Feature Test & Measurement
igh voltage insulation resis- tance testers (IRTs) have tradi- tionally been designed for manual operation - the user connects the instrument to the device under test (DUT) and, after setting the operating parameters, presses the test button to initiate the test. For many applications, this method of working is convenient and entirely appropriate, but that’s not always the case. A motor manufacturer, for example, may wish to automate insulation resis- tance testing of items in order to improve productivity and reduce labour costs. Undoubtedly a test jig will be used to provide the necessary connec- tions to the item under test, but the test itself can only be carried out automati- cally if an IRT with facilities for remote control and test result transfer is used. Testing transformers, circuit breakers and similar equipment routinely used in power transmission and distribution systems will also benefit from remote control. In these applications, particu- larly when the testing is being per- formed in an electrically noisy environment, it is advantageous to keep the test connections as short as possible. However, if testing is, for example, being carried out on top of a large transformer, keeping the connections short inevitably means that the IRT will be in a hard to access location and, quite apart from the inconve- nience, if the IRT has to be operated locally, there may well be safety con- cerns over working at height with HV equipment. Remote control provides a complete solution, as it means that even if the tester is on top of the trans- former, it can be operated safely and conveniently from ground level.
Hazardous locations
In addition, testing often must be carried out in electrically hazardous environ- ments, such as EHV substations. In such cases, once the test set has been put in place and connected, the user can, with the benefit of remote control, retreat to a safe distance, and perform the testing with virtually no risk. The IRT could even be left in place and monitored remotely in instances where it is neces- sary to look for changes in insulation resistance over a period of time. Another interesting example is the testing of products during development. Because there may be a significant risk of the product failing during the test, it
Testing with remote control H
Clive Pink of Megger looks at some of the applications and advantages of using high voltage insulation test sets that have provision for remote control
Left: the Megger S1 with beacon, connected to computer
is often desirable to carry out such tests within a test cage or other enclosure. With remote control, the insulation tester can be conveniently located within the enclosure and connected to the DUT by short leads, while the opera- tor initiates the tests from a safe location outside the enclosure. With such an arrangement, it is also easily possible to use a solenoid oper- ated lock on the enclosure door, and arrange for this to be linked with the test set’s remote control system so that the test cannot be initiated until the door is proved closed and locked (and the door cannot be opened while the test is in progress).
Benefits in action Tronic, a Siemens Subsea Business, is an example of a company that has ben- efited from some of these options, as Chris Harrison, a senior engineer with the company explains.
Thermal cameras go wireless F
“For us, insulation testing is a very commonplace activity. The introduc- tion of a remotely operable IRT - in our case, a Megger S1-series instrument - is allowing us to improve our electrical testing safety, as it means we can now site the IRTs within interlocked test bays. A further advantage is that with the remote control facility, we can con- trol the testing from our in-house soft- ware, which means we can semi-automate certain processes. This offers significant time savings and reduces our paperwork burden by allowing us to log test data directly to our own network locations.”
There are many other applications where the opportunity for automation offered by remote control is a major benefit. These include the testing of underwater cable during manufacture, where the insulation resistance test has to be repeated at regular intervals while the pressure on the cable (which is held in a pressurised tank during testing) is raised. Similarly, it is usually considered desirable to perform regular insulation resistance tests on underwater power cables during the cable laying operation, so that any problems can be immedi- ately detected. Once again, automation, made possible by an IRT with remote operation facilities is the key, allowing the necessary tests to be performed reli- ably and on schedule without the need for operator intervention. Remote control of HV IRTs has much
luke has introduced the capability to collect test measurements wirelessly on thermal imaging cameras. Models from the Fluke
Ti(R)1xx family can receive captured data from Fluke CNX 3000 wireless testers at distances of up to 20m and display them. These measurements can also be documented together with thermal images using the SmartView software included with the thermal imager, adding validity to the analysis and making inspections more thorough. As part of Fluke’s 65th anniversary celebrations, purchasers of a
Fluke Ti100, Ti105, Ti110 or Ti125 Thermal Imager can receive a free Fluke CNX i3000 iFlex AC Current Measurement Kit, while purchasers of a Fluke TiR105, TiR110 or TiR125 Thermal Imager can receive a free Fluke Wireless CNX 3000 HVAC System. The Fluke Ti(R)110 and Ti(R)125 models feature the IR-OptiFlex focus system, IR-PhotoNotes annotation system, focus-free video, and IR-Fusion technology (also for the Ti(R)105). Fluke
www.fluke.co.uk T: 0207 942 0700
Electrical Engineering JULY/AUGUST 2013
to offer, but its full potential will only be realised if it is well implemented. A cru- cial requirement is impeccable isolation between the remote control interface and the measuring circuits, as this is essential for safe operation. And, partic- ularly in production line applications, a clearly visible beacon that provides at a glance, confirmation that the remote control system is functioning, is often a useful feature.
The new Megger S1 range of HV insulation testers, which are available in both 5kV and 10kV versions, have been designed with remote control firmly in mind.
Providing remote control facilities for a high voltage insulation test set may ini- tially seem like a relatively small enhancement but, as we’ve seen, this provision has the potential to open up a wide range of operational opportunities, and to provide many ways of improving operator safety.
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Megger
www.megger.com T: 01304 502 101
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