Short-Circuit Protection Schemes for LVDC Microgrids Based on the Combination of Hybrid Circuit Breakers and Mechanical Breakers
Table 1
Comparison between different protection schemes.
Method
Speed
Selectivity
Sensitivity
Reliability
Cost
Advantages
Disadvantages
Overcurrent protection
Medium
Low/Medium
Low/Medium
Medium
Low
(1) Simple method (2) No communication link that improves reliability
(1) Vulnerable to noise and other disturbances (2) Requires a communication link to increase selectivity and coordination
Directional overcurrent protection
Medium
High
Low/Medium
Medium
Medium
(1) Applicable for networks with different types of DGs
(1) Requires a communication system to a central processing unit
Derivative fault protection
High
Low
High
Low/Medium
High
(1) Discriminates internal and external faults
(1) The rate of change of current is highly sensitive to fault impedance, and it is difficult to design an appropriate di/dt protection scheme (2) Requires a communication system to a central processing unit (3) Needs fast and accurate data synchronization (4) Requires SSCB to achieve high-speed performances
Differential protection
High
High
High
Medium
Very high
(1) Reduced dependency on the fault impedance and rate of rise of current (2) Not dependent on the current direction
(1) Requires high bandwidth communication link between device terminals (2) Errors with communication link impacts its reliability (3) Unsatisfactory performance in noisy conditions (4) Needs fast and accurate data synchronization (5) Requires SSCB to achieve high-speed performances
Distance protection
Medium
High
Low/Medium
Medium
Medium
(1) Identification of the fault location
(1) More sensitivity to fault resistance (2) Limited accuracy in short lines and for DC systems (3) Requires synchronization between voltage and current measurement
Proposed method
Medium
Medium/High
Medium
High
Low
(1) Simple method (2) Applicable in DC grids with different types of DGs (3) No communication link that improves reliability (4) Can be applied in DC grid with traditional MCBs
(1) Requires the transient disconnection of the sources
