0
A reverse current relay senses Power in (uses both voltage and current, and looks at the phase angle between these), and operates if power is flowing in the reverse direction, and the current is above a set point. An overcurrent relay looks at only current, and operates if it is above a set point regardless of power flow direction. Reverse current relays are often referred to as reverse power relays.
it is the short circuit condition.it is provided by using circuit breakers and relays.
AnswerAn overcurrent is either an overload current or a short-circuit current. Overload currents occur when the load draws more current than the circuit is designed to handle on a continuous basis. Short-circuits occur when the line and neutral or the line and earth (ground) conductors make accidental contact. Overcurrent protection is provided by using either a fuse or a circuit breaker.
A circuit can be protected from current overload with the help of circuit breakers. A high load can be carried by them without excessive heating.
A breaker or fuse with an appropriate current and voltage rating.
Add your answer:
Earn +20 pts
What are electrical fuses?
Safety devices used in electrical circuits.AnswerA fuse is an overcurrent protection device, and will operate in the event of a sustained overload current or a short-circuit current.
Difference between overcurrent relay and fuse?
Current is flow of electricity charge. Voltage is a measure of potential energy or charge. Fuse. Is a device that opens when the current rating is exceeded this stopping the flow of current.
Why Normal time-overcurrent relays are not adequate for generator backup protection?
Setting the time-overcurrent relays high enough to prevent tripping for normal overloads may result in them not tripping at all due to the decaying characteristic of the generator fault current. Using the system voltage to control the overcurrent characteristic resolves this problem, since the voltage should drop very little for overloads, but will collapse to a small value for external faults. The 51V protection function uses the system voltage to adapt the operation of a time overcurrent element, using either voltage-restraint (51VR) or voltage-control (51VC).
What is the difference between over current and overload condition?
The term, 'overcurrent', describes either an 'overload current' or a 'short-circuit current'.An 'overload current' is a current that is higher than a circuit's 'rated current'. For example, if you have too many loads plugged into the same circuit, then the resulting current is an 'overload current'.A 'short-circuit current' is a large current resulting when a line ('hot') conductor accidentally makes contact with either a neutral conductor or an earth (ground) conductor.
What is produced first current or voltage?
current flows as a result of potential difference i.e. in a circuit if there is no voltage difference between two points, no current can flow between those two points. So voltage has to be produced first.
What is the difference between overload and overcurrent?
Overload occurs when a circuit is drawing more current than its designed capacity, leading to overheating and potential damage. Overcurrent, on the other hand, refers to any situation where current flow exceeds the rated value of the circuit or equipment, which can result from overload or other faults like short circuits.
What does OPD mean in electric terms?
'Overcurrent protection devices' are used to protect conductors from excessive current flow... a fuse
What is over current protaction?
'Overcurrent protection' is a means of protecting a cable and its load from damage due to an overcurrent. An 'overcurrent' is defined as either an 'overload current' (due to an excessive load) or a 'short-circuit current'. In its simplest form, overcurrent protection is provided by means of a fuse, but it can also be provided by means of a circuit breaker. In the case of high-voltage systems, the circuit breaker is tripped by the operation of one or more overcurrent protection relays which monitor the circuit using current transformers.
What is the difference between voltage restrained overcurrent protection and voltage controlled overcurrent protection?
The voltage-restrained overcurrent relay adjusts the pickup setting and characteristic curve of the overcurrent function based on the system voltage. The relay is set pickup greater than overload, and sensitivity increases as the voltage drops. The voltage-controlled overcurrent relay uses an undervoltage element to supervise the operation of the overcurrent element. When the voltage drops below a predetermined level, the undervoltage element permits the operation of the time overcurrent units. Voltage-restrained overcurrent relays can provide faster backup protection than voltagecontrolled overcurrent relays, particularly in cases where the generator voltage does not drop significantly below rated voltage during fault conditions. If the generator voltage always drops below a given voltage level for all faults in which operation is required, the voltage-controlled overcurrent unit may be set to provide faster overall clearing speed
Can a numerical relay give protevtion to over current over voltage and short circuit current at the same time?
Yes. Most microprocessor based relays that have both voltage and current inputs can provide overcurrent and over voltage protection simultaneously. Short circuit current is the same as overcurrent.
A fuse has low melting point why?
This is necessary because a fuse is a protection against an overcurrent; excessive current produce melting.
What is meant by residual overcurren?
Residual overcurrent protection is often provided in modern microprocessor based relays that have three phase inputs, and no neutral input. Sometimes this is provided even if a neutral input is present. It is similar to neutral overcurrent, where the neutral current is directly measured through the neutral input of the relay. for residual overcurrent, the three phase currents are vectorially summed together to form the residual overcurrent. This relay measured 3I0 current, or ground current.
What are electrical fuses?
Safety devices used in electrical circuits.AnswerA fuse is an overcurrent protection device, and will operate in the event of a sustained overload current or a short-circuit current.
What are the functions of an electrical circuit beaker?
A: Its function is to trip if the current across it coil is its tripping pointAnswerA circuit breaker is an overcurrent protection device which can break a fault current.
What is Over Current fault?
An overcurrent fault occurs when the current flowing through a circuit exceeds its rated capacity, leading to potential damage to the equipment or risk of fire. This can be caused by short circuits, overload conditions, or faulty equipment. Overcurrent protection devices such as fuses or circuit breakers are used to prevent damage in such scenarios.
Difference between overcurrent relay and fuse?
Current is flow of electricity charge. Voltage is a measure of potential energy or charge. Fuse. Is a device that opens when the current rating is exceeded this stopping the flow of current.
Do you choose a breaker for wire or equipment protection?
A breaker is typically chosen for wire protection. It is selected based on the ampacity of the wire to prevent overheating and potential fire hazards. Equipment protection is usually handled by fuses or specialized circuit breakers that are designed to protect specific equipment from damage due to overcurrent or short circuits.
