Hi, I bought my Zanussi ZCV663MWC cooker ten years ago, I replaced the top element four months ago and its been fine until now. When I turn the top oven on it heats up then after ten minutes it trips the mains. Also I have never used the bottom oven but when I turned it on it also tripped the mains but this was after just two minutes. The four hot plates are working fine, could anybody help please.