My guess is these Ballasts are being spiked / surged, from one (or more) of the Tenants connected to the same Service Section / Transformer.
The noise is bursting outwards, and affecting the HID Ballasts at Night when the Site / Parameter / Area Lighting is on - which is, of course, fed from the House Panel, through the House Meter, which is tapped from the Meter Section, common to the Tenants'.
As stated before, the "Electronic HID Ballasts" are relatively new in the Industry, and are still going through a kind of "Public Sector, In-Use Beta Test" thing, in order to "Find The Bugs".
Expect a more stable version in a few more years.
The same was experienced when Electronic Fluorescent Ballasts for Linear fluorescent Lamps, were first introduced to the Industry.
Failure rates were high in the first few years (some were higher than ever expected!).
After time, the Manufacturers gathered failure data, tried newer approaches, and eventually came up with stable versions used today.
If the failures are not _DIRECTLY_ resulting from TVS/S generated by the Tenants, or other Customers, the problems may be from the operation of the Lamp, applied to an erroneous Ballast design - or due to unstable Line Voltages.
To be specific;
* What are the Lamps' Wattage + Type?
I kind of think they are 55 Watt Metal Halide, Pulse Start Lamps.
* Is the Power Factor > 0.95?
If you are not sure, just list the Line Input Amps, and the Lamp's rated Wattage, for a given Ballast.
* The Measured 124-125VAC: was this taken at daytime, or night; and were the Lights on or off; and was the test done at the first fixture, last fixture, or at the Panelboard?
I am really curious about this scenario! Want to find out what is going on, not only because I want to help get this problem under control, but also because we have a few Clients requesting HIDs driven by Electronic Ballastry.
I have been explaining the "Learning Curve" for failure rates experienced with newer Technologies, and suggesting them to wait a few more years for the Technology to improve, so their investments are worthy - not a significant loss from maintenance nightmares due to large failure rates.
Lastly, the issues of failure may be from the Lamp's operation, and / or the Ballast's counter-action with the Lamp.
Simply, the Lamp may be causing the Ballast to "Push-Back" Spikes and/or Surges of Voltage - either as high levels of Harmonic Distortion (and the "Line Input" components are suffering from this noise), or the overall Power Factor is leading too much (< 0.7), resulting in a High Voltage being "Pushed-Out" of the Ballast, which damages the Line Input Components.
Please let me know what Lamps are used, the Wattage, and the Ballast information, so I can research this.
Also, if you have the opportunity to open one or two damaged ballasts, get some pictures of the fried components, plus mark down the Identifier marked on the PCB / Component; then post the information / pictures here.
Alternately, just make note of the smoked Components (ID, location on board, description of the Component, etc.), and post the info. here.
Good luck.
Scott
