04 protective device coordination

8/12/2019 04 Protective Device Coordination

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STAR DEVICE COORDINATION

ANALYSIS

SUPRIYANTO, ST., [email protected]

[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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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


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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04 protective device coordination

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