FIELD OF INVENTION :

This invention relates to the development of Remote Terminal Unit for use in Supervisory Control and Data Acquisition (SCADA) for Distribution Management System (DMS) and also to the manner in which the modules are assembled in the rack and their interfacing.

BACKGROUND OF THE INVENTION & PRIOR ART :

Remote terminal Unit (RTU) plays a significant role in the Distributed Management System (DMS) and Supervisory Control and Data Acquisition (SCADA). RTU provides remote monitoring and control of a utility’s power system related assets and networks.
Remote Terminal Unit supporting several substation protocols have been designed for DMS applications. Electronic interface modules acquire signals from various field sensors. Master/Client and Slave/Server functionality has been implemented for IEC 60870-5-101, 103, 104, Modbus, DNP3.0 protocols. IEC 61850 client functionality has also been implemented, to enable the RTU to acquire data from the IEC 61850 servers. Each of the 8 communication ports can be configured as Master or Slave handling data over any one of the defined protocols. Provision for communication

allows for connection to other devices in the network. Maximum of 32 devices can be connected to each port to form a network. As a Master, RTU can be configured to interface to the field devices for monitoring / control purposes either directly through hardwired interface or through slave / server devices, which are in turn hardwired to the field devices. The data / control are mapped between the RTU and the upper layer RTU or SCADA. Cyclic data, General Interrogation, Counter Interrogation, Group interrogation modes of data acquisition and Control features have been implemented. A few related examples on Remote terminal Unit (RTU) can be found in the earlier patents mentioned below:
US007437203B2 discloses RTU assembly having a number of independently operational cells for systems functions.
US 20070248027A1 recites on the configuration utility as being stored on the remote terminal unit.
US 20090326731A1 recites the method comprising: acquiring a sensor data from an electrical distribution line using an intelligent RTU.
US 20160006300Α1 discloses according to the invention, the equipment comprising means for and also monitoring the LV network.
WO 2015/148106 Α1 defines the RTU which includes input/output (I/Ο) terminals configured to be coupled to the field devices. The RTU also includes one or more I/Ο modules having one or more reconfigurable I/Ο channels configured to be coupled to the I/Ο terminals.

WO 2016/025242 Α1 describes a Controller module comprising at least one processing device configured to communicate with at least one industrial field device via the I/O channels of the I/O modules.
US006529857B1 discloses Distribution automation remote terminal unit comprising at least two separate independently operable units with separate power supplies, each of the units performing a different system function to the other unit;
The instant invention on the other hand illustrates a novel RTU, contrast to the above prior arts.
OBJECT OF THE INVENTION:
The main object of this invention is to develop interfacing of the data acquisition cards with the Single Board Computer (SBC) and their arrangement in the rack. In this centralized architecture the SBC acts as an interface for data exchange between the data acquisition cards and field communication.
The other object of this invention is to develop application code in Real Time Operating System (RTOS) environment and running on x86 hardware. The application software running on real time operating system provides hard real time-stamp and better metering accuracies.

Further object of this invention is the PC based configuration tool for configuring the RTU functionalities. The PC based configuration tool provides for on-line and off-line configuration, thus saving configuration time. The user friendly screens with user management allows for selective access and better control.
SUMMARY OF THE INVENTION:
The invention is directed towards development of a non-cellular and centralised approach based Remote Terminal Unit having one microprocessor and number of data acquisition modules. As all data processing is done by single processor, there are no data losses and accuracies are increased at the same time.
The configuration tool herein is loaded in the station PC and configuration can be done in offline mode, without the need for RTU, thus saving time. There is no extra memory requirement in RTU to store configuration utility. The User friendly tool provides for easy navigation and less dependency.
In the present development RTU obtains the data from the sensors, amplifies and phase correct the data, extracts fundamental using Discrete Fourier Transform (DFT) technique. The computed value is then mapped to substation protocols viz IEC60870-5-101 and IEC60870-5-104 for upward transmission to control

centre. The DFT techniques provides better fundamental component extraction and metering accuracies.
The used substation protocols are standardized by IEC and provide interoperability and better data transmission between RTU and control centre.
The disclosed system consists of sensors for monitoring the voltages and currents from 2 different levels. The data captured from low-end sensors is sent by the RTU to upper layer SCADA over suitable protocol. All the data acquisition modules are housed in a single EMI/EMC compliant rack. Each of the data acquisition modules perform a designated I/O function like analog input, analog output, digital input, digital output. A common power supply is used to power all the modules. As there is no differentiation in the modules for MV and LV, the modules are generic and can be used interchangeably. This provides modularity and ease of maintenance.
In the present development the functionality of input and output module is fixed. The analog input module will acquire the data and send it to SBC module for further communication. Similarly digital input module will acquire the digital field data and sent it to SBC for further communication. Analog input, Digital input and output modules can be configured from the configuration tool. The fixed functionality modules are advantageous from the point of view of fault diagnosis and easy maintenance.

The Remote Terminal Unit includes a single board computer and number of data acquisition modules for acquiring analog and digital data. Each data acquisition module contains number of I/O channels. The field connectors on the data acquisition card, acquire field data and transfer data to SBC via FRC (Flat Ribbon Cable) Connector. The power supply is fed separately through power cable to all the data acquisition modules and the SBC. The separation of power cable and data cable provides less interference to the data signals and improve the reliability.
In the present invention there is one RTU unit with one power supply. The measurement, control and communication is performed by one unit only. As one unit is handling all the functions there is no data transfer delays, in addition to better accuracies and no dependencies.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Fig 1 shows the General card arrangement of the cards in the cabinet and their
interconnection.
Fig 2 shows the General architecture of the RTU along with the Configuration
tool, Meters and SCADA [205].
Fig 3 shows data flow in monitoring direction.

Fig 4 shows data flow in control direction.
Fig 5.1 – 5.15 shows the Configuration Tool screens.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION:
The RTU [207] designed around an EMI compliant 19 inch enclosure is powered by a universal input power supply. The various electronic modules present carry out functions like analog / digital data acquisition, signal conditioning, field device actuation etc. All these functions are controlled and coordinated by a central processor module, which is an SBC (Single Board Computer). The following are the inputs from the field, which are subjected to the required signal conditioning before digitizing:
1. Phase Voltages / Currents.
2. 4-20mA sensor signals.
3. Status / Control signal from / to the switchgear in the form of binary data
The electronic modules placement and their interconnection is shown in the Figure 1. All the modules are powered by 24V DC, which is derived from a universal input power supply. Field connectivity is provided from the rear side of the rack. The various modules and their functionalities are:

1. The analog inputs from the field such as the phase voltages / currents are stepped-down by the instrument transformers located on the CT/PT module. The filter module does band limiting and amplitude scaling to the input analog signals, before they are digitized.
2. The Digital Input modules provide isolation and level translation to the status inputs signal to 5V level. Each DI module has a provision for reading 24 status inputs. Status inputs from 4 digital modules are routed to two 50-pin connectors of the ADD-ON board.
3. Digital outputs from the SBC are routed to the relay module via base board. Each relay module caters to 16 digital outputs.
4. 4 number of Analog Outputs from the SBC module are routed to the field by the filter module.
5. Communication module having 4 numbers of RS232, 2 number of RS485 and 2 number of LAN ports for communicating with the lower end Multi-function meters and High End SCADA [205].
6. Front panel LEDs for displaying the status of active communication over a particular protocol.
7. The RTU [207] uses x86 based SBC module which processes various hardwired and software inputs / outputs and communicate the same from / to the upper SCADA [205].

8. Interconnection and data transfer between the two modules is via Flat Ribbon Cable (FRC).
Application code has been developed in C language in Real Time Operating System (RTOS) environment. Real-time Operating system provides greater timings accuracy. The application is designed as multiple processes with multiple threads. Each thread is designed to perform a particular task. Algorithms have been developed for Analog and Digital Data acquisition, Measurement, Sequence of Events (SOE) recording, Alarms recording and Data transfer over substation protocols. The various processes and their function are:
1. Firmware Utility: The process is responsible for launching the other applications – processes at S No 2,3,4,5 below and also provide communication to/from the PC based configuration tool.
2. Application code: The process is responsible for Analog and Digital Data acquisition, Measurement, Sequence of Events (SOE) recording, Alarms recording and Data transfer over substation protocols
3. SNTP Client 1: The process is responsible for setting the RTU [207] time from connected SNTP server source 1.
4. SNTP Client 2: The process is responsible for setting the RTU [207] time from connected SNTP server source 2.

In addition to acquiring signals from the field, RTU [207] obtains data from the Multi-function meters, IEDs, Relays etc. over Serial/TCP media using one or more of the below mentioned protocols:
1. IEC60870-5-101, Master and Slave over Serial media.
2. IEC60870-5-103, Master and Slave over Serial media.
3. IEC60870-5-104, Master and Slave over Ethernet media.
4. DNP3.0, Master and Slave over Serial and Ethernet media.
5. Modbus RTU & TCP, Master and Slave over Serial and Ethernet media.
6. IEC61850, Client over Ethernet media.
When RTU [207] is powered ON, the application software loads the database file which is configured by the configuration tool. The database file contains information about the hardware Analog/Digital tags and also configuration details of individual port which is configured as Master / Slave. The application reads the master settings and tags through which the RTU [207] acquires the data. The acquired data in the master tags are mapped to the slave tags. These tags send the data to the upper layer SCADA [205] over any one of the user required protocols. Figure 2 illustrates the communication architecture of RTU [207]. Transmission of data in two directions is defined below (depicted in Figures 3 and 4)

Data in Monitor Direction: Data in the monitored direction is transferred from the lower-end slave/server [201,202] to the SCADA [205] via RTU [207]. This includes data generated due to an event, cyclic data, general interrogation, group interrogation etc.
Data in Control Direction: Data in the control direction is transferred from the HMI-SCADA [205] to the lower-end slave/server [201,202] via RTU [207]. This includes direct command, SBO commands, clock synchronization, Analog output etc.
A PC-based configuration tool [206] allows for setting the Master / Slave functionality on the particular communication port. When a port is configured as Master, port configuration parameters, protocol configuration parameters and tags are defined to fetch the data from the Multi-function-meters [201], Multi-function transducers [202] or a relay [203]. When a port is configured as Slave/server, port configuration parameters, protocol configuration parameters, Trusted IP settings and tags are defined to fetch the data from the master tags. The configured database file is uploaded to the RTU [207] application for communication. Following features are supported by the tool: A.Master and Slave selection on 8 ports, B.Port communication parameter configuration[Fig 5.1],
C.Protocol parameter configuration. Configuration of general settings, analog and digital tags [Fig 5.2 & 5.3].

D.Hardware Signal matrix for configuring channels in Digital Input Modules [Fig 5.5], Digital Output Modules, LED Module.
E. Alarm configuration [Fig 5.6].
F. Event and Alarm Viewer [Fig 5.9 & 5.10].
G.Online display of RMS values of hardwired Current & Voltage, sensor data, Digital
channels ON/OFF status [Fig 5.7]. H.Diagnostics for validating configured database file, Available License, Database file
successful read status, real-time protocol Communication Log [Fig 5.4 & 5.13]. I. User management. J. Facility for upgrading the application code of RTU [Fig 5.12].

WE CLAIM
1) A remote terminal unit (RTU) (207) for supervisory control and data acquisition (SCADA) in a distribution management system (DMS) comprising, a no. of data acquisition modules (103- 106), a central processor module, a single board computer (SBC) along with SBC card (102), PC based configuration tool (206) , universal input power supply (108) unit.
2) The RTU as claimed in claim 1, wherein data acquisition modules (103- 106) performing a designated I/O functions of analog input, analog output, digital input, digital output.
3) The RTU as claimed in claim 1, wherein the single processor undertakes all the data processing ensuring no data losses and increased accuracy.
4) The RTU as claimed in claim 1, wherein, SBC card (102) interconnecting/ interfacing with the electronic modules for communication.
5) The RTU as claimed in claim 1, wherein, PC based configuration tool (206) setting the master/slave functionality on the particular communication port, when the port is configured as master or slave, loaded in the station PC.

6) The RTU as claimed in claim 1, wherein, universal power supply unit (108) provides power to all the modules from the single source.
7) The RTU as claimed in claim 1, wherein all the data acquisition modules are housed in a single EMI/EMC compliant rack.
8) A method of measurement, control and communication by acquiring analog and digital field data and transferring the same to SBC via FRC (Flat ribbon cable).
9) The method as claimed in claim 8, wherein the control of data is undertaken from 2 different levels, wherein the data captured from low- end sensors sent by the RTU to upper layer SCADA over suitable protocol.
10)The method as claimed in claim 8, wherein the fundamentals of the data are extracted by way of DFT (Discrete Fourier Transform), the computed values mapped to substation protocols and for upward transmission to control centre.
11)The method as claimed in claim 8, wherein, the application code developed in C language in real time operating system (RTOS) environment.