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An introduction to SCADA programming for telemetry systems

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SCADA technology is a more modern incarnation of network alarm monitoring technology that's been used since the 60's. The broader term defining those more-traditional systems is "DCS" (Distributed Control System). Factories are big users of this technology.

The trouble with DCS, however, was that it wasn't intended to cover a large geographic area. Think "manufacturing plant" rather than "gas distribution network".

SCADA, on the other hand, was built to meet the need of covering a large territory (or even an entire nation). This opened up new doors and remote-management possibilities in several industries, including: manufacturing, water and sewage, electric power generation and mass transit. For this reason, SCADA programming is a very important skill in the modern economy.

Real-world physical conditions must be translated into machine language and then into signals that humans can read, record, and analyze. Therefore, SCADA system development involves programming at various levels. In SCADA programming, data is collected at the Remote Telemetry Unit (RTU) and has to be converted into signals, which is followed by interpreting this data that requires Human Machine Interface (HMI). Often, this data also has to be compiled and stored (history databases) for recognizing trends and analysis work. As a result, customized database systems have to be developed. Networks and communication systems bring in more varied requirements.

What is involved in SCADA programming?


With more and more SCADA systems being deployed globally, the odds are increasing that you may be called on someday to program a system. So what will that involve?

How exactly you'll do your programming depends on the system. In some setups, you'll be designing logic sequences to be executed when certain "trigger events" occur. This is common in manufacturing. If you work with a large-scale network (telco, power utility, railway, government, etc.), it's more likely that you'll be working in simpler configuration interfaces and won't really be "programming" in the traditional sense. You won't be writing code on a dark terminal somewhere.

An RTU web interface is a great example of "configuring" a SCADA implementation rather than "programming". After you've wired various inputs into the RTU, you'll have to tell the RTU (via its web interface) what to call each item. Did you wire in a temperature sensor? A generator voltage? Something else?

Higher up the chain, you'll need to perform similar provisioning of your master station (HMI). This is important, because your master station brings together all of your disparate RTU/PLC elements into a single view. "Programming" in a master/HMI context involves creating maps or diagrams that provide important situational awareness in an emergency. You want to see exactly WHERE a problem is, not some cryptic code number or label.

Software Languages used in SCADA Programming
Most commercial SCADA systems are now programmed using standard interfaces whenever possible. Most programs are written in C, or a derived programming language, but you shouldn't have to dig that deep unless you're a really advanced user. As a SCADA professional, you are required to maintain the software programs on your SCADA systems, including updating software and applying bug fixes and enhancements, but you won't typically be working with the program code itself.

SCADA configuration example:
One client came to DPS with the following requirements:

  • Need to have a SCADA system to manage water flow and quality in a pipeline approx 2 miles long
  • Pipe is 36" in diameter and already has SCADA-actuated valves installed (unknown valve brand and quantity at this time but they are new)
  • Pipe has existing threaded access holes for sensors (quantity, hole size, tooth count, and pitch unknown at this time)
  • Sensors for the following needed: flow rate & salinity (possible pH and temp as well but not sure)
  • scada system must also remotely turn on/off and manage electric-based water pump motor rpm for flow control
  • Communication between RTUs and T/MONs would be IP Ethernet based (via VPN WANs or LANs)
  • High-availability and redundant T/MONs and RTUs not initially needed
  • A central office (NOC) will be hosting the T/MON
  • RTUs will be installed in field-based communication "shacks" using local solar-based DC power stations using typical battery systems
  • Number of sensors: approx 4
  • Number of valves: approx 2-4
  • Number of electric pumps: approx 2
A basic solution for this scenario would include:
  • An RTU at each end of the pipeline (2) to communicate with the sensors and valves
  • One T/MON of appropriate size to support the two RTUs
  • Water flow sensors (maybe 2)
  • Water quality combination sensors (maybe 2)
  • Water pump electric motor RPM sensors (maybe 1-2)
  • Relays or something similar to interface with the existing scada-based actuated valves
  • Field shack sensors: ambient air temp sensors, voltage (power) level sensors
  • Relays or something similar to interface with the electric water pump motors
  • recommended backup/spare parts and components

The T/Mon master station and NetGuardian RTUs would need to be "programmed" (configured/provisioned) in their respective interfaces to complete the deployment of this particular SCADA implementation.

Recommended White Paper:

The DPS Telecom SCADA Guide is a tutorial that teaches the fundamentals of SCADA with a practical focus. This guide also recommends product features that you can ask vendors about when you are expanding your monitoring.

While SCADA technology was developed somewhat later, similar monitoring systems have been in use since the 1960s. Such systems are collectively called DCS (Distributed Control System). DCS have conventionally been used for facilities like factories.

However, such systems are not effective in covering large geographical areas like those involved in gas transport systems.

SCADA has been specifically developed to meet requirements covering large territories. Therefore, such a system can be used in various industries and for industrial processes, including: manufacturing, water and sewage, electric power generation and mass transit. This is why SCADA programming plays such a crucial role in the system's development.

It can also be used for facility processes in private or public facilities, including: buildings, airports, ships, or space stations in order to monitor and control: HVAC, access control, and energy consumption management. The possibilities are endless.

A Practical Approach To SCADA

Even with all this being said, SCADA systems are being implemented with a greater regularity in today's ultra-competitive manufacturing environments. While SCADA systems are used to perform 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.

Data collection begins at the PLC level and includes readings and equipment statuses that are communicated to a master as required. Data is then compiled and formatted in such a way that a control room operator using an interface terminal can make appropriate supervisory decisions that may be required to adjust or override normal PLC controls. The tags (data) are collected locally in the SCADA software database or into a Historian (distributed database) to allow trending and other analytical work. SCADA programming by a technician adjusts the system as needed.

These distributed measurement and control systems provide manufacturers with a flexible software solution that can be tailored to meet their specific manufacturing needs.

How SCADA Works

A SCADA system at the machine level consists of a central station for gathering data and managing the overall operation. It also has sensors (these could be Remote Terminal Units or RTUs, or Programmable Logic Controller) placed in proximity to where the action is. The RTU or the PLC collects the information locally and then passes it on to the central station, which can be located several miles away.

RTUs and PLCs today are capable of controlling the operations within their range of vision through closed loop feedback systems. The central station oversees the overall performance of the one or more RTUs/ PLCs under its control. SCADA systems also allow operators or supervisors to change the settings as appropriate at the level of the RTU or the central station. Alarming conditions like high temperature can then be recorded and displayed.

What Can SCADA Offer You?

Some of the significant features of a modern SCADA system are as follows:

  • User-friendly (windows/graphics) interface.
  • Automatic control.
  • Off-line processing.
  • Integrated environments.
  • Extensive Historical data manipulation.
  • Extensive processing power.
  • Extremely high data throughput.
  • Extremely quick response.
  • On-line complex electrical network analysis.
  • Real time supply/demand-side economic calculations.
  • Automatic voltage and power factor correction.
  • Distributed processing power.
  • Custom SCADA programming capability.
For examples of Scada Systems

Where SCADA Programming Comes In

All of this requires that physical conditions be translated into machine language and then into signals that humans can read, record and analyze. Thus, a full-fledged SCADA system has to comprise of both hardware and software elements. We have already seen how today's sophisticated SCADA systems include input/output signal devices, control equipment, HMI (Human Machine Interface), networking, communication systems, databases and software.

Therefore, SCADA system development involves programming at various levels. In SCADA programming, data is collected at the RTU and has to be converted into signals, which is followed by interpreting this data that requires HMI. Often this data also has to be compiled and stored (history databases) for recognizing trends and analysis work. As a result, customized database systems have to be developed. Networks and communication systems bring in more varied requirements for SCADA programming

Add to this the fact that SCADA programming systems are still in the process of evolving. Industries are awakening to challenges like the possibility of terrorist strikes.

It is therefore necessary for research and development to be instrumental in creating a better, more foolproof system for both hardware and software levels to be integrated with SCADA programming.

Software Languages used in SCADA Programming

Most commercial SCADA systems are now programmed using standard software languages whenever possible. Most programs are written in C, or a derived programming language. As a SCADA professional you are required to maintain the software programs on your SCADA systems, including updating software and applying bug fixes and enhancements.

It is therefore easy to see that SCADA programming has a lot of possibilities.

Future Trends In SCADA

The current SCADA industry trend is the movement to completely open systems. The next generation of SCADA systems (and many current products) will have completely open architectures, allowing RTUs to be interchanged between systems from different vendors. The costs of SCADA systems are still dropping, while capabilities are increasing.

Become An Expert In SCADA and SCADA Programming

It is vital to understand that good SCADA programming can make a difference in your operations. However, this cannot be fulfilled unless you know the basics of SCADA systems. In order to be much better prepared for SCADA programming, you need information that has been gathered from hundreds of successful monitoring system deployments. Information that is geared towards real-world professionals, and not IT theorists.

The DPS Telecom SCADA Guide is a tutorial that teaches the fundamentals of SCADA with a practical focus. This guide also recommends product features that you can ask vendors about when you are expanding your monitoring.

Mac Smith - DPS Sales
Mac Smith
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