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How can you have a ground fault protection in a 3 phase 3W system?
Wiki User
∙ 15y ago
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.
Wiki User
∙ 15y ago
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Why short circuit and accidental ground is the most dangerous faults?
These are the most dangerous faults because you will be dealing with very high fault levels. Phase to phase will have very little to limit the impedance of the fault current. And phase to ground faults can be high since most systems are solidly grounded. Arching faults and faults through an impedance will be lower and cause less electrical and mechanical stress on the system.
What is grounding - grounded - neutral?
A) If low resistance configuration is chosen, then, ground fault current is greater than 25% of 3-phase value. B) If high resistance configuration is chosen, then, ground fault current is between 1 to 5% of 3-phase value. C) Ground fault protection scheme is important because affects resistor thermal rating, hence size. D) For B) above, ground fault current must not be less than system charging current produced by phase to ground capacitance in 11 kV system. E) For D) above, total capacitance calculation must include line to ground capacitance of cables, motors, transformers, and (often forgotten) surge protection capacitors, as well as lightning arrestors. shirish prajapati
How do you calculate 3 phase earth fault loop?
You can't have a three phase earth fault, you can have a phase to phase or a phase to earth fault. If you want the potential phase to earth fault current it will be your voltage times your impedance. If you want the phase to phase potential fault current then you should just double the above result.
What is neutral to ground fault?
Neutral, by definition, is grounded at the distribution panel, and also at the distribution pole. That is how the hot to ground voltages are prevented from exceeding their normal voltage and encroaching on truly lethal voltages, such as 7.6kV in a typical US 13.2kV system, in a wye configuration.Note: and this is critical, do not depend on the fact that neutral is grounded and consider that it is the same as protective earth ground. It is not. Protective earth ground is a different wire.
What is neutral negetive sequence current?
Negative sequence current is defined as 3I2 = (phase 1)*(1angle 0) + (phase 2)*(1angle 240) + (phase 3)*(1angle 120) Negative sequence current is seen in three phase power systems due to natural system imbalance. Also during unbalanced fault conditions such as line to line, Line to ground, and line to line to ground faults. It is not seen in purely balanced three phase faults.
What is residual earth fault protection?
Earth fault protection is protection based on ground, or zero sequence current. If current is coming up from the ground (or going down to the ground), this protection should operate. Residual usually refers to 3*I0, which is the same as the ground current, and is the vector sum of the current in all three phases. This can be measured by connected all three phase CTs in wye, and placing a single phase overcurrent relay in the wye path to ground.
What is a disconnect installation fault?
I have never heard a fault type referred to as a "disconnect installation fault". In general there are a few types of faults - phase to ground or ground faults, phase to phase, phase to phase to ground, three phase, and three phase to ground. I'm guessing what you're referring to is a fault on a disconnect switch. Disconnects are used to isolate equipment. When a disconnect faults, it usually faults to ground.
What sort of protection scheme do you suggest for the protection of a 10 HP motor?
1)Instantaneous overcurrent protection. 2.Ground fault protection. 3.Thermal overload protection. 4.Stalling Protection. 5.Phase unbalance protection.
What is phase to ground fault?
There will a only one phase on home electricity.AnswerThere is no such thing as a phase-to-phase-to-ground fault'; the correct term is 'line-to-line-to-ground fault. It occurs when two or more line conductors make contact with each other and to ground; for example, when a JCB accidentally cuts through a three-phase cable.
How is a IDMT relay used to give protection against a phase to earth fault a phase to phase fault on a feeder?
As with any IDMT relay the higher the fault current the quicker the trip time.
What is the difference between balanced earth fault and restricted earth fault?
There is such a thing as a three phase to earth fault, so maybe this is what you mean by a "balanced earth fault". I don't believe any earth or ground currents would flow in this case. A restricted earth fault is a typical phase to earth fault, where the zone of protection is restricted to a specific area, such as around a transformer. "Restricted" is referring to the protection method, not what is actually going on with the currents and voltages.
What is the Y in 480Y voltage?
The Wye (also know as Star - especially in the motor rewind industry) is a 4-wire system which provides two different supply voltages. The center-point of the Wye is the system neutral and is usually solidly grounded. Where it is desirable to limit the phase-to-ground fault magnitude the center-point of the Wye may be connected to ground through and neutral grounding resistor or a current limiting reactor. Because the system is tied to ground it is easy to provide system ground fault protection. Three-phase loads can be connected phase-to-phase and singlephase loads can be connected from any phase to the system neutral. On a wye system, the phase unbalance currentis carried by the system neutral. On a Wye system the line current is equal to the phase current i.e. ( ILine 1 = IPhase A) and the line-to-line voltage is equal to the vector sum of two individual phase voltages i.e. (E Line1-2 = E PhaseA + E PhaseB' ). In a Wye system the phase-to-phase voltage is 1.732 x the phase-to-ground voltage. Some typical Wye system voltages are: 120/208Y, 277/480Y, 2400/4160Y, 4160/7200Y, 7200/12470Y, 7620/13200Y,and 19920/34500Y
Explain the open delta fault in the power system.what is the use of the protection.?
There some kind of relays that need measure zero sequence voltage. For instance: - To polarize a phase-to-neutral distance relay - To detect a fault-to-ground in a system grounded by thre-phase generator with star connection. A TP in a star-open delta connection can provide a 3V0 information.
What are the types of faults in ehv transmission lines?
The three types are Line to ground faults line to line fault double line to ground fault three phase line to ground fault
Which is most severe fault in power system?
Three phase fault is the most severe.
Short circuit bar on the railway?
What is the question? Assuming you're talking about short circuiting the live circuit, as soon as a phase to ground fault occurs protection will operate, opening a circuit breaker.
Which phase of a three phase system should current transformer be installed?
current transformers used for relaying and metering purposes should ideally be installed on all three phases. For specific purposes, you may only use CT's on two phases, such as when implementing certain types of ground relaying, but even in this instance three phase CT's are necessary for phase to phase fault protection. I know it is sometimes a utility practice to only meter off of two phases, as long as system voltages and currents are well balanced.
