In order to have real time monitoring of the network it becomes important that SCADA (Supervisory Control and Data Acquisition) acquires real time information from various equipment installed at 11kV Level. This valuable information thus received can then be used in various modules of SCADA to identify overloading, faulty section, unbalancing, low power factors etc., with the help of which SCADA can take prompt action in order to normalize the network.
- Distribution Management System (DMS): This system can help SCADA achieve all the above requirements. DMS system acquires data as received from the field devices (like RMUs, DTs, ACB Panels etc.) and analyses the same on real time basis to provide the best possible solution.
The basic architecture for DMS implementation over SCADA is as shown below:
The Distribution Management System works on the inputs provided by the SCADA. Major pillars for effective Distribution Management System are as below:
Robust and Reliable Communication Network
Major communication methodologies adopted are:
- GSM SIM-based communication GPRS GSM based communication can be used for communication with the existing SCADA. Same can be used for taking signals from distribution sub-stations (11/0.415kV) to SCADA using modem, which communicates with the SCADA. In addition to signal availability, Cyber Security shall also be ensured when choosing a service provider for taking GPRS-based SIM. White listed SIM capable of communicating only to SCADA is one solution that limits any outer interference in the GPRS Network.
Major setbacks
- Poor Network availability in Rural areas.
- Data gets stuck in the FRTU/Modem memory due to unavailability of communication signal.
- Monthly recurring charges for each and every location.
The Communication network for the GSM mode of communication is illustrated below:
- Fibre Optic-based communication
Another way of establishing the communication with SCADA is by the use of Fibre Optic Communication Network. The Fibre optic communication link will act as a communication bridge and all the real time communication can happen over the same.
In order to have fibre optic communication link, fibre optic network should be available at all the locations.
The Fibre Optic Network shall be connected in a Ring form in order to ensure that in case of any breakage from one source, the communication to the respective RMU can be done from other source. This will ensure maximum online availability of the field devices at SCADA level.
A typical Fibre Optic Network is illustrated below:
The Fibre Optic Network as indicated above will be used for FRTU communication with the SCADA. In case, if there is a break in the Fibre Network on one side, the communication can still be made using the other side of the network.
Major setbacks of the Fibre Optic Network
- Providing FO in one go would be very costly since the distribution network is widely spread across the areas.
- High maintenance cost for repair of FO network.
Major benefits of the Fibre Optic Network
- The recurring cost involved for maintaining the services is minimum. However, it shall be ensured any breakage in FO network shall be repaired at
the earliest. - The communication is independent of any third party communication medium (like mobile service provider etc.).
Accurate Network Mapping
The Network mapping (EHV, HV) in DMS becomes of prime importance since all the analyses and calculations are done on the basis of the Network Mapping. In order to ensure that accurate calculations/solutions are provided by DMS, the following points should be kept in mind:
- Accurate feeder/network mapping should be done in the SCADA/DMS
- The network parameters (like Transformer rating, Cable type, Cable length, conductor type etc.) shall be accurately mapped in order to have near to 100% accuracy in calculations
- All the changes in the feeder/network shall be timely updated in the SCADA/DMS platform in order to ensure that no unsafe/fatal operations are made by SCADA remotely.
Accurate Signal Mapping from Field Devices to SCADA
All the signals from the field devices to SCADA are mapped using standard IEC104/IEC61850 protocol. The signal mapping (Digital/analogue) shall be accurately mapped in order to ensure that the right signal is coming to SCADA and the same is used for the calculations. Major focus shall be kept on CT Ratios, PT Ratios selection while mapping to ensure that DMS Calculations are done on actual field data.
Proper Maintenance of Field Devices to Ensure 100% Connectivity between Equipment and SCADA
The electrical devices are often installed in harsh outdoor environments. These harsh environments can often lead to damaging the communication equipment, which can lead to breakage of information flow from Field device to SCADA.
Mechanism should be built in order to ensure that any breakage of information flow from the field equipment is quickly attended. This will ensure that no unsafe operations are done by SCADA and all the calculations are working perfectly.
Conclusion
With the increasing power demand and distribution network being transformed into an ‘ACTIVE DISTRIBUTION NETWORK’ (due to infusion of more and more Solar, EV Charging, Vehicle 2 Grid, Battery Energy Storage System directly in distribution network etc.), it becomes important that the automation tools like Advanced Distribution Management System be used for most effective network utilization. Needless to say that this requires working on all four pillars together along with ADMS implementation.
Vaibhav Vaish is the General Manager at BSES Rajdhani Power Limited.
