Question

What is the CT ratio of 33kV?

Answer 1

The **CT ratio** (Current Transformer ratio) for a **33kV** system depends on the specific application and the amount of current you need to measure or protect against. In general, the CT ratio is defined as:

\[
\text{CT Ratio} = \frac{\text{Primary Current}}{\text{Secondary Current}}
\]

For medium-voltage systems like 33kV, the primary current (the current flowing through the high-voltage line) would usually be quite large, while the secondary current (output of the CT, which goes to the protection and metering equipment) is typically standard (like 5A or 1A).

### Example:
1. **Primary current calculation**: Suppose you are measuring the current in a 33kV line feeding a load, and the load is rated for 1000A (just an example).
2. **CT secondary**: Common secondary ratings are 5A or 1A.

Let's say you choose a CT with a **secondary current of 5A**. If the load is 1000A, the CT ratio would be:

\[
\text{CT Ratio} = \frac{1000A}{5A} = 200:1
\]

This means the CT will scale down the current by a factor of 200, so 1000A in the primary would correspond to 5A in the secondary.

### Typical CT Ratios for 33kV:
- The ratio depends on the expected current and the type of protection or metering needed.
- For industrial applications, common ratios might range from **100:5** to **2000:5**, but this can vary.

In short, **CT ratios for 33kV** systems typically depend on the system's current requirements and the protection scheme, but they often fall between **100:5** to **2000:5** or other similar values.