In this project we will monitor transmission line fault. The steady state operating mode of a power system is balanced 3-phase ac. However, due to sudden external or internal changes in the system , this condition is disrupted. When the insulation of the system fails at one or more points or a conducting object comes in contact with a live point , a short circuit or fault occurs. The causes of faults are numerous , e.g., lighting , heavy winds , trees falling across lines , vehicles colliding with towers or poles, birds, line breaks, etc. A fault involving all the three phases is known as symmetrical fault while one involving only one or two phases is known as unsymmetrical fault .we are working on monitoring these faults during occurring on transmission line. In this project we indicate the fault on LCD. These faults are monitoring by using microcontroller. We used 16*2 LCD display to indicate fault. We used Microcontroller 8051. 8051 is 8 bit single chip CPU. It contains inbuilt 8 kb ROM and 256 byte RAM.
8051 is 40 pin IC having four ports p0, p1, p2 and p3. Benefit on using 8051 is low cost. We can design PLC-programmable logic controller using 8051. We detected different types of faults and checked fault at different locations. We display faults at LCD. We connected LCD 16*2 at port0. We connected RS,RW and EN at pin p2.5, p2.4 and p2.3 respectively. We first of all step down the voltage then will give to rectifier. For rectification purpose we will use IN4007 diode. After rectification we filtered DC supply. After rectification we will convert 12 v to 5v using LM7805. 78 indicate +ve voltage and 5v.For the regulated power supply we use IC 7805 as a regulator to provide a fix 5 volt power supply.
Precautions:
While wiring, assembly and installation of the circuit ,make sure that you
1. use good quality wires.
2. use good quality relay
3. Iron soldering temperature should be below 350 degree cent.
4.Use good quality soldering wire.
BASIC COMPONENTS
There are number of basic components , using in this project these are
(i). Power Supply for the circuit.
(ii) . Voltage regulator
(iii). Diode
(iv). Rectifier
(v). Transformer.
(vi). Resistors.
(vii). Capacitors.
(viii). Micro controller 8051
(ix). Lcd display
FAULT (power engineering):
In an electric power system, a fault is any abnormal flow of electric current. For example a short circuit is a fault in which current flow bypasses the normal load. An open circuit fault occurs if a circuit is interrupted by some failure. In three phase systems, a fault may involve one or more phases and ground, or may occur only between phases. In a "ground fault" or "earth fault", current flows into the earth. The prospective short circuit current of a fault can be calculated for power systems. In power systems, protective devices detect fault conditions and operate circuit breakers and other devices to limit the loss of service due to a failure.
In a polyphase system, a fault may affect all phases equally which is a "symmetrical fault". If only some phases are affected, the "asymmetrical fault" requires use of methods such as symmetrical components for analysis, since the simplifying assumption of equal current magnitude in all phases is no longer applicable.
There are various types of fault occurs in transmission line .
Transient faults :
A transient fault is a fault that is no longer present if power is disconnected for a short time.
Many faults in overhead power lines are transient in nature. At the occurrence of a fault power system protection operates to isolate area of the fault. A transient fault will then clear and the power line can be returned to service. Typical examples of transient faults include:
- momentary tree contact
- bird or other animal contact
- lightning strike
- conductor clash
In electricity transmission and distribution systems an automatic reclose function is commonly used on overhead lines to attempt to restore power in the event of a transient fault. This functionality is not as common on underground systems as faults there are typically of a persistent nature. Transient faults may still cause damage both at the site of the original fault or elsewhere in the network as fault current is generated.
Persistent fault :
A persistent fault does not disappear when power is disconnected. Faults in underground power cables are often persistent. Underground power lines are not affected by trees or lightning, so faults, when they occur, are probably due to damage. In such cases, if the line is reconnected, it is likely to be only damaged further.
Symmetric fault:
A symmetric, symmetrical or balanced fault which affects each of the three-phases equally. In transmission line faults, roughly 5% are symmetry. This is in contrast to an asymmetric fault, where the three phases are not affected equally. In practice, most faults in power systems are unbalanced. With this in mind, symmetric faults can be viewed as somewhat of an abstraction; however, as asymmetric faults are difficult to analyze, analysis of asymmetric faults is built up from a thorough understanding of symmetric faults.
Asymmetric fault:
An asymmetric or unbalanced fault does not affect each of the three phases equally. In practice, most faults in power systems are unbalanced; however, as asymmetric faults are difficult to analyze, analysis of asymmetric faults is built up from a thorough understanding of symmetric faults.
Common types of asymmetric faults.
- line-to-line - a short circuit between lines, caused by ionization of air, or when lines come into physical contact, for example due to a broken insulator.
- line-to-ground - a short circuit between one line and ground, very often caused by physical contact, for example due to lightning or other storm damage
- double line-to-ground - two lines come into contact with the ground (and each other), also commonly due to storm damage.
Single line to ground fault:
In this fault out of three phases any one of the line is grounded. When this fault occurs this fault sense by microcontroller and send to the LCD screen and we can detect this fault easily.
TWO-LINE TO GROUND FAULT:
In this fault out of three phases any two of the line is grounded. When this fault occurs this fault sense by microcontroller and send to the LCD screen and we can detect this fault easily.
LINE TO LINE FAULT:
In this fault out of three phases any two of the line are touch to each other. When this fault occur this fault sense by microcontroller and send to the LCD screen and we can detect this fault easily.
Components:
DESCRIPTION OF POWER SUPPLY:
This circuit is a small +12 volts power supply, which is useful when experimenting with digital electronics. Small inexpensive wall transformers with variable output voltage are available from any electronics shop. Those transformers are easily available, but usually their voltage regulation is very poor, which makes them not very usable for digital circuit experimenter unless a better regulation can be achieved in some way. The following circuit is the answer to the problem. This circuit can give +12V output at about 1A current. The circuit has overload and terminal protection.
Working of power supply circuit:
In this project we use for power supply use various components such as centre tapped step down transformer, diode, electrolyte, voltage regulator.
First 220v ac supply given to the centre tapped transformer which step down the 220v ac supply in to 12v ac supply. After step-down transformer we use rectifier to convert ac supply in to dc supply. For rectification of power we use diode which rectifies ac supply into dc supply. After rectification of power its converted in dc but this dc is pulsating so we use electrolyte which gives the static dc. After the electrolyte we use voltage regulator.
Voltage regulator maintains the terminal voltage of different voltage sources within required limits despite variations in input voltage or load. Voltage regulator gives the 5v dc supply to the circuit and again gives to the electrolyte circuit to give static dc.
Then we connect power supply circuit to the vcc of micro controller.
Microcontroller :
A microcontroller (sometimes abbreviated µC, uC or MCU) is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM. Microcontrollers are designed for embedded applications, in contrast to the microprocessors used in personal computers or other general purpose applications.
Microcontrollers are used in automatically controlled products and devices, such as automobile engine control systems, implantable medical devices, remote controls, office machines, appliances, power tools, and toys. By reducing the size and cost compared to a design that uses a separate microprocessor, memory, and input/output devices, microcontrollers make it economical to digitally control even more devices and processes. Mixed signal microcontrollers are common, integrating analog components needed to control non-digital electronic systems.
Some microcontrollers may use four-bit words and operate at clock rate frequencies as low as 4 kHz, for low power consumption (millwatts or microwatts). They will generally have the ability to retain functionality while waiting for an event such as a button press or other interrupt; power consumption while sleeping (CPU clock and most peripherals off) may be just nanowatts, making many of them well suited for long lasting battery applications. Other microcontrollers may serve performance-critical roles, where they may need to act more like a digital signal processor (DSP), with higher clock speeds and power consumption
Microcontroller 8051:
The Intel 8051 is an 8-bit microcontroller which means that most available operations are limited to 8 bits. There are 3 basic "sizes" of the 8051: Short, Standard, and Extended. The Short and Standard chips are often available in DIP form, but the Extended 8051 models often have a different form factor, and are not "drop-in compatible". All these things are called 8051 because they can all be programmed using 8051 assembly language, and they all share certain features (although the different models all have their own special features).
Some of the features that have made the 8051 popular are:
- 8-bit data bus
- 16-bit address bus
- 32 general purpose registers each of 8 bits
- 16 bit timers (usually 2, but may have more, or less).
- 3 internal and 2 external interrupts.
- Bit as well as byte addressable RAM area of 16 bytes.
- Four 8-bit ports, (short models have two 8-bit ports).
- 16-bit program counter and data pointer
PORT P1 (Pins 1 to 8): The port P1 is a general purpose input/output port which can be used for a variety of interfacing tasks. The other ports P0, P2 and P3 have dual roles or additional functions associated with them based upon the context of their usage.
PORT P3 (Pins 10 to 17): PORT P3 acts as a normal IO port, but Port P3 has additional functions such as, serial transmit and receive pins, 2 external interrupt pins, 2 external counter inputs, read and write pins for memory access.
PORT P2 (pins 21 to 28): PORT P2 can also be used as a general purpose 8 bit port when no external memory is present, but if external memory access is required then PORT P2 will act as an address bus in conjunction with PORT P0 to access external memory. PORT P2 acts as A8-A15, as can be seen from fig 1.1
PORT P0 (pins 32 to 39) PORT P0 can be used as a general purpose 8 bit port when no external memory is present, but if external memory access is required then PORT P0 acts as a multiplexed address and data bus that can be used to access external memory in conjunction with PORT P2. P0 acts as AD0-AD7.
PIN 9: PIN 9 is the reset pin which is used reset the microcontroller’s internal registers and ports upon starting up. (Pin should be held high for 2 machine cycles.)
PINS 18 & 19: The 8051 has a built-in oscillator amplifier hence we need to only
connect a crystal at these pins to provide clock pulses to the circuit.
PIN 40 and 20: Pins 40 and 20 are VCC and ground respectively. The 8051 chip needs +5V 500mA to function properly, although there are lower powered versions like the Atmel 2051 which is a scaled down version of the 8051 which runs on +3V.
PINS 29, 30 & 31: As described in the features of the 8051, this chip contains a built-in flash memory. In order to program this we need to supply a voltage of +12V at pin 31. If external memory is connected then PIN 31, also called EA/VPP, should be connected to ground to indicate the presence of external memory. PIN 30 is called ALE (address latch enable), which is used when multiple memory chips are connected to the controller and only one of them needs to be selected. We will deal with this in depth in the later chapters. PIN 29 is called PSEN. This is "program select enable". In order to use the external memory it is required to provide the low voltage (0) on both PSEN and EA pins.
VOLTAGE REGULATOR:
A device that maintains the terminal voltage of a generator or other voltage source within required limits despite variations in input voltage or load. Also known as automatic voltage regulator; voltage stabilizer.
Voltage regulators are used on distribution feeders to maintain voltage constant, irrespective of changes in either load current or supply voltage. Voltage variations must be minimized for the efficient operation of industrial equipment and for the satisfactory functioning of domestic appliances, television in particular. Voltage is controlled at the system generators, but this alone is inadequate because each generator supplies many feeders of diverse impedance and load characteristics. Regulators are applied either in substations to control voltage on a bus or individual feeder or on the line to reregulate the outlying portions of the system. These regulators are variable autotransformers with the primary connected across the line. The secondary, in which an adjustable voltage is induced, is connected in series with the line to boost or buck the voltage.
DIODE:
A Diode is a two-terminal electronic component that conducts electric current in only one direction. The term usually refers to a semiconductor diode, the most common type today. This is a crystalline piece of semiconductor material connected to two electrical terminals. A vacuum tube diode (now little used except in some high-power technologies) is a vacuum tube with two electrodes: a plate and a cathode.
The most common function of a diode is to allow an electric current to pass in one direction (called the diode's forward bias direction) while blocking current in the opposite direction (the reverse direction). Thus, the diode can be thought of as an electronic version of a check valve. This unidirectional behavior is called rectification, and is used to convert alternating current to direct current, and to extract modulation from radio signals in radio receivers.
TRANSFORMER:
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is called mutual induction.
Center tap transformer:
A center tap is a connection made to a point half way along a winding of a transformer or inductor, or along the element of a resistor or a potentiometer. Taps are sometimes used on inductors for the coupling of signals, and may not necessarily be at the half-way point, but rather, closer to one end. A common application of this is in the Hartley oscillator. Inductors with taps also permit the transformation of the amplitude of alternating current (AC) voltages for the purpose of power conversion, in which case, they are referred to as autotransformers, since there is only one winding. An example of an autotransformer is an automobile ignition coil. Potentiometer tapping provides one or more connections along the device's element, along with the usual connections at each of the two ends of the element, and the slider connection. Potentiometer taps allow for circuit functions that would otherwise not be available with the usual construction of just the two end connections and one slider connection
RESISTOR:
A resistor is a two-terminal electronic component that produces a voltage across its terminals that is proportional to the electric current through it in accordance with Ohm's law:
V = IR
Resistors are elements of electrical networks and electronic circuits and are ubiquitous in most electronic equipment. Practical resistors can be made of various compounds and films, as well as resistance wire (wire made of a high-resistivity alloy, such as nickel-chrome).
In this project we use carbon resistor.
Carbon resistor is divided into three types. …
a. Carbon composition resistors are made by mixing carbon grains with
binding material (glue) and modeled in the form of rods. Wire leads
are inserted at the two ends. After this an insulating material seals the
resistor. Resistors are available in power ratings of 1/10, 1/8, 1/4 ,
1/2 , 1.2 watts and values from 1 ohm to 20 ohms.
b. Carbon film resistors are made by deposition carbon film on a ceramic
rod. They are cheaper than carbon composition resistors.
c. Cement film resistors are made of thin carbon coating fired onto a
solid ceramic substrate. The main purpose is to have more precise
Resistance values and greater stability with heat.
CAPACITORS:
A capacitor can store charge, and its capacity to store charge is called capacitance. Capacitors consist of two conducting plates, separated by an insulating material (known as dielectric). The two plates are joined with two leads. The dielectric could be air, mica, paper, ceramic, polyester, polystyrene, etc. This dielectric gives name to the capacitor. Like paper capacitor, mica capacitor etc.
Capacitors can be broadly classified in two categories, i.e., Electrolytic capacitors and Non-Electrolytic capacitors .
In the project we use electrolytic capacitor.
Electrolytic Capacitor:
An electrolytic capacitor is a type of capacitor that uses an electrolyte, an ionic conducting liquid, as one of its plates, to achieve a larger capacitance per unit volume than other types. They are often referred to in electronics usage simply as "electrolytic".
They are used in relatively high-current and low-frequency electrical circuits, particularly in power supply filters, where they store charge needed to moderate output voltage and current fluctuations in rectifier output. They are also widely used as coupling capacitors in circuits where AC should be conducted but DC should not. There are two types of electrolytic; aluminum and tantalum.
Electrolytic capacitors are capable of providing the highest capacitance values of any type of capacitor. However they have drawbacks which limit their use. The voltage applied to them must be polarized; one specified terminal must always have positive potential with respect to the other. Therefore they cannot be used with AC signals without a DC bias. They also have very low breakdown voltage, higher leakage current and inductance, poorer tolerances and temperature range and shorter lifetimes compared to other types of capacitor.
LCD DISPLAY:
A liquid crystal display (LCD) is a thin, flat electronic visual display that uses the light modulating properties of liquid crystals (LCs). LCs do not emit light directly.
They are used in a wide range of applications including: computer monitors, television, instrument panels, aircraft cockpit displays, signage, etc. They are common in consumer devices such as video players, gaming devices, clocks, watches, calculators, and telephones. LCDs have displaced cathode ray tube (CRT) displays in most applications. They are usually more compact, lightweight, portable, less expensive, more reliable, and easier on the eyes. They are available in a wider range of screen sizes than CRT and plasma displays, and since they do not use phosphors, they cannot suffer image burn-in.
LCDs are more energy efficient and offer safer disposal than CRTs. Its low electrical power consumption enables it to be used in battery-powered electronic equipment. It is an electronically-modulated optical device made up of any number of pixels filled with liquid crystals and arrayed in front of a light source (backlight) or reflector to produce images in colour or monochrome.
Circuit Description:
Above is the quite simple schematic. The LCD panel's Enable and Register Select is connected to the Control Port. The Control Port is an open collector / open drain output. While most Parallel Ports have internal pull-up resistors, there are a few which don't. Therefore by incorporating the two 10K external pull up resistors, the circuit is more portable for a wider range of computers, some of which may have no internal pull up resistors.
We make no effort to place the Data bus into reverse direction. Therefore we hard wire the R/W line of the LCD panel, into write mode. This will cause no bus conflicts on the data lines. As a result we cannot read back the LCD's internal Busy Flag which tells us if the LCD has accepted and finished processing the last instruction. This problem is overcome by inserting known delays into our program.
The 10k Potentiometer controls the contrast of the LCD panel. Nothing fancy here. As with all the examples, I've left the power supply out. You can use a bench power supply set to 5v or use a onboard +5 regulator. Remember a few de-coupling capacitors, especially if you have trouble with the circuit working properly.
DETAIL OF EQUIPMENTS USE IN SYSTEM
| Sr.no | Equipment name | Specification | Quantity |
| 1 | Transformer (centre tap) | 220/12v,750ma | 5 |
| 2 | Diode | 1N4007,1amp | 10 |
| 3 | Capacitor | 16v,50v,1000uf,470uf,10uf | 11 |
| 4 | Resistance | 340ohm | 7 |
| 5 | Voltage regulator | IC-7805 | 5 |
| 6 | Led | | 6 |
| 7 | Crystal | 12mhz | 1 |
| 8 | Battery | 9v | 1 |
| 9 | Thermocouple | | 1 |
| 10 | Microcontroller | 8051 | 1 |
| 11 | Lcd | 16*2 | 1 |
| 12 | Connecting wire | | As need |
ADVANTAGE OF SYSTEM:
1. Conventional fault detectors response is slow in nature and even they might not be able to detect the fault due to low level of fault current. However, designed network could perform well even in the presence of considerable amount of fault resistance.
2. It is more accurate, reliable, than conventional system.
3. Minimize the energy consumption of distributed sensor participating in fault management.
4. By this system short circuit faults are relatively easy to detect and locate the fault position.
5. We can also protect transformer using overheating device and position of transformer also locate.
6. It is easy to install and use in system refurbishment.
FURTHER IMPROVEMENTS:
1. We can use the wireless technique for fault indication.
2. This model can be modified for long distance transmission faults.
3. . With the help of this model we can determine the location of a fault on a transmission line between a master station and a remote station.
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