Putting the blame for a February nuclear accident squarely on Consolidated Edison, New York Gov. George E. Pataki signed a bill today requiring the company to repay customers more than $100 million collected to pay expenses from the accident and prohibiting it from collecting tens of millions more. The governor's decision to sign the bill, which could cost the utility about $200 million, stunned nearly everyone involved in the dispute, and came after attempts by the Pataki administration to reach a negotiated settlement with the company had failed.