GB2582760A

GB2582760A - Fault current limiter

Info

Publication number: GB2582760A
Application number: GB1904516.0A
Authority: GB
Inventors: Shane Jemmoth Jermaine
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-03-31
Filing date: 2019-03-31
Publication date: 2020-10-07
Also published as: GB201904516D0

Abstract

Fault current limiter limits electrical fault when it occurs either short circuit or open circuit in a high voltage high current line. The earthing resistor 110 which has high resistance ensures very low earth current flow which saves humans life and protects home/factory appliances from being damaged through fire. This device can be used to regulate the fault current to any desired minimum limit that the user wishes to have. The fault current limiter may comprise fuses 101, capacitor 102 in parallel with resistor 103, bridge rectifier 104 and triac 107. The circuit may also use a ferromagnetic instead of a rectifier (see figure 2)

Description

Fault current limiter

Background

The present invention relates to a device to limit ground fault current when an electrical fault occurs.

Electrical fault has high danger to human beings, animals and electrical equipment; electrical fault reduces the lifespan of electrical equipment and insulation. When an electrical fault occurs either short circuit or open circuit in a high voltage line, current flow through the path which has low resistance. Due to low resistance the value of current flowing through the fault line increases rapidly to a very high value 200A to 6000A and above depending on the voltage.

Effect of an electric fault include danger to human being as well as animals, electrical fault can lead to fire and explosion of equipments in building and mega companies, and the high current due to fault causes equipment to overheat which lead to reduction of life span of their insulation.

In order to get extremely low fault current, one will need to increase the resistance of the earth wire. This means that the wire must be thick and long enough to increase the resistance of the wire or use different wires e.g. steel.

To do this kind of earth fault current installation there are means for protection but most of them are very expensive hence only companies have them install into their system.

The present invention of fault current limiter is effective, efficient to lowering fault current to a very low value and cheaper which can help in solving the current problem. The present invention solve the problem of having high fault current (from amp to kA) which is risky to human beings, equipment destruction and fire which occur due to sparks caused by high current. The invention solve the problem by reducing those high fault current to Amps, milliamps or micro amps for example 0.0000054A which is safe to human being, low current cannot destroy equipments, it cannot cause fire in the vicinity.

Finally the present invention reduces the rate of fault current by increasing the earth fault resistance.

Statement of invention

The present invention reduces high earth fault current to very low fault current ( from Amps, milliamps or micro amps) which will have no impact anyone or thing.

Advantages The present invention is to ensure the safety of human beings, animals and electronic equipment.

Preferably, the present invention is cheaper compared to other protection devices.

Preferably, the present invention is efficient (lowers fault current to a very low value) and very reliable.

Introduction to drawings

An example of the invention will now be described by referring to the accompanying Drawings: Figure 1 shows a flowchart to show how the present invention works.

Figure 2 shows a flowchart to show how the present invention works.

Detailed description

The following detailed description is of the best currently contemplated modes of carrying out exemplary embodiments of the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention.

In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present technology. It will be apparent, however, to one skilled in the art that the present technology can be practiced without these specific details. In other instances, structures and devices are shown in block diagram form only in order to avoid obscuring the present technology.

Moreover, although the following description contains many specifics for the purposes of illustration, anyone skilled in the art will appreciate that many variations and/or alterations to said details are within the scope of the present technology.

Similarly, although many of the features of the present technology are described in terms of each other, or in conjunction with each other, one skilled in the art will appreciate that many of these features can be provided independently of other features. Accordingly, this description of the present technology is set forth without any loss of generality to, and without imposing limitations upon, the present technology.

Ground resistance is used to limit ground fault current when an electrical fault occurs. The higher the value of the ground resistance the lower the ground fault current will be and if ground resistance is lower the ground fault current will be high.

This device can basically be used to regulate the fault current to any desire minimum limit that the user wishes to have. The size of the device can be fitted into any wall socket, fitted in any plug or replace circuit breakers.

Testing To test the present invention, we connected a multifunctional tester to test the earth fault current from wall socket. The reading was 240v / 0.8ohm = 300A (earth fault current).

When added the present invention to the wall socket and connect the multifunctional tester, we got different reading for all 4 of the present invention as the following: First prototype: 240v / 250ohm =0.96A (earth fault current).

Second prototype: 240v / 470ohm = 0.5A (earth fault current).

Third prototype: 240v / 50ohm = 4.8A (earth fault current).

Forth prototype: 240v / 44 000 000 000 ohm = 0.000 000 0055A (earth fault current). My multifunctional tester can't give me any reading for this because it's too low.

All the calculations are correct and give the same results that I got from the multifunctional tester. To further support this research and work, we have carried out a secondary test.

The fault current reading is 0.000 000 0055A 240v and to further support our work I use the equation to find the answer (earth fault current = v / r). The input from the wall socket is rated at 250v 13A. We then took the earth wire and attach it to the live wire. This caused a micro spark. We couldn't really see the spark as it was too small unless the lights were off. After we had carried out the test, I have notice that the circuit breakers didn't trip (circuit breakers are rated at 30mah) but the lights came off due to Ov and OA in the line. I then turn off the switch and disconnect the earth wire from the live wire and then turn back on the switch. The lights came on.

Schematic for the invention are in two models L -Live wire, N -Neutral wire, E -Earth wire Figure 1 and 2 have the same components only that figure 2 have ferromagnetic core which have been added, referring to figure 1 and figure 2, the parts and components required for the device are: Figure 1 101 -Fuses Used to cut flow of current by blowing when it's above the rated value 102 -Ceramic capacitor It is used because it can handle high voltage 103 -Resistor The resistor is connected in parallel with the capacitor to ensure safety of the one handling the device 104 -Bridge rectifier Made of 4 diodes to convert AC voltage to DC voltage -Zener diode It is used as a voltage reference for our case its 5V so it is rated 5.1V 106 -Electrolytic capacitor Used to smoothen the output DC voltage because it has ripples 107 -Triac Consist of cathode, anode and gate. Used to connect or disconnect the flow of current between anode and cathode by triggering the gate by supplying 5V through the gate and if the 5V is stopped the connection between anode and cathode is disconnected.

108 -MOC2303 driver It is one of the drivers used to drive the triac 109 -Micro circuit breaker Break the connection to the gate and makes the load not to have any power -Earthing resistor It lowers the fault current to very low value hence ensure safety 111 -Load connection point Where the load is connected Figure 2 201 -Ferromagnetic When the device is powered the power flows to the load but the load does not get powered because the triac gate have not been triggered yet hence no power reaches the neutral connection point of the load, the AC power through the rectifying diode is rectified to 5V DC which is used to trigger the gate hence the load is powered once the gate is triggered.

When fault current occurs, the current goes through the earth wire resistor and at this stage it trips the micro circuit breaker and the triac gate is not powered, hence the connection to the load is not complete.

The main concept of this device to is limit the rate of fault current. This is to protect the home appliances/ factory appliances from damaging. When fault occurs, the fault current becomes more than 10 times than a normal load current, we reduce this sudden rise by increasing the earth fault resistance by following ohm's law.

V

R T

The resistor and micro circuit breaker will be either in every plug, wall socket or replace circuit breakers. A user can choose to either put this on their earth wire at the circuit breaker or anywhere.

Due to high resistance of the earth resistor the current is very low; hence it wouldn't reach the main circuit breaker because the current is below the rating of the CB.

To explain how does the present invention work and referring to Fig. 1, we will start from the left with L that is refer to live wire where the power go to the fuses 101 that is used to cut flow of current by blowing when it's above the rated value then the power go to the ceramic capacitor 102 this type of capacitor is used because it can handle high voltage then they is resistor 103 that is connected in parallel with the capacitor to ensure safety of the one handling the device then the power flow to the bridge rectifier 104 that is made of 4 diodes to convert AC voltage to DC voltage then the Zener diode is used as a voltage reference for our case its 5V so it is rated 5.1V then flow to the electrolytic capacitor 106 that is used to smoothen the output DC voltage because it has ripples, then the power flow to the triac 107 that is consist of cathode, anode and gate, the triac 107 is used to connect or disconnect the flow of current between anode and cathode by triggering the gate by supplying 5V through the gate and if the 5V is stopped the connection between anode and cathode is disconnected, MOC2303 driver 108 is one of the drivers used to drive the triac, micro circuit breaker 109 that break the connection to the gate and makes the load not to have any power supply, when the fault occurs current will flow through the earthing resistor 110, it lowers the fault current to very low value hence ensure safety, then the load connection point 111 where the load is connected.

Referring to Fig. 2, it shows the alternative schematic of the invention, the only difference with fig. 1 is ferromagnetic core 201 have been added to the schematic the phase and neutral conductor winding are around it changing magnetic field is created when current flow through the conductor. The third winding is connected with a relay the changing magnetic field produces current in to the winding which activates the relay and disconnect the circuit.

The foregoing descriptions of specific embodiments of the present technology have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present technology to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present technology and its practical application, to thereby enable others skilled in the art to best utilize the present technology and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present technology.

While several possible embodiments of the disclosure have been described above and illustrated in some cases, it should be interpreted and understood as to have been presented only by way of illustration and example, but not by limitation. Thus, the Breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments.

The above specification provides examples of how certain inventive aspects may be put into practice. It will be appreciated that the inventive aspects can be practiced in other ways than those specifically shown and described herein without departing from the spirit and scope of the inventive aspects of the present disclosure.

Claims

Claims 1. A Fault current limiter device is to limit ground fault current when an electrical fault occurs by reducing high earth fault current to very low fault current which will have no harmful impact humans, buildings, electrical equipments or components.
2. A fault current limiter device as claimed in claim 1 comprises the following components: fuses used to cut flow of current by blowing when it's above the rated value; a ceramic capacitor to handle high voltage; a resistor connected in parallel with the capacitor to ensure safety of the one handling the device; a bridge rectifier made of four diodes to convert AC voltage to DC voltage; a zener diode used as a voltage reference and an electrolytic capacitor used to smooth out the output DC voltage because it has ripples; a triac consist of cathode, anode and gate used to connect or disconnect the flow of current between anode and cathode by triggering the gate by supplying 5V through the gate and if the 5V is stopped the connection between anode and cathode is disconnected; a MOC2303 driver that It is one of the drivers used to drive the triac; a micro circuit breaker to break the connection to the gate and makes the load not to have any power; an earthing resistor to lower the fault current to very low value hence ensure safety; a load connection point where the load is connected; and, a ferromagnetic for schematic option 2.
3. A fault current limiter device as claimed in claim 1 and claim 2 include a method to limit ground fault current when an electrical fault occurs, wherein when the device is powered the power flows to the load but the load does not get powered because the triac gate has not been triggered yet, hence no power reaches the neutral connection point of the load, the AC power through the rectifying diode is rectified to 5V DC which is used to trigger the gate hence the load is powered once the gate is triggered.
4. A fault current limiter device as claimed in claim 3 wherein when fault current occurs, the current goes through the earth wire resistor and at this stage it trips the mini circuit breaker and the triac gate is not powered, hence the connection to the load is disconnected.
5. A fault current limiter device as claimed in claim 3 wherein the device limits the rate of fault current, so that to protect the home appliances, buildings and humans, when fault occurs, the fault current becomes more than 10 times than a normal load current, we reduce this sudden rise by increasing the earth fault resistance by this ohm's law
6. A fault current limiter device as claimed in claim 3 wherein the resistor and mini circuit breaker will be either in every plug, wall socket or replace circuit breaker, the user can choose to put this on the earth wire itself.
7. A fault current limiter device as claimed in claim 3 wherein the device reduces the rate of fault current by increasing the earth fault resistance.
8. A fault current limiter device as claimed in claim 3 wherein the fault current limiter limits electrical fault when it occurs either short circuit or open circuit in a high voltage, high current line, the earthing resistor which has high resistance ensures very low earth current flow which saves humans life and protects home/factory appliances from being damaged through fire, the device can basically be used to regulate the fault current to any desire minimum limit that the user wishes to have.
9. A fault current limiter device as claimed in claim 3 wherein the device reduces the high fault current to amp, milli or micro amps for example 0.0000054A which is safe to human being.
10. A fault current limiter device as claimed in claim 3 wherein the device limits the fault current from 1A, 200A, 300A, and even 18000A to a minimum of = 0.000 000 0057A or less, the device is rated at 600v max, this means it can handle a maximum of 600v, the maximum fuse used is 13A, the device can be redesign to handle any voltage and current rating.
11. A fault current limiter device as claimed in claim 3 wherein the device can basically be used to regulate the fault current to any desire minimum limit that the user wishes to have.