Short-Circuit Protective Device Coordination & Arc Flash Analysis
08 - Device Coordination
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ETAP 5.0ETAP 5.0
Copyright 2004 Operation Technology, Inc.
Protective DeviceCoordination
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 2
Agenda• OC Protective Device Coordination
– Concepts & Applications
• STAR 5.0.0 Overview– Features & Capabilities
• STAR Example 1
– Advance Topics• STAR Example 2
– PD Sequence of Operation– Device Libraries– ETAP ARTTS
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 3
Definition
• Overcurrent Coordination– A systematic study of current responsive
devices in an electrical power system.
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 4
Objective
• To determine the ratings and settings offuses, breakers, relay, etc.
• To isolate the fault or overloads.
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 5
Criteria
• Economics
• Available Measures of Fault
• Operating Practices
• Previous Experience
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 6
Design
• Open only PD upstream of the fault oroverload
• Provide satisfactory protection for overloads
• Interrupt SC as rapidly (instantaneously) aspossible
• Comply with all applicable standards andcodes
• Plot the Time Current Characteristics ofdifferent PDs
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 7
Analysis
When:
• New electrical systems
• Plant electrical system expansion/retrofits
• Coordination failure in an existing plant
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 8
Protection vs. Coordination
• Coordination is not an exact science
• Compromise between protection andcoordination– Reliability
– Speed
– Performance
– Economics
– Simplicity
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 9
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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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 10
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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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 11
Coordination
• Limit the extent and duration of serviceinterruption
• Selective fault isolation
• Provide alternate circuits
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 12
Coordination
t
I
C B A
C
D
D B
A
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 13
Equipment
• Motor
• Transformer
• Generator
• Cable
• Busway
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 14
Capability / Damage Curves
t
I
I22t
Gen
I2t
MotorXfmr
I2t
Cable
I2t
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 15
Transformer CategoryANSI/IEEE C-57.109
Minimumnameplate (kVA)Category Single-phase Three-phase
I 5-500 15-500II 501-1667 501-5000III 1668-10,000 5001-30,000IV above 1000 above 30,000
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 16
Infrequent Fault Incidence Zones for Category II & III Transformers
* Should be selected by reference to the frequent-fault-incidence protection curve or fortransformers serving industrial, commercial and institutional power systems with secondary-sideconductors enclosed in conduit, bus duct, etc., the feeder protective device may be selected byreference to the infrequent-fault-incidence protection curve.
Source: IEEE C57
Source
Transformer primary-side protective device(fuses, relayed circuit breakers, etc.) may beselected by reference to the infrequent-fault-incidence protection curve
Category II or III Transformer
Fault will be cleared by transformerprimary-side protective device
Optional main secondary –side protective device.May be selected by reference to the infrequent-fault-incidence protection curve
Feeder protective device
Fault will be cleared by transformer primary-sideprotective device or by optional main secondary-side protection device
Fault will be cleared byfeeder protective device
Infrequent-FaultIncidence Zone*
Feeders
Frequent-FaultIncidence Zone*
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 17
Transformer
t(sec)
I (pu)
Thermal200
2.5
I2t = 1250
2
25Isc
Mechanical
K=(1/Z)2t
(D-D LL) 0.87
(D-R LG) 0.58
Frequent Fault
Infrequent Fault
Inrush
FLA
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 18
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 19
Transformer Protection
MAXIMUM RATING OR SETTING FOR OVERCURRENT DEVICEPRIMARY SECONDARY
Over 600 Volts Over 600 Volts 600 Volts or Below
TransformerRated
Impedance
CircuitBreakerSetting
FuseRating
CircuitBreakerSetting
FuseRating
Circuit BreakerSetting or Fuse
Rating
Not more than6%
600 % 300 % 300 % 250% 125%(250% supervised)
More than 6%and not more
than 10%
400 % 300 % 250% 225% 125%(250% supervised)
Table 450-3(a) source: NEC
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 20
Protective Devices• Fuse
• Relay (50/51 P, N, G, SG, 51V, 67, 46, 79, 21, …)
• Thermal Magnetic
• Low Voltage Solid State Trip
• Electro-Mechanical
• MCP
• Overload Heater
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 21
Fuse
• Non Adjustable Device
• Continuous and Interrupting Rating
• Voltage Levels
• Characteristic Curves
– Min. Melting
– Total Clearing
• Application
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 22
Minimum MeltingTime Curve
Total ClearingTime Curve
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 23
Current Limiting Fuse(CLF)• Limits the peak current of short-circuit
• Reduces magnetic stresses (mechanicaldamage)
• Reduces thermal energy
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 25
Symmetrical RMS Amperes
Pea
k Le
t-Thr
ough
Am
pere
s
100 A
60 A
15% PF (X/R = 6.6)
12,500
5,200
230,000
300 A
100,000
Let-Through Chart
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 26
Fuse
Generally:
• CLF is a better short-circuit protection
• Non-CLF (expulsion fuse) is a betterOverload protection
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 27
Selectivity Criteria
Typically:
• Non-CLF: 140% of full load
• CLF: 150% of full load
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 28
Molder Case CB
• Thermal-Magnetic
• Magnetic Only
• Integrally Fused
• Current Limiting
• High InterruptingCapacity
Types
• Frame Size
• Trip Rating
• Interrupting Capability
• Voltage
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 29
Thermal Minimum
Thermal Maximum
Magnetic(instantaneous)
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 30
LVPCB
• Voltage and Frequency Ratings
• Continuous Current / Frame Size
– Override (12 times cont. current)
• Interrupting Rating
• Short-Time Rating (30 cycle)
• Fairly Simple to Coordinate
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480 kV
CB 2
CB 1
CB 2CB 1
IT
ST PU
ST Band
LT PU
LT Band
If =30 kA
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 32
Motor Protection
• Motor Starting Curve
• Thermal Protection
• Locked Rotor Protection
• Fault Protection
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 33
Motor Overload Protection(NEC Art 430-32)
• Thermal O/L (Device 49)
• Motors with SF not less than 1.15– 125% of FLA
• Motors with temp. rise not over 40– 125% of FLA
• All other motors– 115% of FLA
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 34
Locked Rotor Protection
• Thermal Locked Rotor (Device 51)
• Starting Time (TS < TLR)
• LRA– LRA sym
– LRA asym (1.5-1.6 x LRA sym) + 10% margin
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 35
Fault Protection(NEC Art 430-52)
• Non-Time Delay Fuses– 300% of FLA
• Dual Element (Time-Delay Fuses)– 175% of FLA
• Instantaneous Trip Breaker– 800% of FLA*
• Inverse Time Breakers– 250% of FLA
*MCPs can be set higher
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200 HP
MCPO/L
Starting Curve
I2T(49)
MCP (50)
(51)ts
tLR
LRAs LRAasym
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 37
Overcurrent Relay
• Time-Delay (51 – I>)
• Short-Time Instantaneous ( I>>)
• Instantaneous (50 – I>>>)
• Electromagnetic (induction Disc)
• Solid State (Multi Function / Multi Level)
• Application
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 39
Time-Overcurrent Unit
• Ampere Tap Calculation– Ampere Pickup (P.U.) = CT Ratio x A.T. Setting
– Relay Current (IR) = Actual Line Current (IL) / CTRatio
– Multiples of A.T. = IR/A.T. Setting
= IL/(CT Ratio x A.T. Setting)IL
IR
CT
51
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 40
Instantaneous Unit
• Instantaneous Calculation– Ampere Pickup (P.U.) = CT Ratio x IT Setting
– Relay Current (IR) = Actual Line Current (IL) / CTRatio
– Multiples of IT = IR/IT Setting
= IL/(CT Ratio x IT Setting)IL
IR
CT
50
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 41
Relay Coordination• Time margins should be maintained between T/C
curves• Adjustment should be made for CB opening time• Shorter time intervals may be used for solid state
relays• Upstream relay should have the same inverse T/C
characteristic as the downstream relay (CO-8 toCO-8) or be less inverse (CO-8 upstream to CO-6downstream)
• Extremely inverse relays coordinates very well withCLFs
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 42
Fixed Points
• Motor starting curves
• Transformer damage curves &inrush points
• Cable damage curves
• SC maximum fault points
• Cable ampacities
Points or curves which do not changeregardless of protective device settings:
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 43
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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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 44
Solution
AInrsuh 328,869412I =×=
A338.4800
5II LR =×=
Transformer: AkV
kVAL 694
16.43000,5I =×
=
IL
CTRIR
Set Relay:
A551.52800
5328,8)50(
1)38.1(6/4.3380.6
4.5338.4%125
=>=×=
==
=×=
AInst
TDATAP
A
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 45
Question
What is ANSI Shift Curve?
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 46
Answer
• For delta-delta connected transformers, withline-to-line faults on the secondary side, thecurve must be reduced to 87% (shift to theleft by a factor of 0.87)
• For delta-wye connection, with single line-to-ground faults on the secondary side, thecurve values must be reduced to 58% (shiftto the left by a factor of 0.58)
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 47
Question
What is meant by Frequent andInfrequent for transformers?
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 48
AnswerInfrequent Fault Incidence Zones for Category II & III Transformers
Source
Transformer primary-side protective device(fuses, relayed circuit breakers, etc.) May beselected by reference to the infrequent-fault-incidence protection curve
Category II or III Transformer
Fault will be cleared by transformerprimary-side protective device
Optional main secondary –side protective device.May be selected by reference to the infrequent-fault-incidence protection curve
Feeder protective device
Fault will be cleared by transformer primary-sideprotective device or by optional main secondary-side protection device
Fault will be cleared byfeeder protective device
Infrequent-FaultIncidence Zone*
Feeders
Frequent-FaultIncidence Zone*
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 49
Question
What T/C Coordination interval should bemaintained between relays?
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 50
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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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 51
Question
What is Class 10 and Class 20Thermal OLR curves?
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 52
Answer
• Class 10 for fast trip, 10 seconds or less
• Class 20 for, 20 seconds or less
• There is also a Class 30 for long trip time
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Copyright 2004 Operation Technology, Inc. – Workshop Notes: Protective Device Coordination Slide 53
Answer