PROTECTIVE RELAYING & COMMUNICATIONS

Transcription

1 PROTECTIVE RELAYING & COMMUNICATIONS

2 TOPICS The Power System Components Protection Principles Protection System Components 2

3 TOPOLOGY OF TYPICAL POWER SYSTEM 3

4 POWER SYSTEM COMPONENTS Generators (Alternators) Power Transformers Bus Transmission Lines Power Circuit Breakers (Live Tank & Dead Tank) Circuit Switchers Disconnect Switches (Manual & Motor Operated) Reactors (Shunt & Series) Capacitors (Shunt & Series) HVDC (High Voltage Direct Current) 4

5 GENERATORS: LARGE STEAM TURBINE 5

6 GENERATORS: WIND TURBINE 6

7 GENERATORS: HYDRO-ELECTRIC 7

8 GENERATORS: OTHERS 8

9 TRANSFORMER: 1Φ, 115/10 VOLT, 5 VA 9

10 TRANSFORMER: 3Φ 345/230/13.8 KV 600 MVA 10

11 BUS: PIPE, BAR, OR STRANDED CONDUCTOR 11

12 TRANSMISSION LINES: 345 KV 12

13 POWER CIRCUIT BREAKER: 230 KV OIL 13

14 POWER CIRCUIT BREAKER: 230 KV GAS (SF6) 14

15 POWER CIRCUIT BREAKER: 345 KV AIR BLAST 15

16 POWER CIRCUIT BREAKER: 345 KV AIR BLAST 16

17 POWER CIRCUIT BREAKER: 345 KV GAS (SF6) 17

18 OTHER POWER CIRCUIT BREAKERS 18

19 CIRCUIT SWITCHER & RL SWITCHER 19

20 DISCONNECT SWITCHES 345 KV MOTOR OPERATED 230 KV MANUAL OPERATED 20

21 REACTORS: 3Φ 13.8 KV, 50 MVAR SHUNT 21

22 REACTORS: THREE 1Φ 525 KV, 82.7 MVAR SHUNT 22

23 REACTORS: THREE 230 KV, 1200 A, 40ΩSERIES 23

24 CAPACITORS: SHUNT USED TO INCREASE SYSTEM VOLTAGE & IMPROVE POWER FACTOR 24

25 CAPACITORS: SERIES Used to reduce transmission line impedance 25

26 HVDC (HIGH VOLTAGE DIRECT CURRENT) The use of high voltage electronics allows direct current power transmission and other applications: SVC, STATCOM, SSSC, connecting asynchronous ac power systems. Protective relaying is done by the control system. 26

27 SCHEMATIC REPRESENTATION GENERATOR TRANSFORMER BUS TRANSMISSION LINE BUS TRANSMISSION LINE POWER CIRCUIT BREAKERS 27

28 WHY ARE PROTECTIVE RELAYS NECESSARY? Faults in electrical circuits are always possible Three-phase circuits can experience a variety of fault types Single-phase-to ground (most common type) Phase-to-phase Phase-to-phase-to ground Three-phase Open conductors Faults are caused by Electrical insulation failure Lightning strikes, strong wind, ice accumulation, contact by foreign objects Elevated current & arcs (>3000 f) cause equipment damage 28

29 PROTECTION SYSTEM COMPONENTS Measuring devices (instrument transformers) Current transformers (CTs): most important measurement Potential or voltage transformers (VTs, CCVTs) Power circuit breakers Circuit switchers Motor operated disconnect switches Protective relays or protection systems Teleprotection equipment 29

30 CURRENT TRANSFORMERS (CTs) Reduce large currents (thousands of amperes) to safe levels for instruments (5 amperes nominal). Are designed to accurately scale down the magnitude and phase of primary currents. Multi-ratio units have taps. Function similar to ideal current sources. Bushing current transformers are placed around the high voltage bushings of equipment like generators, transformers and power circuit breakers. Free-standing current transformers are separate high voltage devices that are connected to buses and lines. 30

31 BUSHING CURRENT TRANSFORMERS 31

32 BUSHING CURRENT TRANSFORMERS 32

33 FREE-STANDING CURRENT TRANSFORMERS 33

34 VOLTAGE TRANSFORMERS (VTs & CCVTs) Reduce large voltages (10s to 100s of kilovolts) to safe levels for instruments ( 115 volt nominal). Are designed to accurately scale down the magnitude and phase of primary voltages. Many provide two ratios. CCVTs are also used to couple high frequency power line carrier signals on to power lines. 34

35 VOLTAGE TRANSFORMERS: 345 KV 35

36 CAPACITOR VOLTAGE TRANSFORMERS: 345 KV 36

37 PROTECTIVE RELAYS IEEE definition of a protective relay: an electric device that is designed to interpret input conditions in a prescribed manner and after specified conditions are met to respond to cause contact operation or other similar abrupt change in associated electric control circuits. Inputs are usually electric, but may be mechanical, thermal, or other quantities. Have evolved over time as technology has advanced: electromechanical, solid state, microprocessor. Most protection functions are the same: different technology. 37

38 ELECTROMECHANICAL PROTECTIVE RELAYS Operate on the principles of electromagnetic attraction and induction using power system voltages and currents. Logical functions can be performed using combinations of series and parallel contacts. Each function usually requires a discrete device, which must be wired to other devices to implement logic. Electromechanical targets for post-operation analysis Rapidly being replaced by newer technology. 38

39 ELECTROMECHANICAL PROTECTIVE RELAYS ELECTROMECHANICAL TRANSMISSION LINE PROTECTION 39

40 SOLID STATE PROTECTIVE RELAYS Convert ac current and voltage input signals from instrument transformers into dc levels and square waves. Use solid state timers and logic gates to measure power system conditions and respond with contact or solid state outputs. Small scale integration (SSI) of electronics and modular circuit boards allow more functions to be incorporated into less control panel space. Much less wiring between protective devices is required since much of it is done on the foil traces of printed circuits LCD displays and LEDS for post-operation analysis. 40

41 SOLID STATE PROTECTIVE RELAYS SOLID STATE TRANSMISSION LINE PROTECTION 41

42 MICROPROCESSOR PROTECTIVE RELAYS Ac current and voltage input signals from instrument transformers are digitized by analog to digital converters. Microprocessors use algorithms to measure power system conditions and respond with contact or solid state outputs. Continuous self-diagnostics raise alarms if problems are detected within the protection system. Large scale integration (LSI) of electronics and modern fast, powerful microprocessors allow an incredible number of functions to be incorporated into very little control panel space. Virtually no wiring between protective devices is required. Extensive data recording capability: oscillographyand sequence of events for post operation analysis. Also called numerical protective relays. Perform so many functions are more correctly called protection systems. 42

43 MICROPROCESSOR PROTECTIVE RELAYS COMPLETELY REDUNDANT LINE PROTECTION 43

44 TELEPROTECTION EQUIPMENT Teleprotection equipment is used with protective relays primarily for transmission line and breaker failure protection schemes. These functions require high speed ( 4 millisecond back-to-back operate time), high dependability, and security against incorrect operation. Equipment used to carry teleprotection signals include metallic cable (short transmission lines), power line carrier, analog microwave, digital microwave, leased telephone lines, fiber optic cable, and spread spectrum radio. Modern microprocessor based transmission line protection systems can be equipped with a variety of built-in communication hardware to interface with the relay at the other terminal: RS232, RS422, G.703, IEEE C37.94 fiber optic, 820 or 1300 nm multi-mode fiber optic, and 1300 or 1550 nm single-mode fiber optic. 44

45 TELEPROTECTION EQUIPMENT The IEEE C37.94 standard defines a point-to-point optical link for synchronous data between a multiplexer and a teleprotection device. Data is usually 64 kbps but the standard allows for speeds up to 64n kbps, where n = 1, 2,F,12. IEEE C37.94 fiber optic interface can be used on multi-mode direct fiber for short-haul applications (up to 2 km) or with C37.94 compliant digital multiplexers for long distance transport. 45

46 TELEPROTECTION EQUIPMENT Fiber optic communications is an excellent application for communications within and between electric power substations because it is immune to electromagnetic interference and ground potential differences. 46

47 WILLISTON COLUMBUS KENMARE (ND_S2) (ND_L18) (BASIN) (ND_L23) 9.4 P20 P KENASTON (ND_S1) P18 P WHEELO P23 NIOBE P17 BLAISDELL PIONEER 30.7 CK (ND_L17) 22.7 (ND_L16) BERTHOLD (ND_L21) (ND_L20) 10 P22 (ND_L14).0 P16 (NNESET Juds MINOT SW 9 1 D_L19) P14 P26 (ND_L13) WILLISTON on TAN P15 9 Mall DE P13 (WAPA) WILLIAMS 6.98 ard.5 0 (ND_L22) LOGAN 1 (ND_L24) BELDEN 1 P12 (ND_L15) (ND_L12) P27 LONESOME Pate PW1 CREEK BENEDICT nt 5 (ND_L11) P11 (ND_L25). Kum 7.8 (ND_L10) Lewis & Gat Richland mer 22 Clark 39 e 72 P10 MW.5 Ridge Squa KILLDEER Squa MOUNTAIN (ND_L26) 6 wgap UNDERWOOD Richland Sub w Gap Sub 7. Roundu LOS (ND_L9) 1 AVS CHARLIE (ND_L7) Rptr p 1 P9 7 (ND_L6a) P6 CREEK P30 GREEN (ND_L6b) (ND_L27) P7 RIVER P5 GLEN FT.CLARK 7 (ND_L28) P31 ULLIN (ND_L8) P8 (ND_L5) CAPITAL P34 MANDAN HILL P4 Belfield 5.0 (ND_L3) (ND_L1) 1 6 P TAYLOR 0 DAGL 6.95 P1 P60 1 P3 (ND_L29) UM P32 NEW SALEM BISMARCK P36 (ND_L4) (ND_L2) 4. 2 SOLEN 9 EAST RAINY (IMCS_L1) Rhame P37 BUTTE Sub (ND_S3) P33 RHAME 38.6 (ND_S4) WESTFIELD NORTH DAKOTA (IMCS_L2) New Microwave Tower Information: Site Name Coordinates (DMS) Tower Height (feet)* SOUTH DAKOTA Berthold Blaisdell Columbus Daglum (Monopole) Groton (Monopole) Judson (Monopole) Kenaston (Monopole) Kenmare (Monopole) Kummer Ridge Lonesome Creek Minot SW Neset Niobe Patent Gate Pioneer PW (Monopole) Roundup Squaw Gap Rptr Squaw Gap Sub (Monopole) Underwood Wheelock * All towers are self supporting except Daglum, Groton, Kenmare, Kenaston, Judson, Richland MW,SquawGap Sub and PW1 MOUND CITY (IMCS_L3) LOWRY (IMCS_L4) ANGORA SIDING (IMCS_L24) P P GETTYSBURG (IMCS_L5) P P HIGHMORE (IMCS_L7) FT.THOMPSON (IMCS_L8) WISHEK (IMCS_L23) LEOLA (IMCS_L21) P P ORIENT (IMCS_L6) P P P FORBES (IMCS_L22) ABERDEEN (IMCS_L20) P P BROADLAND (IMCS_L12) CROW LAKE (IMCS_L9) New Microwave Hop Existing Microwave Site New Microwave Site Existing Microwave Hop New Microwave Hop Existing Microwave Hop (to be replaced) Fiber Optic Path Substation Location P New Path 2017 New Microwave Site Equipment in Cabinet P P ORDWAY (IMCS_L19) CRANDALL (IMCS_L17) CLARK (IMCS_L14) ALPENA (IMCS_L11) P P P P48 HURON 2.52 (IMCS_L13) STORLA (IMCS_L10) GROTON (IMCS_L18) P P P WALLACE (IMCS_L16) P WTO WAPA RPTR WATERTO WN BASIN (IMCS_L15a) (IMCS_L15b) Map Updates 03/14/2017 JAB 47

48 PROTECTION FUNCTIONS ANSI /IEEE standard C37.2 standard for electrical power system device function numbers, acronyms, and contact designations 21 -Distance relay 46 - Reverse-phase or phase-balance current relay 50 - Instantaneous overcurrent relay 51 -AC inverse time overcurrent relay 59 -Overvoltage relay 67 - AC directional overcurrent relay 87 - Differential protective relay Ninety-nine different defined functions 48

49 51 - OVERCURRENT FUNCTION As current magnitude increases operating time decreases. When a short circuit occurs on a power system element the current it draws greatly increases. 49

50 21 - DISTANCE FUNCTION Distance functions operate on the impedance plane plotted using the R & X axis. They possess a characteristic shape that defines the border of the operate and restraint regions. The mho circle is one of the most commonly used shapes in protective relaying. Other shapes like the quadrilateral are also used. Transmission line protection is a common application. When a short circuit occurs on a power system element the impedance measured by its protective relay changes suddenly and dramatically. 50

51 21 - DISTANCE FUNCTION MHO CHARACTERISTIC QUADRILATERAL CHARACTERISTIC 51

52 21 - DISTANCE FUNCTION THREE-ZONE STEPPED DISTANCE SCHEME LINE F1 2 F

53 21 - DISTANCE FUNCTION X Z = E / I RESTRAINT REGION OPERATE REGION LINE IMPEDANCE FAULT IMPEDANCE LOAD IMPEDANCE R 53

54 87 - DIFFERENTIAL FUNCTION Operates on the difference of two quantities Current differential protection widley used on generators buses, transformers, reactors, and short transmission lines Current differential protection operates on the principal of Kirchoff s current law: Σ i = 0 Voltage differential is used on capacitor banks 54

55 87 -DIFFERENTIAL FUNCTION (CURRENT) GENERATOR TRANSFORMER LOAD CURRENT BUS TRANSMISSION LINE BUS LINE 87 Σ I = 0 55

56 BASIC OBJECTIVES OF PROTECTIVE RELAYING Reliability Selectivity Speed Simplicity Economy 56

57 RELIABILITY Protection systems spend 99.9% of their service time monitoring power system elements and very little of it operating so they must work when called on. Periodic testing of protective relays is done to verify that they are functioning properly. Electromechanical and solid state protective relays provided no indication that they had failed until they incorrectly operated. Microprocessor relays use selfdiagnostics that will alarm on many failures. 57

58 SELECTIVITY Maximizes continuity of service for power system elements. When faults do occur the minimum amount of high voltage equipment must be disconnected: only that required to isolate the fault. Prevents larger, cascading power outages. 58

59 SPEED Quick clearing of faults minimizes damage and enhances power system stability. Modern EHV protection system equipment can clear a fault in less than four cycles (.067 seconds). Human eye blink = seconds. 59

60 SIMPLICITY Utilizing the minimum amount of equipment and the simplest schemes to provide protection saves time and money and maximizes the odds of a scheme working correctly. K.I.S.S. (Keep it simple) 60

61 ECONOMICS Minimum total cost is important for everyone that uses electricity. Cheap electricity enhances a nation's prosperity. With their greatly increased capabilities and smaller size modern protection systems are a bargain compared to legacy (electromechanical & solid state) systems. Fully optioned modern transmission line protection systems can be purchased for $10k to $15k. They are extremely versatile and can do practically anything the protection engineer desires. 61

62 ZONES OF PROTECTION Are defined by the locations of current transformers. Allow protection systems to isolate only the faulted element. Will discuss four zones: Generator Bus Transformer Transmission line 62

63 ZONES OF PROTECTION GENERATOR TRANSFORMER BUS TRANSMISSION LINE BUS LINE 63

64 GENERATOR PROTECTION Faults Phase or ground faults in the stator or protection zone Ground faults in the rotor (field windings) Abnormal conditions Loss of or low excitation Overload Overvoltage Low or high frequency Motoring Connecting to grid out of synchronism Loss of synchronism with the grid 64

65 BUS PROTECTION Ground faults Phase faults Overvoltage protection normally not applied 65

66 TRANSFORMER PROTECTION Ground and phase faults (87) Overvoltage (59) Overload or backup protection (51, 21) 66

67 TRANSMISSION LINE PROTECTION Ground and phase faults (21, 87, 67n) Overvoltage (59) Time delayed backup protection ( 2, 21) High speed clearing of faults is dependent upon communications between protective relays at the ends of the line: pilot or communications based protection schemes 67

68 TYPES OF PILOT PROTECTION Pilot wire (requires a cable) Directional comparison systems DCB - directional comparison blocking DCUB - directional comparison unblocking POTT - permissive overreaching transfer trip (popular) DUTT - direct underreaching transfer trip (permissive and non-permissive Phase comparison Current differential (87) [increasing in popularity] 68

69 PILOT WIRE RELAYING For fault at F2 or for load vs at bus 1 and 2 have opposite polarity For fault at F1 vs at bus 1 and 2 has same polarity. 1 LINE F1 2 F2 TRIP PCB 1 87 PILOT WIRE CABLE 87 TRIP PCB 2 69

70 PILOT WIRE RELAYING (HCB-1) 70

71 NOT PILOT WIRE RELAYING 71

72 DCB -DIRECTIONAL COMPARISON BLOCKING 21 R 21 F 1 LINE F1 2 F2 21 F TRIP PCB 1 16 MS R X T X TELEPROTECTION (PLC) TX RX 21 R AND TELEPROTECTION (PLC) 16 MS TRIP PCB 2 72

73 POTT -PERMISSIVE OVERREACHING TRANSFER TRIP 21 1 LINE F1 2 F2 21 TRIP PCB 1 RX TX TELEPROTECTION TX AND RX TELEPROTECTION TRIP PCB 2 73

74 PROTECTIVE RELAY OPERATION URL El Dorado 500 Kv Switch.url 74

75 PROTECTION SYSTEM FAILURE URL Transformer Fire.url 75