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STAR DEVICE COORDINATION
ANALYSIS
SUPRIYANTO, ST., [email protected]
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Objective
Menentukan rating dan setting fuses ,
breakers, relay
Isolasi gangguan arus lebih
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Spectrum Of Currents Load Current
Up to 100% of full-load
115-125% (mild overload)
Overcurrent
Abnormal loading condition (Locked-Rotor)
Fault Current
Fault condition
Ten times the full-load current and higher
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Protection
Prevent injury to personnel
Minimize damage to components
Quickly isolate the affected portion of the system
Minimize the magnitude of available short-circuit
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Coordination
Limit the extent and duration of service
interruption
Selective fault isolation
Provide alternate circuits
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Coordination
t
I
CB A
C
D
D B
A
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Protection vs. Coordination
Coordination is not an exact science Compromise between protection and
coordination
Reliability Speed
Performance
Economics
Simplicity
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DATA
One-line diagrams (Relay diagrams)
Power Grid Settings Generator Data
Transformer Data Transformer kVA, impedance, and connection
Motor Data
Load Data
Fault Currents
Cable / Conductor Data
Bus / Switchgear Data Instrument Transformer Data (CT, PT)
Protective Device (PD) Data Manufacturer and type of protective devices (PDs)
One-line diagrams (Relay diagrams)
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PROSEDUR Prepare an accurate one-line diagram (relay
diagrams) Obtain the available system current spectrum
(operating load, overloads, fault kA)
Determine the equipment protectionguidelines
Select the appropriate devices / settings
Plot the fixed points (damage curves, )
Obtain / plot the device characteristics curves Analyze the results
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TIME CURRENT CHARACTERISTICS
TCC Curve / Plot / Graphs
4.5 x 5-cycle log-log graph
X-axis: Current (0.510,000 amperes) Y-axis: Time (.011000 seconds)
Current Scaling (x1, x10, x100, x100)
Voltage Scaling (plot kV reference) Use ETAP Star Auto-Scale
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TCC Scaling Example
Situation:
A scaling factor of 10 @ 4.16 kV is selected for TCC
curve plots.
Question
What are the scaling factors to plot the 0.48 kV
and 13.8 kV TCC curves?
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TCC Scaling Example
Solution
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Fixed Points
Cable damage curves
Cable ampacities
Transformer damage curves & inrush points
Motor starting curves
Generator damage curve / Decrement curve SC maximum fault points
Points or curves which do not change regardlessof protective device settings:
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Capability / Damage Curves
t
I
I22t
Gen
I2t
MotorXfmr
I2t
Cable
I2t
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Transformer Protection
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Transformer CategoryANSI/IEEE C-57.109
Minimum nameplate (kVA)
Category Sin le- hase Three-phase
I 5-500 15-500II 501-1667 501-5000
III 1668-10 000 5001-30,000
IV above 1000 above 30,000
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Transformer Categories I, II
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Transformer
t
(sec)
I (pu)
Thermal200
2.5
I2t = 1250
2
25Isc
Mechanical
K=(1/Z)2t
(D-D LL) 0.87
(D-RLG)0.58
Frequent Fault
Infrequent Fault
Inrush
FLA
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Transformer ProtectionMAXIMUM RATING OR SETTING FOR OVERCURRENT DEVICE
PRIMARY SECONDARY
Over 600 Volts Over 600 Volts 600 Volts or Below
Transformer
Rated
Impedance
Circuit
Breaker
Setting
Fuse
Rating
Circuit
Breaker
Setting
Fuse
Rating
Circuit Breaker
Setting or Fuse
Rating
Not more than
6%
600 % 300 % 300 % 250% 125%
(250% supervised)
More than 6%
and not morethan 10%
400 % 300 % 250% 225% 125%
(250% supervised)
Table 450-3(a) source: NECAny Location Non-Supervised
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Transformer Protection
Turn on or inrush current
Internal transformer faults
External or through faults of majormagnitude
Repeated large motor starts on thetransformer. The motor represents amajor portion or the transformers KVA
rating. Harmonics
Over current protectionDevice 50/51
Ground current protectionDevice50/51G
DifferentialDevice 87
Over or under excitationvolts/ Hz
Device 24 Sudden tank pressureDevice 63
Dissolved gas detection
Oil Level
Fans
Oil Pumps
Pilot wireDevice 85
Fault withstand
Thermal protectionhot spot, top of oiltemperature, winding temperature
Devices 26 & 49
Reverse over currentDevice 67
Gas accumulationBuckholz relay
Over voltageDevice 59
Voltage or current balanceDevice 60
Tertiary Winding Protection if supplied
Relay Failure Scheme Breaker Failure Scheme
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Recommended Minimum
Transformer Protection
Protective system Winding and/or power systemgrounded neutral grounded Winding and/or power systemneutral ungroundedUp to 10 MVA Above 10 MVA Up to 10 MVA Above10 MVA
Differential - - Time over current Instantaneous restricted
ground fault - -Time delayed ground
fault
- -Gas detection
- Over excitation - Overheating - -
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Question
What is ANSI Shift Curve?
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Answer
For delta-delta connected transformers, withline-to-line faults on the secondary side, the
curve must be reduced to 87% (shift to the left
by a factor of 0.87)
For delta-wye connection, with single line-to-
ground faults on the secondary side, the curvevalues must be reduced to 58% (shift to the left
by a factor of 0.58)
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Question
What is meant by Frequent and
Infrequent for transformers?
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Fuse (Power Fuse) Non Adjustable Device (unless electronic)
Continuous and Interrupting Rating
Voltage Levels (Max kV)
Interrupting Rating (sym, asym)
Characteristic Curves
Min. Melting
Total Clearing
Application (rating type: R, E, X, )
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Fuse Types
Expulsion Fuse (Non-CLF)
Current Limiting Fuse (CLF)
Electronic Fuse (S&C Fault Fiter)
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Minimum MeltingTime Curve
Total Clearing
Time Curve
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Current Limiting Fuse
(CLF)
Limits the peak current of short-circuit
Reduces magnetic stresses (mechanical damage)
Reduces thermal energy
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Current Limiting Action
Current(peakamps)
tm ta
Ip
Ip
tc
ta= tctm
ta= Arcing Time
tm= Melting Time
tc= Clearing Time
Ip= Peak Current
Ip = Peak Let-thru CurrentTime (cycles)
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1996-2009 Operation Technology, Inc.Workshop Notes: Protective Device Coordination
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Symmetrical RMS Amperes
PeakLet-ThroughAmperes
100 A
60 A
7% PF (X/R = 14.3)
12,500
5,200
230,000
300 A
100,000
Let-Through Chart
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FUSE
Generally:
CLF is a better short-circuitprotection
Non-CLF (expulsion fuse) is a better Overload
protection
Electronic fuses are typically easier to
coordinate due to the electronic control
adjustments
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Selectivity CriteriaTypically:
Non-CLF: 140% of full load
CLF: 150% of full load
Safety Margin: 10% applied to Min Melting(consult the fuse manufacturer)
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Molded Case CB Thermal-Magnetic
Magnetic Only
Motor Circuit Protector(MCP)
Integrally Fused (Limiters)
Current Limiting
High Interrupting Capacity
Non-Interchangeable Parts
Insulated Case (InterchangeParts)
Types
Frame Size
Poles
Trip Rating
Interrupting Capability
Voltage
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MCCB
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MCCB with SST Device
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LVPCB Voltage and Frequency Ratings
Continuous Current / Frame Size / Sensor
Interrupting Rating
Short-Time Rating (30 cycle)
Fairly Simple to Coordinate
Phase / Ground Settings
Inst. Override
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CB 2
CB 1
IT
ST PU
ST Band
LT PU
LT Band
480kV
CB 2
CB 1
If=30 kA
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Inst. Override
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Overload Relay / Heater
Motor overload protection is provided by a
device that models the temperature rise of
the winding
When the temperature rise reaches a point
that will damage the motor, the motor is de-
energized
Overload relays are either bimetallic, meltingalloy or electronic
Overload Heater (Mfr Data)
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Overload Heater (Mfr. Data)
What is Class 10 and Class 20 Thermal OLR
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QuestionWhat is Class 10 and Class 20 Thermal OLR
curves?
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Answer
At 600% Current Rating:
Class 10 for fast trip, 10
seconds or less
Class 20 for, 20 seconds or less
(commonly used)
There is also Class 15, 30 for
long trip time (typically
provided with electronic
overload relays)
6
20
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Answer
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Overcurrent Relay
Time-Delay (51I>)
Short-Time Instantaneous ( I>>)
Instantaneous (50I>>>)
Electromagnetic (induction Disc)
Solid State (Multi Function / Multi Level)
Application
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1996-2009 Operation Technology, Inc.Workshop Notes: Protective Device Coordination
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TIME-OVERCURRENT UNIT
Ampere Tap Calculation
Ampere Pickup (P.U.) = CT Ratio x A.T. Setting
Relay Current (IR) = Actual Line Current (IL) / CT
Ratio
Multiples of A.T. = IR/A.T. Setting
= IL/(CT Ratio x A.T. Setting)IL
IR
CT
51
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Instantaneous Unit
Instantaneous Calculation
Ampere Pickup (P.U.) = CT Ratio x IT Setting
Relay Current (IR) = Actual Line Current (IL) / CT
Ratio
Multiples of IT = IR/IT Setting
= IL/(CT Ratio x IT Setting)IL
IR
CT
50
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Situation
Calculate Relay Setting (Tap, Inst. Tap & Time Dial)For This System
4.16 kV
DS 5 MVA
Cable
1-3/C 500 kcmilCU - EPR
CB
Isc= 30,000 A
6 %
50/51 Relay: IFC 53CT 800:5
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Solution
AInrsuh 328,869412I
A338.4800
5II LR
Transformer: AkV
kVA
L 69416.43
000,5
I
IL
CTR
IR
Set Relay:
A551.52800
5328,8)50(
1
)38.1(6/4.3380.6
4.5338.4%125
AInst
TD
ATAP
A
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Q
Berapa diskriminasi waktu antar rele proteksi ?
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Answer
At
I
B
CB Opening Time
+
Induction Disc Overtravel (0.1 sec)
+
Safety margin (0.2 sec w/o Inst. & 0.1 sec w/ Inst.)
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Recloser
Recloser protects electrical transmission systems from temporary voltagesurges and other unfavorable conditions.
Reclosers can automatically "reclose" the circuit and restore normal powertransmission once the problem is cleared.
Reclosers are usually designed with failsafe mechanisms that preventthem from reclosing if the same fault occurs several times in succession
over a short period. This insures that repetitive line faults don't causepower to switch on and off repeatedly, since this could cause damage oraccelerated wear to electrical equipment.
It also insures that temporary faults such as lightning strikes ortransmission switching don't cause lengthy interruptions in service.
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Recloser Types
Hydraulic
Electronic
Static Controller
Microprocessor Controller
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Recloser Curves
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