* Q1 EBITDA 4.9 bln crowns vs forecast 5.2 bln crowns * Hit by lower wind speeds, cable problems * Shares fall almost 4% (Adds details, CFO comments, updated share reaction) COPENHAGEN, April 29 (Reuters) - Lower wind speeds and cable problems hit first-quarter earnings at Denmark’s Orsted , sending shares in the world’s biggest offshore wind farm developer lower on Thursday. Earnings before interest, tax, depreciation and amortisation (EBITDA) came in at 4.9 billion Danish crowns ($799 million), missing analysts’ consensus forecast of 5.2 billion crowns. However, Chief Executive Mads Nipper said the company’s operational performance “was good during Q1 2021 and slightly exceeded our expectations”. Nipper took the helm in January. His predecessor, Henrik Poulsen, stepped down after leading the energy company’s transformation away from fossil fuels. Orsted said quarterly earnings suffered from significantly lower wind speeds compared to last year, and a warranty provision of 800 million crowns made after it discovered cable problems at its offshore wind farms in Europe. Investigations into the extent of the issue are ongoing, Chief Financial Officer Marianne Wiinholt told a media briefing, but added the problem was limited to ten offshore wind farms at most. They are in the United Kingdom and Continental Europe and equipped with a cable protection system Orsted no longer uses. Orsted estimated fixing the problems could cost 3 billion crowns in total between 2021 and 2023. Sydbank analyst Per Fogh described the issue as a “significant expense”, but said Orsted’s underlying business was doing well, despite earnings coming in below expectations. Orsted shares were down 3.8% at 0929 GMT, having dropped more than 30% since an early January high. Citi analyst Jenny Ping said the results could dampen hopes of upgrades this year. Citi has a “sell” rating on the shares. Orsted kept its full-year guidance and said it would present an updated strategy with new long-term targets on June 2.