Their theory, design, and practical operation
By Victor H. Todd
McGraw-Hill book company, Inc. , 1922
In preparing a work of this nature, it will be realized that the subject is so broad and varied in its scope as to preclude an author's intimate personal knowledge of each and every system described. Attempt has been made to cover the subject the first principles of Protective Relays to the protection of high tension net-works, the object being to make the work of value not only to the operator and tester who has a fair knowledge of electricity and is seeking more information, but also to the designer of the system who may find many points not previously
taken into consideration in his calculations.
Consequently, many reliable sources of information were freely consulted and in several instances, passages were quoted verbatim a booklet entitled "Performance of Instrument
Transformers" and "Protective Relays" which in turn was reprinted an article by Mr. L. N. Crichton in The Electric Journal. Full credit is hereby given to the Westinghouse Electric & Manufacturing Company for such excerpts; also to the American Institute of Electrical Engineers for several paragraphs quoted its June, 1919, Proceedings.
Some of this material has been published in the form of articles by the author in Power, Power Plant Engineering, Electrical Record and Southern Engineer, and thanks are hereby given to their editors for permission to use the text and electro-types for illustrations.
The author also wishes to extend his thanks and appreciation to Mr. F. A. Annett, Associate Editor of Power, for personal interest and assistance in the preparation of the work; to Mr. L. N. Crichton, Relay Engineer of the Westinghouse Electric & Manufacturing Company, and writer of several articles which much valuable information was obtained, who kindly read this manuscript, and offered many helpful suggestions and constructive criticisms; and to officials of the Westinghouse Electric & Manufacturing Company, the General Electric Company and the Condit Electric Company, for valuable assistance in procuring photographs for illustrations.
What are Protective Relays
Early SystemsŚFire RisksŚInsulated FusesŚObjectionsŚAutomatic SwitchesŚDefinitionŚReasons for RelaysŚRequirementsŚ SavingsŚPrinciples of OperationŚNomenclature.
Circuit Breakers and Releases
ClassesŚPrinciples of OperationŚAdjustmentŚShunt-trip AttachmentŚUnderload ReleaseŚUndervoltage ReleaseŚOvervoltage ReleaseŚWhy Releases are not Always Sufficient.
Trip Circuits and Time Delays
Object of TripŚTrip Circuit SourcesŚShunt TripŚAuxiliary ContactsŚCircuit Opening or Series TripŚObjectionsŚTransfer RelaysŚTime DelaysŚClassificationsŚInverse-time LimitŚDefinite TimeŚInverse-definite TimeŚHow Time Delays are Obtained.
Plunger-type Protective Relays
Various FormsŚAdjustmentsŚMore FormsŚDefinite-time Relay Ś Bellows-typeŚObjectionsŚSimple System Ś Typical A.C. Plunger-typeŚIllustration of SettingŚRelays RequiredŚ More Bellows TypesŚOil Dashpot TypesŚLimitationsŚDefinite-timeŚTripping Sources.
D.C. Power-directional Relays
Necessity of this TypeŚD'Arsonval TypeŚUsed as Excess-current RelayŚPolarized TypeŚMoving Iron TypeŚBusbar Types.
Applications of D.C. Power-directional Relays
Limitations to UseŚStorage Battery ProtectionŚOther Methods ŚStandby BatteriesŚFailure of Prime MoversŚLoss of Field ProtectionŚParallel Feeders on D.C.ŚRing System on D.C.ŚWider ApplicationsŚUndercurrent ProtectionŚOvervoltage ProtectionŚUndervoltage Protection.
Induction-type Current Relays
DevelopmentŚTypical RelayŚSettingsŚTorque CompensatorŚTime DelaysŚContinuity of Trip IndicatorŚInduction vs. Solenoid-plunger RelaysŚRelay ContactsŚLoad on TransformerŚRelay Specifications.
A.C. Power-directional Relays
Early developmentŚMost Common UseŚOverload and Reverse-current RelaysŚObjections and FailingsŚLatest DevelopmentsŚThe Contactor SwitchŚThe Torque CompensatorŚStray Field EffectŚOther TypesŚDifferential Power-directional Relay
Characteristics op A.C. Disturbances
Important PointsŚEffects of OverloadŚNature of Short-circuits on Transmission LinesŚCalculation of the Short-circuit CurrentŚnator and Transformer ConstantsŚEffect of Low VoltageŚEffect of Unbalanced Short-circuitsŚCharacteristics of Relays.
Instrument Transformers and Groupings
Current and Voltage TransformersŚInherent ErrorsŚRatio EirorŚMagnetization of CoreŚEffect of Secondary LoadŚOther Sources of ErrorŚSingle-phase GroupingsŚTwo-phase GroupingsŚNecessity for Three Transformers on Three-phaseŚAdvantages of the Z-connectionŚOpening of SecondaryŚVoltage TransformersŚVarious ErrorsŚPolyphase GroupingsŚLoad on TransformersŚUse of Both Current and Potential TransformersŚ
Connections to Watt RelayŚStar-delta ConnectionŚDetermining Phase Rotation.
Protection op Motors, Transformers, Generators and Lines
Protection of MotorsŚSettingsŚTwo-phase ProtectionŚThree-phase ProtectionŚProtection of Synchronous
MotorsŚProtection of Rotary ConvertersŚTransformer ProtectionŚProtection in BanksŚPower-directional Relay ProtectionŚOther Differential MethodsŚPolyphase Transformer ProtectionsŚProtecting Three-phase Star-delta BanksŚProtection of GeneratorsŚProtection by Power-directional RelaysŚProtection of Single LinesŚProtection
Protection of Parallel Feeders
ObjectsŚVarious MethodsŚInverse-time-limit DiscriminationŚBalanced Protection SystemŚDifferential Balance Relay ProtectionŚSplit-conductor SystemŚThe Pilot Wire SystemŚProtection by Power-directional RelaysŚCross-connected Power-directional RelaysŚDifferential Power-directional or Double-contact RelaysŚDisadvantages of Cross-connected Systems.
Protection op Radial Ring and Network Systems
Simple Radial SystemŚSelecting the Proper RelayŚLimit of DivisionsŚThe Ring SystemŚTime SettingsŚParallel Feeders on RingŚRings with More than One SourceŚProtection of NetworksŚThe Under voltage and Excess-current System.
Over and UndervoltageŚUndercurrentŚOverload TelegraphŚReversed PhasesŚService-restoring RelaysŚInteresting OscillogramsŚBell-ringing RelaysŚD.C. Temperature RelaysŚA.C. Temperature RelaysŚRelay SwitchesŚTransfer RelaysŚHigh-tension RelaysŚTiming Relays with a Cycle CounterŚPrinciple of Cycle CounterŚTiming a Circuit-closing RelayŚTiming a Circuit-opening RelayŚTiming the Breaker or Oil SwitchŚ
Testing Direct-current Relays
Ground-testingŚTesting Relay SwitchesŚVarious Loads and Testing SourcesŚTesting Millivolt-type RelaysŚTesting Plunger-type RelaysŚTesting Time-limit RelaysŚCurves and TablesŚConclusions.
Testing nating-current Relays
Reasons for TestingŚRelays Requiring Current OnlyŚSourcesŚRheostatsŚPhantom LoadsŚStandardsŚCurrent Transformers ŚTrip CircuitsŚTiming the RelayŚAn Actual TestŚThe Cycle CounterŚMaking the AdjustmentŚAdditional PrecautionsŚTesting Voltage RelaysŚPower-directional RelaysŚReverse-phase RelaysŚTemperature RelaysŚConclusion.
Locating Faults in Feeders and Wiring
Most Common FaultsŚApparatus RequiredŚTesting for Opens, Shorts or GroundsŚAccurately Locating the Short-circuitŚLocalizing a GroundŚCalculating the LocationŚTwo-ammeter MethodŚThe Fault LocalizerŚL and N Power BridgeŚBurning out the Fault.
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