Sneaky Voltage Swell Events

Long time, no post! A pandemic will do that to you . . . suffice it to say I am healthy, relatively happy, and staying busy with both my engineering work (mostly stable through the troubles) and my yoga studio work (very different these days but busier than ever with online classes and the need to provide appropriate technology).

Today’s engineering bon-bon involves a trio of voltage swell events. Seemingly caused by a short circuit (another facility load fault, perhaps utility lighting arrestors) that causes a 1/4 cycle drop-out on one phase and resultant voltage swell following. The swell has a serious overvoltage, likely to cause problems for many types of equipment / power supplies.

This event was captured as a minor RMS voltage swell (5.1% above nominal) – but the peak voltage is very high (540 V vs 395 V normal). Note the ~30 Amp peak current swell.
This event was barely detectable as an RMS voltage swell (4.8% above nominal) – once I recognized the nature of these events, I went looking for more and came up with just this one. Almost no resultant current swell.
This is the big smoking gun event. Even though it did not register as a sag / swell event at all (the voltage drop-out being balanced by the following swell, just 3.25% over nominal) it was captured as a current swell (the highest current event over 6 weeks of data capture) – 650 Amps waveform peak. Something within the client load saw this event as a problem and drew a slug of current.

I’m just the hired gun reviewing the data, pulling out events and issues, writing a report. So I won’t be following this to a resolution or further troubleshooting on site. But this is a good example why automated report writing is not always sufficient – the Fluke 1750 analysis tools would see these events as minor voltage swells (if that). It takes a human being with some experience (I’ve reviewed over 5000 power quality data sets since 2003) to see something unusual, scratch one’s head, and dig in a bit deeper.

Pandemic Crisis: Danger / Opportunity

Things have been very interesting in the yoga world since the COVID-19 pandemic forced the studio to close in March 2020. I taught my last in person class on March 11th; the studio last class was noon on March 13th.

After a weekend of stunned silence, we were back the following Monday. We started with free classes, live-streamed via Facebook Live and archived there and on YouTube. We started simple – an iPad on a tripod, and slowly added lights, sound (headsets and ambient microphones) as we realized this was not going away quickly. Unable at that time to monetize classes, we set up a couple of membership levels for those wishing to support the studio (whose revenues went to zero almost immediately). Lots of work for the studio technologist (me) to do both in terms of physical hardware, as well as online work as we transitioned away from in person classes.

Eventually, we followed our peers, teaching virtual classes via the Zoom platform. More tech work for me – setting up a zoom station at the studio as well as at home.

My home yoga room zoom set-up (left) is also handy to watch online concerts.
The studio zoom cart (right) is perhaps the 3rd iteration of the tech – with a wifi extender, on board lights, multiple cameras and a USB microphone. We can roll it anywhere!

Once the weather warmed up, we took our show on the road, teaching 7-8 outdoor classes each week. We’ve been doing free WHY in the Parks classes for many years through the local town Parks & Rec – now we ratcheted it up, with mandatory registration (to limit capacity and facilitate contact tracing), providing for donations and paid classes. We’d get up to 100 people at some classes. Opportunities for the studio techie to set up a second battery powered speaker, to figure out a way to daisy-chain (left / right speakers for larger classes), and to manage multiple wireless headsets. Oh yeah, and haul out the trusty iPad for some time-lapse videos!

Long terms, we knew that we’d be back teaching live classes, albeit capacity limited and socially distanced, so I started to build up some technology competence. I found a low cost video switcher, and some low cost HDMI cameras (think glorified security cams) and cobbled together a four camera set up that we used first for in-studio zoom classes and eventually to capture live classes.

Left: iPad confidence / stream monitor (what the end user sees)
Center: Laptop zoom computer
Right: Preview monitor and Blackmagic ATEM Mini video switcher
AIDA HD-100A cameras with Arducam lenses – top is the wide shot, bottom is the close shot. We’ve got two other cameras off to the side. HDMI cables + 12V power run into the studio office / control area.

We started with a temporary setup to prove concept and technology (HDMI cables on the floor, cameras on tripods or clamped to carts) – eventually moving to a permanent, four camera installation. You can see the end result on the studio Vimeo page here – https://vimeo.com/westhartfordyoga