Читать книгу Practical Power Plant Engineering - Zark Bedalov - Страница 48

Now we can determine the incoming 230 kV breaker as follows: It has to have interrupting capacity of at least 4000 A. We select 3 phase, 245 kV, 1200 A, 40 kA fault interrupting, basic impulse level BIL: 1050 kV peak (see Figure 2.5).

Why 40 kA? This may sound too excessive for our requirements, but these are the ratings at the low end for the 230 kV equipment.

The transformer differential protection scheme and metering would need current transformers (CTs) on the grid side of the HV breaker.