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Take a seat where you feel comfortable

Help yourself to coffee or tea

Please fill in the attendance register.

WELCOME

Workshop will start at 8:30

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Administrative Details Workshop programStart.....08.30

Refreshment Break....10.00 to 10.20

Lunch....12.30 to 13.30 approximately

Refreshment Break...15.00 to 15.20

Close... 17.00

Test-A-Relay

Practical

Power Systems Protection

For the Electrical Industry

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The LecturerWho am I?I am Dave Duncan and I am employed by TEST-A-RELAY CONSULTING

What is my background?I have been in the protection business for 33 years, both industrial and powertransmission & distribution

Am I contactable after this workshop?Yes

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The WorkshopThis workshop is for you!Interaction with you is important.Ask any question - don’t be intimidated by your peers.

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The WorkshopRelate any relevant experiences you have to other attendees.Time is precious, please keep any unrelated questions/experience to the breaks.Above all enjoy yourself. A good joke is always welcome.

Beep.TRY THATQUESTION AGAIN.

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Topics for the Day Introduction

Need for ProtectionFault Types and their effectsCauses of unbalanceSystem Earthing & Faults

ApplicationProtection calculations

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IntroductionWorkhorse of industry

Electrical energy to rotational energy

Squirrel cage induction motors (TEFC) very popular

Expected lifetime of up to 40 years

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Motor ProtectionMain Functions

1. To safeguard the motor to ensure continuity of use.

2. To minimise damage and repair costs.

3. To ensure safety of personnel.

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Power System ProtectionBasic Requirements

1.Selectivity: to detect and isolate the faulty item only.

2.Stability: to leave all healthy circuits intact to ensure continuity of supply.

3.Speed: to operate as fast as possible when called upon to do so, thereby minimising damage, production downtime and promoting safety to personnel.

4.Sensitivity: to detect even the smallest value of fault current or system abnormalities and operate correctly at its setting.

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Types of Motor FailuresFAILURES OF MOTORS

%

a) OVERLOADSb) POLLUTION (corrosive atmosphere)c) PHASE FAILURE (EARTH FAULTS)d) BEARING FAILUREe) AGEING (ambient temp too high)f) ROTOR FAULTSg) MISCELLANEOUS

301914131059

FIGURE 1ACKNOWLEDGEMENT TO SCHNEIDER SA

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Main causes of damage

26%

30%

20%

5%

19% Long timeoverheatingInsulation failure

Rotor or bearingfaultFaulty Protection

Other causes

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Protective functions needed

26%

30%

20%

5%

19%

Thermal overload

Short circuit & Earthfault

Start-up supervision andthermal sensor unit

Continuous self testing ofprotection relay

Other protectionfunctions/undertectablefaults

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Motor Capability Curve

1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0MOTOR CURRENT IN PER UNIT OF FULL LOAD

FIGURE 2 - MOTOR CAPABILITY LIMITS

0.1

1.0

10.0

100

1000

NO

RM

AL O

PER

ATIN

G A

RE

A

MOTOR START CURVE

FAU

LT O

N C

ABLE

OR

IN T

ERM

. BO

X

ROTOR LIMITATION AREASTATOR

LIMITATIONAREA

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Temperature rise versus time

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Equivalent Circuit of Squirrel cage

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Protection PhilosophySelectivity - Stability - Speed - Sensitivity

Emphasis on Speed for the following reasons:To minimise damage and repair costs.To reduce production downtime.To prevent undue thermal and magnetic overstressing of healthy equipment on through fault.To keep voltage depressions as short as possible in the interests of plant stability.Above all, to ensure the safety of personnel.

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Power System ProtectionQualities

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DependabilityIt must trip when called upon to do so

SecurityIt must NOT trip when it is not supposed to trip.

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Time Constants

FIGURE No 3

100%

80%

60%

40%

20%

0%0 1 2 3 4 5

TIME IN TERMS OF t/Tau (Tau = TIME CONSTANT)

HEATING

COOLING

PER

CE

NTA

GE

OF

FIN

AL

TEM

P R

ISE

63%

36%

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Fused Protection

FIGURE No 4

FAULT CURRENT IN AMPS

0,1

1

10

10 100 1000 10000

100

1000

TIM

E IN

SEC

ON

DS

CONTACTORCURRENTBREAKING LIMIT

FUSETHERMAL

PROTECT

MOTORFULLLOAD

MOTOR START

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Effect of Motor Heating

FIGURE No 5

MULTIPLES OF MOTOR FULL LOAD CURRENT

0,1

1

10

0 1 2 3 4 5 6

100

1000

AB

C

D

A - MOTOR CAPABILITY COLD , Tau = 30minB - P&B GOLD COLD, SET TO 105%, 14minC - P&B GOLD HOT, SET TO 105%, 14minD - MOTOR CAPABILITY HOT, Tau=30min, 10% TIME LEFT

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Motor contribution to a Fault

CURRENT INFEED FROM AN INDUCTION MOTOR TO AN EXTERNAL FAULT

10

8

6

4

2

00 5 10 15 20 25TIME FROM BEGINNING OF EXTERNAL FAULT - mS

AM

PS

IN P

ER

UN

I T I

full

loa d

FIGURE No 6

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(A) Phase-to-Earth (E) Three Phase-To-Earth

(B) Phase-to-Phase (F) Phase-to-Pilot

(C) Phase-to-Phase-to-Earth (G) Pilot-to-Earth

(D) Three Phase

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Motor Unbalance Capability

2 4 6 8 10 12 14

VOLTAGE UNBALANCE (E2/E1 x 100%)

% O

F M

OTO

R F

ULL

LO

AD

FIGURE 7

20

40

60

80

100

Z1/Z2 = 4

Z1/Z2 = 6

Z1/Z2 = 8

REDUCTION OF MOTOR OUTPUT FORWITH UNBALANCED SUPPY VOLTAGES

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Typical Motor Start

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Motor Current during start

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Blocked Rotor Condition

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CausesHIGH ROTOR TEMPERATURERS

CAUSED BY

a) TOO LONG A START TIME

c) TOO MANY STARTS WITH

b) A LOCKED ROTOR FAULT WITH LOCKED ROTOR TIME BEING

EXCEEDED

INSUFFICIENT COOLING TIMEBETWEEN STARTS

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Effect Of Unbalance

FIGURE No 8

I1

I2

CORRECT ROTATION ANTI CLOCKWISE FOR I1

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Positive/Negative/Zero Components

120º 120º

120º

120º 120º

120º

RotationRotation

Vb2

Va0 Vb0 Vc0Vc2 Va2Va1Vc1

Vb1

The Positive, Negative and Zero ComponentsOpposite rotation

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120º 120º

120º

120º 120º

120º

RotationRotation

Vc2

Va0 Vb0 Vc0Vb2 Va2Va1Vc1

Vb1

The Positive, Negative and Zero ComponentsSame rotation

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Maximum Continuous Output vsVoltage unbalance

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Unbalance Measurement

FIGURE 10

TIME

SIGNAL AT POINT `A'

I ave `B'

I ripple `C'

RELAY MEASUREMENTI max - I minI ave

TYPICAL CIRCUIT FOR UNBALANCED 'RIPPLE'

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Ratio of Unbalance to I2

1.4

1.5

1.6

1.7

0 60 120 180 240 360

ANGLE OF I WITH REFERENCE TO I2 1

II 2

FIGURE 11

I = I - I MAX MIN

300

FOR

RATIO OF UNBALANCE TO I2

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Motor Torques

TOR

QU

E

S=0

S=1S=-1

1è-POS SEQ

1è-NEG SEQ

NORMALVOLTAGE

FIGURE No 12

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Unbalance Tripping

2 4 6 8 10 12 14

VOLTAGE UNBALANCE (E2/E1 x 100

% O

F M

OTO

R F

ULL

LO

AD

FIGURE 13b

20

40

60

80

100

RESPONSE OF RELAY FORI FROM AN NPS FILTER

Z1/Z2 = 6

RELAY RESPONSE(DOES NOT VARY WITH PHASE ANGLE OF I2 W.R.T. I1 )

2 4 6 8 10 12 14

VOLTAGE UNBALANCE (E2/E1 x 100%)

% O

F M

OTO

R F

ULL

LO

AD

FIGURE 13a

20

40

60

80

100

RESPONSE OF RELAY FOR Imax - I average

Z1/Z2 = 6

RELAY RESPONSE (VARIES WITH PHASE ANGLE OF I2 W.R.T. I1 )

I average2

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Winding Earth Fault

NEUTRAL IMPEDANCE - Z

X%

V fault =

If

Vpn * X/100

If ÷ V fault / Z= X/100 * Vpn / Z

FIGURE No 14

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Basic Circuit of High Impedance Current Balance Scheme

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Calculation of stability setting

9000 A300/1

300/1

Calculate setting of stabilising resistor for the above REF protection. The relay is a type CAG14, rated 1A with 10-40% setting range (burden = 1.0 va)

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Calculation of stability setting

3Ω (Rct)

1Ω (Rl) 1Ω

3Ω

300/1

30A

300/1

Secondary fault current = 9000 x 1/300 = 30 amps

Relay operating current : Choose 10% tap on CAG14 relay rated at 1 amp.

Relay operating voltage : VA (burden) = 1.0 = 10 volts

I (current) 0.1

Stabilising voltage V = I(Rct + Rl) = 30( 3+1) = 120 volts

Resistor = (120 – 10) / 0.10 = 110/0.10 = 1100 ohms

120 v10v

110v

CAG14

relay

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Method of Earth Fault Detection

FIGURE No 15

M

THERMAL ETC

E/FSTAB R

DOTTED LINES SHOW ALTERNATE CT FOR E/F (NO STAB R)

F

NOTE:- CORE BALANCE GIVESNO PROTECTION FOR FAULT F

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Ground Fault Protection

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Useful Data

FIGURE No 16

FRAME SIZE (shaft height in mm)

AVERAGE THERMAL TIME CONSTANTS Tau IN MINUTES

MOTORDESIGN 355 400 450 500 560 630 710 800 900 1000

ORU

20 25 28 30 35 40 50 60 65 70- - - 45 50 55 60 70 80 90

30 35 40 45 50 - - - - -

O - OPEN TYPER - ENCLOSED WITH FORCED COOLING (DIN IP54)U - COMPLETELY ENCLOSED WITH COOLING RIBS (DIN IP

BBC INDUCTION MOTORS - FRAME SIZE AND DESIGN

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Single Phasing

FIGURE No 8a

VR

VR1

VR2

VB1

VB2

VW1

VW2

VWVB

VW-BSINGLE PHASE VOLTAGE

NOTE:- MAGNITUDE V pos = MAGNITUDE V neg = 0.5 V ph-nFOR SINGLE PHASING (NO OTHER LOADS & STARTING)

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CausesHIGH ROTOR TEMPERATURERS

CAUSED BY

a) TOO LONG A START TIME

c) TOO MANY STARTS WITH

b) A LOCKED ROTOR FAULT WITH LOCKED ROTOR TIME BEING

EXCEEDED

INSUFFICIENT COOLING TIMEBETWEEN STARTS

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Protection with FusesFUSES

a) CANNOT PROVIDE CLOSE THERMAL

b) DO NOT OPERATE FOR SYSTEM UNBALANCE

c) MUST BE SIZED LARGER FOR MULTIPLE

PROTECTION

MAY BE CAUSE OF SINGLE PHASING

STARTS TO COVER TOTAL TIME

DISADVANTAGES FOR MOTOR PROTECTION

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Bimetallic StripsBI-METALLIC ELEMENTS

a) TIME CONSTANT NOT FIELD ADJUSTABLE

b) COOLING AND HEATING TIME CONSTANT

c) SINGLE SHAPE CURVE TO COVER THERMAL

EQUAL - NO PROTECTION FOR MULTIPLE

OVERLOAD AND STARTING

RESTARTS

DISADVANTAGES FOR MOTOR PROTECTION

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Starting

METHODS OF DETECTION

a) DEFINITE TIME LAG FOR START CURRENT

b) a) PLUS CUMULATIVE START TIME

c) a) PLUS MAXIMUM HOT/COLD STARTSPER HOUR

d) DEPENDENT TIME LAG FOR STARTINGCURRENT (COMBINED WITH MOTOR STATOR TEMPERATURE ie I + 6I )

2

1

2

2

MOTOR STARTING PROTECT

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Relay gives stall protection

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Relay does not give stall protection

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Negative Sequence / Unbalance

MOTOR PROTECTION

a) WEIGHTED COMBINED HEATING EFFECT

b) A DEPENDENT I TIME CHARACTERISTIC

c) AN INDEPENDENT TIME CHARACTERISTIC

d) AN INDEPENDENT TIME CHARACTERISTICBUT OPERATES FOR I - I TOOLARGE

NEGATIVE SEQUENCE

IN THERMAL MODEL (I + 6I )2

1 2

2

2

MAX AVE

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Under Voltage ProtectionSYSTEM UNDERVOLTAGE

MOTOR TORQUE IS PROPORTIONAL TO I2

MAX TORQUE @ FULL VOLTAGE USUALLY 200%

100% TORQUE AVAILABLE AT 70% VOLTAGE

UNDERVOLTAGE TRIPPING BELOW 70% VOLTA

POS SEQ. or 3x SINGLE PHASE RELAYS

TRIP BEFORE AN AUTO RECLOSE

BUSBAR VOLTAGE DETECTION SUITABLE FOR A GROUP OF MOTORS

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Motor Information

Modern Relays require extra information

Manufacturers cannot always supply the required information

Information is difficult to obtain for old existing motors

Empirical tables may need to be used

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Accuracy of Settings

CTs USUALLY HAVE A NEGATIVE ERROR

CLASS 10P10 - 3%

CLASS 5P10 - 1%

-3% ERROR COULD ALLOW 6% OVERLOAD

WHICH WILL REDUCE INSULATION LIFE

THERMAL REPLICA FORMULA

THE RELAY HAS DEFINED INACCURACY (2%)

t = Tau ln I

I - (kI )

where `k' VARIES FROM 1.0 TO 1.05

for different manufacturers

H

B

2

2 2

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Additional Options

i) STORAGE OF FAULT DATA

ii) COMMUNICATION PORTS TO ALLOW:-

a) INTERROGATION & SETTING OF RELAY

MICROPROCESSOR RELAYS CAN INCLUDE

b) CONTROL OF BREAKER/CONTACTOR

c) DUAL SETTINGS FOR

DIFFERENT SYSTEM CONDITIONS

iii) MULTIPLE, MATRIX SELECTED OUTPUTS

iv) STARTER FUNCTIONS USED FOR BZone

v) SELF SETTING ADAPTION WITHEXTERNAL TEMPERATURE SENSORS

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Motor Bearing Failure

i) FAILURE CANNOT BE DETECTED BY I CHANGING

ii) COMPLETE FAILURE IS VERY RAPID

iii) MOTOR PROTECTED BY STALL PROTECTION

SLEEVE BEARINGS ON LARGER MOTORS

ROLLER / BALL BEARINGS ON SMALL MOTORS

a) FAILURE MODE IS SLOWER THAN BALL

b) TEMPERATURE RISE OF BEARING CAN

BEARINGS

BE USED FOR PROTECTION

ON BEARING FAILURE

c) MOTOR PROTECTED BY STALL PROTECTION

ON BEARING FAILURE

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Insulation Classes

A E B F H

CLASS OFINSULATION

AC WINDINGS - >200kW to <5000kW

AC WINDINGS - 600W to ó200kW

PERMANENTLY SHORT CIRCUITED

ROTOR WINDINGS

6060

7575

8080

105 125105 125

TEMPERATURE RISE SHALL

NOT BE DETRIMENTAL TO

OTHER INSULATION

ALLOWABLE TEMPERATURE RISE OF WINDINGS(MEASURED BY RESISTANCE METHOD)

TABLE No 1

A E B F H

CLASS OFINSULATION

ADJUSTMENT DECREASE FACTOR 0.6 0.7 0.8 1.0 1.25ON 1% PER 100m FOR CLASS F

ADJUSTMENT OF TEMPERATURE RISE FOR CLASS F INSULATIONIS 1% FOR EVERY 100m ABOVE 1000m. ADJUSTMENT FIGURESFOR OTHER CLASSES IS GIVEN ABOVE.

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Effect of Height above Sea Level

TABLE No 2

CLASS OFINSULATION

ALTITUDE A E B F H35øC 40øC 35øC 35øC 35øC

10001500200025003000

35øC40øC 40øC 40øC 40øC

1,000,97

1,001,001,00 1,001,041,031,011.000.98

0,980,970,950,94

1,031.021,000,980,96

0,980,960,950,93

1.03 1,03 1.021,010,990,970,95

0,980,960,940,92

1,000,970,950,92

0,950,920,89

0,990.960,920,89

0,970,940,900,87

m

MOTOR DERATING FACTORS FOR ALTITUDE AND AMBIENT TEMPERATURE

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Thank You

We hope you benefitted from the workshop.

We don’t stop here...

...if you have any further queries or require

help we would be delighted to assist you.

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Remember...I can be contacted at any time(012) 665 0545(082) 578 2558

OR

E-mail me at dave@test-a-relay.co.zaAlternatively office@test-a-relay.co.za