Arbexpress software

It looks like the software has translated this increased pulse width into more pulses across the reference waveform as opposed to wider individual pulses. Lets see what happens when the amplitude of the pulses is increased to mV peak to peak. The screenshot below shows what the scope captures. The Phase Resolved Plot below shows the increased amplitude of the pulses captured by the software. The pulse location has remained consistent with the previous plot at the lower amplitude.

I reconfigured both of the test files to have a higher number of negative pulses, but left the number of positive pulses the same. This is what the scope captured at the higher pulse amplitude.

You have to look closely, but a higher number of negative pulses can just be made out. At the higher mV level, the negative cluster of pulses appears to be more dense, but the software reports the same Qm values as before.

At the lower amplitude, the negative pulse activity is again more dense, but is showing a lower mV level. This did happen on all three phases, so appears to be consistent, but is not what was expected. The expectation is that the Qm- value would have increased. This will require further investigation and testing. I then tried this same signal on the system input to the TGA-B. Although the plot obtained was relatively consistent across all three phases, it was completely different to the plot obtained from the same signal applied to the machine input.

This is again another area that will need further investigation. One final test was to create extra pulses across the waveform to see if the TGA-B would capture them. The pulses were the same magnitude and width as the initial pulses.

The oscilloscope screenshot shows the extra pulses across the waveform. As can be seen below, the TGA-B recorded the extra pulses across the waveform which was the expected outcome. This aspect of the testing has worked out relatively well. Some of the results were not as expected and will need further investigation, which will require the creation of different test waveforms, so will move towards a long-term goal. Tektronix offer two software packages for their arbitrary waveform generators and both are free to download once you are registered on their website.

It will load the 'isf' files created by the 3 Series MDO, but will only save files in its native format that the 3 Series will not read.

Waveform manipulation within the SourceXpress package seemed to be via a datable of the points in a similar manner to the Excel file manipulation. I must confess though that I did not investigate this much as soon as I learned that I could not output the waveform in a format suitable for the 3 Series MDO. The other package available from Tektronix is the ArbXpress software made for their range of arbitrary waveform and function generators.

The screen capture below identifies which models it is compatible with and it can be seen that the 3 Series MDO does not appear to be amongst them, despite some of the MDO oscilloscopes having compatibility.

The software however, will load both 'isf' and 'csv' file formats and editing can be carried out in the waveform window by either copying and pasting existing waveform elements, 'joystick' style manipulation of waveform points or manually drawing a waveform. File load options is well supported with 'isf' 'wfm' and 'csv' compatible with the Tektronix Oscilloscopes.

It will only save to 'wfm' or 'csv' formats for import to an oscilloscope. The other formats I believe are for their waveform generators. Unfortunately, the 'csv' format produced by the ArbExpress software is not the same format as the 'csv' file created by the 3 Series MDO and they will not load directly into it.

The 'csv' file from ArbExpress places the data column first and then seems to use clock data for formatting the waveform. The easiest way I found to overcome this was to edit the waveform and save as 'csv' and then copy the data column from this 'csv' file into an existing 'csv' file from the 3 Series MDO.

The oscilloscope will then read this file and load the waveform and as the last picture shows in the gallery, I can zoom into the PD pulse simulated in the ArbExpress software. It is a bit messy and time consuming, but ultimately I can achieve pulse modification and play it back into the TGA-B and observe the effects. For me it would have been nicer if Tektronix had given a little more thought into the software integration of the function generator within the 3 Series MOD and its compatibility with their other hardware and existing software.

The next test was to take the 3 Series MDO on a trip to a power station to capture partial discharge data from a generator alongside the TGA-B analyser. This particular generator operates at a line voltage of 21kV, just over 12kV to earth. Connection is made to the busbars via 80 pF capacitive couplers as in the graphic from the Iris literature.

With this system, I can simply replace the TGA-B analyser with the oscilloscope and use the zoom and horizontal timebase to capture data of specific interest. The image below shows the scope connected to the coupler termination box at the top of the picture.

To maximise the screen, only one phase was connected at a time. The initial screenshot shows quite clearly the six pulses across each cycle that are created by the rectification of the supply to create the DC excitation voltage for the generator. This actually shows up better on the oscilloscope than it does on the TGA-B. The third pulse in each half cycle appears to be much smaller, this was again detail not picked up on the TGA-B analyser.

Away from site, the captured waveform can easily be loaded back into the oscilloscope and zoomed in to take a closer look at the pulses along the waveform. This type of extended pulse with a long oscillating tail is more typical of noise than genuine partial discharge activity.

The zoom facility of the scope allows individual pulses to be looked at more closely. The cursors are relatively easy to use and when they disappear off screen due to zooming can easily be recovered by bringing up the cursor menu or right clicking the mouse on a blank part of the screen to bring up a context menu.

The cursor menu has a function to bring both cursors onto screen and the 'right' click menu has the option to bring either cursor to that point on the screen.

This is a relatively friendly environment for the 3 Series MDO to be transported to. The transport bag works well and offers good protection whilst being transported in the car and carried around site. Whilst the scope can easily collect the data, I did find it easier to carry out analysis back in an office environment as it did become time consuming to manually look at the different pulses across the waveform.

An extra job was carried out on this site in the form of partial discharge measurement on the outgoing cables of the step-up transformer to the kV switchyard. This measurement has been carried out with an UltraTEV analyser using the same RFCT, but this is a relatively basic analyser that is very susceptible to noise.

Monitoring the kV cables with this device, gives a high level reading, that puts the cable into an alarm category. I was keen to utilise the 3 Series MDO to carry out some further analysis on the partial discharge activity on these cables. The first picture shows the RFCT clamped around the earth cable to the sheath. The RFCT looks just like a split core current transformer, and it is, only having a much higher bandwidth than a standard power current transformer.

The second picture shows the overall set-up. Some would regard this as quite a harsh environment for this type of instrument, but it seemed to cope with it quite well.

The ability for the handle to fold down and widen the base of the oscilloscope certainly helped with the stability on the pebbles covering the bund floor grating. The third picture shows the first capture of data from the RFCT, pretty messy, but you can just make out a 50 Hz sine wave together with a serious amount of activity.

The reading was found to be around pico-Coulombs pC but had reached up to pC, this would be considered as a worrying level of activity if it is genuine partial discharge. Not much analysis can be done out on site, but the initial impression from the screenshot on the scope is that this is just noise, there may be some partial discharge activity hidden away within all these spikes, but it will be negligible and extremely difficult to find without specialise software for the analysis.

With the waveforms captured on the oscilloscope in its native 'isf' waveform format, I could return to the office to take a closer look at the data. The 'isf' file can either be loaded back into one of the reference channels of the oscilloscope or canoe viewed on a computer using the TekScope Anywhere software.

On this occasion, I stuck to carrying out the analysis using just the oscilloscope. Called back into the reference channel, this is what one of the captures looked like.

I am not sure why the grey bar has appeared on the screen. It seems to occur occasionally when the zoom function is utilised, although it appears to be part of the screen save message, as saving the screenshot gets rid of it. There are a number of sharp spikes standing out across the waveform, that I would like to take a quick look at, although their regularity suggests they are also noise. The first three screenshots are capturing individual pulses, to look at their shape and duration.

Partial discharge pulses are characterised by their fast rise time, usually less than 6 ns and their short duration, less than ns, this does vary based upon the type of detection and the medium the discharge pulse is travelling through.

The scope clearly shoes that all of these three pulses are longer than expected for a discharge pulse, their general shape is also more representative of noise than a partial discharge pulse. The last two screenshots are more generalised to show the level of noise across the waveform.

Throughout the process, the zoom function performed well and the touch screen allowed for easy manipulation of the waveform. Personally, I found that having a mouse plugged in to one of the USB ports aided the operation. Whilst working out on one site, the opportunity arose to carry out a high voltage test on a 12 kV breaker to verify the integrity of the vacuum within the contact bottles. This is carried out by monitoring the leakage current through the open contacts with 20 kV applied across them.

As it is an over voltage test, this generally also creates partial discharge activity across the bottle surface. The test set-up can be seen below. The background activity, with the test voltage removed, can be seen on the oscilloscope screen above and also on the UltraTEV below.

The increase in activity can also be seen on the oscilloscope in th following screen capture. Instead of using the oscilloscope for signal analysis, I utilised the TekScope Anywhere software available from Tektronix.

This is a licensed software package, but a 30 day trial can be downloaded for evaluation purposes. I have to confess that I found it much easier and quicker to manipulate the waveform in the software rather than on the oscilloscope. It was a reasonably simple matter to determine which pulses were genuine partial discharge activity from those that are much more likely to be noise.

This aspect of the roadtest was expected to be more challenging. Whilst the oscilloscope aspect of the 3 Series MDO can capture partial discharge data, trying to utilise the waveform generator aspect to modify and playback test waveforms was not as easy to achieve.

It can be done, but is not as easy as it could be if Tektronix had provided support for the 'wfm' file format within the oscilloscope or adopted the same 'csv' file format as their ArbExpress software.

Partial discharge simulation pulses were created and successfully played back into the TGA-B from the waveform generator built into the oscilloscope. The kPTS limit of the waveform generator did ultimately affect the results of the tests. I suspect that I would be better off in utilising the 3 Series to collect the data and then look at their AFG series function generator to create the waveforms.

This would be interesting as they have a dual channel option that could be utilised with the TGA-B to test both machine and system channels at the same time.

Out on site the 3 Series MDO performed perfectly well. The option to use the handle as part of the stand for the oscilloscope gives it a solid platform even when working on the cobble stones of a transformer pen. It travels without any issues within its protective soft-case and was easily carried around site. Data can easily be collected and stored for analysis at a later date.

The size of the files created due to the memory depth utilised meant that data could only be saved to an external USB and not to internal memory, but this is no different to any other oscilloscope I have. Whilst the scope can be used for analysis, I found it easier to control with a mouse and this isn't always easy or possible out on site.

In an office environment, the mouse can easily be used with the scope, but this also opens up the option to use the TekScope Anywhere software that complements the 3 Series very well. It was found to work in a similar manner to the oscilloscope and provided extra analysis options that aren't available on the oscilloscope. Up to this point, I have deliberately left out descriptive information on partial discharge in high voltage insulation systems, as it is a very complex subject and I didn't want it to detract from the use of the 3 Series MDO that this blog is really about.

It is important for insulation engineers to monitor the partial discharge as it effectively eats into the insulation around a high voltage component and thins out the insulation until the electrical stress over the remaining insulation is so great that it is punctured and an electrical flash over occurs. This is usually highly disruptive and can cause apparatus to be out of service for months whilst repairs are made, not to mention the risk to personnel. You can see the areas marked in-between a stator coil and the support ties.

It is also another nuisance on this kind of environment, in that as it eats into the insulation it causes a larger gap, that in turn increases the amount of partial discharge. It can also cause the tie to become loose, this will then add mechanical vibration to the failure mechanism that will increase the speed at which the insulation is rubbed away.

In this picture the partial discharge has been caught early in its life and can therefore be repaired. This picture from Doble Engineering, shows what happens if the partial discharge goes on for too long and causes a puncture in the insulation. Depending on how much copper damage there is, there are repair techniques to rebuild the insulation, or it may be that the whole bar has to be removed and a new one installed, which is likely to have the machine down for one to three months.

This is extremely useful for automotive, medical, and industrial applications where recreating sensor output is critical to analyzing the integrity of the design. SignalExpress supports the range of Tektronix bench instruments enabling you to connect your entire test bench.

You can then access each instrument from one intuitive software interface. This allows you to automate complex measurements requiring multiple instruments, log data for an extended period of time, time-correlate data from multiple instruments, and easily capture and analyze your results, all from your PC.

Only Tektronix offers a connected test bench of intelligent instruments to simplify and speed debug of your complex design. Using the front-panel USB host port, you can save your customized waveforms or instrument settings onto a USB memory stick. Reloading the data is easily done by plugging the device back into the USB host port. The 2U height and half-rack width form factor allow the AFG to be stacked on other bench instruments, such as digital multimeters, power supplies, and frequency counters, saving valuable bench space.

View Cart My Account Superior Performance at an Affordable Price Most electronic devices, circuits, and systems are designed to handle some form of a signal. Frequency Range. ArbExpress Software. Data Sheet: KB Manual: 3.