Iec code on transformer breaker sizing

A very specific and technical question!

The IEC (International Electrotechnical Commission) code for transformer breaker sizing is IEC 60228-1:2013, "Conductors for low-voltage circuits - Part 1: General requirements".

However, the actual calculation for transformer breaker sizing is based on the IEC 60228-1:2013 standard, which provides guidelines for the selection of conductors and cables for low-voltage circuits. The standard takes into account various factors such as:

  1. Voltage rating of the transformer
  2. Current rating of the transformer
  3. Temperature rise of the transformer
  4. Insulation level of the transformer
  5. Type of load (resistive, inductive, or capacitive)

The calculation involves determining the maximum current that the transformer can handle, taking into account the voltage rating, current rating, and temperature rise of the transformer. The maximum current is then used to determine the required conductor size and breaker rating.

Here is a general outline of the calculation:

  1. Determine the maximum current rating of the transformer (I) based on the voltage rating, current rating, and temperature rise of the transformer.
  2. Calculate the maximum current that the transformer can handle (I_max) using the following formula:

I_max = I x (1 + (ΔT / T))

where: I = maximum current rating of the transformer ΔT = temperature rise of the transformer T = temperature rating of the transformer

  1. Determine the required conductor size (A) based on the maximum current that the transformer can handle (I_max) and the insulation level of the transformer.

A = I_max / (k x (1 + (ΔT / T)))

where: k = insulation level of the transformer (e.g., 1.4 for 1.4 kV)

  1. Determine the required breaker rating (I_b) based on the maximum current that the transformer can handle (I_max) and the type of load (resistive, inductive, or capacitive).

I_b = I_max x (1 + (ΔT / T))

Note that this is a simplified outline and actual calculations may require more detailed analysis and consideration of specific factors such as transformer design, installation, and operating conditions.

It's also important to note that the IEC 60228-1:2013 standard provides more detailed guidelines and formulas for calculating the required conductor size and breaker rating, and it's recommended to consult the standard for specific guidance on transformer breaker sizing.