# Transformer as an Isolation Device   Whatsapp  The transformer is frequently used to isolate one portion of an electrical system from another. Isolation implies the absence of any direct physical connection. As a first example of its use as an isolation device, consider the measurement of line voltages on the order of 40,000 V (Fig. 1). Fig. 1: Isolating a high-voltage line from the point of measurement.
To apply a voltmeter across 40,000 V would obviously be a dangerous task due to the possibility of physical contact with the lines when making the necessary connections. By including a transformer in the transmission system as original equipment, one can bring the potential down to a safe level for measurement purposes and can determine the line voltage using the turns ratio. Therefore, the transformer will serve both to isolate and to step down the voltage.
As a second example, consider the application of the voltage $v_x$ to the vertical input of the oscilloscope (a measuring instrument) in Fig. 2. Fig. 2: Demonstrating the shorting effect introduced by the grounded side of the vertical channel of an oscilloscope.
If the connections are made as shown, and if the generator and oscilloscope have a common ground, the impedance $Z_2$ has been effectively shorted out of the circuit by the ground connection of the oscilloscope. The input voltage to the oscilloscope will therefore be meaningless as far as the voltage $v_x$ is concerned. Fig. 3: Correcting the situation of Fig. 2 using an isolation transformer.
In addition, if $Z_2$ is the current-limiting impedance in the circuit, the current in the circuit may rise to a level that will cause severe damage to the circuit. If a transformer is used as shown in Fig. 3, this problem will be eliminated, and the input voltage to the oscilloscope will be $v_x$.

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