Part 8 – Prosumers Installation
| Which of the following statements is false considering protection against overcurrent in PEIs? |
A.
| The selection of overcurrent protective devices must consider the maximum short-circuit current for the setting of the tripping characteristics of the short-circuit protective device |
B.
| The selection of overcurrent protective devices must consider the maximum short-circuit current for the setting of the tripping characteristics of the short-circuit protective device |
C.
| When batteries are connected in parallel with the solar photovoltaic cells, the short-circuit current will be higher |
D.
| The selection of overcurrent protective devices must consider the maximum short-circuit current for the selection of breaking capacity |
The right answer is A.
Explanation:
| A. The purpose of overcurrent protective devices in a protective earthing conductor (PEI) is to protect against overcurrents that could cause damage to the installation, equipment, or pose a safety hazard. The overcurrent protective devices in a PEI are typically fuses or circuit breakers. In order to ensure that the overcurrent protective devices in a PEI operate effectively to protect against short-circuits, the MINIMUM short-circuit current for the circuit must be taken into account. The minimum short-circuit current is the lowest amount of current that could flow through the circuit in the event of a short-circuit. The tripping characteristics of the short-circuit protective device must be set so that it will operate and disconnect the circuit within the required time when the minimum short-circuit current flows through it. This ensures that the overcurrent protective device will operate as intended and clear the fault before any damage or safety hazard occurs. B. Operating mode influences the overcurrent magnitude: The magnitude of overcurrent that can occur in a PEI can vary depending on the operating mode. For example, if a motor is starting up, the initial inrush current may be higher than the normal operating current, and this must be taken into account when selecting overcurrent protective devices. C. When batteries are connected in parallel with the solar photovoltaic cells, the short-circuit current will be higher: When batteries are connected in parallel with solar photovoltaic cells in a PEI, the overall short-circuit current may be higher than when the batteries are not connected in parallel. This is because the batteries can supply additional current in the event of a fault, and this must be taken into account when selecting overcurrent protective devices. D. In order to provide adequate protection against overcurrent in a PEI, the selection of overcurrent protective devices such as circuit breakers or fuses must consider the maximum short-circuit current that can occur in the electrical installation. The maximum short-circuit current is the highest amount of current that can flow through a circuit in the event of a fault, and it is important to ensure that the overcurrent protective device has a sufficient breaking capacity to interrupt this current safely. If the breaking capacity of the protective device is not sufficient for the maximum short-circuit current, it may not be able to interrupt the fault current and protect against the risk of fire or electric shock. This can also lead to damage to the electrical installation or equipment. |
| Reference in the book: 826.1.2 , P364 |