Type 2 Co Ordination in LV switchgear
Transcript of Type 2 Co Ordination in LV switchgear
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TOPICS
1) REQUIREMENTS AS PER STANDARDS.
2) FAULT LEVEL CALCULATIONS.
3) TYPE 2 CO-ORDINATION
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L.V. SWITCHGEAR STANDARDSIEC 60947/IS:13947
PART 1
PART 2
PART 3
PART 4
FUSES
MCBs
GENERAL RULES
CIRCUIT BREAKERS
SDF/SD
CONTACTORS,RELAYS, STARTERS,
IS:13703
IS:8828/IEC 60898
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Standards for Circuit Breakers
IS 13947 ( Part 2 )
IEC 60947-2
EN 60947-2
BSEN 60947-2
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Highlights of New Standards
Utilization category - A & B New short circuit duties - Ics, Icu & Icw
Special Sequence of testing
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UTILIZATION CATEGORY
Category : A
Circuit breakers not specifically intendedfor selectivity under short circuitconditions
(i.e.) without an intentional time delay andtherefore without a short time withstandcurrent rating
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UTILIZATION CATEGORY
Category : B
Circuit breakers specifically intended for
selectivity under short circuit conditions.Such breakers must have an intentional timedelay option and a short time withstandrating (Icw).
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TEST SEQUENCEAs Per IS 13947 (Part 2) / IEC 60947.2
Test Sequence I - Tests
General performanceTripping limits & characteristics
Dielectric properties characteristics
Mechanical operation and electrical operations
Overload performance (6In, 12 operations)Verification of dielectric withstand
Verification of temperature rise
Verification of overload release
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Minimum expectations
Ie (A)No. of Operating Cycles
Without
Current
With
Current
Total
0 - 100 8500 1500 10000
100 - 315 7000 1000 8000
315 - 630 4000 1000 5000
630 - 2500 2500 500 3000
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Implication of Sequence 1
Minimum mechanical and electrical lifespecified for different current ratings
Temperature rise to be done on breakerafter the mechanical/electrical life/overload tests are done.
Re-Verification of dielectric test and
overload characteristics at the end ofmechanical /electrical/overload tests
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TEST SEQUENCEAs Per IS 13947 (Part 2) / IEC 60947.2
Test Sequence II - Tests
Rated service S/C breaking capacity
(O-CO-CO)Verification of operational capability(Electrical life = 5%)
Verification of dielectricwithstandVerification of temperature riseVerification of overload release
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Implication of Ics rating
Must clear three S.C. faults: O - CO - COcycle
Must pass dielectric strength test
Overload characteristics to be maintained Must be able to carry full load current
without excessive temperature rise (
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TEST SEQUENCEAs Per IS 13947 (Part 2) / IEC 60947.2
Test Sequence III - Tests
Verification of overload release
Rated ultimate s/c breaking capacity (O-CO)
Verification of dielectric withstand
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Implication of Icu rating
Must clear two S.C. shots : O - CO Cycle
Must pass dielectric strength test
May not be able to carry full load current
Needs immediate replacement
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TEST SEQUENCEAs Per IS 13947 (Part 2) / IEC 60947.2
Test Sequence IV - Tests
Rated Short Time Withstand current (Icw)
Pass claimed value of Icw for claimed time.
Combined Sequence
Do Icw, Ics on the same breaker
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FAULT LEVEL
CALCULATIONS(As per IS 13234 : 1992 &
IEC Pub 909 : 1988)
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FAULT LEVEL AT ANY
GIVEN POINT OF THEINSTALLATION IS THEMAXIMUM CURRENT THAT
CAN FLOW IN CASE OFS/C AT THAT POINT
WHAT IS FAULT LEVEL
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PURPOSE OF FAULT LEVELCALCULATIONS
FOR SELECTING S.C.P.Ds OF ADEQUATES/C BREAKING CAPACITY
FOR SELECTING BUSBARS, BUSBARSUPPORTS, CABLES & SWITCHGEARS,DESIGNED TO WITHSTAND THERMAL &MECHANICAL STRESSES BECAUSE OF S/C
TO DO CURRENT BASED DISCRIMINATIONBETWEEN CBs
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FAULT LEVEL CALCULATIONS
TYPES OF FAULTS
SYMMETRICAL ASYMMETRICAL
LINE TO LINE
DOUBLE LINE TO
EARTH
LINE TO EARTH
THREE PHASE FAULT
LVSM4.PPT/NRS
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SOURCES OF SHORTCIRCUIT CURRENTS
ELECTRIC UTILITY SYSTEMS
D.G SETS CONDENSERS
MOTORS
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NATURE OF SHORT CIRCUITCURRENT
THE SHORT CIRCUIT CURRENT WILL
CONSIST OF FOLLOWING COMPONENTS :
THE AC COMPONENT WITH CONSTANTAMPLITUDE
THE DECAYING DC COMPONENT
SOURCE : UTILITY SYSTEM
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NATURE OF SHORT CIRCUIT CURRENT
TOP ENVELOPE
DECAYING DC COMPONENT
CURRENT
BOTTOM ENVELOPE
IP
TIME
WAVEFORM
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CALCULATION ASSUMPTIONS
TYPE OF SHORT CIRCUIT : THREE PHASEBOLTED SHORT CIRCUIT
IMPEDANCES OF BUSBAR/SWITCHGEAR/C.T.
/JOINTS ARE NEGLECTED TRANSFORMERS ARE CONNECTED TO
INFINITE BUS ON H.T. SIDE
TRANSFORMER TAP IS IN THE MAX. POSITION
S/C CURRENT WAVEFORM IS A PURE SINEWAVE
DISCHARGE CURRENT OF CAPACITORS ARENEGLECTED
WHAT ?
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CALCULATION OF SHORT CIRCUIT CURRENT
LVSM4.PPT/NRS
IS/C =
1 . 05 * LINE VOLTAGE
3 * ( Z TR + Z CABLE )
Z TR =
(in ohms)
% Z * 10 * KV 2
KVA
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CASE STUDY
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STEP 1 : SINGLE LINE DIAGRAM
)
)
)
)
)
)
F1
F2
PCC
MCC BUSBAR
U/G CABLE
M2M1 M3 M4
11
21 22 23 24
31
150HP 100HP 100HP 150HP
) CB
SDF
STARTER
G
)
)
12
13
STANDBY GENERATOR
1250 KVA
TRANSFORMER
1600 KVA
350 A 300 A 300 A
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STEP 2 : SYSTEM DATA
TRANSFORMER: 11/0.433 KV1600 KVA
%R = 0.94
%X = 5.46%Z = 5.54
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STEP 2 : SYSTEM DATA
CABLE : R = 0.062 /KMX = 0.079 /KM
LENGTH OF CABLE, 21 TO 31= 100M
INDUCTION MOTORS : M1, IrM = 200AM2, I
rM= 135A
M3, IrM = 135A
M4, IrM = 200A
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STEP 3 : CALCULATION OFRT & XT
RT =10 (%R)(SECONDARY KV)2
KVA
10 (0.94)(0.433)2
1600= = 0.001102 OHMS
XT
=10 (%X)(SECONDARY KV)2
KVA
10 (5.46)(0.433)2
1600= = 0.006398 OHMS
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STEP 4 : CALCULATION OFRL & XL
RL = 0.062
0.1 = 0.0062 OHMS
XL = 0.079 0.1 = 0.0079 OHMS
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STEP 5 : CALCULATION OFZ UP TO THE POINT OF
FAULT
TOTAL Z UP TO FAULT LOCATION F1
= (RT)2 + (XT)2 = (0.001102)2 + (0.006398)2= 0.00649
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STEP 5 : CALCULATION OF
Z UP TO THE POINT OFFAULT
TOTAL Z UP TO FAULT LOCATION F2
= (RT + RL)2 + (XT + XL)2 = (0.007302)2 + (0.01430)2= 0.01606
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STEP 6 : CALCULATION OF RMSVALUE OF S/C CURRENT AT
THE POINT OF FAULT
IK AT FAULT LOCATION F1 = c Un3 Z= 1.05 4153 0.00649= 38765 A OR 38.77 kA
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STEP 6 : CALCULATION OF RMSVALUE OF S/C CURRENT AT
THE POINT OF FAULT
IKAT FAULT LOCATION F2 = c Un3 Z=
1.05 4153 0.01606
= 15665 A OR 15.67 kA
STEP 7 : CALCULATION OF
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STEP 7 : CALCULATION OFMAKING CAPACITY AS PER
STANDARD IEC 60947-2
2.20.250< I
2.10.2520< I
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STEP 8 : CALCULATION OF
PEAK VALUE OF S/CCURRENT AT THE POINT OFFAULT
IP AT FAULT LOCATION F1 = 2.138.77
= 81.41 kA (PEAK)
IP AT FAULT LOCATION F2 =2 15.67
= 31.34 kA (PEAK)
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CALCULATION OF X AND R FORGENERATOR
The value of xd will be given in percentageterms.
Calculate xd in ohms.
Calculate R in ohms as per data in standard: Rg =0.15 xd for generators less than 1000V Rg =0.07 xd for generators up to 100MVA Rg =0.05 xd for generators 100MVA and
above.Apply correction factor and recalculate R and X. Find Z and use in the formulae.
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TYPE 2 CO-ORDINATION WITHFUSES/MCCB/MPCB
for
MOTOR FEEDERS
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MOTOR FEEDER
S.C.P.D.: Fuse / MCCB/MPCB(Isolation & Short Circuit Protection)
Starter:
Contactor - Normal / overloadoperations
+
Relay - Overload protectionup to locked rotor currentM
S.C.P.D.
Starter
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Types of Co-ordination( IS 13947 / IEC 60947 )
TYPE 1
Damage to contactor & overload relay is
acceptable. No discharge beyond the enclosure is
permitted.TYPE 2
No damage to overload relay or other parts is
allowed. Light welding of contacts of the contactoris permitted if they can be easily separated (e.g. bya screw driver) without significant deformation
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Ie(AC3) Prospective current r in A
0-16A 1kA
16-63A 3kA
63-125A 5kA
125-315A 10kA
315-630A 18kA
630-1000A 30kA1000-1600A 42kA
r current values
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CURRENT
TIME
CONTACTOR BREAKING
CAPACITY
Relay H.R.C. Fuse
Ico
Discrimination
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Type 2 Co-ordination benefits
Safe and reliable performance of productsduring normal and overload conditions
Proper and proven co-ordination with short
circuit protective device
IS / IEC / EN now make verification of co-ordination with S.C.P.D. a mandatoryrequirement
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THANK YOU