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Protection Fundamentals

Protection Fundamentals. By Craig Wester, John Levine. Outline. Introductions Tools Enervista Launchpad On – Line Store Demo Relays at ISO / Levine Discussion of future classes Protection Fundamentals ANSI number handout, Training CD’s. Introduction. Speakers:

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Protection Fundamentals

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

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

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

  4. 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. 4 GE Consumer & Industrial Multilin

  5. Tools 5 GE Consumer & Industrial Multilin

  6. 6 GE Consumer & Industrial Multilin

  7. 7 GE Consumer & Industrial Multilin

  8. Demo Relays with Ethernet • Working with James McRoy and Dave Curtis • SR 489 • SR 750 • G30 • MIF II • Training CD’s 8 GE Consumer & Industrial Multilin

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

  10. 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 CD’s, 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 – Ct’s and PT’s 10 GE Consumer & Industrial Multilin

  11. Protection Fundamentals 11 GE Consumer & Industrial Multilin

  12. Desirable Protection Attributes • Reliability: System operate properly • Security: Don’t trip when you shouldn’t • 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: Don’t break the bank 12 GE Consumer & Industrial Multilin

  13. Art & Science of Protection • 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 13 GE Consumer & Industrial Multilin

  14. Art & Science of Protection • 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 zone’s 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) 14 GE Consumer & Industrial Multilin

  15. 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). 15 GE Consumer & Industrial Multilin

  16. 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. 16 GE Consumer & Industrial Multilin

  17. 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 17 GE Consumer & Industrial Multilin

  18. 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 18 GE Consumer & Industrial Multilin

  19. (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 19 GE Consumer & Industrial Multilin

  20. Time Overcurrent Protection (TOC) • Selection of the curves uses what is termed as a “ time multiplier” or “time 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 20 GE Consumer & Industrial Multilin

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

  22. 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 23 GE Consumer & Industrial Multilin

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

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

  25. 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 26 GE Consumer & Industrial Multilin

  26. 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 27 GE Consumer & Industrial Multilin

  27. 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 28 GE Consumer & Industrial Multilin

  28. 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 29 GE Consumer & Industrial Multilin

  29. Z T B 2 Z A T 1 21 21 A B Source Impedance X Z L • Relay in Zone 1 operates first • Time between Zones is called CTI R 30 GE Consumer & Industrial Multilin

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

  31. Transformer zone Bus zone Bus zone Bus zone Unit Generator-Tx zone Line zone Motor zone Transformer zone ~ XFMR Bus Motor Line Bus Bus Generator XFMR ProtectionZones • Generator or Generator-Transformer Units • Transformers • Buses • Lines (transmission and distribution) • Utilization equipment (motors, static loads, etc.) • Capacitor or reactor (when separately protected) 34 GE Consumer & Industrial Multilin

  32. Relay Zone A Relay Zone A Zone B Zone B Zone A Zone A Relay Zone B Relay Zone B CTs are located at both sides of CB-fault between CTs is cleared from both remote sides CTs are located at one side of CB-fault between CTs is sensed by both relays, remote right side operate only. Zone Overlap • Overlap is accomplished by the locations of CTs, the key source for protective relays. • 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. 35 GE Consumer & Industrial Multilin

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

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

  35. 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 42 GE Consumer & Industrial Multilin

  36. 1-Line Symbols [1] 43 GE Consumer & Industrial Multilin

  37. 1-Line Symbols [2] 44 GE Consumer & Industrial Multilin

  38. 1-Line Symbols [3] 45 GE Consumer & Industrial Multilin

  39. 1-Line Symbols [4] 46 GE Consumer & Industrial Multilin

  40. 1-Line [1] 47 GE Consumer & Industrial Multilin

  41. 1-Line [2]

  42. 3-Line 49 GE Consumer & Industrial Multilin

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

  44. Lock Out Relay 55 GE Consumer & Industrial Multilin

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

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

  47. Current Transformers • 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 58 GE Consumer & Industrial Multilin

  48. Standard IEEE CT Relay Accuracy • 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) 59 GE Consumer & Industrial Multilin

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

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

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