PROTECTIVE RELAYING & COMMUNICATIONS

2

TOPICS

• The Power System

• Components

• Protection Principles

• Protection System Components

3

TOPOLOGY OF TYPICAL

POWER SYSTEM

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)

5

GENERATORS: LARGE

STEAM TURBINE

6

GENERATORS: WIND TURBINE

7

GENERATORS: HYDRO-ELECTRIC

8

GENERATORS: OTHERS

9

TRANSFORMER:

1Φ, 115/10 VOLT, 5 VA

10

TRANSFORMER:

3Φ 345/230/13.8 KV 600 MVA

11

BUS: PIPE, BAR,

OR STRANDED CONDUCTOR

12

TRANSMISSION LINES: 345 KV

13

POWER CIRCUIT BREAKER:

230 KV OIL

14

POWER CIRCUIT BREAKER:

230 KV GAS (SF6)

15

POWER CIRCUIT BREAKER:

345 KV AIR BLAST

16

POWER CIRCUIT BREAKER:

345 KV AIR BLAST

17

POWER CIRCUIT BREAKER:

345 KV GAS (SF6)

18

OTHER POWER CIRCUIT

BREAKERS

19

CIRCUIT SWITCHER & RL

SWITCHER

20

DISCONNECT SWITCHES

345 KV MOTOR OPERATED 230 KV MANUAL OPERATED

21

REACTORS: 3Φ 13.8 KV,

50 MVAR SHUNT

22

REACTORS: THREE 1Φ 525 KV,

82.7 MVAR SHUNT

23

REACTORS: THREE 230 KV,

1200 A, 40Ω SERIES

24

CAPACITORS: SHUNT

USED TO

INCREASE SYSTEM

VOLTAGE &

IMPROVE POWER

FACTOR

25

CAPACITORS: SERIES

Used to reduce transmission line impedance

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.

27

SCHEMATIC REPRESENTATION

GENERATOR TRANSFORMER BUS

POWER CIRCUIT BREAKERS

BUSTRANSMISSION

LINE

TRANSMISSION

LINE

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

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

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.

31

BUSHING CURRENT

TRANSFORMERS

32

BUSHING CURRENT

TRANSFORMERS

33

FREE-STANDING CURRENT

TRANSFORMERS

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.

35

VOLTAGE TRANSFORMERS:

345 KV

36

CAPACITOR VOLTAGE

TRANSFORMERS: 345 KV

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.

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.

39

ELECTROMECHANICAL

PROTECTIVE RELAYS

ELECTROMECHANICAL TRANSMISSION LINE PROTECTION

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.

41

SOLID STATE PROTECTIVE RELAYS

SOLID STATE TRANSMISSION LINE PROTECTION

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: oscillography and sequence of

events for post operation analysis.• Also called numerical protective relays. Perform so many functions

are more correctly called protection systems.

43

MICROPROCESSOR

PROTECTIVE RELAYS

COMPLETELY REDUNDANT LINE PROTECTION

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.

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.

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.

47

NEW

SALEM(ND_L4)

CAPITAL

HILL(ND_L1)

MANDAN(ND_L3)

BISMARCK(ND_L2)

WISHEK(IMCS_L23)

SOLEN(IMCS_L1)

WESTFIELD(IMCS_L2) FORBES

(IMCS_L22)

MOUND

CITY(IMCS_L3)

LOWRY(IMCS_L4)

LEOLA(IMCS_L21)

GETTYSBURG(IMCS_L5)

ABERDEEN(IMCS_L20)

HURON(IMCS_L13)

BROADLAND(IMCS_L12)

ALPENA(IMCS_L11)

FT.THOMPSON(IMCS_L8)

HIGHMORE(IMCS_L7)

CRANDALL(IMCS_L17) WALLACE

(IMCS_L16)

WATERTO

WN

BASIN(IMCS_L15a)

(IMCS_L15b)

CROW

LAKE(IMCS_L9)

STORLA(IMCS_L10)

GROTON(IMCS_L18)

SOUTH DAKOTA

NORTH DAKOTA

ORDWAY(IMCS_L19)

ORIENT(IMCS_L6)

ANGORA

SIDING(IMCS_L24)

CLARK(IMCS_L14)

21.68

26.72

26.891.36

6.95

23.10

28.53

35.98

28.64

28.94

22.02

36.97

27.64

15.45

37.31

21.25

21.51

20.82

2.52

36.50

36.

10

23.94

23.93

15.07

13.77

10.75

38.69

22.94

43.19

43.06

P1

P2

P3

P4

P8

P36

P37

P38

P39

P40

P41

P42

P43

P44

P45

P46

P47

P48

P49

P

5

0

P51

P52

P53

P54

P55

P56

P57

P58

P59

P60

(NNESET

D_L19)MINOT SW(ND_L13)

LOGAN(ND_L12)

BENEDICT(ND_L10)

UNDERWOOD(ND_L9)LOS

(ND_L7)

FT.CLARK(ND_L8)

TAYLOR(ND_L29)

AVS(ND_L6a)

(ND_L6b)GREEN

RIVER(ND_L28)

WILLIAMS(ND_L24)

CHARLIE

CREEK(ND_L27)

WILLISTON

(WAPA) (ND_L22)

EAST RAINY

BUTTE(ND_S3)

COLUMBUS(ND_L18)

KILLDEER

MOUNTAIN (ND_L26)

BELDEN(ND_L15)

BLAISDELL(ND_L16)

21.91

26.85

42.00

29.08

27.92

25.26

12.59

20.17

38.6

20.94

32.59

22.96

6.98

25.74

Belfield

67

41

P6

P7P5

P9

P10

P11

P12

P14

P16

P20

P27

P22

P18

P30

P31

P33

P34

P32

WILLISTON

(BASIN) (ND_L23)

P26

9.96

BERTHOLD(ND_L14)

KENASTON (ND_S1)

KENMARE (ND_S2)

Existing Microwave Site

New Microwave Site 2012-2014

Existing Microwave Hop

New Microwave Hop 2012-2014

Existing Microwave Hop (to be replaced)

Fiber Optic Path

Substation Location

RHAME

(ND_S4)

GLEN

ULLIN(ND_L5)

WHEELO

CK (ND_L20)

PIONEER(ND_L21)

30.7

P23

Map Updates 03/14/2017 JAB

LONESOME

CREEK(ND_L25)

New Microwave Tower Information:

Site Name Coordinates (DMS) Tower Height (feet)*

Berthold 48-19-34.35 101-45-35.3 250

Blaisdell 48-20-58.46 102-04-40.31 290

Columbus 48-46-25.3 102-46-04.10 290

Daglum 46-39-27.9 103-04-22.0 60 (Monopole)

Groton 45-22-26.8 98-06-11.3 100 (Monopole)

Judson 48-08-56.00 103-46-15.70 120 (Monopole)

Kenaston 48-37-54.3 102-06-20.9 100 (Monopole)

Kenmare 48-40-34.30 102-06-15.2 150(Monopole)

Kummer Ridge 47-47-55.69 102-55-43.85 290

Lonesome Creek 47-47-38.0 103-34-40 290

Minot SW 48-07-33.68 101-21-44.06 190

Neset 48-24-30.5 102-51-39.8 290

Niobe 48-38-31.4 102-18-12.4 190

Patent Gate 47-51-59.97 103-28-12.62 190

Pioneer 48-13-56.99 103-57-09.99 150

PW1 47-56-2.9 101-14-50.7 125 (Monopole)

Roundup 47-24-35.57 102-45-50.18 190

Squaw Gap Rptr 47-31-55.0 103-51-41.4 290

Squaw Gap Sub 47-32-43.49 103-49-46.17 120 (Monopole)

Underwood 47-26-53.5 101-07-12.90 150

Wheelock 48-20-23.37 103-18-18.51 290

* All towers are self supporting except Daglum, Groton, Kenmare, Kenaston, Judson, Richland MW,Squaw Gap Sub and PW1

P15

P21

P19

35.95

25.43

23.94 PW1(ND_L11)

P13

NIOBE(ND_L17)

22.7

9.4

9.4

22.7

P17

7.8

12.81

WTO

WAPA RPTR

Equipment in Cabinet

Squa

w Gap

Rptr

Pate

nt

Gat

e

Kum

mer

Ridge

Roundu

p

Juds

on Mall

ard

New Microwave Hop 2015-

2016

New Microwave Site 2015-

2016

Squa

w Gap

Sub

22

.5

9

29.

39

1.7

6

2

5

.

5

72

0.

0

8

9.02

1

9

.

0

7

13

.5

1

1

.

9

9

10

.0

9

7.

0

1

DAGL

UM

1

0

5.0

6

Richland

MW 20.

15

New Path 2017

Lewis &

Clark

Richland Sub

2

.

6

TAN

DE

1

4

.

2

9

1

7.

1

7

1

0

Rhame

Sub

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

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.

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.

51

21 - DISTANCE FUNCTION

MHO CHARACTERISTIC QUADRILATERAL CHARACTERISTIC

52

21 - DISTANCE FUNCTION

21LINE

F1 F2

THREE-ZONE

STEPPED

DISTANCE

SCHEME

21

-3

21

-2

21

-1

21

-1

21

-2

21

-3

53

21 - DISTANCE FUNCTION

R

X

LINE IMPEDANCE

LOAD IMPEDANCE

FAULT IMPEDANCE

RESTRAINT REGION

OPERATE

REGION

Z = E / I

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

55

87 - DIFFERENTIAL FUNCTION

(CURRENT)

GENERATOR

TRANSFORMER BUS BUSTRANSMISSION

LINE

LINELOAD CURRENT

Σ I = 0

87

56

BASIC OBJECTIVES OF

PROTECTIVE RELAYING

• Reliability

• Selectivity

• Speed

• Simplicity

• Economy

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 self-diagnostics that will alarm on many failures.

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.

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 = 0.100 - 0.400 seconds.

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)

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.

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

63

ZONES OF PROTECTION

GENERATOR TRANSFORMER

BUS BUS

TRANSMISSION

LINE

LINE

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

65

BUS PROTECTION

• Ground faults

• Phase faults

• Overvoltage protection normally not applied

66

TRANSFORMER PROTECTION

• Ground and phase faults (87)

• Overvoltage (59)

• Overload or backup protection (51, 21)

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

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]

69

PILOT WIRE RELAYING

21LINE

PILOT WIRE CABLE

F1 F2

TRIP

PCB 2TRIP

PCB 1

• 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.

8787

70

PILOT WIRE RELAYING (HCB-1)

71

NOT PILOT WIRE RELAYING

72

DCB - DIRECTIONAL

COMPARISON BLOCKING

21LINE

R

XT

XTELEPROTECTION (PLC)TELEPROTECTION (PLC)

F1 F2

TRIP

PCB 2

TRIP

PCB 1

21

R

21

F

16

MS

21

F

21

R

TX

RXAND

16

MS

73

POTT - PERMISSIVE

OVERREACHING TRANSFER TRIP

21LINE

TELEPROTECTIONTELEPROTECTION

F1 F2

TRIP

PCB 2

TRIP

PCB 1

21

21

TX

RXAND

TX

RX

74

PROTECTIVE RELAY OPERATION

URL El Dorado 500 Kv Switch.url

75

PROTECTION SYSTEM FAILURE

URL Transformer Fire.url