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AQ: OPC drivers advantage

A few years back, I had a devil of time getting some OPC Modbus TCP drivers to work with Modbus RTU to TCP converts. The OPC drivers could not handle the 5 digit RTU addressing. You need to make sure your OPC driver that you try actually works with your equipment. Try before you buy is definite here. Along with some of the complications, like dropping connections due minor network cliches, a real headache and worth a topic all its own, is the ability us tag pickers and the like. The best thing to happen to I/O addressing is the use of Data Objects in the PLC and HMI/SCADA. The other advantage OPC can give you the ability to get more Quality Information on your I/O. Again, check before you buy. In my experience, the only protocol worse than Modbus in the Quality Info department is DDE and that pretty well gone. This still does not help when the Modbus slave still reports stale data like its fresh. No I/O driver can sort that out, you need a heartbeat.

A shout out to all you Equipment manufactures that putting Modbus RTU into equipment because its easy, PLEASE BUILD IN A HEATBEAT us integrators can monitor so we can be sure the data is alive and well.

Also, while you try before you buy, you want your HMI/SCADA to be able to tell the difference between, Good Read, No Read and Bad Read, particularly with a RTU network.

AQ: Home automation concept

The concept of home automation on a global scale is a good concept. How to implement such a technology on a global scale is an interesting problem, or I should say issues to be resolved. Before global approval can be accomplished the product of home automation may need a strategy that starts with a look at companies that have succeeded in getting global approval of their products.

If we look at what companies that have the most products distributed around the world we see that Intel is one of these companies. What’s interesting is that this company has used automation in their Fabs for decades. This automation has allowed them to produce their products faster and cheaper than the rest of the industry. The company continues to invest in automation and the ability to evolve with technology and management. We have many companies that compete on the world stage; I don’t think many of these companies distribute as much product. So to compete at a level to make home automation accepted and to accomplish global acceptance the industry and the factories have to evolve to compete. That mission by the automation can be accomplished by adapting a strategy that updates their automation in their factories, stop using products that were used and developed in the 1970s (another way of saying COTS) and progress to current and new systems. A ten years old Factory may be considered obsolete if the equipment inside is as old as the factory.

Now for cost, when I thank of PLC or commercial controllers I see a COTS product that may be using obsolete parts that are not in production any more or old boards. So I see higher cost for manufacturing, a reduction in reliability. Now many procurement people evaluate risk in such a way that may rate older boards lower in risk for the short term, not a good evaluation for the long term. The cost is a function of how much product can be produced at the lowest cost and how efficient and competitive the company that produces the product. So time is money. The responsibility for cost is the company and the ability to produce a competitive product, not the government.

Now into control systems and safety, if the automation system is used in the house safety has to be a major consideration. I know at Intel Fabs if you violate any safety rule you won’t be working at that company long. To address safety the product must conform to the appropriate standards. Safety should be a selling point for home automation. Automation engineers should get and remember safety is one of the main considerations for an engineer. If someone gets hurt or killed because of a safety issue the first person looked at is the engineer.

Now 30% energy saving in my book is not enough, 35 to 40 percent should be a goal. Now solar cells have improved but the most efficient in the south west US. The Sterling engines are 1960 designs and use rare gases such as helium which may not be a renewable resource, Wind generators need space and are electromechanical so reliability and maintenance needs improving.

Now on to the interface standards, most modern factories that produce processors use the Generic equipment Manufacture standard, good deal works. As far as what and when to uses a standard interface, on BOX produced by one company may use RE-422 where another company may use RS 485 so the system engineer should resolve these issues before detailed design starts. Check with IEEE. Or you may be able to find the spec at every spec.com this is a good place to look for some of the specs needed.

So I conclude, many issues exist, and when broken down home automation is viable and needs a concerted effort and commitment from at least the companies and management that produce products for automation and a different model for manufacturing and growing the home systems.
Home automation with a focus on energy savings as a goal is a good thing. We have a lot of work to ma

AQ: Electronic industry standards

You know standards for the electronic industry have been around for decades, so each of the interfaces we have discussed does have a standard. Those standards may be revised but will still be used by all segments of our respective engineering disciplines.

Note for example back in the early 1990s many big companies HP, Boeing, Honeywell … formed a standards board and developed the Software standards( basic recommendations) for software practices for programming of flight systems. It was not the government it was the industry that took on the effort. The recommendations are still used. So an effort is first needed by a meeting of the minds in the industry.

Now we have plenty of standards on the books for the industry, RS-422, RS-232, 802.1 … and the list goes on and on. The point is most of the companies are conforming to standards that may have been the preferred method when that product was developed.

In the discussion I have not seen what the top preferred interfaces are. I know in many of the developments I have been involved in we ended up using protocol converters, Rs-232 to 802.3, 422 to 485 … that’s the way it’s been in control systems, monitoring systems, Launch systems and factory automation. And in a few projects no technology existed for the interface layer, had to build from scratch. Note the evolution of ARPA net to Ethernet to the many variations that are available today.

So for the short hall if I wanted to be more comparative I would use multiple interfaces on my hardware say usb, wireless, and 422. Note for new developments. With the advancement in PSOCS and other forms of program logic interface solutions are available to the engineer.

Start the interface standards with the system engineers and a little research on the characteristic of the many automation components and select the ones that comply with the goals and the ones that don’t will eventually become obsolete. If anything, work on some system standards. If the customer is defining the system loan him a systems engineer, and make the case for the devises your system or box can support, if you find your product falls short build a new version. Team with other automation companies on projects and learn from each other. It’s easy to find issues as to why you can’t succeed because of product differences, so break down the issues into manageable objectives and solve one issue at a time. As they say divide and concur.

AQ: SCADA & HMI

SCADA will have a set of KPI’s that are used by the PLCs/PACs/RTUs as standards to compare to the readings coming from the intelligent devices they are connected to such as flowmeters, sensors, pressure guages, etc.

HMI is a graphical representation of your process system that is provided both the KPI data and receives the readings from the various devices through the PLC/PAC/RTUs. For example you may be using a PLC that has 24 i/o blocks that are connected to various intelligent devices that covers part of your water treatment plant. The HMI software provides the operator with a graphical view of the treatment plant that you customize so that your virtual devices and actual devices are synchronized with the correct i/o blocks in your PLC. So, when an alarm is triggered, instead of the operator receiving a message that the 15th i/o block on PLC 7 failed, you could see that the pressure guage in a boiler reached maximum safety level, triggering a shutdown and awaiting operator approval for restart.

Here is some more info I got from my colleague who is the expert in the HMI market, this is a summary from the scope of his last market study which is about a year old.

HMI software’s complexity ranges from a simple PLC/PAC operating interface but as plant systems have evolved, HMI functionality and importance has as well. HMI is an integral component of a Collaborative Production Management (CPM) system; simply you can define that as the integration of Enterprise, Operations, and Automation software into a single system. Collaborative Production Systems (CPS) require a common HMI software solution that can visualize the data and information required at this converged point of operations and production management. HMI software is the bridge between your Automation Systems and Operations Management systems.

An HMI software package typically performs functions such as process visualization and animation, data acquisition and management, process monitoring and alarming, management reporting, and database serving to other enterprise applications. In many cases, HMI software package can also perform control functions such as basic regulatory control, batch control, supervisory control, and statistical process control.

“Ergonometrics,” where increased ergonomics help increase KPI and metric results, requires deploying the latest HMI software packages. These offer the best resolution to support 3D solutions and visualization based on technologies such as Microsoft Silverlight. Integrating real-time live video into HMI software tools provide another excellent opportunity to maximize operator effectiveness. Live video provides a “fourth dimension” for intelligent visualization and control solutions. Finally, the need for open and secure access to data across the entire enterprise drives the creation of a single environment where these applications can coexist and share information. This environment requires the latest HMI software capable of providing visualization and intelligence solutions for automation, energy management, and production management systems.

AQ: Differences of Grounding, Bonding and Ground Fault Protection?

Grounding (or Earthing) – intentionally connecting something to the ground. This is typically done to assist in dissipating static charge and lightning energy since the earth is a poor conductor of electricity unless you get a high voltage and high current.

Bonding is the intentional interconnection of conductive items in order to tie them to the same potential plane — and this is where folks get the confusion to grounding/earthing. The intent of the bonding is to ensure that if a power circuit faults to the enclosure or device, there will be a low-impedance path back to the source so that the upstream overcurrent device(s) will operate quickly and clear the fault before either a person is seriously injured/killed or a fire originates.

Ground Fault Protection is multi-purpose, and I will stay in the Low Voltage (<600 volts) arena. One version, that ends up being seen in most locations where there is low voltage (220 or 120 volts to ground) utilization, is a typically 5-7 mA device that’s looking to ensure that current flow out the hot line comes back on the neutral/grounded conductor; this is to again protect personnel from being electrocuted when in a compromised lower resistance condition. Another version is the Equipment Ground Fault Protection, and this is used for resistive heat tracing or items like irrigation equipment; the trip levels here are around 30 mA and are more for prevention of fires. The final version of Ground Fault Protection is on larger commercial/industrial power systems operating with over 150 volts to ground/neutral (so 380Y/220, 480Y/277 are a couple typical examples) and — at least in the US and Canada — where the incoming main circuit interrupting device is at least 1000 amps (though it’s not a bad idea at lower, it’s just not mandated); here it’s used to ensure that a downstream fault is cleared to avoid fire conditions or the event of ‘Burn Down’ since there’s sufficient residual voltage present that the arc can be kept going and does not just self-extinguish.

In the Medium and High Voltage areas, the Ground Fault Protection is really just protective relaying that’s monitoring the phase currents and operating for an imbalance over a certain level that’s normally up to the system designer to determine.

AQ: 1:1 ratio transformer

A 1:1 ratio transformer is primarily used to isolate the primary from the secondary. In small scale electronics it isolates the noise / interference collected from the primary from being transmitted to the secondary. In critical care facilities it can be used as an isolation transformer to isolate the primary grounding of the supply from the critical grounding system of the load (secondary). In large scale applications it is used as a 3-phase delta / delta transformer equipment to isolate the grounding of the source system (primary) from the ungrounded system of the load (secondary).

In a delta – delta system, the equipment grounding is achieved by installing grounding electrodes of grounding resistance not more 25 ohms (maximum or less) as required by the National electrical code. From the grounding electrodes, grounding conductors are distributed with the feeder circuit raceways and branch circuit raceways up to the equipment where the equipment enclosures and non-current carrying parts are grounded (bonded). This scheme is predominant on installations where most of the loads are motors like industrial plants, or on shipboard installations where the systems are mostly delta-delta (ungrounded). In ships, the hull becomes the grounding electrode. Electrical installations like these have ground fault monitoring sensors to determine if there are accidental line to ground connections to the grounding system.

AQ: Voltage transmission & distribution

If you look back over history you will find how things started out from the early engineers and scientists looking at materials and developing systems that would meet their transmission goals. I recall when drives (essentially ac/dc/ac converters) had an upper limit around 200 to 230 volts). In Edison and Tesla days there was a huge struggle to pick DC or AC and AC prevailed mainly because it was economical to make AC machines. Systems were built based on available materials and put in operation. Some worked great some failed. When they failed they were analyzed and better systems built. Higher and higher voltages lowered copper content and therefore cost as insulators improved. Eventually commitees formed and reviewed what worked and developed standards. Then by logical induction it was determined what advances could be made in a cost effective and reliable manner. A lot of “use this” practice crept in. By this I mean for example, I worked at a company and one customer bought 3,000 transformers over the course of ten years, They had a specific size enclosure they wanted.

Due to high volume purchase the cost of the enclosure was low. Other small jobs came thru and this low cost enclosure was used on them to expedite delivery and keep cost minimum. Guess what, that enclosure is now a standard enclosure there because it was used on hundreds of designs over ten years. Is it the most economical box, probably not in the pure engineering sense but changing something that works is seldom a good idea. Today, they are raising voltage levels to new high values. I read of a project in Germany to run HVDC linesover huge distance. They are working to overcome a problem they foresee. How do you break the circuit with HVDC economically. If you ever put DC thru a small contactor maybe 600VDC you find quickly that the arc opening the contactor melts the contacts. Now, what do you do at 800kVDC or 1.2MVDC. What will the cost of the control circuit be to control this voltage level. (Edison and Tesla all over again)And there you have it, my only push for the subject of history to be taught.

AQ: Simulation interpretation in automation industry

Related to “automation industry”, there are generally 3 different interpretations of what simulations is:
1) Mechanical Simulations – Via various solid modeling tools and cad programs; tooling, moving mechanisms, end-effectors… are designed with 3D visualizations, connecting the modules to prevent interference, check mass before actual machining…
2) Electronics Simulations – This type of simulations are either related to the manufacturers of “specific instrumentations” used in automation industry (ultrasonic welders, laser marking systems,…) or the designers of circuit boards.
3) Electrical & Controls Simulations.
A) Electrical Schematics, from main AC disconnect switch, down to 24VDC low amps for I/O interface.
Simulation tools allow easy determinations of system’s required amperage, fuse sizes, wire gauges, accordance with standards (CE, UL, cUL, TUV…)…
B) Logic Simulations, HMI interface, I/O exchange, motion controls…
a) If you want to have any kind of meaningful simulations, get in the habit of “modular ladder logic” circuit design. This means, don’t design your ladder like one continuous huge program that runs the whole thing; simulating this type of programs is almost impossible in every case. Break down the logic to sub-systems or maybe even down to stand alone mechanisms (pick & place, motor starter…), simulating and troubleshooting this scenario is fairly easy.
b) When possible, beside automated run mode of the machine or system, build “manual mode logic” for it as well. Then via physical push-buttons or HMI, you should have “step forward” & “step back” for every “physical movement or action”.

Simulating the integrity of the “ladder logic program” and all the components and interfaces will be a breeze if things are done meticulously upfront.

AQ: Transformer uprating

I once uprated a set of 3x 500KVA 11/.433kv ONAN transformers to 800KVA simply by fitting bigger radiators. This was with the manufacturers blessing. (not hermetically sealed – there were significant logistical difficulties in changing the transformers, so this was an easy option). Limiting factor was not the cooling but the magnetic saturation of the core at the higher rating. All the comments about uprating the associated equipment are relevant, particularly on the LV side. Increase in HV amps is minimal. Pragmatically, if you can keep the top oil temperature down you will survive for at least a few years. Best practice of course is to change the transformer!

It is true that you can overload your transformer say 125 %, 150 % or even greater on a certain length of time but every instance of that overloading condition reflects a degradation on the life of your transformer winding insulation. Overload your transformer and you also shorten the life of your winding insulation. The oil temperature indicated on the temperature gauge of the transformer is much lower than the hotspot temperature of the transformer winding which is a critical issue when considering the life of the winding insulation. Transformers having rating of 300 KVA most probably do not even have temperature indicating gauge. The main concern is how effectively can you lower the hotspot temperature in order that it does not significantly take away some of the useful life of your transformer winding insulation.

AQ: What is true power and apparent power?

KW is true power and KVA is apparent power. In per unit calculations the more predominantly used base, which I consider standard is the KVA, the apparent power because the magnitude of the real power (KW) is variable / dependent on a changing parameter of the cos of the angle of displacement (power factor) between the voltage and current. Also significant consideration is that the rating of transformers are based in KVA, the short circuit magnitudes are expressed in KVA or MVA, and the short circuit duty of equipment are also expressed in MVA (and thousands of amperes, KA ).

In per unit analysis, the base values are always base voltage in kV and base power in kVA or
MVA. Base impedance is derived by the formula (base kV)^2/(base MVA).

The base values for the per unit system are inter-related. The major objective of the per unit system is to try to create a one-line diagram of the system that has no transformers (transformer ratios) or, at least, minimize their number. To achieve that objective, the base values are selected in a very specific way:
a) we pick a common base for power (I’ll come back to this point, if it should be MVA or MW);
b) then we pick base values for the voltages following the transformer ratios. Say you have a generator with nominal voltage 13.8 kV and a step-up transformer rated 13.8/138 kV. The “easiest” choice is to pick 13.8 kV as the base voltage for the LV side of the transformer and 138 kV as the base voltage for the HV side of the transformer.
c) once you have selected a base value for power and a base value for voltage, the base values for current and impedance are defined (calculated). You do not have a degree of freedom in picking base values for current and impedance.

Typically, we calculate the base value for current as Sbase / ( sqrt(3) Vbase ), right? If you are using that expression for the base value for currents, you are implicitly saying that Sbase is a three-phase apparent power (MVA) and Vbase is a line-to-line voltage. Same thing for the expression for base impedance given above. So, perhaps you could choose a kW or MW base value. But then you have a problem: how to calculate base currents and base impedances? If you use the expressions above for base current and base impedance, you are implicitly saying that the number you picked for base power (even if you picked a number you think is a MW) is actually the base value for apparent power, it is kVA or MVA. If you insist on being different and really using kW or MW as the base for power, you have to come up with new (adjusted) expressions for calculating base current and base impedance.

And, surprise!, you will find out that you need to define a “base power factor” to do so. In other words, you will be forced back into defining a base apparent power. So, no, you cannot (easily) use a kW/MW base. For example, a 100 MVA generator, rated 0.80 power factor (80 MW). You could pick 80 as the base power (instead of 100). But if you are using the expressions above for base current and base impedance, you are actually saying that the base apparent power is 80 MVA (not a base active power of 80 MW).