Slide 11: Primary Equipment Components • Transformers - to step up or step down voltage level • Breakers - to energize equipment and interrupt fault current to isolate faulted equipment • Insulators - to insulate equipment from ground and other phases • Isolators switches - to create a visible and permanent isolation of primary equipment for maintenance purposes and route power flow over certain buses. • Bus - to allow multiple connections feeders to the same source of power transformer. Presented by C.GOKULAP/EEE Velalar College of Engg Tech Erode. Slide 12: Primary Equipment Components • Grounding - to operate and maintain equipment safely • Arrester - to protect primary equipment of sudden overvoltage lightning strike. • Switchgear – integrated components to switch protect meter and control power flow • Reactors - to limit fault current series or compensate for charge current shunt • VT and CT - to measure primary current and voltage and supply scaled down values to PC metering SCADA etc. • Regulators - voltage current VAR phase angle etc.

Slide 33:  A power system fault may be defined as any condition or abnormality of the system which involves the electrical failure of primary equipment such as generators transformers busbars overhead lines and cables and all other items of plant which operate at power system voltage.  Electrical failure generally implies one or the other or both of two types of failure namely insulation failure resulting in a short-circuit condition or conducting path failure resulting in an open-circuit condition the former being by far the more common type of failure. FAULT IN POWER SYSTEM.

Slide 57:  Primary Relay: relay connected directly in the circuit  Secondary Relay: relay connected to the protected circuit through CT VT.  Auxiliary Relay: relay operate in response to opening or closing of another relay.  Measuring Relay: It performs the measurement of normal abnormal conditions in the power system.  Electro Magnetic Relay: It operates on the principle of Electromagnetic induction.  Static RelaySolid-state relay: They use diodes transistors SCRs Logic gates etc.

Is not compulsory, unless specifically stated, and you are free to take other action Switchgear And Protection book written by M V. Bakshi, published by Technical Publications has been. Free User Manual Guide And eBook PDF MMXIIIRoME. ROME 1-4 JULY, 2013. ABSTRACT BOOK. Jul 22, 2017. Switchgear Protection And Power Systems has 141. Power system protection and switchgear Download power system protection and switchgear or read online here in PDF or EPUB Pdf of switchgear and protection DOWNLOAD!. Power System Protection And Switchgear By Bakshi Pdf Free Download:.

Static circuit is the measuring circuit no moving parts  Microprocessor Based Relay: All functions of a relay can done by using microprocessor. Relays are programmable.

ΜP can compare compute and send trip signals. Slide 58:  Thermal Relay: It operates on the principle of Electro- thermal effect.  Distance Relay: relay measures the impedance or reactance or admittance.

 Impedance Relay: relay measures the impedance of the transmission line.  Reactance Relay: relay measures the reactance of the transmission line.  Over-current Relay: relay operates when the current exceeds a pre-set value.  Under-voltage Relay: relay operates when the voltage falls a pre-set value.  Directional Relay: relay able to sense whether fault lies in forward or reverse direction.  Polarized Relay: relay depends on the direction of the current.

Slide 77:  If inductance L of appropriate value is connected in parallel with the capacitance of the system the fault current IF flowing through L will be in phase opposition to the capacitive current IC of the system. If L is so adjusted that IL IC then resultant current in the fault will be zero.

This condition is known as Resonant Grounding. When the value of L of arc suppression coil is such that the fault current IF exactly balances the capacitive current IC it is called resonant grounding. Slide 79: • Suppose line to ground fault occurs in the line B at point F. The fault current IF and capacitive currents IR and IY will flow as shown in Fig • Note that IF flows through the Peterson coil or Arc suppression coil to neutral and back through the fault. The total capacitive current IC is the phasor sum of IR IY as shown in phasor diagram in Fig. • The voltage of the faulty phase is applied across the arc suppression coil.

Therefore fault current IF lags the faulty phase voltage by 90°. • The current IF is in phase opposition to capacitive current IC See Fig. By adjusting the tappings on the Peterson coil the resultant current in the fault can be reduced. If inductance of the coil is so adjusted that IL IC then resultant current in the fault will be zero. Rod gap:  It is a very simple type of diverter and consists of two 1.5 cm rods.  One rod is connected to the line circuit and the other rod is connected to earth.

 The distance between gap and insulator must not be less than one third of the gap length so that the arc may not reach the insulator and damage it.  The rod gap should be so set that it breaks down to a voltage not less than 30 below the voltage withstand level of the equipment to be protected. Presented by C.GOKULAP/EEE Velalar College of Engg Tech Erode. Slide 105: 3.

Valve type  Valve type arresters incorporate non linear resistors and are extensively used on systems operating at high voltages.  It consists of two assemblies i series spark gaps and ii non-linear resistor discs  The non-linear elements are connected in series with the spark gaps. Both the assemblies are accommodated in tight porcelain container.  The spark gap is a multiple assembly consisting of a number of identical spark gaps in series.  Each gap consists of two electrodes with fixed gap spacing. Slide 106:  The spacing of the series gaps is such that it will withstand the normal circuit voltage.  An over voltage will cause the gap to break down causing the surge current to ground via the non- linear resistors.

 The non-linear resistor discs are made of inorganic compound such as thyrite or metrosil.  These discs are connected in series.  The non-linear resistors have the property of offering a high resistance to current flow when normal system voltage is applied but a low resistance to the flow of high surge currents. Slide 134: ii Solenoid type relay • It consists of a solenoid and movable iron plunger arranged as shown. • Under normal operating conditions the current through the relay coil C is such that it holds the plunger by gravity or spring in the position shown. • However on the occurrence of a fault the current through the relay coil becomes more than the pickup value causing the plunger to be attracted to the solenoid.

The upward movement of the plunger closes the trip circuit thus opening the circuit breaker and disconnecting the faulty circuit. Slide 140: • If φ1 and φ2 represent the fluxes produced by the respective pairs of poles then torque produced is proportional to φ1 Φ2 sin α. • where α is the phase difference between the two fluxes. A control spring and the back stop for closing of the contacts carried on an arm are attached to the spindle of the cup to prevent the continuous rotation. • Induction cup structures are more efficient torque producers than either the shaded-pole or the watthour meter structures.

Therefore this type of relay has very high speed and may have an operating time less then 0.1 second. Slide 144: Constructional details It consists of a metallic aluminium disc which is free to rotate in between the poles of two electromagnets.

The upper electromagnet has a primary and a secondary winding. The primary is connected to the secondary of a C.T. In the line to be protected and is tapped at intervals. The tappings are connected to a plug- setting bridge by which the number of active turns on the relay operating coil can be varied thereby giving the desired current setting. The secondary winding is energized by induction from primary and is connected in series with the winding on the lower magnet. The controlling torque is provided by a spiral spring.

The spindle of the disc carries a moving contact which bridges two fixed contacts connected to trip circuit when the disc rotates through a pre-set angle. This angle can be adjusted to any value between 0° and 360°. By adjusting this angle the travel of the moving contact can be adjusted and hence the relay can be given any desired time setting. Slide 145: Operation The driving torque on the aluminium disc is set up due to the induction principle. This torque is opposed by the restraining torque provided by the spring. Under normal operating conditions restraining torque is greater than the driving torque produced by the relay coil current. Therefore the aluminium disc remains stationary.

If the current in the protected circuit exceeds the pre-set value the driving torque becomes greater than the restraining torque. Nba 2k14 Updates Shoes here. Consequently the disc rotates and the moving contact bridges the fixed contacts when the disc has rotated through a pre-set angle.

The trip circuit operates the circuit breaker which isolates the faulty section. Slide 151: Due to phase difference between two flux quantaties i.e. Α 90-θ Φ 1 α V φ 2 α I Hence T φ 1 φ 2 sin α φ 1 φ 2 sin90- θ VI COS θ POWER  Hence the relay activated only when there is a specific direction of power flow  when power flows in normal direction both driving torque and restraining torque twists in same direction and relay does not operates.  when the power flow is in reverse direction driving torque and restraining torque acts in opposite direction and relay operates.therefore CB operates and disconnects faulty section. Slide 154: Directional overcurrent relay makes use of two relays i directional power relay directional element ii Non directional current relay non-directional element Construction: 1 Directional element: It is similar in construction to directional power relay.

 it consists of upper magnet which is E-shaped and carries primary winding which is excited by voltage of the circuit to be protected through secondary of PT.  The lower magnet is U-shaped carries secondary winding which is excited by current of the circuit to be protected through secondary of CT.  The secondary winding is extended to lower magnet primary winding as shown.  The trip contacts 1 2 are connected in series with secondary winding of lower magnet. Therefore for the relay to operate at first directional element should be activated first. Slide 155: 2 Non directional element: It is activated only by current flowing in the circuit  it is similar in construction to non-directional over current relay. For this element to operate at first directional element should be activated first.

 the secondary winding is further connected to PSM not shown for current setting. Operation:  When short circuit occurs current tend to be reversed.Hence directional element starts operating and closes the trip contact.  with closing of trip contact the secondary winding of non directional element is complete and disc starts rotating. When moving contact bridges fixed contact the circuit breaker operates and separates the faulty section. Slide 173: Now I 1 leads I R by 30 o while I 2 lags I R by 30 o. Similarly the current I B gets divided into two equal parts I 3 and I 4.

The current I 3 lags I 4 by 60 o. From equation 1 we can write I B /√3 I 3 I 4..2 The current I 4 leads by I B while current I 3 lags I B by 30 o. The current entering the relay at the junction point B in the Fig. 1 is the vector sum of and. I relay Ī 1 + Ī 3 + Ī Y I Y + I R /√3 leads I R by 30 o + I B /√3lags I B by30 o  when the load is balanced and no negative sequence currents exist.

Slide 179: • In case of electrical quantities exceed a predetermined value a current differential relay is one that compares the current entering a section of the system with current leaving the section. • Under normal operating conditions the two currents are equal but as soon as fault occurs this condition no longer applies. The difference between the incoming and outgoing currents is arranged to flow through relay operating coil. If this difference is equal to or greater than the pick up value the relay will operate and open the circuit breaker and isolate the faulty section. • Any type of relay when connected in a particular way can be made to operate as a differential relay. It is not the relay construction but the way in which relay is connected in a circuit makes it a differential relay.

Slide 180: There are three fundamental systems of differential or balanced protection: I. Current differential relay II. Voltage differential relay III.

Biased beam relay or percentage differential relay i Current balance protection Fig 16 a shows an arrangement of an over current relay connected to operate as a differential relay. A pair of identical current transfonners is fitted on either end of the section to be protected alternator winding in this case. The secondaries of CT’s are connected in series in such a way that they carry the induced currents in the same direction.

The operating coil of over current relay is connected across the CT secondary circuit. This differential relay compares the current at the two ends of the alternator winding. Slide 181: Under normal operating conditions suppose the alternator winding carries a normal current of 1000 A.

Then the current in the two secondaries of CT’s are equal as in figure. These currents will merely circulate between the two CT’s and no current will flow through the differential relay as shown in the diagram fig 16 a. Therefore the relay remains inoperative. If a ground fault occurs on the alternator winding as shown in fig 16 b.

The two secondary currents will not be equal and the current flows through the operating coil of the relay causing the relay to operate. The amount of current flow through the relay will depend upon the way the fault is being fed. Slide 184: Under healthy conditions equal currents will flow in both primary windings.

Therefore the secondary voltages of the two transformers are balanced against each other and no current will flow through the relay-operating coil. When a fault occurs in the protected zone the currents in the two primaries will differ from one another and their secondary voltages will no longer be in balance. This voltage difference will cause a current to flow through the operating coil of the relay which closes the trip circuit. Slide 186: The biased beam relay also called percentage differential relay is designed to respond to the differential current in terms of its fractional relation to the current flowing through the protected section. It’s called percentage differential relay because the ratio of differential operating current to average restraining current is a fixed percentage. It’s called bias relay because restraining known as biased coil produces the bias force.

Software For Iomega External Hard Drive. Fig 17 a shows the schematic arrangements of biased beam relay. It is essentially an over current balanced beam type relay with an additional restraining coil. The restraining coil produces a bias force in the opposite direction to the operating force. Biased beam relay or percentage differential relay. Slide 190: • The static relay is the next generation relay after electromechanical type. • The Solid Static relays was first introduced in 1960’s.

The term ‘static’ implies that the relay has no moving mechanical parts in it. • Compared to the Electromechanical Relay the Solid Static relay has longer life-span decreased noise when operates and faster respond speed. • The static relays have been designed to replace almost all the functions which were being achieved earlier by electromechanical relays. Slide 198: Fault and Abnormal Conditions  Generator: Over Current Over Voltage Under Voltage Under Frequency Unbalanced Current Loss of Excitation Reverse Power Winding Inter turn Fault Winding Earth Fault etc.

 Transformer: Over Current Winding Inter turn fault Excessive Temperature Rise Unbalance Current Over fluxing etc.  Motors: Over Current Under Voltage Unbalance Current Winding Short Circuit Stator Earth Fault etc.  Transmission Line: Single Phase to ground fault Phase to Phase Fault three phase to ground fault Over Current etc. Slide 222: Introduction  Generator is the electrical end of a turbo-generator set.

Without Generator turbine/boiler/any Power Plant Equipment is meaningless. Generator is the most precious/valuable equipment in PP which actually converts the mechanical energy of turbine into electricity. So Generator should be protected from faults occurring within generator and also from external faults/abnormal operating condition in the GRID which affected the generator.  Various relays/devices are used to detect the abnormalities in operations and whenever fault conditions appear they can give warning alarms to the operators or trip the unit automatically.  Generally automatic tripping are provided if the time for operator to take corrective action is less or the fault is likely to cause serious damage to the unit. Slide 230: 100 STATOR EARTH FAULT:  In this protection where neutral voltage measurement is made at generator terminals By Broken Delta the third harmonic voltage element is used.  First earth fault very near to neutral produces negligible current as driving voltage is nearly zero.

But if a 2nd earth fault occurs at machine terminal line to ground fault is not limited by NGR. The resulting fault current can be high. Hence the 1st E/F very near to neutral has to be detected early and isolated.  All generators produce continuous current of 3rd harmonic voltage. Under normal condition 3rd harmonic voltage is present. If there is a fault near neutral the amount of 3rd harmonic voltage comes down and this is used for detection.

Slide 232: ROTOR EARTH FAULT:  Since rotor circuits operate ungrounded a single earth fault is caused by insulation failure due to moisture ageing of insulation or vibration of rotor etc. But existence of single ground fault increases the chance of a second ground fault. The occurrence of second earth fault can cause fault current flows. This results unsymmetrical flux distribution. The air gap flux is badly distorted. The rotor is displaced enough to rub stator leading to severe vibrations and can damage the bearing.

 Although a machine can continuously run on a single earth fault but second rotor earth fault if allowed to occur should be detected immediately and generator should be tripped. Slide 234: DIFFERENTIAL PROTECTION  Differential protection is very reliable method for stator winding phase to phase fault. In this currents on both sides of the generator are compared.  Under normal condition or for a fault outside of the protected zone current i1s is equal to current i2s. Therefore the currents in the CTs secondaries are also equal i1si2s and no current flows through the current relays.

 If a fault develops inside of the protected zone current i1s and i2s are no longer equal therefore i1s and i2s are not equal and therefore a current flowing in the current relay. Slide 236: Negative Phase Sequence Protection:  When the generator is connected to a balanced load the phase currents are equal in magnitude and displaced electrically by 120°. The ATs wave produced by the stator currents rotate synchronously with the rotor and no eddy currents are induced in the rotor parts.  If there is an unbalanced loading of the generator and then the stator currents have a –ve sequence component.

The stator field due to these –ve sequence currents rotates at synchronous speed but in a direction opposite to the direction of the field structure on the rotor. Thus the –ve sequence stator armature mmf rotates at a speed –Ns while the rotor field speed is +Ns. There is a relative velocity of 2Ns between the two.  These causes double frequency currents of large amplitude to be induced in the rotor conductors and iron part. So both the eddy currents as well as the hystersis losses increase due to these double frequencies induced currents in the rotor.  Unbalanced loading affects a Rotor heating b Severe vibration heating of stator.

Slide 237: FIELD FAILURE PROTECTION:  Acts as an Induction Generator.  Possible Causes  AVR Fault  Tripping of Field C.B.  Open circuit or Short circuit occurring in the D.C.  PMG failure  In normal condition generator when running shares the reactive demand of the system. If excitation fails synchronous generator runs at a super-synchronous speed draws reactive power from the power system instead of supplying the Qe. In case the other generators can’t meet the requirement of reactive power this shall result in large voltage drop which may ultimately result in instability.

 In this case slip becomes –Ve result in slip frequency currents. Rotor gets heated up due to induced currents in the rotor winding core or damage the winding if this condition is sustained. Stator heats up due to high stator currents due to increase in reactive current from the system.  By monitor i Field current If  ii Phase current voltage. Slide 238: REVERSE POWER PROTECTION:  This protection is provided to protect against motoring.  A generator is expected to supply active power to the connected system in normal operation. If the generator primover fails a generator that is connected in parallel with another source of electrical supply will to begin to motor.

This reversal of power flow due to loss of prime mover can be detected by reverse power element.  Possible Causes:  When immediately after Synchronising control valves are not operated which may happen due to some fault in the system or some delay by the operating personnel.  In case of sudden closure of stop valves or control valves when the generator unit is still connected to the grid.  Reverse power operation is harmful to the turbine since without steam flow in the turbine. If the turbine continues to rotate it will result in heating of turbine blades due to churning action. However the period for the turbine to overheat may vary from a few seconds to minutes depending upon the turbine operating conditions.

Slide 250: Differential Protection • Differential protection may be considered the first line of protection for internal phase-to-phase or phase-to-ground faults. Summation method with six CTs: • If six CTs are used in a summing configuration during motor starting the values from the two CTs on each phase may not be equal as the CTs are not perfectly identical and asymmetrical currents may cause the CTs on each phase to have different outputs. • The running differential delay can then be fine tuned to an application such that it responds very fast and is sensitive to low differential current levels.

Slide 267: Two Busbar Protection Schemes: Low Impedance - using time overcurrent relays  inexpensive but affected by CT saturation.  low voltage application 34.5kV and below • High Impedance - using overvoltage relays this scheme loads the CTs with a high impedance to force the differential current through the CTs instead of the relay operating coil.  expensive but provides higher protection security.  115kV and above voltage application or some 34.5kV bus voltages which require high protection security. Busbar Protection.

Slide 279: Current and Voltage Transformers in Protective Relaying System  Protective Relays in A.C. Power Systems are connected from the secondary circuits of C.T.  Current Transformers: C.T.

Are used for measurement and Protection. Its step down the current from high value to low current value. Their ratio is constant for given range of Primary Secondary Current.  Potential Transformer: P.T. Are used for measurement and Protection. Its step down the high voltage to low voltage value. The ratio is constant for given range of Primary and Secondary voltage.

Slide 285: The ARC The electric arc constitute a basic indispensable and active element in the process of current interruption. 1.Basic theory of electric discharge The conduction of electricity is through the gases or vapors which contain positive and negative charge carriers and all types of discharge involve the very fundamental process of production movement absorption of these carriers which is the mode of carrying the current between the electrodes. The gas discharge phenomena can broadly classified as: a. The non-self sustained discharge b. The self sustaining discharges Presented by C.GOKULAP/EEE Velalar College of Engg Tech Erode.

Slide 318: Prevention of restrikes  To produce a good ionizing arc the space between two walls of arc chute can be narrowed to restrict the arc  At the same time it can be broken into number of arcs by inserting a grating of vertical metal plane Dissipation of stored energy  A protective spark gap can be used across the CB to reduce the size of the commuting capacitor.  It will keep the abnormal voltage produced at the switching time below the undesired level  By means of high frequency currents the spark gap acts as an energy dissipating device. Slide 338: 4.

SF6 CIRCUIT BREAKERS  It contains an arc interruption chamber containing SF 6 gas.  In closed position the contacts remain surrounded by SF 6 gas at a pressure of 2.8 kg/cm 2.  During opening high pressure SF6 gas at 14 kg/cm 2 from its reservoir flows towards the chamber by valve mechanism.  SF 6 rapidly absorbs the free electrons in the arc path to form immobile negative ions to build up high dielectric strength.  It also cools the arc and extinguishes it.

 After operation the valve is closed by the action of a set of springs.  Absorbent materials are used to absorb the byproducts and moisture. Slide 344: Why 'Testing of Circuit Breaker' is Necessary A Circuit Breaker should be capable of carrying making and breaking under normal and abnormal conditions. In any power system circuit breaker has to withstand power frequency over voltages and transient over voltages due to switching and lightning.

The performance of a circuit breaker under normal and abnormal conditions can be verified by performing different type of tests on circuit breakers. The main purpose of testing of circuit breakers is to confirm if circuit breaker is able to work on particular voltage and current ratings or not. Slide 348: In this test the C.B. Is open and closed 500 times or other value as agreed to between the purchaser and the supplier.the test are carried out without current through the main circuit of the C.B.Out of the total number of tests 10 should be closed-open operationthat is with the trippingmechanism energized by the closing of main contacts.During the testsoccasional lubricationbut no mechanical adjustments are permissible.after the testsall parts including contacts should be in good condition and there should be no permanent distortion and undue wear of the parts. Slide 350: 1 Breaking capacity Test:- • Sequence of performing this tests is as follows:-  First of allthe master circuit breaker MBand the breaker under test TBare closed.  The s.c.current is passed by closing the make switch.  The circuit breaker under testTB is opened to interrupt the s.c.current at desired moment.

• The following measurements related to the breaking capacity performance are taken from the oscillogram during the test:-  Symmetrical breaking current  Asymmetrical breaking current  Amplitude factor  Natural frequency of oscillations and RRRVRATE OF RISE OF RISTRIKING VOLTAGE. Slide 352: 3 Short Time Withstand Current Capacity •In this test the rated short-time withstand current is applied to the circuit breaker under test for the specified duration of the time. •The rated short time withstand current is equal to be rated short circuit breaking current and standard value of rated duration of short circuit current is 1 second or 3 seconds. •The current is measured by taking an oscillograph of the short circuit current wave. After the test there should be no mechanical or insulation damage and any contact welding. Slide 360: PPT References Unit 1:  Power System Protection Fundamentals by Dr. Mobarak  PROTECTION RELAY SCHEMES  Earthing by Er.

Satnam Singh LecturerElectrical engg. GPC Mohali Khunimajra  ET 601 – POWER SYSTEM PROTECTION  POWER SYSTEM PROTECTION by Chandra Bhushan Singh  EE 445 Course Presentation Power System Protection by Mohammed AL-Zeer  SURGE DIVERTER by NEHA KARDAM FARHEEN KHAN  INTRODUCTION TO SWITCHGEAR by R.J.Phansalkar  Symmetrical Components I by Dave Angell Idaho Power. Slide 362: PPT References Unit 3:  Motor Protection Principles  TRANSFORMER PROTECTION  GENERATOR TRANSFORMER MOTOR AND TRANSMISSION LINE PROTECTION PROTECTIONS  GENERATOR PROTECTION by ABU SAMAH ABU HASANINSTITUT LATIHAN SULTAN AHMAD SHAHTENAGA NASIONAL BERHAD MALAYSIA  Protection of Transmission Lines by Rohini Haridas  Generator Protection Switchgear by Bhushan Kumbhalkar  Fundamentals of Transformer Protection by Bhuvanesh Oza  Transformer protection ELE304  TRANSFORMER PROTECTION - USAID  MOTOR PROTECTION by R.J. Phansalkar RD CS Electric.