Introduction To SCADA and Telemetry Joe Mullaney Senior I&C Engineer MSE Technology Applications, Inc. Tetragenics Division joe.mullaney@mse-ta.com
Overview Definitions What is SCADA? What is Telemetry? What is Data Acquisition? Components of SCADA System Typical System Configurations HMI and Example HMI Screens Auto Dialers Tips in Planning Your SCADA System Maintenance of Your System Q&A Overview
Definition SCADA What is SCADA? SCADA (Supervisory Control And Data Acquisition) system refers to the combination of telemetry and data acquisition. It consists of collecting information, transferring it back to a central site, carrying out necessary analysis and control, and then displaying this data on a number of operator screens. The SCADA system is used to monitor and control a plant or equipment. Control may be automatic or can be initiated by operator commands. SCADA
Definition - Telemetry What is telemetry? Telemetry is usually associated with SCADA systems. It is a technique used in transmitting and receiving information or data over a medium. The information can be measurements, such as voltage, speed or flow. These data are transmitted to another location through a medium such as cable, telephone or radio. Information may come from multiple locations. A way of addressing these different sites is incorporated in the system. Telemetry
Definition Data Acquisition What is data acquisition? Data acquisition refers to the method used to access and control information or data from the equipment being controlled and monitored. The data accessed are then forwarded onto a telemetry system ready for transfer to the different sites. They can be analog and digital information gathered by sensors, such as flowmeter, ammeter, etc. It can also be data to control equipment such as actuators, relays, valves, motors, etc. Data Acquisition
Components of SCADA System Remote Station Communication Network Central Monitoring Station (CMS) Field Instrumentation SCADA Components
Remote Station Field instrumentation connected to the plant or equipment being monitored and controlled are interfaced to the remote station to allow process manipulation at a remote site. It is also used to gather data from the equipment and transfer them to the central SCADA system. The remote station may either be an RTU (Remote Terminal Unit) or a PLC (Programmable Logic Controller). RTU/PLC
Communication Network The Communication Network refers to the communication equipment needed to transfer data to and from different sites. The medium used can either be cable, telephone or radio. Remote sites are usually not accessible by telephone lines. The use of radio offers an economical solution. Radio modems are used to connect the remote sites to the host. An on-line operation can also be implemented on the radio system. For locations wherein a direct radio link cannot be established, a radio repeater is used to link these sites. Communication Network
Central Monitoring Station (CMS) The Central Monitoring Station (CMS) is the master unit of the SCADA system. It is in charge of collecting information gathered by the remote stations and of generating necessary action for any event detected. The CMS can have a single computer configuration or it can be networked to workstations to allow sharing of information from the SCADA system. EPA/DEQ maintenance reports can be generated from the CMS CMS
Field Instrumentation Field Instrumentation refers to the devices that are connected to the equipment or machines being controlled and monitored by the SCADA system These are sensors for monitoring certain parameters; and actuators for controlling certain modules of the system Field instruments are usually either discrete or analog, but sometimes are digital in type Field Instrumentation
Field Instrumentation (Analog Devices) Tank Level These instruments convert physical parameters (i.e., fluid flow, velocity, fluid level, etc.) to electrical signals (i.e., voltage or current) Some of the industry standard analog outputs of these sensors are 0 to 5 volts, 0 to 10 volts, 4 to 20 ma and 0 to 20 ma Signals using current (ma) are more common because they can be used for longer distances with less error due to signal loss Analog Devices
Field Instrumentation (Discrete Devices) Digital inputs and outputs are used to differentiate the discrete status of the equipment Usually, <1> is used to mean EQUIPMENT ON and <0> for EQUIPMENT OFF status. This may also mean <1> for FULL or <0> for EMPTY Discrete signals can either be AC or DC type Discrete Devices
Field Instrumentation (Digital or Smart Devices ) Instruments that provide more than one variable on one pair of wires (turbidity, temp, ph, etc.) Usually wired on a bus network Saves installation cost in wiring Provides diagnostic information of instruments Digital/Smart Devices
Typical System Configurations Three Basic Types Point-to-Point Point-to-Multipoint Peer-to-Peer May also require store and forward or repeaters if using a radio network System Configurations
System Configurations Point-to-Point Most simple type of communications One station talks directly to the other (ie: water tank to well pump) Point to Point Pump station polling a tank for level and starting and stopping pump. Point-to-Point
System Configurations Point-to-Multipoint Lift Station Point to Multipoint Master Polling Several Remote Sites Usually has one master polling location Sometimes CMS Most common type Pump Station Water Tank Dam Point-to-Multipoint
System Configurations Peer-to-Peer All sites talk directly with each other Communications protocol has to be able to support this type of communication Manufacturing facilities and treatment plants are good examples that use this type of communications Peer-to-Peer
Store/Forward Store/Forward and Repeaters Some systems will use one site to poll and store information from another site, then relay data back to the master. Repeaters Some systems use a repeater to relay multiple or one sites data back to master. This is a commonly used strategy. Store/Forward and Repeaters
Human Machine Interface (HMI) A graphical representation of a process (GUI) Usually a software application on a PC at CMS to let the operator interface with control system Has control functionality Alarm capabilities Data Historian and trending HMI can be incorporated into specialized RTUs Typical software packages: Tetragenics MC3000, Wonderware, Intelution and RSView32 HMI
SCADA HMI Examples Remote Stations SCADA HMI
SCADA HMI Examples Central Monitoring Station SCADA HMI
Auto Dialers Hardwire Sensors are wired directly to dialer (analog and discrete) A dialer is needed at each location Limited I/O count for dial out A phone connection is needed at each site (perpetual operating cost) A large system is expensive ($2K-$4K per site) Very dependable Proven over many years Hardwire
Auto Dialers Software Usually built into or linked to HMI software on the CMS PC is your dialer Unlimited points for alarm dial out One phone line Less expensive for larger systems ($1.5K to $3K) Can send messages to pagers Can generate audio reports for dial in to system Text to voice technology Easy to set up callout schedules Relies on SCADA communications for alarm messages from remote sensors Software
Tips in Planning your SCADA System Get involved with your engineer for vendor and equipment selection Check references of integrators past installations Select vendor that can respond quickly if needed Select the most state-of-the-art equipment that the project can afford (avoid buying obsolete equipment) Select systems that can be serviced by another integrator in the event of having to change integrators Hire integrator that has background with your process requirement If using radios, a path study is highly recommended Bury fiber optic cable when possible (this is fairly inexpensive during new construction) Enter a yearly maintenance contract with the vendor SCADA Planning Tips
Maintenance of your system Check antenna connections and other communications equipment yearly Calibrate instruments regularly, as per manufactures recommendations (at least quarterly) Backup your data at least once a month Have backups of HMI and other software applications Have a spare hard drive formatted and ready to go Keep spare parts for field instruments in inventory Maintenance
Q&A