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How do you calculate internal fault loop impedance?
by calculating the loop current
What minimum current will activate a ground fault circuit interrupter?
30 mAmp rating devices are commercially available.
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.
How to calculate fault current for transformer?
The fault current of a power transformer will depend on the following; Transformer Rating (in KVA/MVA) per unit impedence of the transformer (%p.u.) line/phase Voltage (VL/VP) the following formula can be used to find the fault current on the secondary side of a transformer Fault Current = Transformer Rating /(per unit impedance x phase voltage) The Values of Transformer Rating, per unit impedance & phase/line voltage will usually be mentioned on the transformer rating plate / data sheet As an example a 500kVA, 11kV/400V/3-Phase/50Hz transformer with 5% p.u impendence will have the following fault levels on the secondary side Fault level = 500/(5%)=10000kVA S=1.732 * VPP * IP Fault current = 500/(5% x 400 x 1.732) = 14.4 kA Remember to use 3phase voltage!
How do you claculate thee Earth fault current level at different different voltage level?
T calculate the fault current level at different voltage levels with the formula F = V / sqrt(P) / ((L x R / 1000) ^ 2 + (L x X / 1000 + V / (A x sqrt(P))) ^ 2) ^ 0.5 + 4 x M + 5 x N. The letter V is the circuit voltage, P is the number of phases, L is distance from the source feeder to point of interest, R is resistance of feeder, A is available fault current, M is total fault current contribution of induction motors, and N is total fault current contribution of synchronous motors.
How do you calculate maximum earth fault current?
transformer max earth fault current
Can all circuit breakers interrupt large fault currents?
All Circuit Breakers have a current rating and a FAULT current rating. The current rating refers to the current at which the circuit breaker is designed to 'break' the circuit and this is generally shown in Amperes (A). FAULT current rating is generally alot higher rating and is therefor shown in kilo Amperes (kA). This kA rating refers to the amount of current which a circuit breaker is designed to handle under fault conditions and can still maintain operation and 'break' contact. Most household circuit breakers are around 7.5 kA, so any fault over 7,500 Amperes could potentially damage the circuit breaker contacts to the point which it can not open the circuit. Larger fault ratings are found in larger applications such as MCC's on plants, minesites or power stations.
How do you calculate internal fault loop impedance?
by calculating the loop current
What is the determining factor in setting the current rating of distribution equipment?
Temperature rise and fault levels.
How do you calculate earth fault current value by knowing the setting in electromagnetic relay?
trh
What minimum current will activate a ground fault circuit interrupter?
30 mAmp rating devices are commercially available.
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 are the functions of switches and fuses?
A switch is a mechanical device for controlling the flow of current in a circuit, switching the current either on or off. A fuse is designed to melt safely when a current exceeding its maximum current rating passes through it, thus protecting the service wiring supplying power to the connected load. For example, if the connected load develops a fault which causes a high short-circuit current to flow in the service wires, if there's no fuse to break the flow of current then the service wires would get very hot and could cause a home fire.
Why ELCB are measured in terms of milliampere. how will we measure the capacity required for any application. how do we calculate it?
ELCB's are "earth leakage circuit breakers". They are used in situations where high impedance grounding is used, meaning a phase to ground fault has very low current levels. This results in standard overcurrent/breaker protection not necessarily "seeing" the fault. And I do not believe ELCBs are usually rated in milliamperes. Their interrupting rating, and load is usually similar to MCCBs. They include a leakage current rating, which is in mA (leakage current is current to ground). You calculate how much ground current you will have from a fault study. If you are intentially high impedance grounding (such as for a generator), then you should know the value of impedance you are using, and this value is usually chosen to limit ground current to a specific current (such as 5 amps). If you are high impedance grounded for some other reason, you need to determine the impedance to ground (the best method to do so will depend on your situation); once you know this, you also know your normal line to ground voltage, and expected current flow is a simple calculation.
Is a foot fault a service fout?
yes it is a service fault
What are the causes of fire on MCB?
loose screws or corroded cables or over current above breakers rating (faulty breaker not tripping when meant to) internal fault with breaker.
What is the reason for using a 10kA breaker rather than a 6kA in simplest possible way possibly with an example?
Breakers are designed to open when there is too much current. For instance, if you have a 100A breaker and you put a 120A load on it, it trips.But what if you drop a wrench or piece of pipe across the wires? Much more than 100A will flow, usually thousands of amps. This is fault current. If the current is too high, the breaker can weld itself closed and fail to trip. This would be very bad.So, breakers have an interrupt rating. It indicates how much fault current the breaker can safely handle and still operate properly. Your 6000A or 10000A is the interrupt rating.You would need a 10000A breaker instead of a 6000A breaker if the fault current could be in excess of 6000A, but less than 10000A.How much fault current can flow in a given situation? It depends on how heavy-duty the utility distribution transformer is, and how big the supply wires are. The utility company can usually supply the information which an electrical engineer can use to calculate the interrupt rating needed. The whole panel, not just the breaker, must carry the same or higher interrupt rating.
