The trigger here is not growth itself. Economic growth is good, and we certainly do not, as some have suggested, live in fear of it. What prompts an increase in the OCR is when growth in demand looks like getting out of line with growth in the capacity of the economy to supply goods and services.
When that looks like happening, there is a risk that inflation will pick up, and in those circumstances an increase in the OCR, to lean against the growth in demand, is in order.