A series street lighting system operates similar to the mini Chirstmas lights, ie; 40 bulbs on 120 volt line = 3 volts per bulb, inside these mini bulbs is a shunt to bypass a failed filiment. The incandescent street light bulbs work the same way, a disc similar to 2 pennies separated by paper will allow a good bulb to operate since the disc has a pre-determined breakdown voltage like 80-150v. An incandescent street lamp uses between 23 and 50 volts, so an 80 volt disc will hold. When a bulb burns out, there is now thousands of volts between the disc paper and will burn through completing the circuit. The constant current regulator/transformer will provide the correct operating voltage in the system. In the case of the mini Christmas lights there is continuous 120 volts and when there are too many burnouts the remaining good mini bulbs are over driven and will have there lives shortened, thus is why they say to promptly replace burnouts, as there is no voltage regulationlike street lights. In the case of HID type series lights like these, MV & HPS, the transformer/ballast provides a continuation of power. There are incandescents that use a series isolation transformer too, as a safety measure separating the high voltage from the lineman replacing the bulb, and for using different current bulbs like a 20 amp bulb on a 6.6 amp line.
Login
>>> Update > I saw it lit, and is MV