4.0
Result and Analysis
After the simulation and
hardware testing, the development of an automatic re-closed Earth Leakage
Circuit Breaker has been done and completely functioned as the simulation. The
prototype of Auto-ELCB that can detect the temporary and permanent fault also
can automatically re-closed the circuit breaker if the temporary fault happens.
The board of Auto ELCB is
powered from the three phase supply and all of the six relay coils obtained DC
voltage and their common point was disconnected from the NC and later moves on
to the NO points by providing logic high at pin 2 of 555 timer U1. During any
of the push button across the relay is been pressed, it disconnects the relay
and in the process, in common contacts moves to the NC position to provide a
logic low to trigger the 555 timer pin. This is to develop an output that
brings the U3 555 timer which is used in astable mode to reset the pin to high.
The astable operation takes place at its output which is also indicated by
flashing D11 LED. (by referring to schematic diagram)
If the push button pressed is
released immediately a temporary fault is created. The 555 Timer detect low
voltage in a short period of time so that the monostable mode could be set and the
astable mode could be disabled. The current would deactivate the 3co relay to
cut the current from supply to the lamp when the button is pressed. However,
after a few second the 555 timer will restart and reactivate the 3co relay so that
the lamp started to operate once again.
If the push button is
pressed longer than 5 second the 555 timer will activate the astable mode and
deactivate the 3co relay permanently. The output which charges the capacitor
C13 through R11 produced the output of the comparator would goes high and
drives the relay to switch off the three phase load so that the lamp will not operate
until the device is reset again.
Figure
15 : Hardware of the project
The output of Op-amp remains high indefinitely
through a positive feedback provided for its pin 1 to pin 3 through a forward
biased diode and a resistor in series. This result in the relay as it will
permanently switch on to disconnect the load connected at its NC contacts. In
order to maintain the flow of DC supply, the star connected secondary set are
parallel through D8, D9 & D10 for an uninterrupted supply to the circuit with
the voltage of 12v DC and 5v DC that were derived out of voltage regulator IC
7805. Figure 15 shows the hardware of the project.
4.1
Hardware Testing
4.1.1 CONTINUITY
TEST:
In electronics,
a continuity test is the
checking of an electric circuit to see if current flows in a complete circuit. A continuity test is
performed by placing a small voltage wired in series with an LED or
noise-producing component such as a piezoelectric speaker across the chosen path.
If electron flow is inhibited by broken conductors, damaged components, or
excessive resistance, the circuit is “open”.
Devices that can be used to
perform continuity tests is multi meter which it could measure current and
specialized in continuity test. The multi meter are cheaper and have more basic
devices. Generally the light bulb would lights up when there is current flows.
An important application is the continuity test of a bundle of wires in order to
find the two ends belonging to a particular one of these wires.
Figure 16 : Continuity Test
For example of the continuity
test is to put one of the multi meter rod at point A and another one at point
B, if the point is connect with each other the beep sound will be heard. This
test is performed just after the hardware soldering and configuration has been
completed. This test aims to find any electrical open paths in the circuit
after the soldering. Most of the times, the electrical continuity in the
circuit is lost due to improper soldering, wrong and rough handling of the PCB,
improper usage of the soldering iron, component failures and presence of bugs
in the circuit diagram. Multimeter was used to perform this test and the
multimeter knob is switch in buzzer mode and connects the ground terminal of the
multimeter to the ground. Then connect both the terminals across the path that
needs to be checked. Figure 16 shows the continuity test of the PCB.
4.1.2 TESTING AND TROUBLESHOOTING:
This test is performed to check
whether the voltage at different terminals is according to the requirement or
not. Multimeter is used and it is switched to the voltage mode. This test is
performed without the IC. Firstly, the output of the transformer was checked
and 12V AC should be obtained.
FIGURE 16 : Hardware in normal mode
Then the voltage was supplied
to the power supply circuit and this test was performed without IC. This is to
avoid the IC from been damage due to the occurrence of any excessive voltage. The
attendance of voltage regulator in the circuit need to be rechecked both at the
input to the voltage is 12V and the required output which is 5V. Figure 16
shows the hardware in normal mode.
The mentioned output from the
voltage regulator is given to the power supply pin of specific IC. Hence, the
voltage level at those pins needs to be checked whether it obtained required
voltage. Similarly, for the other terminals for the required voltage need to be
checked. This can assure that the voltage at all the terminals is as per
requirement.
4.2
BENEFIT AND CONTRIBUTION
In Malaysia it is common, the faults that might occur
could be LG (Line to Ground), LL (Line to Line), 3L (Three lines) in the supply
systems and these faults that were in three phase supply system can affect the
power system. To overcome this problem, a system was built where it can sense
these faults and automatically disconnects the supply to avoid large scale
damage to the control gears in the grid sub-stations. After fault happened,
Automatic Earth Leakage Circuit Breaker (Auto-ELCB) will automatically open due
to the occurrence of temporary fault. After the fault has been distinguished,
the power will be supplied continuously to consumer. Alarm system in most houses also can activate
continuously to guard the house and prevent from the thief while owner is not
at home.
Auto-ELCB also has advantages where it is less sensitive to
fault conditions, and therefore have fewer nuisance trips. (This does not mean it
always do, as practical performance depends on installation details and the
discrimination enhancing filtering in the ELCB). Therefore by electrically
separating cable armor from the cable circuit protective conductor, an ELCB can
be arranged to protect against cable damage only and not trip on faults in down
line installations.
5.0
CONCLUSION AND RECOMMENDATION
This project is designed in the form of hardware
for three single phase transformers 230v to 12V of output. This project purpose
is to develop an automatic tripping
mechanism for the three phase supply
system during the occurrence of temporary fault and permanent fault. The 555 timer
is used with relay for the temporary or permanent fault and the hardware is
built after simulation testing.
Development of
Auto ELCB prototype is a success and the result of the prototype is similar
with the simulation which if the push button pressed and released
it immediately, a temporary fault is created. The 555 Timer detects low voltage
in a short period of time so it would set a monostable mode and disable the
astable mode. During the button being pressed, the current deactivate the 3co
relay to cut the current from supply to the lamp but after a few second the 555
timer will restart and activate the 3co relay again so that the lamp start to function
again. However, if the push button is pressed longer than 5 second, the 555
timer will activate the astable mode and deactivate the 3co relay permanently.
The output which charges capacitor C13 through R11 will cause the output of the
comparator goes high and drives the relay to switch off the three phase load so
that the lamp will not on until the device is reset again.
From this project, the upgraded circuit
breaker instruments from conventional Earth Leakage Circuit Breaker (ELCB) has
been created and it is safer to human instead of to protect them from
electrical danger. The Automatic Earth Leakage Circuit Breaker (Auto-ELCB) also can be used in factory with some modifying in
order to make it suitable for the factory based. When the circuit
breaker automatically reclosed after the temporary fault has been extinguished,
the power will be supplied continuously to consumer.
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