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GFI's (Ground Fault Interruptors) measure the difference between the hot conductor current and the neutral current. In a normal (no fault) circuit, every single milliamp of current flowing out of the hot should return through the neutral. In other words, the two currents should be equal. If there is a ground fault, at least some of the current flows from the hot. through the fault path, to ground. In this case the neutral current is less than the hot current by however much is flowing to ground. The GFI senses this difference and trips, opening the circuit. GFI's are designed to protect equipment from damage and trip at around 30 ma. of differential current. GFCI receptacles (Ground Fault Circuit Interruptors) like the ones you might find in your bathroom, and GFCI circuit breakers are designed to protect people, and trip much lower, around 5 ma.
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BlakeIn generally, protection for ground faults. There are some outlets that include ground fault protection. These use small current Transformers to compare the current on the two power wires - this current should always sum to zero. Under a ground fault condition, current will flow out one of these, and into ground. Since the other wire never sees this current, an imballance between the two appears, resulting in the ground fault protection circuitry openning the circuit.
When an electrical circuit is working correctly the current is carried in the live and neutral wires, and there is no current in the earth wire. Therefore a current in the ground wire indicates a fault that could be dangerous, and the circuit breaker is designed to cut the supply off. In the UK this device is called an Earth Leakage Circuit Breaker (ELCB).
Answer
Under normal conditions, the current supplied to the load through the line conductor is identical to the current returned to the supply through the neutral conductor. A GFI monitors these currents and, when there is any imbalance the device trips. The imbalance is due to a ground fault. GFIs are designed to protect users, rather than the circuit or the load and operate faster than circuit breakers.
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In relation to electric what does the term fault protection mean?
Protective devices - relays, CT,PT, isolators, circuit breakers are used for fault protection. Fault protection means If there is a fault in the circuit, the circuit must be cut off before any damage occurs due to fault.
Is a ground fault protection for equipment required even if the neutral will not be used?
Yes, ground fault protection for equipment is requiredeven if the neutral will not be used.However, the question implies that it might not be required if there is a neutral. That is not true. With two exceptions, ground fault protection is always required in the US, and it is probably required in other countries as well.The exceptions are the use of an electric cooking range, and an electric clothes dryer. In those cases, the US NEC allows the neutral conductor to also be the ground fault conductor, except for the case where the range or dryer is in a mobile home. In the case of the mobile home, the ground fault conductor and the neutral conductor must be maintained separate and distinct all the way back to the distribution panel.In every other case, including where local code overrides the US NEC's exceptions, it must be understood that ground fault protection (protective earth ground) is not the same as neutral, even though the neutral conductor is grounded.
How can you have a ground fault protection in a 3 phase 3W system?
3 phase ground fault detection on a 3 phase system requires that the vector summation of all three phase currents be measured. The vector sum of these currents should equal zero, or nearly zero for a balanced system. If a ground fault exists, then the vector sum will not equal zero. This condition must be validated using i2t techniques in order to eliminate false trips.
In 3 pH Delta motor connection the upstream ACB is tripping due to ground fault protection while motor starts with soft starter why?
Check the earth fault trip off set limit of the ACB. It may be too low.
The device used to deenergize circuits automatically when a very small ground-fault flows is the?
Ground Fault Circuit Interrupter (GFCI).
