An LED lamp arrangement adapted for fitting in a luminaire, the luminaire adapted for a fluorescent tube and having a ballast, the LED lamp arrangement comprising: a plurality of LEDs (25, 26, 27); two or more electrodes for releasably connecting to the luminaire and for receiving a current from a ballast for supply to the plurality of LEDs (25, 26, 27); a sensor circuit adapted to measure one or more parameters representing the current received from the ballast in a first operation mode; and a protection circuit electrically connected to at least one of the electrodes and in series with the plurality of LEDs (25,26,27), wherein the LED lamp arrangement is arranged to operate in a plurality of operation modes, including the first operation mode and a second operation mode, wherein current from the ballast is conducted through the LEDs (25, 26, 27) in each operation mode, wherein the protection circuit is adapted to control the amount of current drawn from the ballast by the LED lamp arrangement by automatically switching from the first operation mode to the second operation mode in reaction to the sensor circuit, if the measured one or more parameters exceed a threshold which indicates whether the ballast is a constant current ballast or a constant power ballast; and wherein the protection circuit comprises an impedance (16, 16a, 16b) comprising an inductor or transformer, and the LED lamp arrangement comprises means for changing a circuit configuration of the protection circuit, such that different components of the protection circuit are interconnected differently in different operation modes, such that in the first operation mode, the LED lamp arrangement has a lowest load impedance among the plurality of operation modes. a plurality of LEDs (25, 26, 27); two or more electrodes for releasably connecting to the luminaire and for receiving a current from a ballast for supply to the plurality of LEDs (25, 26, 27); a sensor circuit adapted to measure one or more parameters representing the current received from the ballast in a first operation mode; and a protection circuit electrically connected to at least one of the electrodes and in series with the plurality of LEDs (25,26,27), wherein the LED lamp arrangement is arranged to operate in a plurality of operation modes, including the first operation mode and a second operation mode, wherein current from the ballast is conducted through the LEDs (25, 26, 27) in each operation mode, wherein the protection circuit is adapted to control the amount of current drawn from the ballast by the LED lamp arrangement by automatically switching from the first operation mode to the second operation mode in reaction to the sensor circuit, if the measured one or more parameters exceed a threshold which indicates whether the ballast is a constant current ballast or a constant power ballast; and wherein the protection circuit comprises an impedance (16, 16a, 16b) comprising an inductor or transformer, and the LED lamp arrangement comprises means for changing a circuit configuration of the protection circuit, such that different components of the protection circuit are interconnected differently in different operation modes, such that in the first operation mode, the LED lamp arrangement has a lowest load impedance among the plurality of operation modes.