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Published by Megger
February 2010 |
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ELECTRICAL
TESTER |
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In this issue |
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A sense of déjà vu |
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Winner of the last ever AVOmeter Eight Mark 7 |
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Wireless energy transfer |
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Hot pictures! |
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A sense of ‘déjà vu’ |
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| Dr Andrew Dodds |
| Director of Group Development |
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| To its proponents, IEC61850 spells out the unique and perfect path to the future of substation automation. Others, however, are not so sure that this heavily promoted standard will deliver on its promises. Dr Andrew Dodds, Director of Group Development at Megger, explains. |
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| When I’m involved in discussions surrounding IEC61850, I have a strong sense of déjà vu. I’ve seen something very like the story that’s now being played out around IEC61850 before, with very similar participants! In a previous career, I was involved with industrial automation and, in particular, with fieldbus systems. |
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| For those who don’t already know, fieldbus systems are essentially networking systems for use in industrial applications, and they are widely used to link together devices like sensors, actuators and programmable controllers of an automation system in industrial or process applications, replacing the parallel-wired control systems of the past. In other words, they do a job that in many ways is very similar to that which networks based on IEC61850 are intended to do in substations. |
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| In the early days, different manufacturers of industrial automation products produced their own proprietary fieldbus systems and these, of course, were not readily interoperable. This is a situation that has been paralleled in the world of substations, as is the subsequent desire for standardisation. After all, standardisation allows products from different vendors to be freely mixed, providing interoperability of devices and increased choice which should drive down market prices. |
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| Eventually in the world of industrial automation a new fieldbus standard – EN50170 – was developed. But did it deliver on its promises? That is debateable as take up for the new technology proved to be very slow. The new standard was adopted by many industrial automation vendors; after all, no one wants to be left out of the club – or off the approved vendor list, once it was apparent that the collection of fieldbus solutions represented within EN50170 was becoming accepted by early end users, especially in Europe. |
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| So far so good; the physical connectivity and the basic communication parameters of the networks had been taken care of. But what about the interoperability and openness of the control system and associated software that would make it possible to use EN50170 with real world devices? This was addressed through IEC1131 (later renumbered as IEC61131) which defined the international standard for programmable controller programming languages which invariably formed the hub of fieldbus systems. |
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| In practice almost every implementation of IEC1131, although based on the standard, has its own vendor-specific refinements and tweaks that provided value over and above the defined programming language. These are often explained away as being necessary to provide additional functionality or to make the systems easier to use. Only a cynic would suggest that the primary purpose of some or even all of them is to preserve a proprietary stranglehold over users while paying lip service to the adoption of the standard. |
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| Be that as it may, the end result is that many IEC1131-compliant programmes that are supposed to have essentially the same software framework do not, which means that they are certainly not interchangeable or portable to another control system, at least not without a lot of rewriting of the original code. |
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| The next major hurdles to be faced concerned interoperability, guarantees, warranties and responsibility. If the system faced commissioning difficulties or later failed where did support come from? Who was to blame and which of the two or more vendors involved was going to take responsibility? And what would be the position in relation to warranties? |
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| Arguably, these issues slowed the implementation of open fieldbus solutions. Many plant owners who considered the risks in comparison to the cost saving decided to remain with conventional parallel wired control systems, while others who could see the advantages of fieldbus solution moved to a single-vendor approach with guaranteed interoperability and defined responsibilities. |
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| Anyone taking an interest in IEC61850 will be all too conscious of the many parallels with industrial automation |
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| fieldbuses. At present, for example, the networking elements of IEC61850 are well defined, as they were with EN50170 but the situation in relation to programming languages and software is far less satisfactory. Suppliers of substation IEDs appear to be enthusiastically adding vendor-specific parameters and functionality not covered by IEC61850 to their products, just as the vendors of the supposed IEC1131-compliant products had done. |
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| Could this, along with warranty and guarantee issues, lead to a move toward single-vendor substation solutions, rather than toward the open multi-vendor scenario that is promoted as a key benefit of IEC61850? Unless these issues are addressed, implementation of IEC61850 will fall short of its original objectives. Let us suppose, however, that it does prove possible to implement multi-vendor protection schemes based on IEC61850. Who will then be responsible for issues relating to risk, compliance and the provision of warranties? And who is culpable when things go wrong? |
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| There’s little doubt that those working on the IEC61850 standard are doing a sterling job on the technical front and that they are devising innovative solutions to many of the problems involved in substation automation. Maybe, however, in an attempt to maximise future-proofing and flexibility, they are leaving just a few too many options open, creating opportunities for divisive vendor-specific functionality, as already discussed. |
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| The proponents of IEC61850 are also vigorous – even strident – in its promotion. It has great potential, for sure, but it’s not ready yet for other than the most limited deployment, so is the unremitting pressure for its adoption truly justified at the present time? |
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| Finally, returning to my earlier theme, it certainly seems that little if any work is being done on the “soft” non-technical issues like warranties, divided responsibility and culpability in multi-vendor installations. These will most certainly be difficult issues to address, but addressed they must be if IEC61850 is ever to come anywhere close to delivering on its promises. |
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| So is IEC61850 a panacea or a chimera? In truth, it’s still too early to offer a final answer. However, given that discussion of IEC61850 implementation often goes hand in hand with SMART grid considerations, we are guaranteed to hear about this subject area for many years, as long substation plant life expectancy together with current low investment levels suggest we are tens of years away from SMART integrated control of power systems. |
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| If lessons are learned from the problems that have afflicted the development and implementation of the industrial fieldbus standard, and if the “soft” issues are fully addressed, then IEC61850 could smooth the path forward. If, however, these problems and issues continue to be overshadowed by the search for technical perfection, the value and future of IEC61850 are far less certain. |
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AVOMETER EIGHT Mk7
multimeter competition winner |
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| Megger is pleased to announce the winner of the last ever AVO Model 8 Mark 7 multimeter to be dispatched by Megger is Nigel Fraser Ker, of IBM Global Technology Services. The judges (Stephen Drennan, Managing Director of Megger Limited; Nick Hilditch, Group Marketing Services Manager; Keith Wilson, Technical Consultant to Megger) felt that Nigel’s entry summed up the features that made the AVOMETER EIGHT Mk 7 so loved around the world - tough, adaptable, essential kit for decades. We felt that awarding the AVOMETER with parachute wings was the ultimate accolade, and Nigel’s entry just trumped some excellent submissions from other entrants. |
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| When I was in the Army, our AVO meters were highly prized amongst the 'sparks' community. On one occasion, The Queen was due to inspect the Battalion on exercise in Germany and, as part of her tour, was due to give a brief address. Everything was almost ready when it was discovered that the public address system had failed and my REME section was called in to fix it. However, in the rush, one particularly gormless soldier managed to drive over our toolkit, smashing our precious AVO. Although we hoped we wouldn't need it, we discovered that some careful work on the amplifier was required and an AVO was deemed an essential tool in the repair. This went all the way up to the General who immediately had one flown in but, due to regulations, the helicopter couldn't land at our location. Luckily, the Army Air Corps were not about to be foiled by red tape and they sent the instrument down to us from the chopper with a make-shift parachute. After a successful 'fix' (which allowed The Queen to give her address) our 'OC' organised an impromptu parade at which the new AVO meter was awarded its Para' wings! |
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| There can be only one winner, but we received nearly 200 entries, and Megger is grateful to everyone who sent in an amusing story. We read every one, and there were sometimes tears of mirth in the judging room! We felt that these stories were worthy of runners-up, and we will send them a modern Megger AVO300 series digital multimeter as a thank-you |
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| A.R Newbould, Dudley, England |
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| Our company manufactures bespoke control systems and many years ago we had a customer who was testing a control system in our workshop that was destined for his factory. |
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| The customer was quite an arrogant bombastic character, anyway he came to me and asked if could borrow an analogue multimeter so that he could see a short electrical pulse that was being generated by the control system as the digital meter he was using was not fast enough to respond. |
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| I leant him my AVO 8 which is perfect for doing what he wanted to do, about 5 minutes later, he reappeared in my office looking somewhat ‘sheepish’, he had managed to blow up my cherished meter by connecting it to the live 230 V pulse whilst it was still set on the resistance scale. |
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| Although it cost me to repair my meter, it was more than worth it to see the ‘sheepish’, look on his face when he came to tell me what he had done. |
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| Leon Kotze, Germiston, South Africa |
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| As a young test technician in the electricity supply utility Escom, South Africa, I was in the process of pre testing a control panel in one of our EHV substation. The construction site was as per normal a hive of activity. Cable trenches were open, panel doors were off and the site was organized chaos. I was in the process of investigating a circuit that wasn’t functioning correctly. I had just tested a circuit for continuity in the yard and was back in the control room to determine the supply to the isolated circuit. In my haste I stepped over an open cable trench and measured the livened supply without adjusting the AVO to read DC. The AVO tripped and in absolute awe saw that the indicator needle had wrapped itself neatly around the remote stopper on the reading scale. The reset pushbutton had also tripped so violently that the push-button top had shot off and disappeared. I contemplated my stupidity for a minute or two and looked for the pushbutton top. I would have to send the instrument to our measurements department for repair with |
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| a devious explanation. I found the pushbutton top perched precariously on top of some cables in the cable trench. I leaned down, supported by the edge of the cable trench to retrieve the evasive item and as I did so the top of my head came in contact with an open live terminal in the panel. The resultant wallop caused me to lose my hand grip on the edge of the trench and I tumbled head first into the trench. |
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| I never found the pushbutton top as it had fallen amongst the many cables in the trench. The instrument was repaired with a replaced movement and other items. My bruises and scrapes healed over in a couple of days but my ego took a lot longer. |
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| Harry Holloway, Chesterfield, England |
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| One day, back in the 70’s, I was with my cousin, who ran a haulage business. |
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| A driver came in carrying an object; a transistor radio, he said, which he had spotted lying on the roadside. “What make is it?” we asked. The driver, after a look, replied:- “Megger”. Sadly, the “tranny” proved useless for picking up Radio One; but did a sterling work in sorting out faults on vehicle wiring! |
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| If you didn’t win - Sorry! |
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| We are well aware of the affection that this iconic meter holds around the world, and in future edition of Electrical Tester, we will feature more of its history. |
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| A further issue that needs to be considered when making SFRA tests is the connections between the test set and the transformer. The more consistent these connections are between tests, the more accurate will be the comparisons between the results obtained. It is particularly important that the connection between the test cable shield and ground should be as near as possible the same for every measurement on a given transformer. |
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| With conventional test leads, such consistency is hard to achieve. Some SFRA instruments, however, such as the Megger FRAX99, 101 and 150, are supplied with test leads that are specifically designed to overcome this problem. With these leads, the braid drops down directly from the bushing connection C-clamp, next to the insulating discs, to the ground connection at the base of the bushing. This arrangement called “shortest braid technique”, is the recommended practice in SFRA standards and creates near identical conditions every time a connection is made, irrespective of whether the bushing is tall or short. |
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| As already mentioned, dismantling a power transformer to determine its condition is hardly ever a practical possibility. It is, however, possible to accurately assess transformer condition by using proven SFRA test techniques. And, the latest SFRA test sets make these techniques more accessible, more convenient and more dependable that ever. |
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Wireless energy transfer |
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| Dr Stan Zurek |
| Magnetics Technical Specialist |
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| In the universe as a whole, the wireless transfer of energy is something quite normal: the gravitational energy holding our feet on the ground is transferred wirelessly, and the sun radiates so much energy over the 150-million kilometre distance that separates it from the earth that the earth remains well above the ambient temperature of the cosmos. |
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| Over the centuries we have developed various means of “wired” energy transfer: ditches for water, pipes for compressed air, wires for electricity, optical fibres for light, and so on. We have even found ways of transferring some forms of energy “wirelessly”, like sound with loudspeakers or heat with lasers. However, at present our civilisation relies on “hardwired” electric energy. It is true that we can communicate wirelessly using signals transmitted by radio waves (radio, TV, mobile phones, etc.) but the energy levels for these are practically negligible. “Real” energy, which moves factory machines, lights our homes and charges our mobile phones and laptops is still wired. Why don’t the scientist and engineers do something about it? |
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| In fact, they have been trying very hard to eliminate the wires for quite a long time. In 1886 Heinrich Hertz proved the existence of electromagnetic waves with an experiment where he sent sufficient energy wirelessly to a receiver to cause an electric spark. Only a few years later in 1891 Nikola Tesla invented his resonant transformer known today as “Tesla coil”. Wireless energy transfer with this device can still produce some of the most spectacular visual displays known today. |
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| Tesla immediately noticed the potential of the wireless energy transfer and began his work on the first commercial application. Alas, the project never became fully operational due to financial problems. |
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| Nevertheless, the work carried out by Tesla proved that useful amount of energy could be transmitted using electromagnetic waves – he managed to power distant light bulbs with his resonant transformers. Nowadays, in a wider sense wireless energy transfer is commonly used in many devices, and is almost always achieved by means of magnetic coupling or electromagnetic radiation. |
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| The energy transferred between the primary and secondary windings of a transformer is, after all, transferred not through a wire, but through a magnetic core. In motors and generators the energy is transferred magnetically – that is, wirelessly – across the air gap between the stator and rotor. The so-called rotary transformer, in which the primary and secondary parts could freely rotate in relation to each other, was used in some NASA satellites. A more down-to-earth and very common application is for charging the batteries in electric toothbrushes. |
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| However, although the amount of energy transferred is significant and can be measured in kilowatts for some of these applications, all of them work over very short distances – usually a few millimetres or a centimetre or so at best. This is because they all rely on magnetic coupling between the energy source (primary winding) and the receiver (secondary winding). The better the magnetic coupling the more energy can be transferred efficiently. |
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| A true “wireless” technique would allow useful power to be transferred some over a distance of at least a few meters. A company called WiTricity recently claimed that it could do exactly that by using resonant circuits operating at MHz frequencies. Power of 60 W was apparently transferred with 40% efficiency over a distance of 2 metres – enough to power up various devices in a typical living room, also through the walls. |
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| However, as far back as the 1960s William Brown built a model helicopter powered entirely wirelessly by a microwave beam. The technique was improved later and it |
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| was shown to be capable of transferring 30 kW over 1 mile at 84% efficiency. This was a serious achievement and it was actually proposed as means of receiving power from satellites in geostationary orbits, which could harvest solar energy from the sun. |
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| However, as with any new technology there are always problems lying in wait. For instance – if I had a wireless energy transfer device in my living room what would guarantee that my neighbour would not simply tap onto this energy source? This problem would be solved if the energy were directed, say by a laser or a microwave beam. It would then be impossible to tap into from the side. |
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| But then again, the energy must be present in the space between the source and the target. In other words, the microwave beam arrangement is simply a supersized microwave cooker and it would create a severe but invisible safety hazard. Thus, capturing the solar energy with satellites and beaming it to earth is probably not such a good idea after all. What if due to some unforeseen circumstances such a beam strays of its receiving target? As much as I like microwave meals I would not like to become one of them! |
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| There is another, possibly even greater hurdle to overcome, namely electromagnetic compatibility (EMC). Any new device must pass rigorous EMC tests for radiation and immunity from electromagnetic fields up to GHz frequencies. As all the manufacturers of the electronic equipment can confirm, achieving EMC is a serious challenge in almost every electronic design. And, if we fill the air around us with lots of energy at MHz frequencies, we’re just asking for problems with EMC. |
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| So what is the answer? Well, we are getting closer and closer to commercially available electric cars. These need quite a lot of energy to get them moving, and that energy certainly can’t be transferred by wires. The solution is to use rechargeable batteries. This isn’t, of course, wireless energy transfer in the pure sense, but it is probably as close as we can realistically get. |
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| There is no dangerous radiation, no EMC and the safety hazards looks manageable. And with some standardisation and recycling it is quite possible to achieve lower impact on environment and reduction of carbon dioxide emissions. This simply has to be a very good thing for the future of our planet. |
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| Batteries – the most efficient source of wireless energy so far! |
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HOT PICTURES! |
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| Matz Öhlén |
| Director - Transformer Test Systems |
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| Thermal imaging is a very useful addition to the armoury of engineers and technicians whose work involves maintenance and faultfinding on electrical equipment. It is fast and convenient to use, and it doesn’t require equipment to be taken out of service. |
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| Thermal imaging can also spot temperature differences that are indicative of an incipient fault long before the problem develops into a full-blown failure and, because it doesn’t involve making electrical connections to the equipment under test, it is easier to use safely than many of the more conventional test techniques. |
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| The results from thermal imaging are, however, very different from those produced by most other tests, as they take the form of a colour picture rather than numerical or graphical data. This can create problems when it comes to incorporating thermal imaging results in test certificates, reports and historical archives of test data since most of the programs used for these purposes have few, if any, facilities for image handling. |
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| Now, however, these limitations have been overcome. The latest version of PowerDB, one of the electrical industry’s most widely used acceptance and maintenance test data management software packages, can import and manipulate images and data from the FLIR Model P65 thermal imaging camera. |
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| Like all thermal imaging cameras, this popular model produces images that are based on the infrared emissions from the equipment undergoing examination. |
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| In these images, variations in temperature are shown by colour contrasts. The images are stored as jpeg files on standard compact flash cards, together with information about the actual temperature of the equipment under investigation. The camera can also take normal visible light photographs, which are invaluable for reference purposes, and store these on the same card. |
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| When a card from a P65 camera is plugged into a reader connected to a computer that is running PowerDB, a sub-menu appears. This offers options for importing both infrared and visible light images and for incorporating them into a test form. A reference point and a problem point can also be highlighted on either or both of the images, as shown in the sample forms in Figures 1 and 2. |
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| The sub-menu also makes provision for selecting different colour palettes for the infrared image as, in some cases, this can provide better contrast and make problem areas easier to spot. |
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| The remainder of the test form provides a structure for entering information about the apparatus shown in the pictures. This can, for example, include detail of load currents, measurements of harmonics and comments. As would be expected, the data and completed forms are stored in the PowerDB database, allowing them to be retrieved rapidly and easily or archived for long-term storage. |
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| PowerDB forms containing thermal imaging data can, of course, be readily incorporated in reports and certificates |
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| Figure 1 – Sample infrared inspection report for dry type cast coil transformer |
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| Figure 2 – Sample infrared inspection report for distribution panel |
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| produced by the software, and can also be exported for use in third party programs. |
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| These new facilities mean that thermal imaging results can now be handled alongside and just as easily as the results from other types of test, making thermal imaging an even more attractive testing option in electrical power applications. |
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