BARCELONA, May 9 - Lewis Hamilton led a Mercedes one-two during the second practice session ahead of the 2014 Spanish GP on Sunday (May 11). Red Bull's World Champion Sebastian Vettel was sidelined for most of the two sessions due to an electrical problem. Race favourite Hamilton was quickest in both, 0.449 of a second faster than championship leading team mate Nico Rosberg in the second session and 0.868 ahead of McLaren's Jenson Button in the first.HAMILTON IN CHARGEWhile Hamilton pounded out the laps, ahead of a weekend that could bring him a fourth successive win, quadruple champion Vettel was little more than a spectator at the Circuit de Catalunya. Vettel, winner of nine races in a row at the end of the 2013 season, was forced to park up by the side of the track early in the day with just four laps completed. Circuit de Catalunya marshals handed him a fire extinguisher as he inspected the car before hitching a ride back to the paddock on a scooter. Red Bull have given him a car built on a different chassis to the one he has used so far in what has been a difficult start to the season but there was no obvious improvement.Red Bull said: "Due to an electrical problem that has damaged the wiring loom of Car No. 1, Sebastian will not be able to take part in FP2 (second practice). The Team will use the time to fix it to be ready for FP3 (the final session before qualifying) tomorrow." The last time Vettel was at a Spanish circuit, testing at Jerez in January 2014, he spent most of his time in the garage watching mechanics work on the car as Renault wrestled with teething problems on the new V6 power unit.Hamilton, four points behind Rosberg after four races, went from strength to strength with a fastest lap of 1min 27.023 seconds set six minutes from the end in the morning. After lunch, his best time was a 1min25.524. BUTTON CATCHING UP?The impressive margins in the Spanish sunshine underlined the Briton's status as the man to watch in F1's first European race of the season. Rosberg, who had said on Thursday he just needed a "normal weekend" to regain the momentum, suffered a cooling issue that cut short his first session and left him fifth fastest before normal service was resumed in the afternoon.Vettel'steam mate Daniel Ricciardo, who has made an impressive start with the team, was third in both sessions with Ferrari's Fernando Alonso, the local favourite for his home race after winning last year, fourth. With the opening long-haul races in Asia and the Middle East out of the way, all teams have brought updates to their cars and Friday's practice sessions were being closely watched for any signs of change in the pecking order. They were also the first chance for many of the fans to hear the new, less noisy engines with engineers already looking at ways of making them louder. In a bizarre early incident, a wing mirror on Sergio Perez's Force India broke off and was left flapping around on a wire. The Mexican completed the lap with it in his hand.2014 Spanish GP:Second practice1 Lewis Hamilton (Britain) Mercedes 1min25.5242 Nico Rosberg (Germany) Mercedes 1min25.973 3 Daniel Ricciardo (Australia) Red Bull 1min26.509 4 Fernando Alonso (Spain) Ferrari 1min27.121 5 Kimi Raikkonen (Finland) Ferrari 1min27.296 6 Kevin Magnussen (Denmark) McLaren 1min27.788 7 Jenson Button (Britain) McLaren 1min27.811 8 Felipe Massa (Brazil) Williams-Mercedes 1min27.824 9 Pastor Maldonado (Venezuela) Lotus 1min27.866 10 Daniil Kvyat (Russia) Toro Rosso 1min28.049 11 Nico Huelkenberg (Germany) Force India 1min28.074 12 Jean-Eric Vergne (France) Toro Rosso 1min28.246 13 Adrian Sutil (Germany) Sauber 1min28.284 14 Valtteri Bottas (Finland) Williams 1min28.698 15 Esteban Gutierrez (Mexico) Sauber 1min29.105 16 Sergio Perez (Mexico) Force India 1min29.129 17 Romain Grosjean (France) Lotus 1min29.493 18 Jules Bianchi (France) Marussia 1min29.991 19 Max Chilton (Britain) Marussia 1min31.148 20 Kamui Kobayashi (Japan) Caterham 1min31.338 21 Marcus Ericsson (Sweden) Caterham 1min31.586 22 Sebastian Vettel (Germany) Red Bull First practiceStay with Wheels24 for the 2014 Spanish F1 GP weekend.