A battery energy storage system, comprising: a battery assembly for storing and providing energy, wherein the battery assembly is rechargeable; a protection system comprising an arc flash protection device (26, 26') for protection against hazards from arc flashes, wherein the arc flash protection device (26, 26') is arranged to sense a battery current (I B) provided by the battery arrangement and to compare it with a predefined maximum current threshold (I Bmax), to sense a voltage (U B) provided by the battery assembly and to compare it with a predefined minimum voltage threshold (U Bmin), and characterized in that the arc flash protection device (26, 26') is arranged to measure a first time duration (t 1) during which the sensed battery current (I B) is greater than the maximum current threshold (I Bmax) and a second time duration (t 2) during which the sensed battery voltage (U B) is smaller than the minimum voltage threshold (U Bmin) and to initiate protective measures to prevent further operation of the battery assembly if the first time duration (t 1) exceeds a first maximum time threshold (T max1) and/or the second time duration (t 2) exceeds a second maximum time threshold (T max2). a battery assembly for storing and providing energy, wherein the battery assembly is rechargeable; a protection system comprising an arc flash protection device (26, 26') for protection against hazards from arc flashes, wherein the arc flash protection device (26, 26') is arranged to sense a battery current (I B) provided by the battery arrangement and to compare it with a predefined maximum current threshold (I Bmax), to sense a voltage (U B) provided by the battery assembly and to compare it with a predefined minimum voltage threshold (U Bmin), and characterized in that the arc flash protection device (26, 26') is arranged to measure a first time duration (t 1) during which the sensed battery current (I B) is greater than the maximum current threshold (I Bmax) and a second time duration (t 2) during which the sensed battery voltage (U B) is smaller than the minimum voltage threshold (U Bmin) and to initiate protective measures to prevent further operation of the battery assembly if the first time duration (t 1) exceeds a first maximum time threshold (T max1) and/or the second time duration (t 2) exceeds a second maximum time threshold (T max2). to sense a battery current (I B) provided by the battery arrangement and to compare it with a predefined maximum current threshold (I Bmax), to sense a voltage (U B) provided by the battery assembly and to compare it with a predefined minimum voltage threshold (U Bmin), and characterized in that the arc flash protection device (26, 26') is arranged to measure a first time duration (t 1) during which the sensed battery current (I B) is greater than the maximum current threshold (I Bmax) and a second time duration (t 2) during which the sensed battery voltage (U B) is smaller than the minimum voltage threshold (U Bmin) and to initiate protective measures to prevent further operation of the battery assembly if the first time duration (t 1) exceeds a first maximum time threshold (T max1) and/or the second time duration (t 2) exceeds a second maximum time threshold (T max2).