type 2 co ordination in lv switchgear

8/4/2019 Type 2 Co Ordination in LV switchgear

1/46

TOPICS

1) REQUIREMENTS AS PER STANDARDS.

2) FAULT LEVEL CALCULATIONS.

3) TYPE 2 CO-ORDINATION


2/46

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


3/46

Standards for Circuit Breakers

IS 13947 ( Part 2 )

IEC 60947-2

EN 60947-2

BSEN 60947-2


4/46

Highlights of New Standards

Utilization category - A & B New short circuit duties - Ics, Icu & Icw

Special Sequence of testing


5/46

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


6/46

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).


7/46

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


8/46

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


9/46

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


10/46


11/46


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


12/46

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 (


13/46


Test Sequence III - Tests

Verification of overload release

Rated ultimate s/c breaking capacity (O-CO)

Verification of dielectric withstand


14/46

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


15/46


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


16/46

FAULT LEVEL

CALCULATIONS(As per IS 13234 : 1992 &

IEC Pub 909 : 1988)


17/46

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


18/46

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


19/46

FAULT LEVEL CALCULATIONS

TYPES OF FAULTS

SYMMETRICAL ASYMMETRICAL

LINE TO LINE

DOUBLE LINE TO

EARTH

LINE TO EARTH

THREE PHASE FAULT

LVSM4.PPT/NRS


20/46

SOURCES OF SHORTCIRCUIT CURRENTS

ELECTRIC UTILITY SYSTEMS

D.G SETS CONDENSERS

MOTORS


21/46

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


22/46

NATURE OF SHORT CIRCUIT CURRENT

TOP ENVELOPE

DECAYING DC COMPONENT

CURRENT

BOTTOM ENVELOPE

IP

TIME

WAVEFORM


23/46

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 ?


24/46

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


25/46

CASE STUDY


26/46

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


27/46

STEP 2 : SYSTEM DATA

TRANSFORMER: 11/0.433 KV1600 KVA

%R = 0.94

%X = 5.46%Z = 5.54


28/46

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


29/46

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


30/46

STEP 4 : CALCULATION OFRL & XL

RL = 0.062

0.1 = 0.0062 OHMS

XL = 0.079 0.1 = 0.0079 OHMS


31/46

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


32/46

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


33/46

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


34/46

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



35/46

STEP 7 : CALCULATION OFMAKING CAPACITY AS PER

STANDARD IEC 60947-2

2.20.250< I

2.10.2520< I


36/46


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)


37/46

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.


38/46

TYPE 2 CO-ORDINATION WITHFUSES/MCCB/MPCB

for

MOTOR FEEDERS


39/46

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


40/46


41/46

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


42/46


43/46

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


44/46

CURRENT

TIME

CONTACTOR BREAKING

CAPACITY

Relay H.R.C. Fuse

Ico

Discrimination


45/46

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


46/46

THANK YOU

type 2 co ordination in lv switchgear

Documents