A consumer reverses the CT connections in a three phase four wire metering arrangement. What is the percentage change in energy registered.

In a three-phase four-wire metering arrangement, current transformers (CTs) are used to measure the current flowing through each phase. Reversing the CT connections in such an arrangement would result in the current being measured in the opposite direction than intended. This means that instead of measuring the actual current flowing into the load, the meter would measure the current flowing out of the load, effectively registering negative energy consumption.

The percentage change in energy registered due to reversing the CT connections can be calculated using the formula:

[ \text{Percentage Change} = \left( \frac{\text{Energy with reversed CT connections} – \text{Energy without reversed CT connections}}{\text{Energy without reversed CT connections}} \right) \times 100\% ]

However, since the energy registered with reversed CT connections would be negative, the percentage change would be the difference between the absolute values of the energies, divided by the energy without reversed CT connections. This is because the actual change in energy would be the sum of the absolute values of the two energies, rather than their difference.

Let's denote:

• ( E_{\text{reversed}} ) as the energy registered with reversed CT connections (negative value),
• ( E_{\text{original}} ) as the energy registered without reversed CT connections (positive value).

The percentage change in energy registered would be:

[ \text{Percentage Change} = \left( \frac{|E{\text{reversed}}| – |E{\text{original}}|}{|E_{\text{original}}|} \right) \times 100\% ]

Since ( E_{\text{reversed}} ) is negative, its absolute value will be considered for calculation. The result of this calculation would give the percentage change in energy registered due to reversing the CT connections in a three-phase four-wire metering arrangement.