Additional considerations to portable dielectric breakdown test sets
The priorities of those who use portable instruments are different in several key areas from those of laboratory instrument users. Among the main points to consider for portable instruments are:
(1) Weight
Portable instruments routinely have to be carried from a van to a transformer. Weight is of particular interest, especially when the instrument has to be carried by just one person. The government or the organisation you work for may have rules on the maximum weight that you should carry; often it is specified at 25 kg. From the user's point of view however, the lighter the instrument the better.
(2) Ease of carrying
How easy the instrument is to carry is an important consideration. Handles on the sides of the instrument are generally easiest to use, as they provide a more natural lifting position than a single handle on the top of the instrument.
(3) Toughness
When an instrument is damaged, testing must stop until it can be repaired. Portable instruments are particularly likely to take a few knocks during transportation and use, and they must be able to withstand this treatment. Items might fall on the instrument when it is in the back of a van, and it is desirable to choose an instrument that has been designed with this type of incident in mind.
Occassionally instruments also get dropped. The most frequent types of damage suffered by oil test sets dropped from a modest height are crumpled corners and/or twisting of the instrument frame. Dielectric breakdown test sets include a heavy transformer that must be properly supported, and a quick look at the underside of the instrument will often give a good idea of whether it has sufficient structural strength. In particular, the corners should be checked to see whether they are likely to be able to withstand impacts. It is also worth bearing in mind that lighter instruments are less likely to suffer damage.
(4) Transfering stored data
When the time comes to transfer stored test data from the instrument to a PC, consider the inconvenience of having to carry the instrument into an office so that it can be connected to the PC. A better solution is to choose an instrument that can store test results on a standard USB flash drive, as then it is only necessary to carry the USB flash drive into the office.
(5) Power sources
Many portable instruments can operate only from their internal battery. Bearing in mind that the typical time needed to fully recharge the battery is around four hours, this can be inconvenient if the instrument is needed urgently and is found to have a discharged battery, or if a large number of tests have to be carried out during a fixed shutdown period. It is better to choose an instrument that can operate either from its internal battery or direct from the mains.
