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Engineering, Technology & Applied Science Research Vol. 10, No. 1, 2020, 5314-5319 5314 
 

www.etasr.com Filipova-Petrakieva & Shopov: Electrical Device Protection from Overvoltage in a DC Power Supply … 

 

Electrical Device Protection from Overvoltage in a 

DC Power Supply Network  
Fast-acting Protection, Realized by an “Artificial” Short Circuit in the Input of the Protected 

Device  

 

Simona Filipova-Petrakieva 

Department of Theory of Electrical Engineering 

Faculty of Automatics 

Technical University of Sofia 

Sofia, Bulgaria 
petrakievas-te@tu-sofia.bg  

Jordan Shopov 

Department of Electrical Apparatus 

Faculty of Electronics and Automation 

Technical University of Sofia 

Sofia, Bulgaria 
shopov@tu-sofia.bg 

 

 

Abstract—In the present paper a protective device based on the 

so-called “artificial” short circuit in the input of the network, is 
proposed. To ensure the necessary time for switching on the 

protection, the increased power supply voltage is delayed to reach 

in the input of the protected device by additional inductance L, 

which is connected in series to the power supply. As a result of 

this forced short circuit, the DC-power supply is switched off by a 

standard protective circuit-breaker. The short circuit is realized 

by a fast-acting semi-conductor device (e.g. diac + thyristor, etc.). 
The controlling signal is formed as a voltage across a capacitor 

that is a part of RC-circuits connected in parallel to the DC-

power supply network. An analytical expression for this voltage, 

using a classical method for transient analysis, is obtained. The 

main aim is to determine the exact time of switching on the 

protection. The research is confirmed with simulations by 
OrCAD PSpice under the exact values of the elements in the RC-

circuits considered. Two rapid increase cases in the power supply 

voltage are considered: positive jump and linear increase. The 

suggested solution is applicable for overvoltage protection of 

different electrical devices. The electrical scheme, based on the 

electronic components, ensures a fast-acting breaking, which 

guarantees secure protection. Based on the analytical expressions, 
the synthesis of the circuit for control and protection is made and 
the respective values of its elements are calculated. 

Keywords—electrical engineering; electronics; overvoltages; 

short circuit’s protection by electronic unit; transients analysis by 

classical method 

I. INTRODUCTION  

Many electrical devices have one DC-power supply (either 
from a current rectifier or from a special network) [1]. During 
normal operation they are subjected to variations of power 
supply network parameters. This can lead to exceeding the 
maximum admissible values guarantying the normal operation 
of these devices. Overvoltage in the DC-power supply network 
occurs due to different atmospheric influences, switching on 
and off of large consumers, etc. The normal operation of a 
number of electrical devices deteriorates and sometimes 
overvoltage is the cause of damage or breakdown. So, the 

purpose of this work is to suggest a simple electrical scheme 
for overvoltage protection. It only consists of RC-groups 
(Figure 1). It guarantees greater reliability than similar 
protection solutions that use additional electronic elements or 
controllers [2-5]. The main disadvantage of most of the existing 
solutions is that they are designed to protect low power and low 
voltage consumers [6-8]. An additional advantage of the 
proposed solution is that it can be applied to form the level of 
the control signal activating the protection at both low and high 
voltages only by an elementary change in the values and 
parameters of the elements in the RC groups. There are also 
simple solutions designed for specialized protection with a 
specific form of voltage (e.g. DC + triangle voltage form [9]). 
Authors in [10] discuss a variety of protection schemes to 
ensure protection from faults causing overvoltage supplying 
some electronic elements working in low voltages. A simple 
method for protecting the analog channel from overvoltage is 
resistive input attenuation ahead of a precision operational 
amplifier. IC device junctions, such as base-collector and JFET 
gate-source junctions, don't exhibit the same degradation in 
performance upon breakdown and the input current should be 
5mA. Overvoltage protection can be achieved using CMOS 
channel protectors. It is possible to break ground loops by 
using digital isolation techniques. To eliminate a possible 
damage, a protection based on the so-called “artificial” short 
circuit in the power supply input of the convertor with semi-
conductor device S (Figure 1) is used. The convertor discharges 
both from voltage and current which is the main advantage of 
this method. It is also faster than the protections realized by 
switching off from the power supply with standard 
commutation apparatus [11]. 

In Figure 1, a fast-acting commutation apparatus S (e. g. 
diac + thyristor) that carries out a short circuit in the input of 
the protected electrical device is shown. A protecting breaker K 
connected in series with the power supply [11-13] is also 
shown in this figure. RC-circuits are connected in parallel to S. 
They form the time and the parameters of the switching off 

Corresponding author: Simona Filipova-Petrakieva



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signal realizing the short circuit. The protected device is 
marked with “El. Device”. 

 

 
Fig. 1.  A short circuit protection on the input of the convertor 

The proposed protection is analyzed below. The parameters 
of the control signal and its variation in order to ensure 
effective protection are determined. The necessary parameters 
for different input signals of the circuit can be realized with the 
variation of the elements’ values. Afterwards, an analytical 
solution for the voltage across the common node of the two 
discussed RC-circuits during an unexpected change of the 
power supply voltage is suggested. This change determines 
both the time dependence of the processes and the parameters 
of the control signal intended for the commutation apparatus S 
that carries out a short circuit in the input of the protected 
device. The classical method for transient analysis is applied 
[14, 15]. The results from the solution are confirmed with 
illustrative examples by computer OrCAD PSpice simulations. 
The paper concludes with remarks about the advantages and 
disadvantages of the proposed protection and with some 
perspectives for a future research. 

II. PROBLEM STATEMENT 

The principal scheme of the proposed protection from 
overvoltage in DC-power supplying network is shown in 
Figure 2. The processes in the circuits that form both the 
parameters of the signals and the moments of switching on the 
protection are very significant. It is necessary to determine the 
connection between the times and the parameters of the 
scheme’s elements in order to make a correct choice of their 
values in each specific case of power supply overvoltage. The 
fact is that different devices have different parameters, different 
power supply voltages, etc. In an emergency, the power supply 
voltage of a given electrical device can rapidly increase. To 
limit this increase a protective system is necessary to be 
applied. In the considered case the system is an electric scheme 
that generates a switching off protective signal applying to a 
fast commutation apparatus S. In the control circuit of S the 
device (e.g. diac – not shown in Figure 2) is included. It 
actuates when the voltage in the main node of C1 and C2 
exceeds the definite value. The parameters of both the signal 
and the reaction time of the protection depend on the specific 
scheme solution and the ratio of the values of the elements. The 
control signal is proportional to the voltage across the R2C2-
group. It is essential to have a capacitor in which a sufficient 
amount of energy is accumulated to activate the protection. 
When the necessary parameters of the control pulse are 
reached, the apparatus S switches on and the power supply of 

the protected electrical device acts as a short circuit. As a 
result, the input current increases and reaches a value that 
causes the opening of the breaker К and the power supply 
voltage is switched off. An additional inductance L can 
improve the effectiveness of the protection (Figure 2(b)). The 
inductance delays the moment when the increased supply 
power voltage is switched on at the input of the device. In this 
way an extra time is ensured for switching on the apparatus S 
and switching off the breaker K due to the increase of the input 
current. 

 

 
(a) 

 
(b) 

Fig. 2.  Protective circuit from overvoltages in DC-power supply network: 

(a) default, (b) with additional inductance L for overvoltage protection  

This method is better than the Laplace transform [16] 
because on each step of the solution the physical interpretation 
of the result can be visualized. 

III. ANALYTICAL SOLUTION TO THE TRANSIENTS VIA 
CLASSICAL METHOD 

In the present paper, an analytical solution based on the 

classical method (using a set of ordinary differential 

equations) for determining the transient of the voltage 
2
( )

C
u t  

(Figure 3) is proposed. This transient appears when the power 

supply voltage increases rapidly and the electrical device 

should be protected. Two cases of power supply overvoltage 

are considered: 

• Positive jump of the power supply voltage (Figure 4(а)) 
( )1 0( ) Vu t u u= > . 

• Linear increasing the power supply voltage (Figure 4(b)) 

( )0( ) . Vu t u kt= +  

Since the studied electric circuit consists of two parallel 
RC-groups connected in series, then the transients are of the 1

st
 

 

u

R

R

C

C

S

El.

device

R

K

 

u

R

R

C

C

S

El.

device

R

K

 

u

R

R

K

C

C

S

El.

device

R

L



Engineering, Technology & Applied Science Research Vol. 10, No. 1, 2020, 5314-5319 5316 
 

www.etasr.com Filipova-Petrakieva & Shopov: Electrical Device Protection from Overvoltage in a DC Power Supply … 

 

order. So, in both cases mentioned above, the transient 
2
( )

C
u t  

satisfies the aperiodic law: 

( )
2

( ) . V
trans

t

T
C
u t Ae

−
=    (1) 

where the time constant is: 
( )

( )
( )1 2 1 2

1 2

.
, s

R R C C
T

R R

+
=

+
. The initial 

conditions also are the same for both cases: 

( )
( )

2 2

0 2

1 2

.
(0 ) (0 ) V

C C

u R
u u

R R
+ −= =

+
   (2) 

 

 
Fig. 3.  Input protection RC-circuit 

 

(a) 

t  (s)

u (t)  (V)

0

u
0

u
1

 

(b) 

t  (s)

u (t)   (V)

0

u
0

 

Fig. 4.  (a) Positive jump of the power supply voltage, (b) linear increase 

of the power supply voltage 

However, the new steady states are different: 

• If ( )1 0( ) Vu t u u= > , then 

( )
( )

2

1 2

1 2

.
( ) V

steady stateC

u R
u t

R R
=

+
   (3a) 

• If ( )0( ) . Vu t u kt= + , then: 

( )

( )
( ) ( )

2

0 2

1 2

0 2

1 2 1 1 1 2 22

1 2

. .
( ) .

. .
. . . V

steady stateC

u R k
u t t

R R

u R k
R R R RC R C k

R R

= +
+

+ + −  
+

   (3b) 

The final solution about the transient is: 

( )

2 2 2

2

( ) ( ) ( )

. ( ) V

trans steady state

steady state

C C C

t

T
C

u t u t u t

Ae u t
−

= + =

= +
   

(4) 

For each of the analyzed cases the following results are 
obtained: 

• When ( )1 0( ) Vu t u u= > ⇒  

( )
( )

( )
( )

( )
( )

( )

2

1 2

1 2

0 1 2

1 2

1 2 1 2

1 2

.
( ) V

.

.
s

steady stateC

u R
u t

R R

u u R
A

R R

R R C C
T

R R

=
+

−
=

+

+
=

+

   (4а) 

• When ( )0( ) . Vu t u k t= + ⇒  

( )

( )
( ) ( )

( )
( )
( )

( )
( )

2

0 2

1 2

0 2

1 2 1 1 1 2 22

1 2

0 2 1 2 2 1 1

2

1 2

1 2 1 2

1 2

. .
( ) .

.
. . . V

. . .

.
s

steady stateC

u R k
u t t

R R

u R
R R R RC R C k

R R

u R R R C RC k
A

R R

RR C C
T

R R

= +
+

+ + + −  
+

−
=

+

+
=

+

   

(4b) 

In the present paper the proposed power supply overvoltage 
protection will switch on (the commutation apparatus S will be 
a short circuit in the input of the protected device) when the 
threshold value of the capacitor voltage has been reached, i.e. 

2
( )

transC threshold
u t u= . 

IV. ILLUSTRATIVE EXAMPLE 

A scheme for power supply overvoltage protection is 
considered (Figure 2). Without some special considerations the 
power supply voltage of u0=300V is chosen. Note that in 
normal operation the power supply voltage can deviate up to 
20% from the nominal one, i. e.: 

( ) [ ] ( )0 300 20 % 240, 360 Vu V= ± = . 

The protection has to be set in such a way that it switches 
on only when the upper bound of the power supply voltage is 
exceeded.The commutation apparatus S has to switch on when 
the threshold voltage uthreshold=20V according to the chosen 
semi-conductor element (e.g. diac), which watches on the value 
of the control signal (in the common point of the RC-groups. 

0
15

threshold

u

u
η = =    (5) 

 

u(t)
R

R

K

C

C u  (t)
2



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The relation between the resistors 
1
R  and 

2
R  is given by: 

1 2

2

15
R R

R
η

+
= ≤    (6) 

To ensure a normal exploitation, the voltage across the 
capacitor C2 has to be smaller than the threshold voltage of 
switching on the commutation apparatus S, i.e.: 

( ) ( )
2 2

0 2

1 2

.
0 0

C C threshold

u R
u u u

R R
+ −= = ≤

+
   (7) 

10.424 V 20V<    (7a) 

On the base of (6) and (7), (7a), the values of the resistors 
R1=100kΩ and R2=3.6kΩ are determined. The capacitances of 
the capacitors C1 and C2 determine the speed of variation and 
the time of the transients. The latter fade away faster when 
these values are smaller, because in this case the time constants 
are also smaller. The specific values are determined based on 
the following condition: The energy stored in the capacitor C2 
has to be enough to activate the apparatus S. The switching 
time depends on the thyristor and it is up to tens of 
microseconds. As an illustration of the process, the following 
values are chosen: C1=2nF and C2=200nF. The analysis of the 
two considered cases follows. 

• Positive jump of the power supply overvoltage (Figure 
4(a)), when u(t)=u1=600V 

• Linear increasing of the power supply overvoltage (Figure 
4(b)), when u(t)=u0+kt=300+50000t (V). 

Simulations with OrCAD PSpice were conducted. The 
scheme and the results are shown in Figures 5-7. 

 

 
Fig. 5.  Simulation of the overvoltage protective circuit in a DC-power 

supply voltage 

The time for switching on the proposed protection for both 
cases of overvoltage in the power supply network is 
analytically calculated by (4), (4а) and (4b) and it is determined 
by the simulations’ graphs. The results are shown in Table I. 
The relative errors from the analytical solution and from the 
simulations for both cases are 12.99% and 0.33% respectively. 

TABLE I. TIME FOR SWITCHING ON THE PROTECTION 

Input power supply voltage Analytical solution Simulation solution 

u(t)=u1=600V 1.77 (ms) 1.54 (ms) 

u(t)=u0+kt=300+50000t 6.02 (ms) 6 (ms) 
 

 

 

Fig. 6.  Voltage 
2
( )

C
u t in a positive jump of the DC-power supply voltage 



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Fig. 7.  Voltage 
2
( )

C
u t in a linear increasing DC-power supply voltage 

V. CONCLUSION 

In the present paper, a method of control and protection of 
the electrical devices (usually electronic) from overvoltage in 
power supply network is suggested. It is realized by a short 
circuit in the input of the protected device. The proposed 
approach for DC surge protection is based on basic theoretical 
knowledge. Its innovation is the simple calculation of the time 
for activating the protection by using the classical transient 
analysis method without the need for mathematical processing 
using Matlab or other similar software. Another major 
advantage is that this scheme is applicable to arbitrary values of 
the supply voltage and its form: DC-jump, linear, saw, etc. 
Unlike other schemes (with a resistive divider only), the use of 
RC-groups in this work increases the sensitivity of the offered 
protection. It can also be used to form control and protection 
signals at both low and high voltages in low and high power 
consumers. To ensure the necessary time for switching on the 
protection, the increased power supply voltage is delayed to 
reach the input of the protected device by an additional 
inductance L, which is connected in series to the power supply. 
Two cases of rapid increase of the power supply voltage are 
considered: positive jump and linear increase. Analytical 

expressions for the voltage 
2
( )

C
u t which determine the moment 

of switching on the protection are given for each case. The 
expressions are obtained using the classical method for 
transient analysis.  

The main advantage of the classical method for transient 
analysis is that in each step of the solution, one should take in 
mind the physical interpretation of the processes considered 
while it is not necessary when using other known methods such 
as Laplace transform, Duhamel’s integral, state space method, 
Fourier transform, etc. One disadvantage of the classical 

method for transient analysis is the tedious and long description 
during the solution. Based on the analytical expressions, the 
synthesis of the circuit for control and protection is made and 
the respective values of its elements are calculated. The 
respective moments for switching on the protection are 
determined analytically and by simulations. The resulting 
relative errors are 12.99% and 0.33%, respectively. This shows 
that the simulations confirm the final analytical solution. The 
differences are due to the different rounding methods applied 
during the calculations. 

A possible perspective for future research of the problem 
considered in this paper is to obtain the analytical expression 
for the control signal to the commutation apparatus S, using 
Duhamel’s integral. 

ACKNOWLEDGMENT 

The authors are grateful to the Scientific Research Sector of 
the Technical University of Sofia for their financial support. 

REFERENCES 

[1] M. H. Rashid, Power electronics handbook, 4
th
 edition, pp. 27-54, 

Elsevier, 2018 

[2] H. V. Nguyen, H. Nguyen, M. T. Cao, K. Hung Le, “Performance 
comparison between PSO and GA in improving dynamic voltage 
stability in ANFIS controllers for STATC”, Engineering, Technology 
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[3] D. N. Truong, V. T. Bui, “Hybrid PSO-optimized ANFIS-based model to 
improve dynamic voltage stability”, Engineering, Technology & Applied 
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[4] D. D. Tung, N. M. Khoa, “An Arduino-based system for monitoring and 
protecting overvoltage and undervoltage”, Engineering, Technology & 
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[5] On Semiconductor, NCP346, Overvoltage protection IC, Semiconductor 

Components Industries LLC, available at: https://www.onsemi.com/ 
pub/Collateral/NCP346-D.PDF 



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[6] http://www.learningaboutelectronics.com/Articles/Overvoltage-
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converter by means of short-circuiting thyristor”, 10th Electrical 

Engineering Faculty Conference, Santa Marina, Sozopol, Bulgaria, 
September 11-14, 2018 

 

AUTHORS PROFILE 

 

Simona Filipova-Petrakieva was born in Sofia, 

Bulgaria in 1971. She received her BSc and MSc in 
Electronics and Automatics in the Technical 

University of Sofia, Bulgaria (1994). She defended a 
PhD Thesis in Electrical Engineering, Electronics 

and Automatics, Theory of Electrical Engineering 
there (2005). From 2009 she teaches as an Associate 

Professor in the Department of Theory of Electrical 
Engineering, Faculty of Automation, TU-Sofia, 

Bulgaria. Her research interests include theory of 
electrical engineering, cluster analysis, graphs 

theory, interval methods for analysis and synthesis of linear circuits and 
systems, discrete event systems, and discrete structures in mathematics. She 

teaches theory of electrical engineering and discrete structures in mathematics. 
She is a reviewer for many scientific journals, such as the Journal of Abstract 

and Applied Analysis, the Journal of Applied Numerical Mathematics, the 
Journal of Mathematical Communication, the Arabian Journal for Science and 

Engineering, etc. 

 

Yordan Metodiev Shopov was born in Gulabnik, 

Bulgaria, (1943). He received his BSc and MSc in 
Electrical Machine and Apparatus in the Technical 

University of Sofia, Bulgaria (1969). He defended a 
PhD Thesis in Electrical Engineering, Electronics 

and Automatics, Theory of Electrical Apparatus 
there (1978). From 1995 he teaches as an Associate 

Professor in the Department of Electrical Apparatus, 
Faculty of Electrical Engineering, TU-Sofia, 

Bulgaria. His research interests include power 
supply current sources, plasma technologies, 

telecommunication power sources, converters for electro-technologies, and 
testing stends and devices for stabilization the AC voltage and home electrical 

appliances. He teaches electrical apparatus, industrial technologies, production 
technologies, technologies in electrical engineering and electronics, circuit 

design, power electronics, contactless apparatus, and home appliances. 
Invention: “Device for reversely supplying of the loads with back e.m.f.”.