What does the burden refer to in relation to instrument transformers?

The burden in relation to instrument transformers refers to the load that is placed on the transformers. This load is often expressed in terms of ohms or VA (Volt-Amperes) and represents the combined influence of any connected measuring instruments or protective devices that are drawing current from the transformer.

When instrument transformers, such as current transformers (CTs) and voltage transformers (VTs), are used in a system, they step down the voltage or current for measurement purposes. The accurate operation of these transformers relies on them not being overloaded, which could result in inaccurate readings or even damage. Therefore, understanding the burden is crucial for ensuring that the transformer operates within its specified limits and provides accurate measurements.

This concept is fundamental in the design and application of measurement and protection systems within electrical networks. Factors such as resistance, the number of connected meters, and the characteristics of the load all come into play when determining the total burden on an instrument transformer.