appa-module 7-protection & coordination
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Module 7
Power System Review Course
Protection & Coordination
By: Dr. Hamid Jaffari
Fuse
Transformer
Typical Distribution System
FOAKVA
FAKVA
OAKVA
%)135(000,10
%)125(9375
7500
FOAKVA
FAKVA
OAKVA
%)135(000,10
%)125(9375
7500
Protection & Coordination
System Protection Instrumentaion
Principals of Protection
Protection Devices (Circuit breakers, Reclosers,
Fuses)
Principals of Coordination
Coordination Study
Fuse-Fuse Coordination
Recloser-Recloser Coordination
Recloser-Fuse Coordination
Relay-Recloser-Fuse Coordination
Power System Review
System Protection
Components
Instrument Transformers
PTs
CTs
Circuit Breakers & Relays
Mechanical
Digital
Reclosers
Fuses
Power System Review
Protective Devices Characteristics
Breaker: Distribution Class 12 kA<Isymmetrical Rating<20 kA Transmission Class> 50 kA Extinguishing arc by means of:
Oil, air blast, sulfur hexafluoride gas (sF6), vacuum, or simple arc chutes
Recloser: 4 kA< Isymmetrical Rating<12 kA Interrupting occurs in Oil or vacuum Designed to “reclose” after fault is cleared
Sectionalizers: interrupting capability<10KA Master minded by Reclosers
Power System Review
Protective Devices Characteristics
Expulsion Fuses: Typically 8 kA to 16 kA Subject to X/R (interrupting capability decreases as ↑ X/R )
Power Fuse are generally available for Operating Voltage <169KV with 15KA<X/R<25KA
Distribution Fuse are generally good for Operating Voltage<40K with 5KA<X/R<15KA
less accurate, inexpensive, but effective.
Current limiting fuses (CLFs) As much as 50 kA May have minimum interrupting capability, additional
protection may be needed
Oil switches: limited current interrupting capability.
Power System Review
Fault calculations
Note: I-fault drops off as inverse of Distance 1/d
Power System Review
Principals of Protective Devices
Definition of Protective Devices: Protective
Devices have Time-Current, Time-Voltage, or
Time-Frequency Characteristics
Protective Devices are responsible for
removing undesired conditions:
Voltage
Current
Frequency
Power System Review
What is the purpose?
Clear Temporary faults and restore power
when possible.
Interrupt Permanent Faults and Lock Out
Interrupt Faults in Proper Sequence
Remove undesired power conditions to
maintain:
Steady State
Stability
Power System Review
EPRI Fault Study
Faults Percentage
Phase-to-Ground 65%
Phase-to-Phase 11%
Phase-Phase to Ground 2%
Three Phase 2%
One Phase on the Ground 15%
Two Phase on the Ground 2%
Others 3%
Power System Review
Protection & Coordination
What is Coordination?
Definition: Proper trip sequencing of protective devices
to isolate the fault and minimizing outage. This means
proper coordination between time and current curves
during power system abnormal conditions.
Coordination is :
1/3 Science
1/3 Art
1/3 Luck
Coordination
Protective Devices with Time-Current characteristics are:
Relays, Reclosers, Fault Interrupters, and Fuses.
How about Sectionalizers??
Device Relay Recloser FI Fuse
Relay Relay-Relay Relay-Recloser Relay-FI Relay-Fuse
Recloser Recloser-Relay Recloser-Recloser Recloser Recloser-Fuse
FI FI-Relay FI-Recloser FI-FI FI-Fuse
Fuse Fuse-Relay Fuse-Recloser Fuse-FI Fuse-Fuse
Fuse-Fuse
Coordination
Fuse Selection Process
Fuse Type/Class
Expulsion(Dist, Substation, etc)
CLF
Voltage Class
Fuse Isymm interrupting capability rating
X/R ratio
Fuse continuous current rating
i.e. K(150%), T(150%), QA(100%)
Fuse Application Fuses are generally:
CLF-used for short-circuit protection
Non-CLF or Expulsion Fuse is used for
Overload protection
Selection Criteria:
Non-CLF: 140% of full load
CLF: 150% of full load
Expulsion Fuse
%
100
ZxII loadfullsc
Fuse Clearing Time
@1/2 cycle
Zero Crossing
Transient Voltage
@
Clearing time
CT = MT+ Arcing Time
Current Limiting Fuse(CLF)
B
Curtsey of www.littlefuse.com
60,000 A
7,400 A
Fuse Types & Porperties
Fuse has two TCC curves
Minimum Melting
Total Clearing
Common fuse types through 27kV are:
Slow: T
Fast: K
Avoid mixing different type fuses for better coordination
Skip at least a size in each fuse class (K, T, H, C, etc)
for better coordination between two fuses(i.e. 20K, 40K,
65K, etc)
Power System Review
Fusing Philosophy
Lateral tap fuse selection Criterion:
I lateral= 2x ILoad
Cold load
Daily/monthly/Seasonal cyclic Load
Peak load
Transformer Fuse Selection Criterion:
Minimum Fuse Size= Irated x 1.2
Cold Load
Inrush Current
Operational Limits
Power System Review
Fuse Speed & Continuous Rating
Fuse Allowable
Continuous
current
Rating(%)
K-tin 150%
K-silver 100%
N 100%
T 150%
QA 100%
S 150%
Fuse speed from fast to slow → N>QA>K>T>S
Power System Review
Fusing Distribution Transformers
Why? In order to protect the transformer against
internal faults, downstream bolted faults, high
impedance secondary faults.
Fuse must withstand transient surge currents
caused by lightening, XFMR magnetizing inrush
current, and cold-load pickup. Therefore, fuse
must be capable of handling:
Cold Load Pickup
Inrush Current
Power System Review
Dist Transformer using…continued
Steps to select XFMR fuse size:
1. Calculate Cold Load Pickup withstand level:
1. I cold-load= 3 x I (full load for 10 seconds)
2. Calculate Inrush Current withstand limits:
1. I inrush= 12 x I (Full Load for 0.1 seconds)
2. I inrush= 25 x I (full load for .01 seconds)
3. Select the nearest primary fuse rating that: 1. Starts with 120% of XFMR rated load: Minimum Fuse Size = IRated x 1.2
2. Meets the Cold load & Inrush Requirements (Steps 1 &2)
4. Select the Fuse type (K, T,H, QA,etc) and coordinate it
with upstream & downstream fuses in service. Note: Using EEI-NEMA type K, T, and T Fuses Provides
protection between 200% to 300% of Rated Load
Power System Review
Example: Determine the minimum size fuse for
a 300 KVA, 13.8kV/277/480 volts XFMR using
“K” type fuse?
AmpkVx
KVAI loadfull 55.12
9.23
300
8.133
300
AmpxI SecloadCold 65.3755.12310@
AmpxI SecInrush 6.15055.12121.0@
AmpxI Secinrush 75.31355.122501.@
?%)160(20?%)120(15: KORKFuseMinimum
Transformer Fusing…continued
Power System Review
Transformer Fusing…continued
Power System Review
Problem Area
Substation Transformer Protection
Plot XFMR operational limits:
Thermal & Mechanical limits (Damage Curve).
Use FA Rating for XFMR Damage Curve Plot
XFMR Inrush &Cold-Load pickup.
Apply applicable NEMA & IEEE Standards:
IEEE C57.109-1993 oil immersed XFMR
IEEE C57.12.59-2001 dry-type XFMR
Example:
FOAKVA
FAKVA
OAKVA
%)135(000,10
%)125(9375
7500%6
16.4/86.22
Z
kVkV
Power System Review
Transformer Operating Limitations
t(sec)
I (pu)
Thermal 200
2.5
I2t = 1250
2
25 Isc
Mechanical
K=(1/Z)2t
(D-D LL) 0.87
(D-R LG) 0.58
Frequent Fault
Infrequent Fault
Inrush
FLA
Power System Review
Devices’ Damage Curves
t
Time
I-Current
I2
2t
Gen
I2t
Motor Xfmr
I2t
Cable
I2t
Power System Review
=Let-through Energy I2t
Transformer Prim Fuse Protection
Capacitor Fusing Capacitor fuse must be between 135% to 165% of its
full load current rating depending on manufacturer.
Example: Find appropriate fuse size for a 1800 KVAR
cap bank installed on a 22.86kV line.
65.1
35.1
xLoadFullFuseCapacitor
or
xLoadFullFuseCapacitor
AmpkVx
KVARI loadfull 5.45
6.39
1800
86.223
1800
FuseQAorKSelect
AmpFuse
FuseCapacitor
6050
5.40
35.1*5.455.1*
Note: Check fuse continuous/overload capability (100%-150%)
Fuse-Fuse Coordination
Fuse-fuse coordination must follow the following
rule:
Desirable coordination: Time Ratio of two fuses
Must Not Exceed the 75% Ratio
%75)(
)(
fuseupstreamMT
fusestreamdownCTofRatioTime
Time
limiton coordinati
MT) of (75%A Fuse
Current
A of MT
B of CT
A CTof
Fuse
A B
Source
Fault
LoadFuse
Power System Review
75.0*)()( upstreamMTfusestreamdownCT tt
Fuse-Fuse Coordination
Example: What is the minimum size fuse that
coordinates with 50K lateral tap fuse if calculated
fault current is 1000Amp at point B?
MT(A Fuse)=0.051 sec for Fault Current @ 1000
Amp
75.0)(
)(
AfuseupstreamMT
BfusestreamdownCT
051.075.075.0051.
)(xCT
BfusestreamdownCT
sec038.0CT
K50
K?amp26
ampI G 1000
BA
Power System Review
50K Fuse-20K Fuse Coordination
Coordination Limit
K50
K20amp26
ampI G 1000
BA
Fuse-Fuse Coordination
Example: Select a fuse size at point C That can
achieve proper coordination with upstream fuses.
K65
K?amp35
ampI Maxfault 1000
B
A
K100
C
amp90
ampI Maxfault 2000
ampI Maxfault 1500
amp80
Power System Review
Fuse-Fuse coordination
K65
K?
amp35
ampI Maxfault 1000
B
A
K100
C
amp90
ampI Maxfault 2000
ampI Maxfault 1500
amp80
Recloser-Fuse
Coordination
Recloser Defined in ANSI/IEEE C37.60
Settings Require Selecting:
Minimum Pick up or Coil size
Curve Selection:
Fast Curve
Slow Curve
Operating Sequence:
Number of Fast Curve shots
Number of Slow Curve shots
Shots to lockout
Reset time
Power System Review
Recloser
Two Types:
Hydraulic
Minimum Pickup is done by selecting appropriate rating for
Series Coil inside the tank
TCC Curve Selection & Settings are done inside the tank
Electronics
Minimum Pickup: Trip Resistors
TCC Curves and Timing plugs are done at the front panel
Control
Hydraulic
Solid State
Microprocessor
Power System Review
Electronic Recloser Settings
TCC Curve
Curve Selection/Type
Settings:
Min Trip Setting
Phase & Ground
Instantaneous Trip Setting
Phase & ground
Constant Time Adder
Amp Multiplier
Reclosing Operation Setting
Typically Two Fast/Two Delay
0.5 sec<Reclosing intervals<60 sec
Power System Review
Electronic Recloser Settings
Phase Trip Setting
Minimum Trip= (Range of 2 to 2.5) x Max Load Current
This facilitates cold load pick up & load growth
Ground Trip Setting
Minimum Trip= (Range of 0.3 to 0.5)x Phase Minimum Trip
Min trip setting helps to protect against high impedance faults
Instantaneous Setting
Trip Setting= (Range of 4 to 16)X Minimum Trip
Power System Review
Hydraulic Recloser Phase Trip-Setting
Estimate the Peak load
Determine the Coil Size:
Inrush Current dictates the coil rating selection
Coil Size(Amp)=1.25 x Peak Load
Calculate the Minimum Phase Trip Setting:
Minimum Trip(Amp)=2 x Peak-Load
Some utilities use factor of 2.5 or 3.0
Example (W type Hydraulic Recloser; coil sizes are 100, 140, 200, 280,
400, and 560):
Assume Peak Load= 150A
Coil Size= 1.25 x 150= 187.5→ Thus select 200 A
Minimum Trip= 2x150= 300A→ Select 400A Min Trip Level
(Note: 200A Coil has Minimum Trip Rating of 400A)
Power System Review
Hydraulic Recloser Ground Trip-Setting
Steps:
1. Calculate the Normal Load Unbalance
2. Calculate the end-of-line minimum fault current level.
The Iground-Trip must be bellow Imin-Fault.
3. Estimate the Ground Minimum Trip Level.
LoadPeakofII %10UnbalanceLoadNormal1
faultMinLineofEndTripMinground II
Device)PhaseSingleLargestthebyCreatedUnbalanceLoad(2Unbalance)LoadNormal(1 III TripMinground
Fuse(Amp)TapLargetsUnbalanceLoadLargest2 II
faultMinLineofEndTripMingroundLoadUnbalance IIIII )( 21
Power System Review
Recloser-Reloser
Hydrolic Reclosers:
Min Trip and continuous current are both dependent of the coil size
Reclosing intervals are 1, 1.5, and 2 seconds
Small Reclosers have Series coil : H, VH, L, and E series
TCC Curve Separation >12 Cycles (0.2 sec); typically 0.25-0.30 sec
Large Reclosers have High-Voltage solenoid : D, V, W, VW series
TCC Curve Separation > 8 Cycles(0.133 sec); typically 0.2 sec
Electronic Reclosers:
Unlike Hydraulic recloses, Min Trip is independent of the Recloser’s
continuous rating
Reclosing intervals are 2, 5, and 15 seconds
Min Trip selection must allow for the cold-load pick up & load growth
TCC Curve Separation > 0.30 Sec
0.30 Sec=0.22 sec (CT saturation& errors)+0.08 sec (Breaker Opening time)
TCC Coordination Time Margins
TCC Coordination Time Margins
Electronic Recloser to Hydraulic Recloser:
TCC Curve Separation > 0.2 Sec; typically 0.25 sec
Recloser-Fuse
Methode#1: Use K factor for Recsloser: Range of
1.25<K<1.8
Methode#2: ADD Recloser Cumulative Times
Add the cumulative reclose interval for a 2A-2C recloser sequence and coordinate with Fuse
Minimum Clearing curve x 0.75
Power System Review
Recloser-Fuse Coordination
Recloser Cumulative Time Method
<Coordination Limit <
Temp Fault:
Recloser operates; Fuse
is saved.
Permanent Fault:
Recloser operates first,
then fuse blows
Current
Time
delay BBA 22B'
'a'ba b
A2A' Fast)(A
curve) damage (fuse curve MT fuse of %75
R
Fuse
'a'b
Power System Review
Recloser-Fuse Coordination
K-Factor Method
<Coordination Limit<
Refer to Manufacturer’s
Supplied Tables
Extract applicable K-Factor
Multiply Curves by K-Factor
Note: K-factor is a t-Multiplier
Current
Time
delay B
'a'ba b
Fast)(A
curve) damage (fuse curve MT fuse of %75
BCurve*KB )Multiplier(Time
ACurve*KA )Multiplier(Time
'a 'b
Power System Review
Cooper Reclosers K-Factor
•What is K-Factor?
•K-Factors are Time
multiplying factors for various
Reclosing Intervals. K-Factor
shifts the curves up
increasing the time value by
K-Factor for the same current
value.
Table Below -Curtsey of Cooper Power Systems
Power System Review
Source Fuse-Recloser Coordination
Phase Trip Setting Steps:
1. Calculate Full Load Iprim & Isec
2. Select an Appropriate Fuse size
Fuse Size: 1.5x126.3A=189.5A → Select 200K
3. Select an Appropriate Recloser Coil Size:
Calculate Coil Size: 1.25x400=500A
Select Coil size: 560A
4. Desired Minimum Phase Trip= 2.5 x Peak Load to
override the Inrush
AIAIprim 694316.4
5000sec3.126
386.22
5000
E1&1
C2&A2
Recloser
2Ag
RX
%6
5000
Z
KVA
kVkV 16.4/86.22
R
FAULTLineofEnd
FUSE
R
AxIPhase 10004005.2
Note: Cooper W & RX type Recloser Ratings:
Coil Size Min Trip Rating Interrupting Rating
560 A 1120 A 10,000 A
3800AFaultG-
4500AFault-3
AFaultG 175
1500AFault-3
400A(Peak)I
Source Fuse-Recloser Coordination Ground Trip Setting Steps:
1. Estimate Normal Load unbalance: 10% of Peak-Load
Example: Iunbalance= 10% of Peak Load
Iunbalance-Normal= 0.1 x 400=40A
2. Estimate the load unbalance created by the largest
single-phase device:
Example: Assume the largest single phase Load is 90A
Fuse. Iunbalance-Load=90A
3. Calculate Unbalanced downline Ground Current:
4. Select Minimum Ground Trip:
AIGround 1304090 LoadunbalanceNormalunbalanceGround III
)A175()A140()A130( FaultMinSettingGroundUnbalancedG III
A140 TripMinIg
Source Side Fuse-Recloser Coordination
Recloser-Fuse (Load Side) Coordination
•Determine an appropriate Fuse size @ Point B
•Which fuse coordinates the best (100K or 140K?)
•Answer 140K; Why?
CA
RX
22
Recloser
%6
5000
Z
KVA
kVkV 16.4/86.22
R
AFaultMin
A
FAULT
600
1900G
FUSE R
Amp400
Amp90
B
Power System Review
Recloser-Fuse (Load Side) Coordination
AK
AK
2380140
1112100
LimitonCoordinatiFuse
AFaultG 175
1500AFault-3
E1&1
C2&A2
Recloser
2Ag
RX
%6
5000
Z
KVA
kVkV 16.4/86.22
R
FAULTLineofEnd
FUSER
3800AFaultG-
4500AFault-3
AFaultG 175
1500AFault-3
400A(Peak)I
B
Relays
Mechanical
&
Digital
Protection System Elements
Protective relays
Circuit breakers
Current and voltage transducers
Communications channels
DC supply system
Control cables
Three-Phase Diagram of the Protection Team
CTs
VTs
Relay
CB
Control
Protected
Equipment
SI
52
TC
DC Station
Battery SI
Relay
Contact
Relay
Circuit
Breaker
52a
+–
Red
Lamp
Most Common Protective Relays
Protection Principles for Transmission &
Distribution Lines:
Overcurrent (50, 51, 50N, 51N)
Directional Overcurrent (67, 67N)
Distance (21, 21N)
Differential (87)
Circuit Breaker Selection
Relay (The Brain)
CT Ratio
PT or VT Ratio
Interrupting Cycle
Voltage Class
K rating=(VMAX/Vmin)
BIL rating
Power System Review
Load
Ib
Relay-Circuit Breaker Operation
Load
Phase relays
Ground relay
CTs
Circuit
Breaker
In
A
B
C
Ia Ib Ic
Ia
Ib Ic
cban IIII
LOAD
Power System Review
Induction-Type Relays
Power System Review
Relay Classification
Overcurrent
Overvoltage
Undervoltage
Differential
Directional
Under Frequency
Distance
Power System Review
Relays for Phase Faults
Time overcurrent 51
Instantaneous & time overcurrent 50/51
Directional Time Overcurrent 67
Instantaneous & directional time over current
50/67
Directional Instantaneous Overcurrent 67
Step Time Overcurrent 51
Directional Instantaneous and directional 67
Zone Distance 21
Power System Review
Relays for Ground Faults
Time Overcurrent 51N
Instantaneous & Time Overcurrent 50N/51N
Product Overcurrent 67N
Instantaneous and Product Overcurrent 67N/50N
Directional time overcurrent 67N
Instantaneous and directional time overcurrent 67N
Directional Instantaneous Overcurrent 67N
Three-zone distance system 21N
Power System Review
Transformer Protection
Open-Phase Condition
CTs=600/5
In
A
B
C
Ia Ib Ic In
Ia
Ic
can III 0
Open
400 a 0 a 400 a
60333.3
886.2666.1
886.2667.1333.3
120333.3,0,0333.3
120
n
n
n
a
Ratio
I
jIn
jI
IcIaIcIbIaI
IcIbI
CT
Ground Relay Could Pickup
60333.3nI
1203.303.3
0
Single-Phase to Ground
Fault
CTs=600/5
In
A
B
C
Ib Ia
Ic
07.46nI
Short 6,000a
400 a 400 a
0666.46
667.1667.150
120333.3120333.3,050
120
n
n
n
a
Ratio
I
I
IcIbIaI
IcIbI
CT
SCI
050aI 1203.3
1203.3
In
SCI
Ground & Phase Relays both Pickup
Line-to-Line to Ground Fault
CTs=600/5
In
A
B
C
Ib Ia
Ic
607.46nI
Short 6,000a
400 a
6067.46
415.40333.23
886.2667.1301.432550
120333.312050,050
120
n
n
n
a
Ratio
I
jIn
jjI
IcIbIaI
IcIbI
CT
SCI
050aI 1203.3
In
aI
Ground & Phase Relays both Pickup
SCI
12050
bI CI
Three-Phase to Ground
Fault
CTs=600/5
In
A
B
C
Ib Ia
Ic
0nI
Short
0
120100120100,0100
120
n
n
a
Ratio
I
IcIbIaI
IcIbI
CT
SCI
0100aI2100aIb
aIc 100
000,12cI000,12bI000,12aI
000,12aI
SCI SCI000,12aI 000,12aI
Only Phase Relays Pickup Ib
Ia
Ic
Relay Settings
Time Overcurrent pickup
& time setting must be
capable of handling:
Peak Load
Cold-Load Pickup
Motor starting
Instantaneous Setting
must be capable of
handling:
XFMR Inrush
Capacitor Inrush
Asymmetrical Faults Safety factor=1.2xSymm Fault
Two Settings:
1. Time Overcurrent
2. Instantaneous
Power System Review
Relay Settings
Phase Time Over Current (TOC) Setting
Phase pick up:
Method 1: 2xImax < I Pick up < I Min (phase-phase Fault current)
Note: Ensure I Min-Fault ≥ 2 x I Peak- Load
I Min=Iphase-to-Phase=0.866 x I Three-Phase fault
Method 2: 25% Margin ; IPickup= Ifull-load/0.80
Ground Time Over Current (TOC) Setting
Ground Pick up:
Method 1: 2xI Normal ground Current < I Pick up< I Min Ground Fault Current
Where; Normal Ground Current Range: 10% to 20% of Load Current
Method 2: Ipickup=(0.40 to 0.75)x Ipeak-Load
Power System Review
Instantaneous Relays Pickup
Settings
Instantaneous Pickup
Range:
Typical Instantaneous Phase & Ground
Pick up= 2x Time Over Current relay pick ups
PickupPhaseeousinsPickupPhase IxIIx 102 tantan
Power System Review
How to determine Pickup &
Time Dial? Step 1: Calculate Short Circuit Current @ each Bus
( usually Phase-Phase Fault)
Step 2: Identify CT Ratio & Breaker Interrupting Cycles at
each Bus
Step 3: Calculate Relay Minimum Pickup for each Device
Step 3: Starts with the last relay and apply Time Margin of
0.3 to 0.4 sec (ANSI/IEEE Std-242 )between Relays:
o CB’s operating time (5 cycles): 0.08 sec
o Relay Over travel time: 0.1 sec
o Safety factor (CT saturation, Errors): 0.22 sec
Total 0.4 Seconds
Power System Review
0.4 Sec
Relay-Relay Setting
Power System Review
TCC Coordination Time
Margins
Relay-Fuse TCC Curve Separation Rule:
Mechanical Relay requires minimum time margin of 0.3 sec
time interval
Digital Relay requires minimum time margin of 0.2 sec time
interval
Relay-Relay (Mechanical) TCC Curve Separation Rule:
According to ANSI/IEEE Std-242:1986, the rime interval
between two relays in series must be 0.3 to 0.4 seconds.
This time interval components are:
Circuit Breaker Operating Time(5cycle): 0.08 sec
Relay Overtravel Time: 0.1 sec
Safety factor for CT Saturation & errors: 0.22 sec
Power System Review
Relay-Relay (Digital)TCC Curve Separation:
Time margin between series Relays must be minimum of
0.25 sec. This time separation consists of the following:
5 Cycle Breaker (0.08 sec)
Relay Accuracy (0.04 sec)
Safety factor & CT Ration (0.13 sec)
Relay-Recloser
Time Margin between Mechanical Relay & Hydraulic
Recloser must be minimum of 0.28-0.30 sec
Time Margin between Mechanical Relay & Electronic
Recloser must be minimum of 0.25 sec
TCC Coordination
Time Margins
Power System Review
Relay-Recloser-Fuse
Coordination In the following CKT coordinate Breaker B1, Cooper
Form-4C Recloser, ABB PCD2000 Reclsoer, and 100K
Tap Fuse.
1B R 3R
1L 2L 3L
400ALoad
4CForm
Cooper
3 2 1MVA25
kVkV 86.22/115
PCD2000
ABB
A1000
A40003
2@
FaultMin
BusFAULT
K100
AFaultMin
A
BusFAULT
443
30003
1@
A2000NΦ
A60003
3@
BusFAULT
2B
300ALoad 200ALoad
231ALoad
BUS
kV115
Power System Review
Relay-Recloser-Fuse Coordination
Relay settings:
Phase setting: PU=2.4 x 400=960A
Ground setting: PU= 960/2=480 A
Cooper Recloser Form 4C settings:
Phase setting: PU=2x300=600A
Ground setting: 160A<PU=600/3=200A<443A
ABB Recloser Model PCD2000 settings:
Phase setting: PU=2x200=400A
Ground setting: 140A<(PU=150 A)<443
Power System Review
Relay-Recloser-Fuse Coordination
Over Voltage Protection
Insulation Voltage Class
Basic Impulse Level (BIL)
Nameplate Rating
Surge arrestors.
Power System Review
Overvoltage Protection
Sources of Overvoltage:
Ferroresonance
Low Order Hormonics
Voltage Regulation (XFMR LTC Malfunction)
Transients caused by:
Lightning surge
Switching operations
Line-to-Ground faults
Capacitor Bank Switching
Protection methods:
Surge Arresters(ANSI C62.1-1981)
Static Wires
Useful IEEE/ANSI Standards Graph of Curves can be found in ANSI/IEEE Standard
C37.91-1985, “Guide for Protective Relay Applications
to Power Transformers,”
ANSI/IEEE C57.109-1993, “Guide for Transformer
Through-Fault Current Duration.”
IEEE/ANSI Standards 141&242
IEEE Std 242 – Buff Book
IEEE Std 141 – Red Book
IEEE Std 399 – Brown Book
•IEEE C37.90 – Relays
IEEE C37.91 – Transformer Protection
IEEE C37.102 – Guide for AC Generator Protection
References
1. J.D. Golver, M.S. Sarma, Power System Analysis and design,
4th ed., (Thomson Crop, 2008).
2. M.S. Sarma, Electric Machines, 2nd ed., (West Publishing Company,
1985).
3. A.E. Fitzgerald, C. Kingsley, and S. Umans, Electric
Machinery, 4th ed. (New York: McGraw-Hill, 1983).
4. P.M. Anderson, Analysis of Faulted Power systems(Ames, IA: Iowa
Satate university Press, 1973).
5.W.D. Stevenson, Jr., Elements of Power System Analysis, 4th
ed. (New York: McGraw-Hill, 1982).
Solution
Answer: 37.5 KVA
Break Time !!!!!
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