A Magnetic Oil level Guage (MOG) is a device used to indicate the position of transformer insulating oil level in conservator of a transformer. This is a mechanical device. A mog in a transformer consists of three main parts:
- One float
- Bevel gear arrangement
- An indicating dial
Construction of Magnetic Oil Gauge or MOG
Let’s explain the construction of magnetic oil gauge (MOG) from its dial parts. The dial of this device has a scale from empty to full. It has some intermediate divisions such as 1/4, 1/1, 3/4.
The prescribed oil level at either 30oC or 35oC ambient temperature may also be indicated on the dial. A mercury switch and bevel gear are fixed with the pointer. When the pointer rotates, the alignment of mercury switch also changes according to the angle of rotation of the pointer.
One ball type or drum type float is attached with a sufficiently long float arm. One unit of bevel gear is fitted on the other side of the float arm. Other unit of the bevel gear is magnetically coupled with pointer and mercury switch arrangement. The bevel gear arrangement is positioned inside the conservator tank of transformer and dial, pointer and mercury switch are positioned outside the conservator tank.
Working Principle of Magnetic Oil Gauge or MOG
All oil-immersed distribution and electrical transformers are provided with expansion vessel which is known as conservator of
Again when oil volume is reduced due to
All large electrical power transformers are therefore provided with a magnetic oil level indicator or magnetic oil gauge. In conventional conservator tank, a
This movement of bevel gear is transmitted to the pointer outside the conservator, as this pointer is magnetically coupled with the bevel gear. The pointer of
As the alignment of mercury switch changes along with the pointer, this switch closes and actuates an audible alarm when
In air cell conservator, the float arm is attached with air cell and alignment of float arm changes with the changing size of