typically used as a means
of communication in hydro power plants.
The system of the present invention makes use of one of the known human
machine interface (HMI) system in the control room for data acquisition. The
system works in a data logger - data retrieval manner. The signals identified for
use of historical functions need to be configured in the remote historian data
logger available at the power plant location. The points configured for storage in
the remote historian data logger will be collected and stored locally in the data
logger.
The remote historian system of the present invention, helps engineers to view
the historical plant data at a remote location that is connected through
microwave link which is far away from the main power plant in trend or log
formats using data stored locally at the remote location.
This will help the engineers located at a remote place to analyze the
performance of the plant machinery and also the causes of trip that has occurred
in the plant.
In a preferred embodiment the present invention provides a historian system for
remote storage of long term realtime data from generating plants, comprising: a
plurality of controllers each provided with input / output modules, said input /
output modules being connected to field elements for acquisition and processing
of plant data and for issuing commands for field operation; a remote historian
data logger for storing the captured long-term plant data; a single port access
unit linked to said data logger and interfaced through a multiplexer on El
framework to a microwave link for transmitting the data to a remote location; a
second single port access unit for receiving through a demultiplexer the data
transmitted on the microwave link; and a remote data retrieval historian for
receiving and storing the long term plant data for retrieval to meet long-term
data analysis requirements.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention can now be explained with reference to the accompanying
drawings where
Figure 1 shows in schematic form a typical DCS system.
Figure 2 shows a schematic representation of remote
historian of the present invention.
Figure 3 shows sample screen of data logger and data
retrieval for remote historian of the invention.
Figure 4 shows sample screen of data retrieved in trend and
log formats for remote historian.
DETAILED DESCRIPTION
As shown in Figure 1 a typical distribution control system (DCS) comprises DCS
cabinets 12 for housing controllers 11 with input / output modules. For data
acquisition, the input / output modules of the controller are connected to field
elements 10 like field sensors, transmitters, actuators, etc. A human / machine
interface (HMI) system 13 is provided for data display and control of historian
data storage. A plant network 14 interconnects all the controllers 11 and the
HMI system 13.
For data acquisition in the control room, the system of the present invention
uses this human / machine interface 13. The system works in a data logger -
data retrieval manner. The signals identified for use of historical functions need
to be configured in the remote historian data logger available at the power plant
location 20. The points configured for storage in the remote historian data
logger 21 will be collected and stored locally in the data logger 21.
The real time data available in the controllers 13, is acquired by the remote
historian data logger 21 for the configured signals. A series of validation and
data storage logic will be applied for each configured signal. The signal that
passes/ crosses the computed value based on these logic's will be stored as
historical data with time stamping done at the remote historian data logger 21.
Delta storage technique is used to optimize the long term data storage
requirement. Percentage change of value or absolute change of value can be
configured for each signal. Additionally, the data of all signals is collected and
stored at a predefined interval irrespective of change in data in the remote
historian 21. The data of all signals as available in customized format in the
remote historian data logger 21 is then transferred to the remote station through
microwave 22. The data can also be backed up to a random access device on the
remote historian data logger 21. Alarm will be generated to indicate to the user
when the storage medium reaches a certain pre-defined limit of total capacity.
If the user fails to replace the storage media, the data is automatically backed up
in the non-volatile memory to avoid data loss. Multi threading is implemented to
execute many activities concurrently.
Remote historian data logger 21 uses a single port access unit 23 for unframed
El for data transfer over microwave link 22. The Single port access unit 23 data
channel has transmission rates which are integral multiples of 56 or 64kbps, up
to a maximum of 2.048Mbps, on twisted pair or coaxial cable. The data logger 21
uses an ethernet RJ45 port to connect to the access unit. The access unit packs
the data channels into the El link in user-selected time slots. For the purpose of
remote data transfer, unframed El at a bit rate of 2.048Mbps is configured in the
access unit 23 and a 4 wire connection from 15-pin, D-type connector is used
from the single port access unit 23 to the microwave interface equipment like a
multiplexer 24. The remote historian located at a remote location 25 uses a de-
multiplexer 26 and a single point access unit 27 to connect to the microwave
network 22.
At the remote location 25, data is received and stored on a remote data retrieval
historian 28 through microwave link 22 as given above. The data can be
retrieved from the retrieval historian 28 by entering start date and time, the time
interval in seconds between data samples and the number of samples of the
given time interval. The logic provided in the data retrieval mechanism in the
remote data retrieval historian 28 will automatically identify the volume number
in which the data is stored and intimate the user to load the correct volume
number of the media in case removable media have been used for storage. The
data retrieval activity will in no way affect the data receiving and storage
functions and both activities will progress concurrently.
The remote data retrieval historian 28 can present the data in two formats, as a
trend graphs or in log formats. Upto six parameters can be retrieved
concurrently from the remote historian 28. Pre defined grouping of signals for
easy selection of signals is also possible. The retrieved data can be exported to a
CSV file that can be viewed in a spreadsheet program.
It is possible to connect a network storage device or any random access device
to increase the historical data storage capacity.
Figure 3 shows a sample screen of data logger interface and a data retrieval
graphical user interface.
Figure 4 shows a sample screen of data retrieved in trend and log formats.
The trend chart displays six parameters simultaneously in different colors. If the
interval of data and no of samples selected is more, the data will be spread
across various pages. Navigational buttons are provided to move forward and
backward, one page at a time. Quick jumping to first and last page is also
possible. Clicking anywhere on the trend graph will display the cursor position
and values at that particular time. Bad quality data is indicated with white color.
The invention provides a novel system to make available the historical data of
power plant as stored locally at the power plant to a faraway remote location
over Microwave by means of a single port access link using unframed El packets
of 2048Kbps size, data, as stored in the data logger at the power plant, is
thereby made available to engineers located at a remote place. This data, as
transmitted over the microwave link using unframed El, is received at the
remote location by a single port El access unit and made available to a remote
data retrieval historian on TCP/IP port. The data is stored in the remote data
retrieval historian in customized files. Engineers can then access these files using
the developed remote data retrieval application package to study the
performance of the plant machinery and also analyze the causes of trips that
may have occurred in the plant by retrieving and studying the historical data
which can be presented in various formats.

WE CLAIM
1. A historian system for remote storage of long term realtime data from
generating plants, comprising:
a plurality of controllers each provided with input / output modules, said
input / output modules being connected to field elements for acquisition
and processing of plant data and for issuing commands for field
operation;
a remote historian data logger for storing the captured long-term plant
data;
a single port access unit linked to said data logger and interfaced through
a multiplexer on El framework to a microwave link for transmitting the
data to a remote location;
a second single port access unit for receiving through a demultiplexer the
data transmitted on the microwave link; and
a remote data retrieval historian for receiving and storing the longterm
plant data retrievable to meet long-term data analysis requirements.
2. The system as claimed in claim 1, wherein said field elements comprise
field sensors, transmitters and actuators for acquisition of data signals
from different locations of the plant.
3. The system as claimed in claims 1 and 2, wherein the acquired signals
identified to be used for historical functions are configured in said
historian data logger before storage.
4. The system as claimed in claim 1, wherein said remote historian data
logger is connected to said access unit by means of an Ethernet RJ 45
port.
5. The system as claimed in the preceding claims, wherein said single port
access unit data channel has transmission rates in integral multiples of 56
or 64 kbps upto a maximum of 2.048 Mbps.
6. The system as claimed in the preceding claims, wherein the data
presentation from said remote data retrieval historian is in the form of
trend graphs or in log formats.
7. The system as claimed in claim 1, wherein upto six data parameters can
be retrieved concurrently from said data retrieval historian.
8. The system as claimed in the preceding claims, wherein data retrieved
from said data retrieval historian can be exported to a CSV file for viewing
in a spreadsheet program.
9. The system as claimed in the preceding claims, wherein said system can
be provided with a network storage device or a random access device for
increasing the historical data storage capacity.
10. A historian system for long term remote storage of realtime data from
generating plants, substantially as herein described and illustrated in the
figures of the accompanying drawings.

The "Remote Historian" system is invented for the storage, transmittal, retrieval
and analysis of the historical data in a power plant at a geographically far away
location from the main Power Station. Long term storage data is captured and
stored on the Remote Data Logger Storian in customized files. The Data logger
Storian is linked to an El single port access unit through Ethernet TCP/IP
connection. The Single port access unit then interfaces through a multiplexer on
El framework to a Microwave link. The data transmitted on the Microwave link is
received back into another Single port access unit and then sent to a Remote
Data retrieval Storian. Various techniques are used to optimize, store and
retrieve the data at the remote location to meet the long term data analysis
requirements. The customized chronological data files stored on a Remote Data
retrieval Storian can then be retrieved, viewed in various formats and analyzed
using the developed Data retrieval application.