An electrical apparatus comprising: first and second terminals for connection to an electrical circuit; a chain-link converter connected between the first and second terminals , the chain-link converter including a plurality of chain-link modules , each chain-link module including at least one switching element and at least one energy storage device , the switching element and the energy storage device of each chain-link module combining to selectively provide a voltage source; and a protection device connected in parallel with an electrical block that includes at least two of the plurality of chain-link modules , the protection device including a plurality of series-connected semiconductor devices , wherein the protection device is adapted to selectively provide a current-conductive path to allow at least part of a current flowing in the electrical apparatus to fully bypass the electrical block ; wherein the protection device is switchable, in use, to a reverse-biased state when at least one chain-link module of the electrical block is configured to provide a non-zero voltage in a non-bypassed mode, and a forward-biased state when all of the chain-link modules of the electrical block are configured to provide a zero voltage in a bypassed mode and the direction of current in the electrical block allows switching of the protection device to a forward-biased state; characterized in that the electrical apparatus further includes a switching control unit , wherein the switching control unit is adapted to control the switching of the chain-link modules of the electrical block to selectively configure at least one chain-link module of the electrical block in the non-bypassed mode so as to maintain the protection device in the reversed-biased state during normal operation of the electrical apparatus . first and second terminals for connection to an electrical circuit; a chain-link converter connected between the first and second terminals , the chain-link converter including a plurality of chain-link modules , each chain-link module including at least one switching element and at least one energy storage device , the switching element and the energy storage device of each chain-link module combining to selectively provide a voltage source; and a protection device connected in parallel with an electrical block that includes at least two of the plurality of chain-link modules , the protection device including a plurality of series-connected semiconductor devices , wherein the protection device is adapted to selectively provide a current-conductive path to allow at least part of a current flowing in the electrical apparatus to fully bypass the electrical block ; wherein the protection device is switchable, in use, to a reverse-biased state when at least one chain-link module of the electrical block is configured to provide a non-zero voltage in a non-bypassed mode, and a forward-biased state when all of the chain-link modules of the electrical block are configured to provide a zero voltage in a bypassed mode and the direction of current in the electrical block allows switching of the protection device to a forward-biased state; characterized in that the electrical apparatus further includes a switching control unit , wherein the switching control unit is adapted to control the switching of the chain-link modules of the electrical block to selectively configure at least one chain-link module of the electrical block in the non-bypassed mode so as to maintain the protection device in the reversed-biased state during normal operation of the electrical apparatus . <EOS>