Design and fabrication of over voltage relay

1. DESIGN AND FABRICATION OF
OVER VOLTAGE RELAY TO BE
INTEGRATED IN POWER
SYSTEM LAB
Presented by:
PREMCHAND KUMAR :-120301ELR055

2. CONTENTS
 INTRODUCTION
 CAUSE OF OVER VOLTAGE
 EFFECTS OF OVER VOLTAGES
 CIRCUIT DESIGN
 COMPONENT REQUIRED
 Working Principal
 CONCLUSION

3. INTRODUCTION
 OVER VOLTAGE:- When the voltage in a
circuit or part of it is raised above its upper
design limit, this is known as overvoltage.

4. CAUSE OF OVER VOLTAGE
Overvoltage can be caused by a number of
reasons, sudden reduction in loads
 switching of transient loads
 lightning strikes
 failure of control equipment such as voltage
regulators
 neutral displacement.

5. EFFECTS OF OVER VOLTAGES
ON POWER SYSTEMS:
 Over voltage tends to stress the insulation of
the electrical equipment’s and likely to cause
damage to them when it frequently occurs
 Over voltage caused by surges can result in
spark over and flash over between phase and
ground at the weakest point in the network,
breakdown of gaseous/solid/ liquid insulation,
failure of transformers and rotating machines.

6. CIRCUIT DESIGN

7. Components Required
• Transformer 12v
• Bridge wave rectifier
• Capacitors-1000micro farads 63v & 1 micro farad 25v
• Regulator 7812 , 7912
• Potentiometer-10k
• Resistances -10k,1k
• IC LM741
• Led
• Diode of IN4007
• Relay
• Load

8. COMPONENT DESCRIPTION
TRANSFORMER:-
 A transformer is a static electrical device that
transfers energy by inductive coupling
between its winding circuits.
 It is use for step down the voltage from 220v to
12v

9. CAPACITOR
 Here the capacitors are used for filtering
purpose.

10. Regulator 7812 , 7912
 Here is circuit Power Regulator +12V,-12V. IC
LM7812 is used for +12V and IC LM7912 is
used for -12V.

11. Potentiometer-10k
 Potentiometer also known as pot is generally
used in circuits to provide variable resistance
or variable voltage.

12. OP-AMP
 The Operational Amplifier is probably the most
versatile Integrated Circuit available.
 The most common Op-Amp is the 741 and it is
used in many circuits.
 The OP-AMP has two inputs, INVERTING ( - )
and NON-INVERTING (+), and one output at
pin 6.

13. PIN DESCRIPTION OF IC LM741

14. WORKING OF OP-AMP 741:
 INVERTING AMPLIFIER:-
 NON-INVERTING AMPLIFIER:

15.  COMPARATOR:

16. Diode(IN4007)
 Diodes are frequently used to conduct
damaging high voltages away from sensitive
electronic devices.
 A diode offers a very low resistance in one
direction and a very high resistance in other
direction, thus permitting an easy current flow
in only one direction.

17. Relay
 A relay is an electromechanical device that
is actuated by an electrical current. The
current flowing in one circuit causes the
opening or closing of another circuit.
 Relays with calibrated operating
characteristics and sometimes multiple
operating coils are used to protect electrical
circuits from overload or faults.

18. Working Principal:-
 We are giving 220 volts ac as a input to the
transformer. We are using step down
transformer it serves to reduce the pressure
remaining 12 volts, through a D1-D4
connected to direct rectifier bridge circuit. This
rectifier converts ac to dc but the obtained dc
is not pure dc it is a pulsating dc, to obtain
pure dc we are using regulator (IC LM7812 &
7912) .

19. continue….
 From IC LM 7812 we obtained +12v & from IC
LM7912 -12v.
 Here the capacitors are used for filtering
purpose.
 The output of 7812 & 7912 regulator is
connected to OPAMP 741.It compares two
input voltages one voltage is reference voltage
(Vref) and the other is called the input voltage
(Vin).Whenever the Vin rises or falls below the
Vref value the polarity of the output changes
thus making it to work as a comparator.

20. continue….
 If the Vin will be greater then Vref then relay
will trip .Thus we can protect our equipment
from overvoltage.

21. CONCLUSION:
 It will indicate the high voltage. Due to this we
can safe guard our home appliances without
damaging the equipments.