How to Calculate Voltage in Potential Transformers: A Simple Guide

Potential transformers (PTs) are used to safely measure high voltages by stepping them down to a lower, manageable level. They are essential for accurate voltage monitoring in electrical systems. But how exactly do you calculate the voltage on the secondary side of a potential transformer? In this blog, we’ll explain the basic formula for calculating voltage in PTs in a straightforward way.

The voltage on the secondary side of a potential transformer can be calculated using a straightforward formula that relies on the turns ratio between the primary and secondary windings. This ratio dictates the amount by which the primary voltage is stepped down.

The formula is:

Vs​=(Ns​​/Np​)×Vp​

Where:

• V_s=  The secondary voltage (the voltage that is measured)
•  N_s = The number of turns in the secondary winding
• N_p =The number of turns in the primary winding
• V_p = Primary voltage (the high voltage you are stepping down)

The turns ratio represents the relationship between the number of turns in the primary winding (N_p) and the secondary winding (N_s) of the transformer. A typical turns ratio might look like this:

Turns ratio (N_s

) = 1:1000

This implies that for every 1 turn in the secondary coil, there are 1000 turns in the primary coil. As a result, the primary voltage is reduced by a factor of 1000 to produce the secondary voltage.

Step-by-Step Example

Let’s say we have the following:

• Primary voltage (V_p) = 12,000 V (12 kV)
• Turns ratio (N_s
  ) = 1:1000

Using the formula:

Vs​=(1/1000)×12,000V=12V

So, a primary voltage of 12,000 V will result in a secondary voltage of 12 V, which can be safely measured using a standard voltmeter.

Knowing how to calculate the voltage in a potential transformer is crucial for:

– Accurate Measurement: Ensuring that voltage readings are correct and within the measurable range.

– Safety: Protecting measuring instruments from high voltages by stepping down the voltage to a safer level.

– System Monitoring: Monitoring electrical systems without the risk of overload or damage.

Calculating the voltage in potential transformers is straightforward when you understand the turns ratio. The formula helps you determine how much the high-voltage primary is stepped down to a safer, manageable secondary voltage. Whether you’re monitoring power systems, protecting equipment, or calibrating instruments, understanding PT voltage calculation ensures safe and accurate electrical measurements.

By mastering the basic formula and concepts, you can confidently work with potential transformers in any electrical application.