Overcurrent protective devices protect the circuit conductors in two ways. They protect the conductors from overload conditions and from short-circuit or ground-fault conditions. If you put too much of a load on the circuit, the overcurrent device will open.
What is the purpose of overcurrent protection?
Overcurrent protection devices are meant to protect against the potentially dangerous effects of overcurrents, such as an overload current or a short-circuit current, which creates a fault current.
Do you need overcurrent protection?
Circuit overcurrent protection is a vital part of every electric circuit. Electric circuits can be damaged or even destroyed if their voltage and current levels exceed the safe levels they are designed for. In general, fuses and circuit breakers are designed to protect personnel, conductors, and equipment.
Why is electrical protective devices are important?
Why are circuit protective devices important? Protective devices are important because they ensure that under fault conditions, a high fault current cannot flow – as well as protecting the installation this, more importantly, ensures that consumers are not injured or killed as a result of an electrical fault.
Why do we need to protect the distribution lines?
Protection on the transmission and distribution system serves two functions: protection of plant and protection of the public (including employees). At a basic level, protection disconnects equipment which experiences an overload or a short to earth.
Why is important not to undersize or oversize a overcurrent protection?
Undersize your overcurrent protective device (OCPD), and normal operations might become impossible. Oversize your OCPD, and the whole place might burn down. … Once you do them for the OCPD, you can reuse the results for the conductors.
Why does overcurrent occur?
An overcurrent occurs when the current exceeds the rated amperage capacity of that circuit or of the connected equipment (such as an appliance) on that circuit. An overcurrent can be caused by overloading the circuit or by a short circuit, a ground fault, or an arc fault.
Do all motors need overload protection?
The NEC electrical code requires thermal overload protection on all motors 1/3 HP and above because circuit breakers and fuses have to be oversized so much to allow for the motor startup current, which is about 6 times the full-load running current.
Why is overload protection needed in motor?
When the motor draws excess current, it is referred to as an overload. This may cause overheating of the motor and damage the windings of the motor. … Overload relays protect the motor, motor branch circuit, and motor branch circuit components from excessive heat from the overload condition.
What is the purpose of the protection system?
Primary function of the protective system is to detect and isolate all failed or faulted components as quickly as possible, thereby minimizing the disruption to the remainder of the electric system.
What are the requirement of protection of lines?
The high level factors influencing line protection include:
- The criticality of the line (in terms of load transfer and system stability),
- Fault clearing time requirements for system stability,
- Line length,
- The system feeding the line,
What are the basic requirements of line protection?
The protection scheme must satisfy the following requirements: a) Under normal conditions the breakers are not tripped. b) Under fault conditions only the breakers closest to the fault on the source side are tripped. c) If the closest breaker fails to operate, the next breaker closer to the source should trip.