Video: B100

Video transcript

What decides how long a power transformer lasts, and the instrument that measures it, records it and acts on it. Start with the asset, not the instrument. A power transformer is not one machine: it is a collection of sub-systems, and its condition is only as good as the worst of them. Windings and insulation, bushings, the tap changer, the oil, the cooling. Of all of them, the one that quietly decides the life

of the unit is the temperature inside the winding. Because the cost of heat is not linear. Under the IEC loading guide, every 6 degrees above 98 doubles the rate at which the paper ages. Nothing gives it back. And yet a transformer is normally protected by mechanical gauges. They stick. And when one sticks, nothing tells you: the needle simply stops where it is, the fans stop being called, and the transformer runs unprotected for months.

This replaces up to 5 of those gauges. Top oil, the hot spot of up to 3 windings, the tap changer differential, cooling control and the alarm and trip contacts, all from one box. The hot spot itself is inside the winding, and no probe can be put there. So it is worked out: from the top oil it can measure, the load current it can measure, and the gradient the manufacturer found in the heat run test. Temperature tells you the transformer is hot. Gas tells you why.

Hydrogen is the first gas a fault produces, and it appears long before anything else does. And with the combined sensor, moisture as well, which is what quietly lowers the dielectric strength of the paper and makes the next fault more likely. Everything it knows is visible 3 ways: on the display in front of the transformer, on web pages from your own network, and in SCADA. And at the transformer nobody needs a laptop:

Four keys reach the whole menu. It is fitted 3 ways, and the outdoor version was made for retrofits: a magnetic mounting kit and a magnetic oil sensor mean an old gauge can be replaced without drilling the tank. And the numbers that decide whether it fits your installation. One last product detail, and it is the one that answers the gauge that sticks. If the monitor itself has a problem, it says so, and its fail safe contact turns the cooling on.

Now what is inside it and how it is set up. Open it and there is one board. The processor and the memory along the top, the relays in a row, and every field connection on plug-in screw terminals along the bottom edge, so a card can be swapped without disturbing the wiring. Those terminals are the whole instrument, so it is worth knowing what each group is for before you open a single gland. Mounting. Four holes, the drilling template that comes with it,

and one measurement people forget: leave clearance on the left and underneath, or the door will not open and the glands will not take a bend. Then the supply. It takes almost anything, but read the label inside the housing rather than assuming: the input depends on how that particular unit was built. And wire everything else before you energise it. A word about the field wiring itself.

Screened cable on the sensors, screens earthed at the earth stud, and ferrules on every stranded conductor. It is the difference between a temperature that is steady and one that wanders. Configuration is a browser and a cable: a standard USB lead into the service port, and the whole thing is web pages. It starts with the temperatures. The first probe is always top oil. The second one you choose: tap changer tank, or ambient, or nothing.

And here is the setting that people get wrong. Every alarm has a set point and a bandwidth. It comes on above the set point, but it does not go off until the temperature has fallen below the set point minus the bandwidth. That gap is what stops a fan bank starting and stopping every 30 seconds. Then the current inputs, which is where the hot spot calculation actually lives. The rated current and the current transformer ratios come from the transformer. The gradient and the current at heat run come from its test report,

and they have to be right, because everything downstream depends on them. The outputs are then wired in software rather than in copper. Any alarm can drive any relay, and a relay can be made to wait for two or 3 conditions at once. Communications next. One Ethernet path, one serial path, and on the serial card two small switches that decide whether it is a two-wire or a four-wire link and whether this unit is the one carrying the terminating resistor.

And finally, commissioning: the handful of things that are easy to leave undone and expensive to leave undone. Transformer monitoring, from Amperis.