SCADA Systems
SCADA is an acronym that stands for Supervisory Control and Data Acquisition.
A SCADA system is a system composed of hardware which provides a central collection point for data generated at local and or remote facilities within the user's realm of activity; and industry. SCADA systems are utilized in various types of industries. Whel-Tech focuses on providing best in class SCADA systems; utilized in the Water and Wastewater applications; of all sizes.
A SCADA system provides a central collection point to: view, monitor and control local and remote assets without having to physically travel to each point. Decisions to make operational changes, from remote locations; should be based on a wealth of valid; and, timely data!
From a centralized point, a proper system provides easy access to the data that is collected. The Central Location is the focal point for interacting with Alarms, monitoring critical statuses, Accessing and changing Set points within the Operation. The ability to see and analyze Real Time data can greatly increase the effectiveness of feedback; allowing the operators & users to make better decisions; regarding operations!
Some SCADA systems are designed to provide Automatic Operation in the event of the loss of communications with Supervisory Control/Master. For these types of systems, the SCADA equipment has the inherent logic capability to automatically control the operation of the local system.
The hardware utilized is built specifically for the Water and Wastewater Municipal User Market. As such, this hardware offers built-in features specifically designed for the operation of water and wastewater applications. These built-in features include various pre-configured water and wastewater control blocks for Duplex, Triplex, Booster Pumping, Flow Monitoring applications. Proper Equipment & hardware selection, saves the municipality money and simplifies the Utility's operations and maintenance.
For the more demanding applications involving the pumping, flow and control of pressure in water or wastewater facilities; we turn to PLCs (programmable logic controllers). PLC’s are the workhorse of your system; when it comes to these demanding needs!
There are a number of benefits in implementing a SCADA System:
- Reducing Labor costs by automating manually collected data
- Provide Early detection of problems to prevent emergencies
- Optimize use of water storage to assure a fresh water supply
- Minimize storage overflows and inadequately low water storage
- Provide energy load shedding to save energy costs during times of peak energy demands
- Save on equipment and repair costs by monitoring equipment usage and preventative maintenance
- Improve water quality and reduce chemical waste by automatically controlling the chemical feed
- Improve response time to plant and distribution alarms via automatic alarm notification to personnel's cell phones, computers, and tablets.
- Identify plant performance issues via systems graphs and trends of the data
- Protect pipes from Water hammer via coordinated start and stop control of all pumps in the system
- Reduce breaking of pipes by automatic pressure control for consistent water Pressure
- Protect Aquifers by automatically monitoring aquifer levels and flow rates
- Reduce pump wear with automatic alternation
- Level out flows through out the treatment system
The Key Building Blocks of a SCADA System
Proper selection of the SCADA system building blocks is the Key to creating a SCADA System that is Reliable, Simple to use, easily maintained, and above all; it must be easily adaptable and expandable for future growth.
The building blocks of a SCADA System include:
1. Central Supervisory Control and Data Management Equipment
The Central site collects, stores and manages all the data from the remote sites. The remote site's RTUs / PLCs collect the data from the field instruments and process equipment and transmit the data to the Central site. The data that is collected at the Central site is used to invoke any Supervisory Control. All of this takes place while the system is logging, trending and managing data; while performing the critical monitoring functionality of the System. The Central Equipment provides the user a single access point to view and interact with the data that is transmitted from the remote sites. But, as you will see the world of SCADA and telemetry has migrated from a "Control Centric" environment; to a "Data Centric" world.
A new revolution in how users own and manage their own data is upon us!
The Central Equipment can be composed of 4 types of configurations including:
A. PLC Hardware-Based Central Equipment
This configuration includes a Master PLC that collects and stores the data that is transmitted from the Field RTUs/ PLCs. Typically the master PLC will have a local Operator Interface Terminal (OIT) that displays the data and allows a user to view the process values and alarms and to interact with the data via a touch screen.
Pros: These types of systems are typically industrial grade and very durable. Since these systems are not PC based they do not have operating systems which can be hacked or obsoleted. PLC Masters have prolonged life cycles and don't typically require a lot of hardware replacements.
Cons: These types of systems do not offer : Reports, Trends, or Remote Alarm Notification.
B. Computer Based Central Equipment.
This configuration includes systems that utilize their own Computer with Custom Software to collect and store data from the Field RTUs and PLCs. The computer's software program (HMI) is programmed to display the data and allow the user to interact with the SCADA system.
Pros: These systems can provide Reports and Trends if the software and programming is added for these options. These computer-based systems have a greater selection of individual components and software modules to choose from and to purchase along with programming and development licenses. These can be very customizable, and is a sole asset of the owner.
The computer-based SCADA system offers options for connection to the internet which can allow a user to remotely access the SCADA system from a remote location. This remotes connection can offer the option for remote notification of alarms to users if the software for this is purchased and programmed.
Cons: These systems require continuous maintenance to keep the software and the computer updated. Annual Development and runtime licenses usually apply. Keeping the system protected from hackers; and malware is a daunting proposition. These system components are not industrial grade and if exposed to harsh environments can quickly cause the components in the computer to fail.
The life cycle of these systems is very contingent on the obsolesce of the operating system. Once the operating system’s software becomes obsolete; typically, the computer and software need to be replaced as well. The net result is incurred costs associated with upgrading the development and runtime licenses. In some cases where the applications are tightly bound to the Operating System, the undertaking requires rewriting of code.
Often times the biggest risk to your system is malware which is usually presented from within the network architecture, or by way of a mass storage device.
C. Hybrid PLC and Computer based Central Equipment.
This configuration includes a Master Telemetry Unit or PLC to collect and manage and display the data locally. These systems can provide Reports, Trends and Alarms. Yet, they utilize powerful machine language like OPC-UA which allows them to share, and utilize data from various remote equipment; tied to the internet. It allows the user the ability to import the data relating to remote applications; and share them with other OPC compliant software.
Pros: This configuration provides the ruggedness of a PLC to perform the critical data management and control of the flow of data. It effectively uses the computer to display the data, and add in the Reports, Trends and Alarms; which are remotely accessible from a web based service provider. With this combination, the user gets the benefits of a PLC based control system; while appreciating the benefits of the Computer, or other smart devices, as an effective user interface.
If the computer were to fail, the SCADA system could continue to operate in the PLC until a new computer is installed. This combination makes the SCADA system very reliable.
This configuration can utilize a remote connection to provide remote notification of alarms to users if the software for this is purchased and programmed.
Cons: There are usually exorbitant fees associated with providers of Monolithic Systems (Fixed I/O). More often than not the customer is paying for empty I/O. While they tout scalability as a key feature… A one Size Fits All approach of these providers… NO LONGER FITS!
Providers of cellular monitoring have refused to relinquish the high rates associated with their monitoring rates despite the tremendous increases in bandwidth over the similar period!
- 2G was Introduced in 1992 in the US. (0.1 Mbps)
- 3G was launched in 2001 and was supported through 2019 (3 Mbps)
- 4G initially launched in 2009 (14 Mbps)
- 4G-LTE network was commercialized in 2009 (30 Mbps)
- 5G Roll Out in the US began in 2019 (100 Mbps)
- Starlink is seeing reported speeds between 20 & 150 Mbps, in initial studies!
Web Based Hosted SCADA Solutions provide full SCADA functionality to a Master PLC or directly to the RTU/PLCs at the remote sites.
When using a Master PLC, the master PLC is connected via a secure data connection to a Managed Data Center that hosts the SCADA software. Or each RTU/PLC in the field can be connected directly via a secure data connection to a Managed Data Center that hosts the SCADA software.
With either configuration, The SCADA data is transferred via a secure data connection (cellular, broadband, satellite, etc) to the secured servers at the Managed data center. In turn, The registered user can access the SCADA data and screens from any web-enabled device. In this solution, there is no SCADA computer hardware, software or licensing to buy or maintain. The system is fully maintained, hosted and designed by a Premier Water and Wastewater Integrator that fully understands the requirements. The quality of the screen design of the Graphics, Reports and Alarm annunciation is streamlined to provide enhanced capability. Each user has secure access to the SCADA system from an internet-enabled device (PC, Tablet, Smart Phone, etc.).
Pros: No computer, computer software, computer maintenance is required for this option. This keeps the equipment costs less. The Secure remote access for any registered user from any internet enabled device is a very powerful tool. This feature increases the ease of accessibility to data in the SCADA system. This tool not only provides convenience to the user but can improve the reaction time to the data to resolving an issue. Utilizing a master PLC to collect the data from the RTUs, provides a level of redundancy to back up the SCADA system if the connection to the managed data center were to be lost.
Cons: These systems are newer technology and are not as well known in the industry.
2. Remote Terminal Units (RTU) and Programmable Logic Controllers (PLC) With Communication
The RTUs/PLCs are the devices that are located at the remote sites that interface with the Supervisory Control Equipment at the Master site. The RTU/PLCs devices gather the data from the field instrumentation and process equipment at the remote sites and transmit that data to the Master site.
The PLC (Programmable Logic Controller) is an industrial computer with inputs and outputs that can be programmed to perform the required control logic, monitor data and communicate to another PLC.
The RTU (Remote Terminal Unit) refers to a device that is designed with built in features for Water and Wastewater applications. These features make the RTU more ideal for municipal Installations for they include typical inputs, outputs, communications without having to add these to the device with customized programming.
RTUs/PLCs are available in various input/output configuration to accommodate the field mounted Instrumentation and equipment signals at each particular remote location in an application. Most RTUs/PLCs have base I/O with expansion capability. It is important to keep in mind future I/O requirements in choosing an RTU/PLC.
A RTU/ PLC require a modem to communicate to the SCADA system. There are many Communication mediums available and many factors involved in determining which communication medium is best for the particular application. It is important to choose the RTU/PLC that has the appropriate communication protocol for the application. A RTU is generally better suited for water and wastewater SCADA applications they have a wide range of Communication protocols built into the firmware. No customer programming is required to access the various protocols.
3. Communications
The communications medium is the link between the SCADA RTU/PLCs and Supervisory location. As stated earlier, many factors contribute to determine which communications medium is best for a particular application. Geographic conditions (mountainous areas, for example) may make radio communications impractical. High costs for leasing dedicated telephone lines as well as the rising costs for some cellular communications make alternative communications means more desirable. There are many communications mediums available.
Some common communications mediums include:
- FM (VHF/UHF) radio
- Dedicated leased telephone circuits
- Metallic signal lines
- Conventional dial-up telephone lines
- Coaxial cable networks
- Spred spectrum radio
- Fiber optic cable
- 900 MHz radio
- Cellular radio
- LoraWan
4. Field Mounted Sensors and Instrumentation and Controllers
A Sensor or Instrument senses a physical change and converts the change into an electrical or electrical/mechanical output signal. These output signals can be transmitted to the SCADA system for monitoring and supervisory control.
These field devices generate output signals in the form of a Discrete signal or an Analog signal. Discrete signals are digital on/off signals or Open/close signals from a contact closure. Analog signals are variable continuous signals which can vary in amplitude over time such as a level, flow or pressure. The analog output signal will be represented in 1-5 Volt, 4-20ma, etc.
A Controller is a device that receives the input signal from the sensor or instrument and compares the output value to a predetermined set-point.. The controller can determine what amount of output signal is required by the sensor to meet a desired action.
All of the signals from the sites can be wired to the RTU/PLC that transmits those signals to the Master PLC or directly to a managed data base center for Supervisory Control.
Examples of Field mounted sensors, instruments and controllers include:
- Limit switches, float switches, probes
- Level, flow and pressure transducers
- Pumps, valves and starters
- Level controllers