This article will discuss about the three common Electrical Measurements we can found in Switchgears and Panel boards. I learned this electrical measurements when I worked with a gas manufacturing plant as a Cadet Engineer. However, this is just few of the measurement devices that we have in the field of Electricity. This article will focus on Current Transformer, Potential Transformer and Tore that are used as metering device. Table of contents 1. Current Transformer 2. Potential or Voltage Transformer 3. Tore or Residual Current Sensor Current Transformer The current transformer makes it possible to reduce a high intensity current to a value of 1A or 5A exploitable by the measurement apparatus and the protection relays. (1A and 5A being standardised values). It includes a primary