estimation of frequency changes in power grid

1. MAHAVEER INSTITUTE OF
SCIENCE & TECHNOLOGY
DETECTING POWER GRID SYNCHRONISATION FAILURE
ON SENSING FREQUENCY & VOLTAGE BEYOND
ACCEPTABLE RANGE & PHASE SEQUENCE CHECKER
Presented by:
A.Ravi Ram 13E31A0203
B.Niharika 13E31A0208
P.Navya 13E31A0232
P.Vineetha 14E35A0210
GUIDE: Dr.R.V.Amarnath
(HOD )

2. Introduction:
 This project is taken to identify the variations in voltage and
frequency on generator before connecting to the bus bars or
grid.
 Phase sequence is also taken into consideration with respect to
grid system or bus bars.
 Synchronization means the minimization of difference in
voltage, frequency and phase angle between the corresponding
phases of the generator output and grid supply. An alternating
current generator must be synchronized with the grid prior to
connection. It can’t deliver the power unless it is running at
same frequency as the grid.

3.  Synchronization must occur
while connecting the
generator to a grid.
Synchronization can be
achieved manually or
automatically. The purpose
of synchronization is to
monitor, access, enable, and
automatically take the
control action to prevent the
abnormalities of voltage and
frequency.

4. Overview of Project:
 Whenever there is a change in voltage or
frequency or difference in the phase sequence
between the generator and the grid ,the micro
controller sends the information to the buzzer
and the voltage ,phase sequence and frequency
values are displayed on liquid crystal display
(LCD).
 This will alert the concerned staff to take
necessary corrective actions.

5. Objective:
 The project is
designed to develop
a system to detect
the synchronization
failure of any
external supply
source to the power
grid, on sensing the
abnormalities in
frequency and
voltage and phase
sequence.

6. Purpose:
 According to the IEEE standard, islanding state
should be identified and disconnected in 2sec.
 This leads to automatic detection of grid
synchronization failure. Thus, main
consideration is to detect islanding in a grid.

7. Principle of Operation:
 This system is based on a microcontroller of 8051 family.
 The microcontroller monitors the under/over voltage being
derived from a set of comparators.
 As the frequency of the mains supply can not be changed, the
project uses a variable frequency for changing the frequency,
while a voltage changer is used to vary the input voltage to test
the function of the model.
 The failure can be either under/over voltage or under/over
frequency.
 This mechanism is popularly known as islanding condition.

8. Methodology Followed:
 There are several generating units connected to the grid such
as solar, hydro, thermal etc. to supply the load.
 The generating unit needs to supply power according to the
rules & regulations of Grid. This rules involves maintaining
voltage and frequency variations within permissible limits
&maintain the Phase sequence.
 If the voltage , frequency exceeds these limits then it will
effect the grid. It cause grid failure.
 This feeder unit is completely disconnected from grid causing
islanding condition to maintain synchronization needed
between the grid and feeder unit.

9. Block Diagram:

10. Advantages:
 It secures the power of the grid coming from different power
stations by detecting the abnormal conditions of frequency and
voltage beyond its acceptable range.
 It prevents the synchronization failure between power grid and
feeder.
 It requires less maintenance and less time for performing the
operation of detection.
 It does not require more expensive parts, so it is low cost,
effective and economical model.
 It is more reliable.

11. INCLUDED TOPICS:
 Circuit diagram
 Functional description
 Specifications
 Test procedure
 Test result
 Conclusion

12. Circuit Diagram:

14. List of Components with Specifications:
S.No Components Range/Type Required
1. Transformer 500mA/12v-0-12v 1
2. Diodes IN4007 4
3. Resistor 330ohms 1
4. LED 2.5V/30mA 1
5. Resistor 10k-ohms 1
6. Resistor 1M-ohms 1
7. MC Atmega8 1
8. LCD 16X2 JHD,10k pot 1
9. Capacitor 470uf 1
10. Piezo buzzer 1-10Mhz 1
11. Pot 100k 1
12. Voltage regulator 7805 1

15. Circuit Description:
 A step down transformer is used with an input of
230v AC & the output of the transformer will be
12v AC.
 The output of the transformer is given to bridge
rectifier. These rectifier converts 12v AC to 12v
pulsating DC.
 The output of the rectifier is given to capacitor. It
gives pure DC output.
 These 12v pure DC is given as input to voltage
regulator. The regulator converts 12v DC to 5v DC
and further it is given to microcontroller.
 Voltage & frequency variable regulators, buzzer,
microcontroller, LCD are made common and then
grounded for proper functioning of the circuit.

16. Contd…
 The inputs of voltage & frequency variable
regulators and buzzer are connected to the pins
C0, C1& B0 in the microcontroller and
through the MC supply is given to the LCD.
 In LCD the D port consists of LED’s and data
pins. The pins of B port namely B5,B6 & B7
are used to perform read, write & reset
operations.
 The C port is used for Analog to Digital
conversion. The pins C0, C1 & C2 of C port
are connected to R,Y,B phases respectively.
 Whenever variations occur in voltage or
frequency then the result is displayed on LCD
followed by buzzer.

17. Functional Description:
 Phase indicators
 Regulated power supply(RPS)
 Voltage & frequency variable regulator
 Phase sequence checker
 Micro controller(ATMEGA8)
 Potentiometer
 Buzzer
 Liquid crystal display(LCD)

18. Phase Select Indicator:
 We have three phase system and by convention
we write three phases as RYB.
 Phase select indicator is the indicator that
determines the phase sequence of the three
phase supply system.
 When we give conventional three phase supply
(i.e. RYB) to the LCD, we can see the
indication on the display.
 We have R Y B wires and R Y B ports. If R Y B
inserted on the correct port microcontroller
detects the right sequence with respect to pre
coded data.
 If any mismatch of R Y B sequence then the
microcontroller displays the alert text in LCD
followed by alarm indication by the buzzer.

19. Regulated Power Supply:
RPS converts unregulated AC into a constant DC. With
the help of a rectifier it converts AC supply to DC. Its function
is to supply a stable voltage to a circuit or device that must be
operated with in rated power supply limits.

20. Voltage & Frequency Variable Regulators:
 The variable regulator is that
whose electrical resistance value
can be adjusted as per
requirement by adjustable
component attached to it is
called variable regulator.
 As we know that the voltage &
frequency will not be varied
automatically so we are using
voltage & frequency regulators
for changing voltage &
frequency.

21. How to adjust Voltage or Frequency:
 It mainly consists of a resistance track & a
wiper contact. The wiper contact moves along
the resistance track when adjustable component
is adjusted.
 The resistance is adjusted at pre set value as
required at the time of circuit building by
adjusting screw.

22. Phase Sequence Checker:
 3-phase-sequence-checker that is
capable of detecting the phase
sequence of a 3-phase supply and
giving an indication by a set of
LEDs if it encounters any incorrect
sequence.
 If a phase sequence is changed
from RBY to YBR, then the logic
circuit develops an output with a
missing pulse during the fixed-time
duration. This signal is fed to the
microcontroller of the 8051family
then the result is displayed on LCD
followed by buzzer.

23. Microcontroller(ATMEGA8):
 ATMEGA8 is a low power
CMOS 8-bit microcontroller.
 ATMEGA8 achieves up to 16
MIPS throughput at 16 MHZ,
in order to maximize
performance and parallelism.

24. Pin Diagram:

25. ATMEGA8 Pins Description:
 Pin and Port Overview:
 GND: Ground (0V)
 VCC: Digital Supply Voltage (2,7 – 5,5V)
 AVCC: Analog Supply Voltage connect to
low-pass filtered VCC
 AREF: Analog Reference Voltage, usually AVCC
 Reset: Low level on this pin will generate a reset
 Port B, Port C, Port D:
 General Purpose 8 Bit bidirectional I/O - Ports
 optional internal pull up-resistors when
configured as input
 output source capability: 20mA

26. Features of ATMEGA8:
 High performance, low
power Atmel 8-bit
microcontroller.
 Advanced RISC
architecture.
 High endurance non-volatile
memory segments.
 External & internal interrupt
sources.
 Peripheral features.
 True read-while-write
operation.

27. Potentiometer:
 The contrast of the 16x2 LCD module is
adjustable by means of potentiometer. It is
prototype potentiometer.

28. Buzzer:
 It is an Audio signalling device
that makes a buzzing noise and
is used for signalling.
 Which may be mechanical,
electromechanical, or
piezoelectric.
 We are using piezoelectric
buzzer in our project.
 Typical use of buzzers include
alarm devices, timers, and
confirmation of user input
such as a mouse click or
keystroke.

29. Liquid Crystal Display(LCD):
 LCD is an electronic display module & find a wide range
of applications.
 A 16x2 LCD is very basic module and is very commonly
used in various devices and circuits.
 A 16x2 LCD means it can display 16 characters per line
and there are 2 such lines. In this LCD each character is
displayed in 5x7 pixel matrix. This LCD has two
registers, namely command and data.

30. LCD Pin Configuration:
The LCD modules has 16 pins for interfacing. The
details are given below

31. LCD Connection:
 Connect the required pins of PORTB &
PORTD.
 The ports are clearly marked in the board.
 For connection you will need single pin female
to female wires. Supply the LCD using on the
board 5v supply output using a 2 pin connector.
 D0 – D4 of LCD is connected to
microcontroller.

32. Project Specifications:
Parameters Observation
Indication
Remarks
Display Alarm
Change in Voltage +2v or –2v over
the mains
supply (230v)
On LCD Through
buzzer
Over or Under
voltage
Change in
Frequency
+1Hz or -1Hz
over the supply
freq (50Hz)
On LCD Through
buzzer
Increment or
Decrement in
frequency
Deviation in phase
sequence
RYB specified
as standard
sequence
On LCD Through
buzzer
Change in
Phases

33. Test Procedure:
 The input 230v, 50Hz 1-phase supply is given to
the system.
 The phase select indicators determines the phase of
the input (R or Y or B).
 We use step down transformer to step down 230v to
12v which is given to RPS.
 Microcontroller receives power from RPS and
works accordingly to the dumped program of
Annexure -1.
 By changing voltage or frequency we are observing
the values on LCD and if any variation in the
voltage or frequency occurs then the buzzer is
activated and the result is displayed on the LCD.

34. Contd...
 On interchanging phase sequences of the system
the result will be displayed on LCD along with
the alarm indication - considered as fault.

35. Test Results:
 If any change in frequency, voltage and
phase sequence are detected then the
change is indicated with a buzzer followed
by fault on LCD display.

36. Conclusion:
The project is designed to develop a system to
detect the synchronization failure of any external supply
source to the power grid on sensing the abnormalities in
frequency, voltage & phase sequence. There are several
power generation units need to be synchronized to meet
the load demand according to the rules of grid. If any
deviation from the acceptable limit of the grid, it is
mandatory that the same feeder should automatically
display on the LCD or should have buzzer sound for
security which is termed as islanding. So it is preferable to
have a system which can warn the grid in advance so that
alternate arrangements are kept on stand by to avoid
complete grid failure.