0
An earth-fault loop is the path taken by the fault current, when an earth-fault occurs within an electrical installation, and comprises a series circuit made up of
- the utility company tranformer's low-voltage winding,
- the utility company's distribution cable's line conductor,
- the consumer's line conductor to the point of an earth fault,
- the consumer's earthing conductor,
- and the resistance of the earth path back to the transformer.
The combined opposition of this series circuit to the flow of fault current is termed the earth-fault loop impedance, expressed in ohms.
Still curious? Ask our experts.
Chat with our AI personalities
Rene
Beau
Ross
Add your answer:
Earn +20 pts
How do you calculate internal fault loop impedance?
by calculating the loop current
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 do you do a earth loop impedance calculation?
The earth-fault loop includes the consumer's line conductor, the consumer's protective conductor, and the earth parth external to the consumer's installation (including the low-voltage winding of the transformer, the distribution line conductors to the installation, and the earth return path.The purpose of this test is to measure the actual value of the earth-fault loop impedance and to confirm that its value complies with the tabulated maximum values listed in BS 7671:2008 Regulations for Electrical Installations, Tables 41.2 - 41.5. The value must be low enough to enable sufficient fault current to flow to cause any overcurrent protection device to operate within the periods specified -i.e. 0.4 s for circuits supplying socket outlets and fixed equipment in bathrooms, and 5.0 s for circuits supplying fixed equipment.The theory behind the test is as follows. With no current flowing around the loop, there are no voltage drops and, so, the transformer's full open-circuit voltage (U1) will appear between the line and protective conductors at the point where the test is conducted.A simulated earth fault is then applied, by inserting a current-limiting resistor between the line and protective conductors. The resulting fault current (IF) is then measured, together with the voltage drop (U2) across the limiting resistor. The duration of this fault should not be allowed to exceed two cycles (40 ms at 50 Hz) to avoid damaging the circuit.The earth-fault loop impedance is then calculated by dividing the difference between the two voltages (U2 - U1) by the resulting fault current (IF), which will give the impedance of the complete loop (including the limiting resistor), from which we must then subtract the value of the limiting resistor.As the simulated earth fault must not exceed 2 cycles, this (theoretical) test obviously cannot be conducted with a voltmeter and an ammeter, and so it is conducted with a commercial instrument, called an earth-fault loop tester, which performs all the measurements (U1, U2, IF), makes all necessary calculations, and provides an digital readout directly in ohms -while, at the same time limiting the duration of the test to less than 40 ms.Before conducting the test, the continuity of the protective conductors must have been confirmed. If the test was to be performed with a break in the protective conductor, then the protective conductor up to the point of that break would represent a safety hazard to anyone in contact with equipment at the time.
How does line earth loop tester find Impedance of Supply System?
OK, well Earth Loop Tester have a permanent magnet in it. When we rotate it, the flux cut the the conductor and consequently an emf is produced. As we connect the two point of the tester to the earth it complete the circuit and current start flowing through it. The ratio of voltage and current give us the Impedance of Earth.
Input impedance of current shunt feedback amplifier?
The input impedance of a current shunt feedback amplifier is the open loop impedance of the amplifier divided by 1+(A*beta)
