You already know that SCADA (Supervisory Control and Data Acquisition) can save you a lot of money and increase profitability, but your SCADA implementation can be a sinkhole of cost overruns, delays and limited capabilities. This guide shows how you can use SCADA effectively and profitably - including concrete applications and examples.
I'll give you an example of the world's simplest SCADA system. Imagine a fabrication machine in a factory that produces widgets. Every time the machine finishes a widget, it activates a switch that turns on a light. That light tells a human-machine operator that a widget has been made. Obviously a real SCADA system does a lot more than that but the idea here is the same. A full-scale SCADA system just monitors more stuff over much greater distances.
Now let's talk about the two elements involved in these supervisory systems. All you need are the system or machine you want to monitor and control, and a data collection system made up of sensors and control outputs used to monitor and control the first system.
A SCADA system performs four functions:
Networked data communication
These functions are performed by four kinds of components:
Sensors (either digital or analog) and control relays
Remote telemetry units (RTUs) or programmable logic controllers (PLC SCADA)
Master unit (HMI SCADA)
The communications network that connects the Master unit to the RTUs in the field
Collection of articles discussing various elements of SCADA.
A SCADA network consists of one of more Master Terminal Units (MTUs), which are utilized by operators to monitor and control a large number of Remote Terminal Units (RTUs). The MTU is often a computing platform, like a PC, which runs SCADA software. The RTUs are generally small dedicated SCADA devices that are hardened for outdoor use and industrial environments.
A SCADA system usually includes signal hardware (input and output), controllers, networks, user interface (HMI), communications equipment and software. Altogether, the term SCADA refers to the entire central system. The central system usually monitors and process data from various sensors that are either in close proximity or off-site (sometimes miles away).
SCADA systems are being implemented with greater regularity in today's ultra-competitive manufacturing environments. While SCADA systems are used to perform real-time data collection and control at the supervisory level, HMI's are typically seen as local user interfaces that allow operators to manipulate the machine or process locally, and perform SCADA programming work to customize the system.
Did you think carefully when you picked your master or did you just pick the first one you found? Maybe you "inherited" a manager when you changed jobs. Whatever the reason, you're probably not positioned as well as you should be when it comes to a master station.
Think for a second about how much easier it would be with your master working constantly to help you.
DNP3 communications take place in the Distributed Network Protocol format. The DNP3 protocol is a protocol that is widely used in the water and electric utility industries.
DNP3 communications are a key part of how process automation systems and devices on networks in these industries work together. DNP3 communications are commonly used within SCADA systems. The various components of these systems communicate using the DNP3 protocol. These devices include the master (or HMI), the RTU's (Remote Terminal Units), and IED's (Intelligent Electronic Devices).
Maintaining high-quality water at De Anza Moon Valley is not a job LaVay takes lightly. "We're on a well, a 600-foot deep well -and I'm in charge of all that," said LaVay, the facility manager. He spends a lot of his time physically monitoring his water-treatment equipment, which primarily consists of analog sensor data. "We do have an existing alarm system, but frankly, it doesn't hold a candle to DPS equipment. I mean, it's not even close..."
Your SCADA system will most likely monitor thousands of individual sensors throughout your network. If two different sensors sent major alarms through the monitoring system, your master would be alerted.
If, for example, one of these alarms indicated a power failure at a site, and another alarm indicated a battery failure at the same location, the RTU would receive these inputs, translate them, and forward them to the master. The monitoring system master would then react to this critical alarm combination with a user-specified control relay, such as activating the back-up generator at the related site, preventing a network failure.
Effective monitoring saves significant expenditures on repairs and lost revenue due to network downtime. These benefits make it crucial for operators to employ a system to thoroughly monitor their network.
A Modbus Human Machine Interface (HMI) is the interface of a Modbus system that allows the operator to interact with the system equipment. This interface is a type of software that presents the Modbus messages in a human-readable form. It is a critical part of the Modbus master.
A Modbus HMI is necessary for an operator to be able to interpret alarm polls and status reports from their Modbus system. As Modbus communications take the form of packets of word bits, it would be extremely difficult and time-consuming for an operator to manually interpret even a single Modbus message. With thousands of alarms and response messages coming in every day, it would be impossible for an operator to monitor their network without a Modbus HMI.
Typically, a Modbus HMI is a type of browser screen. In this screen, network operators can view their Modbus alarms and other messages in their English form. The Modbus HMI simply uses the codes programmed into the system to retrieve the information from the packets of bits.
SCADA security is a topic of increasing concern for network operators. As these systems can be utilized to transmit sensitive data, it is important to develop the system in a way that prevents this information from being released onto the Internet.
SCADA control functions are what enable a system to automatically respond to certain situations with a programmed response. Sensors cannot generate or interpret protocol communications. RTU devices along the network interpret the information from these sensors and translate it into a language the master can understand.
The master can utilize the information it receives from various inputs to enact control relays at the RTU level. This means that whenever a user-specified combination of alarms occur, the RTU will automatically respond with a control relay that has been programmed into the system, securing the network by responding to the Change-of-State (COS) event indicated by the alarm.
Telecom SCADA integration is the process of integrating SCADA capabilities into a telecom system, such as a network alarm monitoring system.
The integration process can only occur when you have a master that supports both telecom and SCADA protocols. To allow for integration within your network, you must find a master that can support SCADA in addition to telecom protocols.
Advanced monitoring platforms support many different communication protocols through a single master, allowing for complete integration. Integrating alarms from these devices of varying protocols allows you to easily view all of your alarms on a single screen.
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