What transformer ratio is typically utilized in instrument transformers?

The typical transformer ratio utilized in instrument transformers is often 400:1. Instrument transformers, including current transformers (CTs) and voltage transformers (VTs), are designed to step down high voltages or currents to manageable levels for measurement and protection purposes. A ratio like 400:1 means that for every 400 units of the primary current or voltage, the secondary output will produce 1 unit, allowing for safer and more accurate reading of high voltage or current levels.

A 400:1 transformation ratio is advantageous because it balances the need for sensitivity with the capability to handle extreme conditions in the electrical system. Higher ratios can lead to saturation and inaccuracies in measurement, which is why ratios like 200:1, 500:1, and 1000:1 are less common for general use in instrument transformers. Instead, they may be used for specialized applications where the measurement range and requirements dictate such ratios.