automated electrical protection system for domestic application

Automated Electrical Protection System for

Domestic Application

A.Z.H. Abd Azzis, *Nursyarizal Mohd Nor, Taib Ibrahim * Electrical & Electronic Engineering Department,

Universiti Teknologi PETRONAS,

Bandar Seri Iskandar, 31750 Tronoh,

Perak, Malaysia.

e-mail: nursyarizal_mnor@ petronas.com.my

1 Abstract—Power outage is a common problem when there are

electrical faults occurred, which would lead to discontinuity of

electrical supply to domestic building. For domestic consumers,

power continuity is very important since some of the appliances such

as refrigerator, aquarium and alarm system require a continuous

electrical supply. However, fault occurred in the system will trip the

earth leakage circuit breaker (ELCB) and disrupt the supply to all the

appliances. Fault may occur due to short circuit, ground fault or

overloading. Thus, the aim of this paper is to develop an automatic

system for single-phase power system to overcome the problems. The

automatic system is able to detect and isolate the fault in order to

ensure the power continuity in the building.

Keywords— current difference, earth leakage circuit breaker

(ELCB), fault location detection, miniature circuit breaker (MCB),

power recovery, residual current device (RCD)

I. INTRODUCTION

ower reliability and continuity is very important and

critical to a domestic building. There are electrical

equipments and appliances which need to be continuously

turned ON even when the occupants leave the building for a

period of time such as alarm system, refrigerator and aquarium

ventilation system. However, power outage may occur at any

time due to several causes such as strong lightning, short

circuit, grid faults and etc..

Single-phase is very common system used in domestic. The

term of single-phase electric power system is refers to the

distribution of alternating current (AC) electric power using a

system in which all the voltages of the supply is vary in load

demand [1]. Although single-phase system has its own safety

protection, i.e. earth conductor, but this not an hundred percent

reliable all the time. In Malaysia, from year 2005 to 2011,

there are 405 accidents due to electrical fault event, and 191

people are died due to the accidents [2]. Therefore, instead of

giving awareness on electrical safety and hazard to the public,

a proper protection devices also need to be considered as part

of electrical safety.

In domestic premises, there are three common factors that

cause electrical problems at home that might lead to fatality or

equipment failure [3]. The three common factors are faulty

wiring in the house, improper flexible cords, and faulty

appliance. Technically, the causes of the above factors are

current/earth leakage fault and overcurrent fault. Earth leakage

fault is exists when unintended path is established between the

normal current carrying conductors which has contact directly

or indirectly with earth [4]. Overcurrent fault is occur when

the current exceeds the rated current carrying capacity of the

conductor [5] and can be divided into two types: overload and

short circuit.

In this paper, Section II explains the working principle of

ELCB and MCB. Section III gives details on the system

operation. Section IV presents the materials components

selection and simulation circuit setup. Then, Section V and

Section VI analyse about the result of experimental test and

actual test using designed prototype. Section VII is the

conclusion of this paper.

II. WORKING PRINCIPLE

Overcurrent and ground faults are very common faults to be

occurred in single-phase power system. Protection devices

such as MCB and ELCB or RCD are used to protect from

overcurrent and ground faults respectively.

A. Earth Leakage Circuit Breaker (ELCB)

Basically, there are two types of ELCB: voltage operated

and current operated [6]. Voltage operated ELCB operates at a

detected potential of around 50 V to open a main breaker and

isolate the supply from the protected zones [7]. But since it

operates at 50 V, it is not been used in newer domestic wiring

as the 50 V is still considered as safe voltage for alternating

current [8]. For newer domestic wiring, current operated

ELCB is more preferable to be installed in premises due to

reliability. Current-operated ELCB is generally known as

residual current device (RCD). The function is similar, which

protects against earth leakage, though the details and method

of operation are different [6].

The RCD operates by measuring the current balance

between two conductors using a differential current

transformer, as illustrated in Fig. 1. The difference current

flow from the load and to the load is known as residual current

is measured. The current leakage is occurring when the

residual current is not equal to zero and the device will open

the contacts [9]. The RCD in buildings must be installed with

residual current rating of 30 mA for protection against shock

P

978-1-4673-5074-7/13/$31.00 ©2013 IEEE

2013 IEEE 7th International Power Engineering and Optimization Conference (PEOCO2013), Langkawi, Malaysia. 3-4 June 2013

23

[10]. The RCD will trip if the residual current or the difference

between current flowing in an out exceeds 30 mA.

Fig. 1 Tripping Mechanism of ELCB

B. Miniature Circuit Breaker (MCB)

The MCB is resettable protective device which designed to

isolate a circuit during an overcurrent (both overload and short

circuit) event without using fuse [11]. MCB is choosing for

building protection rather than fuse because of its resettable

capability [12]. MCB typically comprises an electrical contact

mounted on a movable contact carrier which rotates away

from a stationary contact in order to interrupt the current path.

The mechanism of operation includes a movable handle that

extends at the outside of the housing.

The handle has basically three stable positions: on, off, and

tripped. These three positions are to indicate the condition of

the contacts when the handle is viewed. The trip mechanism is

automatically releasable to effect tripping operations and is

manually resettable following tripping operations. The

mechanism will respond to instantaneous high current to open

the contact and therefore interrupt the current flow [12].

III. SYSTEM OPERATION

The automatic system is designed for domestic electrical

system to auto-reset ELCB and auto-detection if any

permanent fault occurred. The system operation is divided

into two parts: power recovery and fault location detection.

A. Power Recovery

Power recovery is a process of turning back the power ON

when electric power encounters unexpected shut down for a

period of time due to tripping or faults. A quick power

recovery is important for equipments or electrical appliances

which require continuous power supply such as refrigerator,

water pump for aquarium, alarm system and others.

Currently, for home electrical system, power recovery is

manually done. In other words, a person has to switch on the

main switch in distribution board to turn the power back on

after tripping occurred. This becomes a problem when the

residents or owner of the house is out for a period of time and

no one is there to turn the power back on.

When fault is occur, ELCB will trip and break the electrical

supply from mains to all feeders (electrical appliances or

loads). An automatic system is needed to switch ON ELCB so

the power supply can be restored. However, if the fault is

permanent, the ELCB will not able to turn ON. Therefore, to

overcome the problem, a system with ability of detecting fault

location need to be developed. Once fault detected and

isolated, ELCB will be switched ON and supply is restored.

B. Fault Location Detection

Domestic electrical fault would normally occur at individual

circuit, either switches or sockets. Electrical fault may occur

due to current leakage or overcurrent condition, such as

overload or high level short circuit, and may occur at any

point in the domestic electric system. Fault location detection

may facilitate the process of power recovery to recover from

unexpected power outage.

To isolate faulty circuit from main line, the location of the

fault must first be identified. This can be done through current

difference between the amount of current travelling into the

load and the current travelling out of the load. Fig. 2 illustrates

a simple domestic electrical wiring diagram, where the current

in live wire (red line) is travelling through ELCB and MCB to

the load. The current then travels out from the load to neutral

bar through neutral wire (black line) and travels back to

ELCB. The amount of current travel in and out is measured

and compared.

Fig. 2 Simple Domestic Electrical Wiring Diagram

The current difference is configured to a 30 mA as the

ELCB trip rating is 30 mA. If the difference exceeds 30 mA,

the system will be able to locate at which MCB is the fault

located. If the difference of any MCBs e.g. MCB 1 exceeds

30 mA, then MCB 1 will be turned OFF and ELCB will reset.

Therefore, the electrical power will be restored since the fault

has been isolated.

IV. COMPONENTS SELECTION AND SIMULATION SETUP

A. Component Selection

There are two main components for this project, the sensor

and microcontroller. The selection of these components is

based on efficiency, cost, size, and the rated values.

1. Current Sensor

It is very important to select an accurate current

sensor in this project. The accuracy of current value

measured by this current sensor will lead to the

accurateness of detecting fault location and fault

isolation from the main line. In general, most home


24

electrical appliances will draw current up to 20 A.

Therefore, a current sensor with rating at least 25 A and

split core for the ease of clamping is chosen in this

project.

2. Arduino UNO Board

The Arduino UNO board is the main microcontroller

board in this project. All calculations and data

collections will be done through this board. This board

is selected based on its friendly-user characteristic,

with ability of receiving analog input data and able to

produce PWM or digital output. This board is different

from other PICs as it can be powered up by using USB

cable connected directly to the PC.

B. Simulation Circuit Setup

A circuit has been setup as in Fig. 3 with two current

sensors (line and neutral) connected to the input of Arduino

board for simulation purpose. The current sensors function to

capture and deliver the current value to the micropocessor.

The program is successfully developed and downloaded to the

Arduino board. The circuit is designed to simulate and observe

the functionality of the developed system.

Fig. 3 Simulation Circuit Setup

In the simulation, the desired hardware (motor, solenoid and

hand phone) used in real prototype is currently represented by

LED, for testing purpose. The function of each LED is

summarized in Table I. The output of the simulation can be

observed through the LCD display and LED.

TABLE I

LED FUNCTION

LED Number Function

0 Indicate power supply

1 Indicate normal condition

2 Indicate fault condition

3 Represent DCmotor, for ELCB auto-reset

4 Represent DC motor, for triggering MCB off

5 Represent hand phone, for call alert

V. EXPERIMENTAL TEST AND ANALYSIS

Three experiments were conducted to analyze the

functionality of the system developed in normal condition,

during ELCB trip and fault detection.

A. Current Sensor Funtionality Test

A test was conducted to verify the functionality of the

current sensor. The test is conducted with several domestic

devices at 240 VAC that commonly used in human daily life

for example lamp, kettle, iron and rice cooker. The reading is

taken by using current sensor, which can be observed through

the serial display of the microcontroller. According to the

datasheet, accuracy of the current sensor is about ±1 %. The

result of the test is summarized in Table II.

TABLE II CURRENT SENSOR TEST RESULT

Device Power (Watt)

Calculated Current (Amp)

Current Reading (Amp)

Lamp 70 0.292 0.350

Rice Cooker

450 1.875 1.887

Iron 1000 4.167 4.204

Kettle 1500 6.250 6.265

From the result in Table II, the reading of the current sensor

is in range of accuracy as in the current sensor’s technical

specifications given by the supplier . The current sensor is

valid to be used as measurement device in this project.

B. Normal Condition

This test is to verify that the system is able to detect normal

condition, at which power is ON (or “1”). When the system

detects a normal condition, LED 1 will light up and the LCD

will display “Normal Condition” as in Fig. 4. Normal

condition means that the circuit is working as usual without

fault, or no fault yet had occurred.

Fig. 4 Normal Condition

C. Auto-Reset ELCB

This section is to test the functionality of automatic ELCB

reset operation. During power outage, at which power is OFF

(or “0”), LED 2 will light up to indicate that the ELCB is

tripped or fault condition is occurred. ELCB will undergo

maximum of three times reset testing. To represent the motor

that will reset the ELCB, LED 3 is set to be ON for 3 seconds

and OFF for 3 seconds as delay. The 3 seconds delay is to

make able for the microprocessor to check if the power is “1”

or “0” and to switch off the motor. If “1”, the system will be

back to normal operation. If “0”, the system will reset ELCB

up to three times. During the reset operation, the LCD will


25

display “ELCB Tripped, Reset Test: (Test Sequence Number)”.

The result of the test is as in Fig. 5.

Fig. 5 ELCB Reset Sequence

D. MCB Check Operation

Once the ELCB reset operation reaches “Reset Test: 3”, and

the power is still “0”, the system will check each MCB since

MCB is installed at individual circuit. The system will check if

the difference between line current and neutral current exceeds

the limit current, which is 30 mA. When entering the MCB

check operation, LED 3 will turn OFF and LED 4 will turn

ON for 3 seconds while the LCD displays “MCB Checking...”

as in Fig. 6. LED 4 then will turn OFF, and LED 3 will turn

ON again for 3 seconds to reset the ELCB. Assume that once

the LED 4 is OFF, the MCB is in OFF position.

Fig. 6 MCB Check Operation

The program will check, if the power is still “0”, the

system will trigger call alert to inform the user that a fault has

occurred at her/his house. Phone alert is represented by LED

5. LED 5 will turn ON for 4 seconds to trigger call alert and

LCD will display “Unknown Fault; MCB Off” as in Fig. 7

since the cause of fault is unknown.

Fig. 7 Unknown Fault with MCB Off

But if power is “1”, or ON, call alert will also be triggered

but the LCD will display “Fault Detected @; MCB 1” as in

Fig. 8 since the fault is known occurred at MCB 1. For testing

purpose, only one MCB is being used and labelled by “MCB

1”.

Fig. 8 Fault Detected at MCB 1

However, if the difference does not exceeds 30 mA, but the

power is still OFF or “0”, the LCD will display “Unknown

Fault; MCB On” and call alert will be triggered as in Fig. 9.

This is due to unknown fault which cannot be detected by the

MCB. This will keep all the MCBs remain at OFF position.

Fig. 9 Unknown Fault with MCB On

VI. PROTOTYPE DEVELOPMENT AND TEST

The develop system will be implemented in a prototype and

hardware. Fig. 10 shows the overall view of the prototype

designed.


26

Fig. 10 Overall View of the Prototype

The prototype is designed with one ELCB and two MCBs

to represent the home distribution board. There are two main

boxes in the prototype, the main and external box. The main

box is where the ELCB and MCBs are placed, while the

external box contains batteries, Arduino board, LCD display

and other electronic components.

The ELCB in the prototype will be connected to the 240 V

input voltage for incoming and distributed to the MCBs. The

MCBs are connected to individual socket which will be

connected to any load.

A. Normal Condition

The first test of the prototype is conducted during a normal

condition. It is a condition where everything is working as

usual, no fault during this period. Fig. 11 shows the result of

the test. In this test, both MCBs and ELCB are in ON position

and LCD display will display “Normal Condition”. An

indicator, the green LED, will light up to indicate the system is

in normal condition.

Fig. 11 Normal Condition of the Prototype

B. Prototype Auto-Reset ELCB

The second test is auto-reset ELCB function by using the

prototype designed. The operation and reset sequence is

similar to the simulation test in Section V, part C, but the

LEDs are replaced with a DC motor. The ELCB reset

sequence is shown in Fig. 12. During fault, ELCB will be in

OFF position. After reset operation, ELCB will be in ON

position. The LCD will display the reset sequence to indicate

the number of reset test done.

The system developed for the auto-reset ELCB will check

for power after each reset sequence is completed. For instance,

after ELCB had completed reset test sequence 1, the system

will check for the electrical power supply. If there is no power

supplied, then the system will go for next reset sequence. But

if power is restored after the first or second sequence, then the

system will indicate “Normal Operation”. The triggering

mechanism for the ELCB is controlled by a DC motor.

Fig. 12 Actual Auto-Reset ELCB Test

C. Fault Location Detection Test

Once the auto-reset ELCB operation is at “Reset Test: 3”,

the system will check for fault at MCB. For testing purpose

and real situation demonstration, electrical fault is

intentionally created at MCB 1. Fig. 13 shows the flow of

MCB checking operation. Once the system enters the MCB

checking stage, it will read current value obtained from line

and neutral current sensors and check for the current

difference at MCB 1.

If the difference exceeds 30 mA, MCB 1 is considered as

faulty. Therefore, MCB 1 will be switched off and ELCB will

be reset again. Once the process of switching off and on MCB

and ELCB is completed, the LCD will display “Fault Detected

@ (Fault Location)”. In this test, it displays “Fault Detected

@ MCB 1”, indicating that an electrical fault had occurred at

MCB 1. Then, the system will trigger call alert to notify the

user. Both MCB 1 and MCB 2 are controlled by a DC motor

allocated for each of the MCBs.


27

Fig. 13 Fault Location Detection Test

D. Unknown Condition Test

There are certain conditions where no fault is detected but

electrical power is still OFF, or the faulted MCB is already

OFF but still there is no supply. For both conditions, two tests

have been conducted.

To test for the first condition, supply is disconnected from

the main box to create no fault situation and with no electrical

power. Result of test is shown in Fig. 14. For the second

condition, supply is disconnected and MCB 1 is intentionally

faulted as in previous test and result shown in Fig. 15.

Fig. 14 Actual Test for Unknown Condition 1

Fig. 15 Actual Test for Unknown Condition 2

VII. CONCLUSION

Automated Electrical Protection System or Auto-EProS can

be considered as a new invention in electrical protection field.

It is an additional feature to the electrical protection system to

enhance the performance of domestic protection system. From

the findings and functionality of the prototype, Auto-EProS

will solve current power problem in domestic electrical

system.

REFERENCES

[1] Stevenson, William D., Jr., “Elements of Power Systems Analysis”, McGraw-Hill Electrical And Electronic Engineering Series (3rd Ed.),

New York, 1975

[2] “191 Mati Akibat Kejutan Elektrik”, Newspaper Article, 2011. [Online] Retrieved from

http://www.utusan.com.my/utusan/info.asp?y=2011&dt=0415&pub=Ut

usan_Malaysia&sec=Dalam_Negeri&pg=dn_10.htm [3] “Energy Guide Book (For Consumers)”, Published for National Energy

Efficient Awareness Campaign (SWITCH), WECAM, 2009

[4] QO and QOB Miniature Circuit Breakers with Ground Fault Protection, Schneider Electric, 2009

[5] “Electrical Safety Hazards Handbook”, Littelfuse USA, 2005

[6] “Earth Leakage Circuit Breaker”. [Online] Retrieved from http://en.wikipedia.org/wiki/Earth_leakage_circuit_ breaker “

[7] Shelton S., “Electrical Installlations”, Nelson Thrones (3rd ed.), 2004

[8] Szoncso F., “Electrical Safety Organisations at CERN”, CERN Safety Commission

[9] “Residual Current Device”. [Online] Retrieved from

http://en.wikipedia.org/ wiki/Residual-current_device [10] “Residual Current Devices in LV”, Cahier Technique no. 114,

Schneider Electric, 2006

[11] “Miniature Circuit Breakers: Application Guide”, ABB Inc., USA, Apr 2009

[12] “Difference between Fuse and Circuit Breaker”. [Online] Retrieved

from http://www.wisegeek.com/what-is-the-difference-between-a-fuse-and-a-circuit-breaker.htm


28