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1 GE Consumer & Industrial Multilin Protection Fundamentals By Craig Wester, John Levine.

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Presentation on theme: "1 GE Consumer & Industrial Multilin Protection Fundamentals By Craig Wester, John Levine."— Presentation transcript:

1 1 GE Consumer & Industrial Multilin Protection Fundamentals By Craig Wester, John Levine

2 2 GE Consumer & Industrial Multilin Outline Introductions Tools –Enervista Launchpad –On – Line Store –Demo Relays at ISO / Levine Discussion of future classes Protection Fundamentals ANSI number handout, Training CDs

3 3 GE Consumer & Industrial Multilin Introduction Speakers: –Craig Wester – GE Multilin Regional Manager –John Levine – GE Multilin Account Manager

4 4 GE Consumer & Industrial Multilin Objective We are here to help make your job easier. This is very informal and designed around ISO Applications. Please ask question. We are not here to preach to you. The knowledge base on GE Multilin Relays varies greatly at ISO. If you have a question, there is a good chance there are 3 or 4 other people that have the same question. Please ask it.

5 5 GE Consumer & Industrial Multilin Tools

6 6 GE Consumer & Industrial Multilin

7 7 GE Consumer & Industrial Multilin

8 8 GE Consumer & Industrial Multilin Demo Relays with Ethernet Working with James McRoy and Dave Curtis SR 489 SR 750 G30 MIF II Training CDs

9 9 GE Consumer & Industrial Multilin Demo Relays at L-3

10 10 GE Consumer & Industrial Multilin Future Classes GE Multilin Training will be the 2nd Friday of every month. We will cover: –March – Basics, Enervista Launchpad, ANSI number and what they represent, Uploading, downloading, Training CDs, etc. –April – 489 Relay –May – MIF II relay –June - 750 Relay –July - UR relay basic including Enervista Engineer –August – UR F60 and F35 relays –September – G30 and G60 including Transformer and Generator in same zone –October – Communications and security –November - Neutral Grounding Resistors –December – Cts and PTs

11 11 GE Consumer & Industrial Multilin Protection Fundamentals

12 12 GE Consumer & Industrial Multilin Desirable Protection Attributes Reliability: System operate properly –Security: Dont trip when you shouldnt –Dependability: Trip when you should Selectivity: Trip the minimal amount to clear the fault or abnormal operating condition Speed: Usually the faster the better in terms of minimizing equipment damage and maintaining system integrity Simplicity: KISS Economics: Dont break the bank

13 13 GE Consumer & Industrial Multilin Selection of protective relays requires compromises: Maximum and Reliable protection at minimum equipment cost High Sensitivity to faults and insensitivity to maximum load currents High-speed fault clearance with correct selectivity Selectivity in isolating small faulty area Ability to operate correctly under all predictable power system conditions Art & Science of Protection

14 14 GE Consumer & Industrial Multilin Cost of protective relays should be balanced against risks involved if protection is not sufficient and not enough redundancy. Primary objectives is to have faulted zones primary protection operate first, but if there are protective relays failures, some form of backup protection is provided. Backup protection is local (if local primary protection fails to clear fault) and remote (if remote protection fails to operate to clear fault) Art & Science of Protection

15 15 GE Consumer & Industrial Multilin 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).

16 16 GE Consumer & Industrial Multilin 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 P&C, metering, SCADA, etc. Regulators - voltage, current, VAR, phase angle, etc.

17 17 GE Consumer & Industrial Multilin Types of Protection Overcurrent Uses current to determine magnitude of fault –Simple –May employ definite time or inverse time curves –May be slow –Selectivity at the cost of speed (coordination stacks) –Inexpensive –May use various polarizing voltages or ground current for directionality –Communication aided schemes make more selective

18 18 GE Consumer & Industrial Multilin Instantaneous Overcurrent Protection (IOC) & Definite Time Overcurrent Relay closest to fault operates first Relays closer to source operate slower Time between operating for same current is called CTI (Clearing Time Interval) Distribution Substation

19 19 GE Consumer & Industrial Multilin (TOC) Coordination Relay closest to fault operates first Relays closer to source operate slower Time between operating for same current is called CTI Distribution Substation

20 20 GE Consumer & Industrial Multilin Selection of the curves uses what is termed as a time multiplier ortime dial to effectively shift the curve up or down on the time axis Operate region lies above selected curve, while no-operate region lies below it Inverse curves can approximate fuse curve shapes Time Overcurrent Protection (TOC)

21 21 GE Consumer & Industrial Multilin Multiples of pick-up Time Overcurrent Protection (51, 51N, 51G)

22 22 GE Consumer & Industrial Multilin Classic Directional Overcurrent Scheme for Looped System Protection

23 23 GE Consumer & Industrial Multilin Types of Protection Differential –current in = current out –Simple –Very fast –Very defined clearing area –Expensive –Practical distance limitations Line differential systems overcome this using digital communications

24 24 GE Consumer & Industrial Multilin Differential Note CT polarity dots This is a through-current representation Perfect waveforms, no saturation

25 25 GE Consumer & Industrial Multilin Differential Note CT polarity dots This is an internal fault representation Perfect waveforms, no saturation

26 26 GE Consumer & Industrial Multilin Types of Protection Voltage Uses voltage to infer fault or abnormal condition May employ definite time or inverse time curves May also be used for undervoltage load shedding –Simple –May be slow –Selectivity at the cost of speed (coordination stacks) –Inexpensive

27 27 GE Consumer & Industrial Multilin Types of Protection Frequency Uses frequency of voltage to detect power balance condition May employ definite time or inverse time curves Used for load shedding & machinery under/overspeed protection –Simple –May be slow –Selectivity at the cost of speed can be expensive

28 28 GE Consumer & Industrial Multilin Types of Protection Power Uses voltage and current to determine power flow magnitude and direction Typically definite time –Complex –May be slow –Accuracy important for many applications –Can be expensive

29 29 GE Consumer & Industrial Multilin Types of Protection Distance (Impedance) –Uses voltage and current to determine impedance of fault –Set on impedance [R-X] plane –Uses definite time –Impedance related to distance from relay –Complicated –Fast –Somewhat defined clearing area with reasonable accuracy –Expensive –Communication aided schemes make more selective

30 30 GE Consumer & Industrial Multilin Impedance Relay in Zone 1 operates first Time between Zones is called CTI R X Z L

31 31 GE Consumer & Industrial Multilin Impedance: POTT Scheme –POTT will trip only faulted line section –RO elements are 21; 21G or 67N

32 32 GE Consumer & Industrial Multilin Power vs. Protection Engineer: Views of the World 180 Opposites!

33 Generation-typically at 4-20kV Transmission-typically at 230-765kV Subtransmission-typically at 69-161kV Receives power from transmission system and transforms into subtransmission level Receives power from subtransmission system and transforms into primary feeder voltage Distribution network-typically 2.4-69kV Low voltage (service)-typically 120-600V Typical Bulk Power System 33 GE Consumer & Industrial Multilin

34 34 GE Consumer & Industrial Multilin 1.Generator or Generator-Transformer Units 2.Transformers 3.Buses 4.Lines (transmission and distribution) 5.Utilization equipment (motors, static loads, etc.) 6.Capacitor or reactor (when separately protected) Unit Generator-Tx zone Bus zone Line zone Bus zone Transformer zone Bus zone Generator ~ XFMR Bus LineBus XFMRBusMotor Motor zone Protection Zones

35 35 GE Consumer & Industrial Multilin 1.Overlap is accomplished by the locations of CTs, the key source for protective relays. 2.In some cases a fault might involve a CT or a circuit breaker itself, which means it can not be cleared until adjacent breakers (local or remote) are opened. Zone A Zone B Relay Zone A Relay Zone B CTs are located at both sides of CB- fault between CTs is cleared from both remote sides Zone A Zone B Relay Zone A Relay Zone B CTs are located at one side of CB- fault between CTs is sensed by both relays, remote right side operate only. Zone Overlap

36 Electrical – Mechanical Parameter Comparisons 36 GE Consumer & Industrial Multilin

37 Electrical – Mechanical Parameter Comparisons

38 Effects of Capacitive & Inductive Loads on Current

39 39 GE Consumer & Industrial Multilin Motor Model and Starting Curves

40 40 GE Consumer & Industrial Multilin 1.One-line diagram of the system or area involved 2.Impedances and connections of power equipment, system frequency, voltage level and phase sequence 3.Existing schemes 4.Operating procedures and practices affecting protection 5.Importance of protection required and maximum allowed clearance times 6.System fault studies 7.Maximum load and system swing limits 8.CTs and VTs locations, connections and ratios 9.Future expansion expectance 10.Any special considerations for application. What Info is Required to Apply Protection

41 C37.2: Device Numbers Partial listing 41 GE Consumer & Industrial Multilin

42 42 GE Consumer & Industrial Multilin One Line Diagram Non-dimensioned diagram showing how pieces of electrical equipment are connected Simplification of actual system Equipment is shown as boxes, circles and other simple graphic symbols Symbols should follow ANSI or IEC conventions

43 43 GE Consumer & Industrial Multilin 1-Line Symbols [1]

44 44 GE Consumer & Industrial Multilin 1-Line Symbols [2]

45 45 GE Consumer & Industrial Multilin 1-Line Symbols [3]

46 46 GE Consumer & Industrial Multilin 1-Line Symbols [4]

47 47 GE Consumer & Industrial Multilin 1-Line [1]

48 1-Line [2]

49 49 GE Consumer & Industrial Multilin 3-Line

50 50 GE Consumer & Industrial Multilin Diagram Comparison

51 51 GE Consumer & Industrial Multilin C37.2: Standard Reference Position 1) These may be speed, voltage, current, load, or similar adjusting devices comprising rheostats, springs, levers, or other components for the purpose. 2) These electrically operated devices are of the nonlatched-in type, whose contact position is dependent only upon the degree of energization of the operating, restraining, or holding coil or coils that may or may not be suitable for continuous energization. The de- energized position of the device is that with all coils de-energized 3) The energizing influences for these devices are considered to be, respectively, rising temperature, rising level, increasing flow, rising speed, increasing vibration, and increasing pressure. 4.5.3) In the case of latched-in or hand- reset relays, which operate from protective devices to perform the shutdown of a piece of equipment and hold it out of service, the contacts should preferably be shown in the normal, nonlockout position

52 52 GE Consumer & Industrial Multilin CB Trip Circuit (Simplified)

53 53 GE Consumer & Industrial Multilin Showing Contacts NOT in Standard Reference Condition Some people show the contact state changed like this

54 54 GE Consumer & Industrial Multilin Showing Contacts NOT in Standard Reference Condition Better practice, do not change the contact style, but rather use marks like these to indicate non- standard reference position

55 55 GE Consumer & Industrial Multilin Lock Out Relay

56 56 GE Consumer & Industrial Multilin CB Coil Circuit Monitoring: T with CB Closed; C with CB Opened

57 57 GE Consumer & Industrial Multilin CB Coil Circuit Monitoring: Both T&C Regardless of CB state

58 58 GE Consumer & Industrial Multilin Current transformers are used to step primary system currents to values usable by relays, meters, SCADA, transducers, etc. CT ratios are expressed as primary to secondary; 2000:5, 1200:5, 600:5, 300:5 A 2000:5 CT has a CTR of 400 Current Transformers

59 59 GE Consumer & Industrial Multilin IEEE relay class is defined in terms of the voltage a CT can deliver at 20 times the nominal current rating without exceeding a 10% composite ratio error. For example, a relay class of C100 on a 1200:5 CT means that the CT can develop 100 volts at 24,000 primary amps (1200*20) without exceeding a 10% ratio error. Maximum burden = 1 ohm. 100 V = 20 * 5 * (1ohm) 200 V = 20 * 5 * (2 ohms) 400 V = 20 * 5 * (4 ohms) 800 V = 20 * 5 * (8 ohms) Standard IEEE CT Relay Accuracy

60 60 GE Consumer & Industrial Multilin Excitation Curve

61 61 GE Consumer & Industrial Multilin Standard IEEE CT Burdens (5 Amp) (Per IEEE Std. C57.13-1993)

62 62 GE Consumer & Industrial Multilin Current into the Dot, Out of the Dot Current out of the dot, in to the dot

63 63 GE Consumer & Industrial Multilin VPVPVPVP VSVSVSVS Relay Voltage (potential) transformers are used to isolate and step down and accurately reproduce the scaled voltage for the protective device or relay VT ratios are typically expressed as primary to secondary; 14400:120, 7200:120 A 4160:120 VT has a VTR of 34.66 Voltage Transformers

64 64 GE Consumer & Industrial Multilin Typical CT/VT Circuits Courtesy of Blackburn, Protective Relay: Principles and Applications

65 65 GE Consumer & Industrial Multilin CT/VT Circuit vs. Casing Ground Case ground made at IT location Secondary circuit ground made at first point of use Case Secondary Circuit

66 66 GE Consumer & Industrial Multilin Equipment Grounding –Prevents shock exposure of personnel –Provides current carrying capability for the ground-fault current –Grounding includes design and construction of substation ground mat and CT and VT safety grounding

67 67 GE Consumer & Industrial Multilin System Grounding –Limits overvoltages –Limits difference in electric potential through local area conducting objects –Several methods Ungrounded Reactance Coil Grounded High Z Grounded Low Z Grounded Solidly Grounded

68 68 GE Consumer & Industrial Multilin 1.Ungrounded: There is no intentional ground applied to the system- however its grounded through natural capacitance. Found in 2.4- 15kV systems. 2.Reactance Grounded: Total system capacitance is cancelled by equal inductance. This decreases the current at the fault and limits voltage across the arc at the fault to decrease damage. X 0 <= 10 * X 1 System Grounding

69 69 GE Consumer & Industrial Multilin 3.High Resistance Grounded: Limits ground fault current to 10A-20A. Used to limit transient overvoltages due to arcing ground faults. R 0 <= X 0C /3, X 0C is capacitive zero sequence reactance 4.Low Resistance Grounded: To limit current to 25-400A R 0 >= 2X 0 System Grounding

70 70 GE Consumer & Industrial Multilin 5.Solidly Grounded: There is a connection of transformer or generator neutral directly to station ground. Effectively Grounded: R 0 <= X 1, X 0 <= 3X 1, where R is the system fault resistance System Grounding

71 71 GE Consumer & Industrial Multilin Grounding Differences….Why? –Solidly Grounded Much ground current (damage) No neutral voltage shift –Line-ground insulation Limits step potential issues Faulted area will clear Inexpensive relaying

72 72 GE Consumer & Industrial Multilin Grounding Differences….Why? –Somewhat Grounded Manage ground current (manage damage) Some neutral voltage shift Faulted area will clear More expensive than solid, less expensive then ungrounded

73 73 GE Consumer & Industrial Multilin Grounding Differences….Why? –Ungrounded Very little ground current (less damage) Big neutral voltage shift –Must insulate line-to-line voltage May run system while trying to find ground fault Relay more difficult/costly to detect and locate ground faults If you get a second ground fault on adjacent phase, watch out!

74 74 GE Consumer & Industrial Multilin System Grounding Influences Ground Fault Detection Methods Low/No Z

75 75 GE Consumer & Industrial Multilin System Grounding Influences Ground Fault Detection Methods Med/High Z

76 76 GE Consumer & Industrial Multilin Basic Current Connections: How System is Grounded Determines How Ground Fault is Detected Medium/High Resistance Ground Low/No Resistance Ground

77 77 GE Consumer & Industrial Multilin Substation Types Single Supply Multiple Supply Mobile Substations for emergencies Types are defined by number of transformers, buses, breakers to provide adequate service for application

78 78 GE Consumer & Industrial Multilin Industrial Substation Arrangements (Typical)

79 79 GE Consumer & Industrial Multilin Industrial Substation Arrangements (Typical)

80 80 GE Consumer & Industrial Multilin Utility Substation Arrangements Single Bus, 1 Tx, Dual supply Single Bus, 2 Tx, Dual Supply 2-sections Bus with HS Tie-Breaker, 2 Tx, Dual Supply (Typical)

81 81 GE Consumer & Industrial Multilin Breaker-and-a-half –allows reduction of equipment cost by using 3 breakers for each 2 circuits. For load transfer and operation is simple, but relaying is complex as middle breaker is responsible to both circuits Utility Substation Arrangements Bus 1 Bus 2 Ring bus –advantage that one breaker per circuit. Also each outgoing circuit (Tx) has 2 sources of supply. Any breaker can be taken from service without disrupting others. (Typical)

82 82 GE Consumer & Industrial Multilin Double Bus: Upper Main and Transfer, bottom Double Main bus Utility Substation Arrangements Main-Reserved and Transfer Bus: Allows maintenance of any bus and any breaker (Typical)

83 83 GE Consumer & Industrial Multilin Switchgear Defined Assemblies containing electrical switching, protection, metering and management devices Used in three-phase, high-power industrial, commercial and utility applications Covers a variety of actual uses, including motor control, distribution panels and outdoor switchyards The term "switchgear" is plural, even when referring to a single switchgear assembly (never say, "switchgears") May be a described in terms of use: –"the generator switchgear" –"the stamping line switchgear"

84 Switchgear Examples

85 85 GE Consumer & Industrial Multilin Switchgear: MetalClad vs. Metal-Enclosed Metal-clad switchgear (C37.20.2) –Breakers or switches must be draw-out design –Breakers must be electrically operated, with anti- pump feature –All bus must be insulated –Completely enclosed on all side and top with grounded metal –Breaker, bus and cable compartments isolated by metal barriers, with no intentional openings –Automatic shutters over primary breaker stabs. Metal-enclosed switchgear –Bus not insulated –Breakers or switches not required to be draw-out –No compartment barriering required

86 86 GE Consumer & Industrial Multilin Switchgear Basics [1] All Switchgear has a metal enclosure Metalclad construction requires 11 gauge steel between sections and main compartments Prevents contact with live circuits and propagation of ionized gases in the unlikely event of an internal fault. Enclosures are also rated as weather-tight for outdoor use Metalclad gear will include shutters to ensure that powered buses are covered at all times, even when a circuit breaker is removed.

87 87 GE Consumer & Industrial Multilin Switchgear Basics [2] Devices such as circuit breakers or fused switches provide protection against short circuits and ground faults Interrupting devices (other than fuses) are non- automatic. They require control signals instructing them to open or close. Monitoring and control circuitry work together with the switching and interrupting devices to turn circuits on and off, and guard circuits from degradation or fluctuations in power supply that could affect or damage equipment Routine metering functions include operating amperes and voltage, watts, kilowatt hours, frequency, power factor.

88 88 GE Consumer & Industrial Multilin Switchgear Basics [3] Power to switchgear is connected via Cables or Bus Duct The main internal bus carries power between elements within the switchgear Power within the switchgear moves from compartment to compartment on horizontal bus, and within compartments on vertical bus Instrument Transformers (CTs & PTs) are used to step down current and voltage from the primary circuits or use in lower- energy monitoring and control circuitry.

89 89 GE Consumer & Industrial Multilin Air Magnetic Breakers

90 90 GE Consumer & Industrial Multilin SF6 and Vacuum Breakers

91 91 GE Consumer & Industrial Multilin A Good Day in System Protection…… –CTs and VTs bring electrical info to relays –Relays sense current and voltage and declare fault –Relays send signals through control circuits to circuit breakers –Circuit breaker(s) correctly trip What Could Go Wrong Here????

92 92 GE Consumer & Industrial Multilin A Bad Day in System Protection…… –CTs or VTs are shorted, opened, or their wiring is –Relays do not declare fault due to setting errors, faulty relay, CT saturation –Control wires cut or batteries dead so no signal is sent from relay to circuit breaker –Circuit breakers do not have power, burnt trip coil or otherwise fail to trip Protection Systems Typically are Designed for N-1

93 93 GE Consumer & Industrial Multilin Protection Performance Statistics Correct and desired: 92.2% Correct but undesired: 5.3% Incorrect: 2.1% Fail to trip: 0.4%

94 94 GE Consumer & Industrial Multilin Contribution to Faults

95 95 GE Consumer & Industrial Multilin Fault Types (Shunt)

96 96 GE Consumer & Industrial Multilin Short Circuit Calculation Fault Types – Single Phase to Ground

97 97 GE Consumer & Industrial Multilin Short Circuit Calculations Fault Types – Line to Line

98 98 GE Consumer & Industrial Multilin Short Circuit Calculations Fault Types – Three Phase

99 99 GE Consumer & Industrial Multilin AC & DC Current Components of Fault Current

100 100 GE Consumer & Industrial Multilin Variation of current with time during a fault

101 101 GE Consumer & Industrial Multilin Variation of generator reactance during a fault

102 102 GE Consumer & Industrial Multilin Useful Conversions

103 103 GE Consumer & Industrial Multilin Per Unit System Establish two base quantities: Standard practice is to define –Base power – 3 phase –Base voltage – line to line Other quantities derived with basic power equations

104 104 GE Consumer & Industrial Multilin Per Unit Basics

105 105 GE Consumer & Industrial Multilin Short Circuit Calculations Per Unit System Per Unit Value = Actual Quantity Base Quantity V pu = V actual V base I pu = I actual I base Z pu = Z actual Z base

106 106 GE Consumer & Industrial Multilin Short Circuit Calculations Per Unit System

107 107 GE Consumer & Industrial Multilin Short Circuit Calculations Per Unit System – Base Conversion Z pu = Z actual Z base Z base = kV 2 base MVA base Z pu1 = MVA base1 kV 2 base1 X Z actual Z pu2 = MVA base2 kV 2 base2 X Z actual Z pu2 = Z pu1 x kV 2 base1 x MVA base2 kV 2 base2 MVA base1

108 108 GE Consumer & Industrial Multilin Information for Short Circuit, Load Flow and Voltage Studies To perform the above studies, information is needed on the electrical apparatus and sources to the system under consideration

109 109 GE Consumer & Industrial Multilin

110 110 GE Consumer & Industrial Multilin Utility Information kV MVA short circuit Voltage and voltage variation Harmonic and flicker requirements

111 111 GE Consumer & Industrial Multilin Generator Information Rated kV Rate MVA, MW Xs; synchronous reactance Xd; transient reactance Xd; subtransient reactance

112 112 GE Consumer & Industrial Multilin Motor Drive kV Rated HP or KW Type –Sync or Induction Subtransient or locked rotor current Is it regenerative Harmonic spectrum

113 113 GE Consumer & Industrial Multilin Transformers Rated primary and secondary kV Rated MVA (OA, FA, FOA) Winding connections (Wye, Delta) Impedance and MVA base of impedance Reactors Rated kV Ohms

114 114 GE Consumer & Industrial Multilin Cables and Transmission Lines For rough calculations, some can be neglected Length of conductor Impedance at given length Size of conductor Spacing of overhead conductors Rated voltage Type of conduit Number of conductors or number per phase

115 115 GE Consumer & Industrial Multilin ANSI 1-Line

116 116 GE Consumer & Industrial Multilin IEC 1-Line

117 117 GE Consumer & Industrial Multilin Short Circuit Study [1]

118 118 GE Consumer & Industrial Multilin Short Circuit Study [2]

119 Short Circuit Study [3] 119 GE Consumer & Industrial Multilin

120 120 GE Consumer & Industrial Multilin A Study of a Fault…….

121 Fault Interruption and Arcing 121 GE Consumer & Industrial Multilin

122 122 GE Consumer & Industrial Multilin Arc Flash Hazard

123 123 GE Consumer & Industrial Multilin Arc Flash Mitigation: Problem Description –An electric arc flash can occur if a conductive object gets too close to a high-amp current source or by equipment failure (ex., while opening or closing disconnects, racking out) The arc can heat the air to temperatures as high as 35,000 F, and vaporize metal in equipment The arc flash can cause severe skin burns by direct heat exposure and by igniting clothing The heating of the air and vaporization of metal creates a pressure wave (arc blast) that can damage hearing and cause memory loss (from concussion) and other injuries. Flying metal parts are also a hazard.

124 124 GE Consumer & Industrial Multilin Methods to Reduce Arc Flash Hazard –Arc flash energy may be expressed in I 2 t terms, so you can decrease the I or decrease the t to lessen the energy –Protective relays can help lessen the t by optimizing sensitivity and decreasing clearing time Protective Relay Techniques –Other means can lessen the I by limiting fault current Non-Protective Relay Techniques

125 125 GE Consumer & Industrial Multilin Non-Protective Relaying Methods of Reducing Arc Flash Hazard –System design modifications increase power transformer impedance Addition of phase reactors Faster operating breakers Splitting of buses –Current limiting fuses (provides partial protection only for a limited current range) –Electronic current limiters (these devices sense overcurrent and interrupt very high currents with replaceable conductor links (explosive charge) –Arc-resistant switchgear (this really doesn't reduce arc flash energy; it deflects the energy away from personnel) –Optical arc flash protection via fiber sensors –Optical arc flash protection via lens sensors

126 126 GE Consumer & Industrial Multilin Protective Relaying Methods of Reducing Arc Flash Hazard –Bus differential protection (this reduces the arc flash energy by reducing the clearing time –Zone interlock schemes where bus relay selectively is allowed to trip or block depending on location of faults as identified from feeder relays –Temporary setting changes to reduce clearing time during maintenance Sacrifices coordination –FlexCurve for improved coordination opportunities –Employ 51VC/VR on feeders fed from small generation to improve sensitivity and coordination –Employ UV light detectors with current disturbance detectors for selective gear tripping

127 127 GE Consumer & Industrial Multilin Fuses vs. Relayed Breakers

128 Arc Flash Hazards 128 GE Consumer & Industrial Multilin

129 Arc Pressure Wave 129 GE Consumer & Industrial Multilin

130 Arc Flash Warning Example [1] 130 GE Consumer & Industrial Multilin

131 Arc Flash Warning Example [2] 131 GE Consumer & Industrial Multilin

132 Arc Flash Warning Example [3] 132 GE Consumer & Industrial Multilin

133 133 GE Consumer & Industrial Multilin Copy of this presentation are at: www.L-3.com\private\Levine

134 134 GE Consumer & Industrial Multilin Protection Fundamentals QUESTIONS?


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