The document describes a project on three-phase fault analysis with an automatic reset mechanism for electrical transmission systems, addressing issues caused by temporary and permanent faults. It highlights the importance of maintaining power quality and introduces the dynamic voltage restorer (DVR) as a solution for voltage sags and swells, detailing its operational principles, advantages, and disadvantages. The conclusion points to future work on power quality problems and the development of an inter-line dynamic voltage restorer (IDVR) for improved system stability.

1. SRINIVASA INSTITUTE OF ENGINEERING
AND TECHNOLOGY,CHEYYURU
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
A PROJECT ON
Three Phase Fault Analysis with Auto Reset for
SUBMITTED BY :
UNDER THE GUIDENCE

2. CONTENTS
❖Abstract
❖I
❖Ob
❖G
❖F
❖V
❖D
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3. ABSTRACT
The project develops an automatic tripping mechanism for the three-phase transmission
system. In the event of a temporary fault, the output of the project resets while it acquires
permanent trip condition in case of a permanent fault. There can occur several failures in a
three-phase supply system that provides power to industrial and domestic consumers. These
failures are results of some faults which may be temporary or permanent in nature. Due to
these faults, the power system may suffer considerable damage. This can lead to disturbance
in power supply and may cause a standstill to various industries linked to the system. In a
three phase power system, these faults are classified as LG (Line to Ground), LL (Line to
Line), 3L (Three lines). This system can overcome such problem which by sensing the fault
automatically and disconnects the system from the supply so that large scale damage to the
system equipment can be avoided. The system automatically differentiates between a
temporary disturbance and a permanent fault and appropriately cuts the supply for a short
duration or long respectively.

5. OBJECTIVE
This works describes the techniques of correcting the supply voltage
sags, swells, interruptions and other power quality issues using most effective
power electronic device DYNAMIC VOLTAGE RESTORER based on the
VSC principle where DVR injects a voltage in series with the system voltage
to correct the voltage sag, swell and interruption.

6. INTRODUCTION
▪ Generally, a high quality sinusoidal waveform is produced at power
stations.
▪ The widespread applications of power electronic based nonlinear devices
as well as, the occurrence of faults cause deviation from pure sinusoidal
waveform .
▪ Customers need constant sine wave shape,constant frequency and
symmetrical voltage with a constant r.m.s value to continue the production.
To satisfy these demands,the disturbances must be eliminated from the
system.

7. POWER QUALITY EVENTS
▪ The small deviations from the nominal or desired value are called “voltage variations” or
“current variations”.
▪ Occasionally the voltage or current deviates significantly from its normal or ideal wave shape.
These sudden deviations are called “events”.

8. VOLTAGE SAGS
▪ A Voltage Sag as defined by IEEE Standard 1159-1995, IEEE
Recommended Practice for Monitoring Electric Power Quality, is a
decrease in RMS voltage at the power frequency for durations from 0.5
cycles to 1 minute, reported as the remaining voltage.
Fig: Voltage sag at SLG Fault

9. Fig:Voltage sag at constant impedance load due to SLG fault (r.m.s)voltage
Fig:Voltage sag at induction motor load due to SLG fault (r.m.s) voltage

10. VOLTAGE SWELLS
• Voltage swells are another type of voltage disturbance, defined as an
increase in the r.m.s supply voltage between 1.1–1.8 p.u., and lasting from
half a cycle to 1 min.

11. CAUSES OF SAGS/SWELLS
CAUSES OF SAGS:
• Faults in power system
• Switching ON large loads
• Starting large motors
CAUSES OF SWELLS:
• switching off large loads
• By energizing capacitor banks
• By faults produced within power systems

12. FACTS DEVICES

13. VOLTAGE SAG MITIGATION USING
DYNAMIC VOLTAGE RESTORER
• The Dynamic Voltage Restorer (DVR) is a power electronic converter based device that has been
designed to protect the critical loads from all supply side disturbances other than the outages.
• It is connected in series with a distribution feeder and is capable of generating or absorbing real and
reactive power at its terminals.
Fig:Configuration of Dynamic Voltage Restorer

14. DVR OPERATING PRINCIPLE
• The basic operating principle behind the DVR is to inject a voltage of the required
magnitude and frequency in series with the incoming supply voltage so as to restore
the load voltage to the pre sag state.
• It is basically consists of power circuit and control circuit.
Fig:Schematic Diagram of DVR

15. DVR POWER CIRCUIT
The power circuit of the DVR has four main parts:
• Voltage Source Inverter (VSI)
• Voltage injection transformer
• DC energy storage device and
• Low pass filter

16. DVR OPERATION MODES
• The basic operation principle of DVR is measuring the missing voltage by using
control unit and injecting the dynamically controlled missing voltage in series to
the line and providing the load voltage unchanged during sag.
• Generally, the operation of the DVR can be categorized into three operation
modes:
a. protection mode
b. standby mode (during steady state) and
c. injection mode (during sag).

17. Fig:Scheme of protection mode Fig:Scheme of standby mode

18. CAPACITY OF DVR
• Maximum injection voltage to system and maximum load current
determine capacity of DVR.
• To Determine capacity of DVR be the needed supply characteristic,
including magnitude of voltage sags and load current.
• MVA rating of DVR:
MVA (DVR) = rated MVA (load) x Maximum voltage injection (pu)
So, rating of DVR must not be the same as the rating of load
served.

19. MATLAB REPRESENTATION
• Modelling and simulation for voltage sags/swells mitigation using DYNAMIC VOLTAGE RESTORER is
carried out by using MATLABR2019b.
Starting MATLAB:
• You can start MATLAB by double-clicking on the MATLAB icon or invoking the application from the
Start menu of Windows. The main MATLAB window, called the MATLAB Desktop, will then pop-up and
it will look like this:

20. SIMULATION DIAGRAM OF DVR

21. INTERNAL CIRCUIT REPRESENTATION OF DVR

22. OUTPUTS

23. ADVANTAGES AND DISADVANTAGES
OF DVR
ADVANTAGES
• Less cost.
• Less weight and volume
because it eliminates the use
of heavy DC link capacitor
(or energy storage element).
• Compensation can be
accomplished for long time.
• Reduced installation area.
DISADVANTAGES
• High no. of switches.
• Limited compensation range
because operation in case of
deep sags may not be
successful.

24. CONCLUTION
• In this paper a brief literature review is done on DVR configurations and
its control strategies. By selecting any one of them we can provide solution
to various power quality problems like voltage harmonics, voltage
sag/swell compensation. To improve the performance of DVR, efforts
needs to be made on energy savings, reduced parts and losses, minimum
power injection, reduced rating, and selective harmonics mitigation.

25. FUTURE SCOPE
• In the future work, we will discuss effect of the power quality problems on the load
(sensitive loads) when this load is fed from two different distribution feeders.
• For mitigation of power quality problems and investigation of power system
stability a new device which is named Inter-line Dynamic Voltage Restorer (IDVR)
will be discussed.
• This device consists of two conventional DVRs which are installed in two different
distribution feeders and the DC link.
• The proposed device (IDVR) and its new control strategy will be modeled and
simulated by PSCAD/EMTDC.

26. THANK YOU