The city gas distribution (CGD) network in the country has been expanding at a rapid pace and several rounds of bidding have been concluded so far. The pipeline network is quite complex and volatile and thus needs to be monitored continuously. To this end, automation and control systems must be implemented.
One of the key operational monitoring technologies is supervisory control and data acquisition (SCADA). Its application in the CGD network helps in solving problems of data acquisition, monitoring and control, scheduling and management. The technology has been deployed by major CGD operators in India with the objective of ensuring safety, service reliability and cost-effectiveness in the pipeline network. Further, its varied applications such as distributed industrial control, predictive maintenance through analytics and timely detection of leakages for safety shutdown make SCADA indispensiable to the functioning of CGD operators.
SCADA architecture
A SCADA system typically consists of the following subsystems:
- Human-machine interface (HMI): The apparatus that presents industrial process data to the operator, which monitors and controls it.
- Supervisory (computer) system: Acquires process data and sends commands.
- RTUs: Remote terminal units (RTUs) are microprocessor-controlled electronic devices that are connected to sensors and can convert sensor signals into digital data, which is then sent to the supervisory system.
- Programmable logic controllers (PLCs): These are used as field devices because they are more economical, versatile, flexible and configurable than special-purpose RTUs.
- Communications infrastructure: Connects the supervisory system to RTUs.
The SCADA system can be customised to have both simple and complex configurations. In a basic SCADA system, information from sensors or manual inputs are sent to the PLCs or RTUs, which further send the information to computers. In a complex SCADA architecture, various wired and wireless media and protocols are involved in getting data back to the monitoring site. Thus, powerful internet protocol-based SCADA networks can be implemented over landline, mixed cellular and satellite systems.
At present, wireless SCADA systems are gaining prominence as they offer better control and speedy transfer of both live and historical data to the organisation’s headquarters. These systems do not entail hefty installation and permit costs, resulting in cost savings. At the same time, wireless systems do not have to face issues such as repair bills, machine failure and downtime when environmental conditions degrade the facilities.
SCADA applications
The SCADA system deployed in a CGD network offers varied functionalities, and ensures operational ease and process optimisation. Some of the functionalities of a SCADA system are the Following:
Distributed industrial control: One of the key applications of SCADA is its ability to provide a distributed industrial control facility to CGD operators when used in conjunction with PLCs or RTUs. It allows operators to remotely monitor and control widely distributed assets and facilities such as sectionalising valves, compressed natural gas (CNG) stations, the pipeline network and transmission stations irrespective of their location. This application has led to the widespread use of the technology.
Detecting leakages: Through SCADA, disruption in the flow of fluid or gas transmission systems can be detected to ensure continued operations. This is crucial as it aids in detecting leakages with high accuracy and significantly reduces the time spent on manually finding the actual location of leakage. It also helps determine the magnitude and possible effects of a leakage beforehand. This, in turn, helps in reducing leakages and minimising their effects such as the loss of energy, transmission lags, environmental disasters and human injuries.
Managing valves: In a SCADA system, all sectionalising valves are integrated. This enables it to monitor and control the on/off status from the central control centre. Apart from this, the technology enables the monitoring of valves on a real-time basis for pressure control and remote shut off, besides providing the facility of raising alarms in case of an unexpected disaster.
SCADA-integrated CNG stations: A SCADA system can be deployed at CNG stations, city gas stations and industrial units. It can be used for the online reconciliation of billed and actual consumption, monitoring losses at CNG stations, centralised monitoring of trends in load and performance, monitoring of upstream pressure for each CNG compressor and gas flow parameters, and identification of pressure loss across the grid, among other facilities. Further, the collated data can be used to provide business analytics, which is embedded in the SCADA system. This also helps in controlling price changes and making revisions at each CNG station.
Business analytics: A large quantum of operational data pertaining to pipeline pressure, flow rate, temperature, gas composition and equipment status is collated by a SCADA system on a real-time basis through sensors and other IoT devices such as automatic meters. This data, collected either on a per minute, or per hour, or a daily basis, enables the operator to generate analytical reports. For this, business analytics software is used along with SCADA. With this, an analysis of diagnosis, and predictive failure, asset optimisation and asset failure can be generated.
Apart from these use cases, an important feature of SCADA is its ability to merge with Google Maps. In this feature, various gas stations are marked in different colours and all the adjacent geographies are marked to provide a detailed view of the area.
Use of SCADA by key CGD players
Many CGD companies have installed SCADA technology and are using it extensively for their gas operations. Reliance Gas Transportation Infrastructure Limited, GAIL (India) Limited, Adani Gas Limited, Gujarat State Petronet Limited, Haryana City Gas Distribution Limited, Indraprastha Gas Limited, Mahanagar Gas Limited and Assam Gas Company Limited are some of the major players that have deployed SCADA.
In sum
With increasing adoption of technology solutions among gas utilities, the efficiency of the CGD segment is improving. At the same time, economic, safety and regulatory pressures, and the emergence of new market conditions in the oil and gas industry are driving the development of next-generation SCADA platforms. They will help ensure critical infrastructure remains online by providing backups and fail-safes. As a result, SCADA system architecture is constantly evolving, a recent advancement being cloud-based SCADA systems with big data functionality. This innovative system provides the ability to authenticate, manage and secure communication with gateways in the field apart from being scalable for streaming complex events. Moreover, the O-Data protocol version 4.0 is likely to gain importance in the years to come as it offers benefits of authentication, real-time access and maintenance of historical data. Further, continuous research and development in SCADA systems will pave the way for better hardware and software, helping organisations further improve their operations.