Electrical protection circuit for energy storage unit

An electrical protection circuit for connecting an Energy Storage Unit (ESU) to a main power line, wherein the electrical protection circuit comprising:

• a first main terminal configured to be connected to the main power line;
• a second main terminal configured to be connected to the main power line, wherein the second main terminal is configured for a lower electric potential than the first main terminal;
• a first ESU terminal configured to be connected to a positive terminal of the ESU;
• a second ESU terminal configured to be connected to a negative terminal of the ESU;
• wherein the first main terminal is connected to the first ESU terminal via a first normally closed (NC) switch;
• and
• a first diode with an anode connected to the first main terminal, and a cathode connected to the first ESU terminal, wherein a parallel combination of the first NC switch and the first diode forms a closed path for a charging current and a discharging current flowing between the main power line and the ESU during operation,
• wherein a discharging circuit comprising a resistor in series with a discharging switch, wherein the discharging circuit is connected between the first ESU terminal and the second ESU terminal, wherein the discharging switch is another normally open (NO) switch;
• wherein the discharging switch is configured to be closed thereby to discharge the ESU through the resistor in order to achieve the electrical protection for the ESU;
• wherein the first main terminal is connected to the second main terminal via a normally NO switch and a second diode being connected in parallel with the NO switch with a cathode connected to the first main terminal, and an anode connected to the second main terminal;
• wherein the first NC switch is configured to be opened thereby to disconnect the ESU from the main power line, and the NO switch is configured to be closed thereby to bypass the ESU from the main power line in order to achieve electrical protection for the ESU;
• a second NC switch connected in series with the first NC switch;
• and
• a third NC switch connected in series with the ESU, wherein a combination of the second NC switch and the third NC switch is configured to disconnect the ESU and the discharging circuit from the main power line thereby achieving electrical protection for the ESU, wherein
• the second NC switch is configured to be opened to disconnect the ESU and the discharging circuit from the main power line;
• and
• the third NC switch is configured to be opened after opening of the second NC switch and discharging of the ESU through the resistor, thereby achieving electrical protection for the ESU.