Transformer fluids provide both dielectric strength and cooling. As the temperature of he transformer goes up, that fluid expands. As the temperature of the oil goes down, it contracts. We measure liquid levels with an installed level gauge. It will tell you the liquid current situation and how you cross reference that information with the oil temperature can tell you if you need to top up your transformer with oil.
The liquid in a transformer, whether it's oil or a different type of liquid, they do two things. They provide dielectric to keep the electricity where it belongs. And they also provide cooling. The transformer is not 100% efficient and that inefficiency shows up as heat. And in fact, as the temperature of the transformer goes up, due again to the losses in the transformer, the oil expands. And it's about 1% for every 10 degrees centigrade that the transformer temperature rises. So how is that measured? Well, you can judge via the float in the level gauge, the level in the transformer, and the gauge has this mark, when the level is sideways here lining up with the needle at 25 degrees centigrade. So a low level would be, of course, if it's resting on low, this arm would follow the liquid level.
And, however, at 25 degrees centigrade, which would be an ambient temperature and the transformer may not be loaded at that point. That's how they set a level to start off with. Now as the temperature goes up and that fluid expands, the float comes up, the needle start to move.
The liquid level gauge monitors the oil or fluid level inside your transformer. The fluid inside padmount and substation transformers insulates the windings and cools the transformer while in operation. It is important to make sure the fluid remains at the right level throughout the life of the transformer..
The 3 main assemblies
In order to identify the different types of transformer oil gauges, it helps to first understand their major components. Each gauge consists of three assemblies:
The Case Assembly, which houses the dial (face) where you read the temperature, as well as the switches.
The Flange Assembly, which consists of the flange that connects to the tank. The flange assembly also consists of the support tube, which extends from the back of the flange.
The Float Rod Assembly, consisting of the float and float arm, which is supported by the flange assembly.
Mounting type
There are two main mounting types available for OLI(oil level indicators).
Direct Mount oil level indicators
Remote Mount oil level indicators
Most transformer oil level indicators are Direct Mount devices, meaning the case assembly, flange assembly and float rod assembly are a single integrated unit. These can be side mounted or top mounted.
Side mount OLIs generally have a float assembly that consists of a float on the end of a rotating arm. Whereas top mount OLIs (aka vertical oil level indicators) have a float within their vertical support tube.
Remote mount OLIs by contrast are designed for use where the point of measurement is not easily viewed by personnel, thus requiring separate or remote indication. For example on a conservator tank. In practice this means the Case Assembly (with the visual dial) is separate from the Float Assembly, connected by a capillary tube.
Post time: Oct-18-2024