ELECTRICAL POWER SYSTEM PROTECTION (EE-475)

COMPLEX ENGINEERING PROBLEM REPORT

ELECTRICAL POWER SYSTEM PROTECTION (EE-475)
FINAL YEAR-ELECTRICAL ENGINEERING
BATCH: 2018

GROUP MEMBERS:
MUHAMMAD MUZAMMIL (EE-18064)
MUHAMMAD UMAR (EE-18083)
MUHAMMAD UMAIR HAROON (EE-18085)
USAMA UMER MALIK (EE-18116)
BILAL AHMED KHAN (EE-18259)

Submitted to: DR. MUHAMMAD MOHSIN AMAN

Submission Date: 31/01/2022

Page | 1
 Design of a OvercurrentRelay Using Arduino
Uno as a Microcontroller
Muhammad Muzammil, EE-18064., muzammil4100883@cloud.neduet.edu.pk
Muhammad Umar, EE-18083, umar4104293@cloud.neduet.edu.pk
Muhammad Umair Haroon, EE-18085., haroon4103853@cloud.neduet.edu.pk
Usama Uemr Malik,EE-18116,malik4107145@cloud.neduet.edu.pk
Bilal Ahmed Khan, EE-18259., khan4103766@cloud.neduet.edu.pk

Abstract— this paper aims to design an overcurrent relay

used to simulate the system. In this paper, a simple digital
with a characteristic of definite time OCR, Instantaneous relay based on Arduino Uno is proposed to protect the
OCR and an IMDT (i.e. standard inverse, extremely inverse electrical system against overcurrent faults.
and very inverse) that can comply with the IEC standard The proposed overcurrent protection relay consists of an
60255. The overcurrent relay which is used to protect single Energy measurement module PZEM-004t V3, an Arduino
phase of an alternating circuit (AC) from the overcurrent Uno as a microcontroller and a circuit breaker. It is designed
disturbances consists of an ArduinoUno as a microcontroller
to have a definite time , instantaneous time and an inverse
to control the operation of the relay, PZEM-004t V3.0 energy
time characteristic and can fulfill the standard IEC 60255.
measurement module with the allowable current up to 10A
used to detect the input current to the relay module. The Time
The proposed relay also needs to have some capabilities
Multiplier Setting (TMS) of the relay was set at 0.1. The trip such as to be selective to different types of AC fault
test of the relay was conducted at avarying TMS from 0.1 to currents andfast responses.
0.4. It can be concluded that the prototype of the digital II. OVERCURRENT PROTECTION
overcurrent relay can fulfill the characteristic of the standard
IEC 60255.
A. Overcurrent relay
KEYWORDS—DIGITAL RELAY, OVERCURRENT RELAY The purpose of the overcurrent protection is to
(OCR), PZEM-004T V3, ARDUINO UNO minimize damages due to overcurrent faults to the
MICROCONTROLLER. electrical system by detecting the abnormalities quickly
and isolating the disturbed components from the healthy
I. INTRODUCTION electrical system selectively. To operate selectively, the
A good power system must be equipped with a proper input current enteringthe overcurrent relay needs to be set
protection system which is intended to prevent and to at certain value. If the input current goes to the overcurrent
protect the system against any faults that might occur during relay greater than its setting value, the relay will operate by
the operation of the system [1]. This protection system sending the electrical signal to the circuit breaker (CB) to
consists of a current transformer, a relay and a circuit trip the electrical circuit immediately [8] as illustrated in
breaker. A current transformer is used to inform the Fig.1.
magnitude of the input current signal to the relay [2]. If the
value of the input current sensed by the relay exceeds the
setting current of the relay, the relay will send the signal to Time Setting
the circuit breaker to trip or open the circuit. Basically, most
of the protection relays are electromagnetic types [3].
Advances in power technology, protection relays based on
a microprocessor have been developed. These types of
relays are also known as numerical relays which convert the
analogue input signal into digital signal. The numerical Input Current Over-Current Relay
relays comprise of a microprocessor, an input module, an Trip Output
output module and a communication module [2,3].
Some studies have been conducted to investigate and
analyze the performance of overcurrent relay based on a
microprocessor [4,5,6]. For example, the trip test was done Plug Setting (Pick-Up)
to examine the response of the relay due to varying fault
currents caused by over load [4], a multifunction relay based
on a microprocessor was also developed to protect against
overcurrent and under voltage faults [5]. An overcurrent Fig.1. The illustration of the operation of an overcurrent relay [8]
relay based on Arduino has been investigated to protect the
electrical system which consists of resistive load and lamps The overcurrent relays are classified into two types based on
against the overcurrent disturbances [6]. In [7], Arduino their operation time, i.e.: an instantaneous relay and a time
Uno has been applied as a protection relay to protect the delay relay.
micro-grid system against the overcurrent faults. The
adaptive model based on the dual simplex algorithm was  Instantaneous Relay

Page 1 of 7
 This kind of overcurrent relay operates quickly
without any delays when the current entering the relay
exceeds its pick-up current value [9]. This relay is used
to protect the outgoing feeder from overcurrent faults
such as due to the short-circuit conditions, transient
conditions and over loads. Its operation time is within
100ms. The construction of the instantaneous relay
comprises of a moving armature, plunger and an
induction disk.
 Time delay Relay
A time delay relay operates with certain time delay.
If the fault current exceeds the pick-up or operating
current of the relay, the relay will send the signal to the
circuit breaker to trip after its time delay is reached [9].
The pick-up current and the time delay of the relay can
be adjusted according to the protection requirement of
the system. The operation of the relay is determined by
the magnitude of the pick-up current and the time delay.
It only operates if two conditions are fulfilled. Even
though the current entering the relay exceeds its pick-up
current such as the starting current and the surge current,
the relay is still not operating if the time delay of the
relay is not met [10, 11, 12]. Based on the variations of
the time delay, the time delay relay can be distinguished
into two types i.e.: the definite time and the inverse
time relays. Basically, both relays with definite and
inverse characteristics have certain time delay. The
definite time delay relay has a constant time delay. The
definite time relays are usually applied as a back-up Fig.2. The Inverse characteristic curves with the time delay [12]
relay [10, 11, 12]. For example, it is used to back-up the The inverse characteristic curves show the relationship
distance relay to protect the transmission line and to
between the operation time in seconds and the fault current of
back-up the differential relay to protect the power
transformer. It alsocan be applied as the main protection the relay as the multiple of its pick-up current [9]. The curve
relay to protect the outgoing feeder and bus coupler. has the asymptote in the vertical axis and it is inverse to the
current that exceeds to the pick-up current. The inversetime
In contract to the definite time relay, the time delay characteristic curve can be shifted up and down by adjusting
of the inverse relay is varied depending on the magnitude the Time Dial Setting (TDS). If the relay reaches its pick-up
of the incoming fault current. Generally, if the magnitude value due to a fault current, then its time delay is set to
of the detected fault current is very high, the time delay of identify that incoming fault current. The relay will sendthe
the relay is also very fast. The characteristics of the inverse signal to the circuit breaker to trip only if the duration of the
time relay can be classified into four types as shown in the fault exceeds its setting time delay. The example of the relay
standard IEC 60255 [1], i.e.: Standard inverse, the Definite
operation is given in Fig.3 where the pick-up current value is
inverse, the Very inverse and the Extremely inverse. Their
characteristic curves are shown in Figure 2. set at 1 Ampere and the TDS is positioned at 0.1. Then the
value of its time delay is adjusted to the magnitude of the fault
The time delay of those different inverse relays can be current relay which is the area under the curve as shown in the
calculated as expressed in (1) to (3) [1]: Fig.3.
Standard Inverse:

(1)

Very Inverse:
(2)

Extremely Inverse:
(3)

where,
t = the time delay of the relay (second)
TMS = the time multiplier setting (second)
Ir = the ratio of the fault current to the setting current

Page 2 of 7
 time and IDMT characteristic. If this overcurrent relay is
applied to protect the radial line, thelowest time delay has to
be set to the relay that is placed at the longest point of the
circuit then the time delay of the following relays are increased
gradually.
III. METHOD

The components of the proposed digital relay consist of

Arduino Uno as microcontroller, PZEM-004t v3.0 as
measurement module, a programmable electromagnetic
switch and a socket to connect the load.

AC source CT load

Fig.3. Operation time of the inverse relay with a TMS setting at 0.1 [12] PZEM-004t Programmable
Arduin Switch
Another example of the relay operation is given in Fig.4 where o Uno
different sets of TDS can be chosen for the overcurrent & earth
fault relay SPAJ 140 C type.

Fig.5. The Design of the proposed digital overcurrent relay

The program for the microcontroller Arduino Uno was
written using the Arduino IDE 1.8.5.0 (sketch). The
Definite time, instantaneous and IMDT was chosen as the
characteristic of the proposed digital relay. all the electrical
components are assembled and connected together as
shown in Fig. 5 to produce the prototype of the proposed
digital relay with standard inversecharacteristic. Not only
the hardware components are connected, but the software
part was also integrated into the prototype to regulate the
operation of the hardware components.
1.) PZEM-004t v3

In this proposed relay the sensor module used is a PZEM-

004TAC communication module. This module is a frugal
solution especially in the AC multifunction measure, the
module is mainly used for measuring AC voltage, current,
active power, frequency, power factor. The sender does not
contain a display, but the data is read through TTL interface.
The measuring range of sensor up to 100A starting measuring
current 0.02A, resolution 0.001A, measuring accuracy 0.5%.
The sensors read the current from the transmission line and
send the reading to the Arduino In order to take the right
decision As shown in Figure 6.
Fig.4. the inverse characteristic curve of the reference relay SPAJ 140
C with different TMS settings [12]

B. Setting the Time-Delay of Overcurrent relay

There are two components that need to be adjusted for the

operation of the time-delay overcurrent relay, i.e.: the current
tap setting or the pick-up current in Ampere and the time-dial
setting [9, 10, 11]. To accurately set the time delay of the
inverse relay, the following considerations are required. Those
are the maximum load that might occur in the protected
electrical system, the maximum fault current, the power Fig.6. The practical connection of current sensor
factor, the tripping speed of the circuit breaker and the ratio of
the current transformer. From those considerations, the
maximum fault current is the most important concern for 2.) Current Sensor
setting the time delay of the overcurrent relay with Definite

Page 3 of 7
 The installation of the current sensor (i.e. CT) 10A is in TABLE 1. The Measurement test of electrical equipment
series to the phase cable where the current flowing through From table 1 which is measurement of quantities test it is very
the circuit as shown in Fig. 5.and 7 The current sensor(i.e.
clear that our pzem-004t sends data to microcontroller and
CT) has the ability to measure the current up to 10Amps.
The sensor works based on the hall sensor effect where the microcontroller display it on serial monitor within a time
magnitude of the current passes through the conductor (IP+ period of 140 mili second which means that this time is
to IP-) is directly proportional to the magnitude of the appropriate selection for decision making.
magnetic field. The generated magnetic fields are
accumulated in the hall and produce the output voltage at the TABLE 2.1. The tripping test during overloading condition with
output terminals of the sensor. The current sensor sends the
reading of the alternating current to Arduino Uno through IMDT (standard inverse method)
PZEM-004t v3 module.
3.) The calculation of the fault duration:
The calculation of the time that is used in the prototype is Plug setting = 100% and TMS=0.1 Error (%)
using the function that is available in the Arduino Uno
which is called the millis() function. If the relay has reached Current
Time Delay of SI The Tripping time
its pick-up current setting, the value of the millis() at that IEC 60255 of the tested relay
(Ampere) (milliseconds) (milliseconds)
condition is used as a reference. Then the increased millis()
value is used as a subtraction to the reference millis() value. 2.02 988.61 1138.61 15.17
Afterward, the difference between the two values is used as 3.01 628.26 778.26 23.87
a stopwatch to calculate the duration time in milliseconds
3.99 498.88 648.88 30.06
(ms).
4.77 441.08 591.08 34.00
4.) Electromagnetic switches
Plug setting = 100% and TMS=0.2 Error (%)
When the magnitude of the fault current occurred exceeds
the setting current value and its duration is longer than the Time Delay of SI The Tripping time
setting delay time of the relay, then the fault is considered Current
60255 of the tested relay
as a permanent fault in the Arduino Uno program. At this (Ampere) (Ampere) (millisecond)
stage, the digital pin of the Arduino Uno has a voltage of 5 2,02 1977.22 2127.22 7.58
Volts a programmable electromagnetic switch is used to
break the electrical circuit when the permanent fault occurs. 3,01 1256.53 1406.53 11.93
a programmable electromagnetic switch is shown in Fig.7. 3,99 997.77 1147.77 15.03
4.77 882.16 1032.16 17.00

Plug setting = 100% and TMS=0.3 Error (%)

Time Delay of SI The Tripping time

Current
60255 of the tested relay
(Ampere) (milliseconds) (milliseconds)
2,02 2965.83 3115.83 5.05
3,01 1884.80 2034.8 7.95
3,99 1496.66 1646.66 10.02
Fig.7.the programmable electromagnetic switch. 4.77 1323.24 1473.24 11.33

Plug setting = 100% and TMS=0.4 Error (%)

IV. RESULTS AND DISCUSSIONS
Time Delay of SI The Tripping time
Current
60255 of the tested relay
The physical construction of the prototype of the (Ampere) (milliseconds) (milliseconds)
proposed relay is shown in Fig.8. To test the performance
2,02 3954.44 4104.44 3.79
of the prototype relay, the following two tests are carried
out, i.e. the Measurement test, and the overloading test. In 3,01 2513.07 2663.07 5.96
this section, the results of the complete tests are given. 3,99 1995.55 2145.56 7.51
4.77 1764.322 1914.23 8.49

Fig.8. the physical construction of the proposed digital overcurrent relay

Page 4 of 7
TABLE 2.2. The tripping test during overloading condition with TABLE 2.3. The tripping test during overloading condition with
IMDT (very inverse method) IMDT (extremely inverse method)
Plug setting = 100% and TMS=0.1
Error (%)
Plug setting = 100% and TMS=0.1 Error (%)
Current Time Delay of The Tripping time
VI IEC 60255 of the tested relay
(Ampere) (milliseconds) (milliseconds) Current Time Delay of The Tripping time
EI IEC 60255 of the tested relay
2.02 1323.53 1473.53 11.33 (Ampere) (milliseconds) (milliseconds)
3.01 671.64 821.64 22.33 2.02 2597.06 2747.06 5.77

3.99 451.50 601.5 33.21 3.01 992.54 1142.54 15.11

4.77 358.09 508.09 41.88 3.99 536.19 686.19 27.97

Error (%) 4.77 367.76 517.76 40.78

Plug setting = 100% and TMS=0.2
Plug setting = 100% and TMS=0.2 Error (%)
Current Time Delay of The Tripping time
VI 60255 of the tested relay
(Ampere) (Ampere) Current Time Delay of The Tripping time
(millisecond)
EI 60255 of the tested relay
2.02 2673.26 2823.26 5.61 (Ampere) (Ampere) (millisecond)
3.01 1343.28 1493.28 11.16 2,02 5194.13 5344.13 2.88

3.99 903.01 1053.01 16.611 3,01 1985.08 2135.08 7.55

4.77 716.18 866.18 20.94 3,99 1072.37 1222.37 13.98

Error (%) 4.77 735.53 885.53 20.39

Plug setting = 100% and TMS=0.3
Plug setting = 100% and TMS=0.3 Error (%)
Current Time Delay of The Tripping time
VI 60255 of the tested relay
(Ampere) (milliseconds) (milliseconds) Current Time Delay of The Tripping time
EI 60255 of the tested relay
2.02 3970.58 4120.58 3.77 (Ampere) (milliseconds) (milliseconds)
3.01 2014.92 2164.92 7.44 2,02 7791.19 7941.19 1.925

3.99 1354.51 1504.51 11.07 3,01 2977.63 3127.63 5.03

4.77 1074.27 1224.27 13.96 3,99 1608.56 1758.56 9.32

Error (%) 4.77 1103.30 1253.3 13.59

Plug setting = 100% and TMS=0.4
Plug setting = 100% and TMS=0.4 Error (%)
Current Time Delay of The Tripping time
VI 60255 of the tested relay
(Ampere) (milliseconds) (milliseconds) Current Time Delay of The Tripping time
EI 60255 of the tested relay
2.02 5294.11 5444.11 2.83 (Ampere) (milliseconds) (milliseconds)
3.01 2686.56 2836.56 5.58 2,02 10525.96 10675.96 1.42

3.99 1806.02 1956.02 8.30 3,01 3970.17 4120.17 3.77

4.77 1432.36 1582.36 10.47 3.99 2144.75 2294.75 6.99

4.77 1471.06 1621.06 10.19

Page 5 of 7
 TABLE 3. The tripping test during overloading condition with Fig.10 The tripping test of the proposed relay at different TMS settings in VI
Mode
Definite time

Current (Ampere) Time (sec) Actual time 12000

time of operation ( msec )

of operation
(m sec) 10000
2.02 2 2.16
8000
3.01 2 2.16
6000
Extremely Inverse
3.99 2 2.16
4.77 2 2.16 4000

2000
TABLE 4. The tripping test during overloading condition with 0
Instantaneous time 1 2 3 4
PSM
Current (Ampere) Time delay ( m sec) TSM 0.1 TSM 0.2 TSM 0.3 TSM 0.4
2.02 150
3.01 150 Fig.11 The tripping test of the proposed relay at different TMS settings in EI
3.99 150 Mode.
4.77 150
2.5
In Instantaneous time there is only a delay of 150 mili
seconds which is the taken during measurement and
2
decision making.
Time in sec

1.5

5000 1
Definite time
4000 0.5
Standard Inverse
Actual time of operation

3000 0
in mili second

0 1 2 3 4 5 6
2000 Current in Ampere

Fig.12 The tripping test of the proposed relay at Definite Mode

1000

0 200
1 2PSM 3 4
TSM 0.1 TSM 02 TSM 0.3 TSM 0.4 150
Delay (msec)

Fig.9. The tripping test of the proposed relay at different TMS settings in SI 100
Mode Instantenous Time
50
6000
0
Actual time of operation

0 1 2 3 4 5 6
4000 Current (A)
Very Inverse
Fig.12 The tripping test of the proposed relay at Instantaneous Mode
2000

0
1 2 3 4 PSM
TSM 0.1 TSM 0.2 TSM 0.3 TSM 0.4

Page 6 of 7
 V. CONCLUSIONS REFERENCES
To sum up that the energy measuring module (i.e. pzem-
004t v3) that is used to sense the fault current has a very [1] B. Pandjaitan, Praktik-praktik Proteksi Sistem Tenaga Listrik,
good accuracy. The prototype digital relay has fulfilled the Yogyakarta: Andi, 2012.
standard inverse characteristic as shown in the standard IEC [2] J. M. Gers and E. J. Holmes, Protection of Electricity Distribution
60255 also Definite time and instantaneous mode of Networks 2nd Edition, London: The Institution of Electrical
operation. It only works to trip if the pick-up current setting Engineers, 2005.
of the relay is reached as well as its time delay. At the same [3] J. L. Blackburn and T. J. Domin, Protective Relaying Principles
TMS setting, the more the magnitude of the fault current and Applications, Boca Roton: CRC Press, 2007.
occurs, the quicker the response of the relayis. For the same [4] Cahayahati and M. Zoni, “Perancangan Rele Arus Lebih Dengan
pick-up current setting, the more value of theTMS effected Karakteristik Standar Invers Berbasis Mikrokontroler Atmega
8535,”Jurnal Nasional Teknik Elektro, vol. 1, no. 2302-2949, pp.
to the longer tripping time. Similarly in definite mode it 51-57, 2012.
break the circuit with defined time with little error which is
[5] Ramarao, G., Sateesh K. Telagamsetti, and V. S. Kale. "Design of
in milli seconds. Furthermore in Instantaneous mode of Microcontroller based Multi-Functional Relay for Automated
operation it breaks the connection instantly with only time Protective System." Engineering and Systems (SCES), 2014
delay which is required to measured and decision making Students Conference on. IEEE, 2014.
which is 150 mili second. [6] Bhattacharya, Sourin, et al. "A Novel Approach to Overvoltage
and Overcurrent Protection of Simple Single Phase Two Terminal
Systems Utilizing Arduino Uno."IRPH, Vol. 10, no. 1, pp. 7-110,
2017
[7] Swathika, OV Gnana, et al. "Optimization Techniques based
Adaptive Overcurrent Protection in Microgrids." J Electr. Syst.
Spec.(3) (2015): 6614-6618.
[8] Paithankar, Yeshwant G., and S. R. Bhide. Fundamentals of
Power System Protection. PHI Learning Pvt. Ltd., 2011.
[9] Glover, J. Duncan, Mulukutla S. Sarma, and Thomas Overbye.
Power System Analysis & Design, SI Version. Cengage Learning,
2012.
[10] Horowitz, Stanley H., and Arun G. Phadke. Power System
Relaying. Vol. 22. John Wiley & Sons, 2008.
[11] Sleva, Anthony F. Protective relay principles. CRC Press, 2009.
[12] Jiguparmar, “Electrical Engineering Portal,” 1 February 2013.
[Online]. Available: http://electrical-engineering-
portal.com/types- and-applications-of-overcurrent-relay-1.
[Accessed 2 January 2018]
[13] Anonymous, “SPCJ 4D29 Overcurrent and Earth-Fault Relay
Module,” ABB, Issued 1995-09-14.

Page 7 of 7
TABLE 1. The Measurement test of electrical equipment

Electrical Rated Values Measured Values Error (%) Time Taken

Equipme to Display the
nt Measurement
(milli sec)
------------- V(v) I(A) P(w) F V(v) I(A) P(w) Q(VAr) pf F(Hz) S(VA) Z(Ω) V(v) I(A) P(w) F ------------------
(Hz) (Hz)

Laptop 100- 1.6 65 50- 240.3 0.44 57 55.02 0.54 50 106.45 542.4 0.125 72 12.3 0 140
charger 240 60 4
Mobile 100- 0.5 5 50- 239.7 0.05 6.30 50.17 0.53 49.7 11.98 4792 0.125 90 26 0.4 140
charger 240 60
Juicer 100- 3 500 50- 239.7 0.58 135.5 -258.53 0.98 49.8 138.92 411 0.125 80.66 72.9 0.4 140
blender 240 60
Iron 100- 5 100 50- 237.1 4.77 1130. 0.00 1 50 1130.2 49.7 1.2 4.6 13.04 0 140
240 0 60 4 6