32 line protection.pdf

Line Protection

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LINE PROTECTION OLEH :

SUPRIYANTO, ST., MT

PROTEKSI JARINGAN DISTRIBUSI

1. Circuit breakers & relays

2. Fuses: Unique in their time-overcurrent characteristics

3. Sectionalizers: Unique in their own right

4. Reclosers

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SETTING OCRGANGGUAN FASA – FASA [ TUNDA WAKTU

.max

%80

2,11,1

maxminmax

minmaxmin

]2....[min8,0max

]1.....[min

max

2

max

arusbebanI

k

k

IIII

IIII

II

k

IkI

D

S

SETSETSETSET

SETSETSETSET

HSSET

D

SSEI

PROTEKSI JARINGAN DISTRIBUSISETTINGS RULES

Selectivity : time dial

Curves are to be adjusted in order to maintain “margin” or separation

• 0.3 seconds between relay curves

• 3 to 6 cycles (0.05—0.1 seconds of this gets “used up” due to device operation (breaker, recloser, etc.)

• Remember to account for differing values of maximum available fault current at each bus…this will allow faster operating times

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KOORDINASI OCR

# DEFINITE TIME

A B C

t

I

0,3 det

0,8 det

1,3 det

det5,04,0

t

ttt

IIII

ABC

HSSASBSC

KOORDINASI OCR

# INVERSE TIME

A B C

t

I

TMS ATMS B TMS C

SETING WAKTU DENGAN PEMILIHAN TD / TMSTD = TIME DIALTMA = TIME MULTIPLE SETTING

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SETTING ELEMEN INSTANTANEOUS

DIMAKSUDKAN UNTUK GANGGUAN 3 FASA ,TETAPI HARUSMEMPERHATIKAN ARUS KETAHANAN KABEL .

abelkemampuankSET

HSSETHS

II

III

2

312 minmin

SETTING INSTANT

212

121

SETSETSETSET

SETSETSETSET

IIII

IIII

KOORDINASI OCR

# INSTANTANEOUS

A B C

CIBinstI

BIAinstI

HSSET

HSSET

3

3

2,1.

2,1.

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KOORDINASI DARI RELAI KOMBINASI TUNDA WAKTUDENGAN INSTANT /

A B C

t

I

TMS ATMS B TMS C

t

I

t A

t B

t Ct INST t INST

t INST t INST

PROTEKSI JARINGAN DISTRIBUSI(SETTINGS RULES)

1. Set pickup at no more than 1/3 minimum fault current in the zone

2. Set pickup at least 2.5x the peak load expected at the device

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Sensitivity (reach) for ground relays:(ground relays “see” LLG, SLG faults)

1. Set pickup at no more than 1/3 of minimum fault current (smallest of the above types) in the zone

2. Typical setting: 240 amps

3. Remember, phase relays react to all faults, ground relays only react to LLG, SLG faults


Selectivity : pickup value

Each device is to be considered in its own zone

• Set pickup• ≤ 1/3 minimum fault current in the zone

• ≥ 2.5x the peak load expected at the device

• Good idea to stagger pickup values along feeder to avoid miscoordination for overload trips; nature of radial loading allows this to be done.

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DISTRIBUTION PROTECTION & SECTIONALIZING DEVICES

Circuit breakers & relays

• Most versatile in terms of settings – pickup and time dial are field adjustable

Fuses: Unique in their time-overcurrentcharacteristics

Sectionalizers: Unique in their own right

Reclosers

• Extremely common device, but they are really just circuit breakers in a specific application…same rules & tactics apply as breakers & relays!

FUSE

Fuse dan Recloser diterapkan pada feeder radial dalambentuk 3 fasa atau satu fasa (Blackburn, J. L. 1998). Fuseyang dirancang untuk tegangan di atas 600V masuk dalamkategori Fuse Cut Out atau tenaga (Gonen, T,1986),meskipun secara spesifik digunakan untuk tegangan 34.5kV atau lebih.

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TIPE LINKLink terdiri dari tipe K (cepat) atau T (lambat). Fusetipe expulsion memadamkan busur api gangguan padasaat arus gangguan mencapai zero crossing. Fusejenis ini paling umum digunakan pada jaringan udara

•Fuse dan Fuse Link

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Karakteristik dari pelebur ialah lamanya waktupemutusan yang tergantung dari besarnya arus yangmengalir pada peleburnya.

Perbedaan kurva antara kedua tipe didasarkan pada“speed ratio”, yaitu perbandingan antar arus lelehminimum pada 0,1 detik dan arus leleh minimum pada300 atau 600 detik. Untuk fuse link tipe “K” (tipe cepat)speed ratio = 6-8. Untuk fuse link tipe “T” (tipe lambat)speed ratio = 10-13. (Gonen, T.,1986).

Fused cutout

Inexpensive

Reliable

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Fuse link

FUSES - GENERAL

Purposes

• To protect equipment from high overload currents

• To protect the system from failed equipment

• For sectionalizing

Design

• Generally consists of a “fusible element” made of soft metal

• All fuses have a maximum load current they can carry

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EXPULSION FUSES - CONTINUED

Operation

• When exposed to the high current of a fault, the fusible element heats and melts

• Heat from arc releases de-ionizing gases from lining of fuse tube

• As these gases build up, the arc is stretched, compressed & cooled

• The arc that is drawn across the severed pieces of metal is then extinguished to open the circuit

• Circuit is interrupted when the current passes through zero

Considered to be “zero-awaiting” devices because they await the passing zero point to extinguish an arc

EXPULSION FUSES - CONTINUED

Application

• Most often located outdoors, typically in fused cutouts

Expulsion fuse “speed” characteristics

• Type KS (Slow links) – Used to protect transformers and distribution lines while remaining relatively insensitive to current transients

• Type K (Faster) – Used to protect tap lines which need to be de-energized quickly whenever a fault occurs, and also to protect capacitor banks

• Many others (T, N, Q, QA, etc.)

Relatively low cost

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TypeNominalRating *

Maximum Load Current150% Nominal (Amps)**

Interrupting Capacity(Amps)

57

101520253040506580

7.510.515

22.530

37.5456075

97.5100 ***

Interrupting capacity is determined by thecutout -- not by the fuse.The cutout can interrupt12,000 Amps (asymmetrical)

7,500 Amps (symmetrical)

100 100 ***

KS

K & KS

K

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KONSEP DASAR KOORDINASI PROTEKSI

Champbell, HE, (1988)

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PERTIMBANGAN TERMAL THD FUSE PADA PROSES REC


KONSEP KOORDINASI PROTEKSI


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Fuses: Unique in their time-overcurrent characteristics


Reclosers


Single phase pole top recloser

Oil-filled tank

Current-operated solenoid

Hydraulic trip & reclose timing mechanisms

Interrupting contacts (oil)

Typical 2,500-4,000 amp interrupting rating

Typical 50-200 amp load rating

Inexpensive, fault sensing & interrupting, automatic reclosing

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Current (Amps)

Tim

e (S

econ

ds)

100 2K300 700 3K0.030.05

1

0.1

0.7

Time-Current Curves for a 50A Hydraulic Recloser

C

B

A

Slow Trips

Fast Trip

7

5

32

0.5

0.3

0.2

0.07

50 4K 5K1K500

Reclosers on Distribution Feeder

Reclosers

FCB

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Fuses: Unique in their time-overcurrent characteristics


Reclosers


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Single phase hydraulic sectionalizer

Works in conjunction with upstream reclosing devices

Inexpensive, fault sensing but non-interrupting

Single phase cutout-mounted sectionalizer

Works in conjunction with upstream reclosing devices

Inexpensive, fault sensing but non-interrupting

Solid dielectric

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Purpose of a Sectionalizer

The purpose of a sectionalizer is to automatically isolate a faultedsection of feeder, but unlike a fuse or recloser, it cannot actuallyinterrupt fault current. Instead, the sectionalizer opens only afterthe line has been temporarily de-energized by an upstream breakeror recloser.

SECTIONALIZER CHARACTERISTICS

Specifically designed for the protection of single-phase lateral lines

Located on the distribution line in locations similar to tap fuses

Cannot actually interrupt fault current

Operates in conjunction with a line recloser or with the substation FCB

Senses the presence and removal of an overcurrent, and drops out while the upstream device is open after that device has operated for a preset number of counts

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SECTIONALIZER CHARACTERISTICS (CONTINUED)

Basically a counting device

• It counts the number of times it sees fault current flow and then subsequently removed.

• If the preset count is reached, the sectionalizer opens while the upstream protective device (recloser or breaker) is open.

• If the preset count is not reached, the sectionalizer will reset to a zero count after approximately 25 seconds.

Sometimes considered a “smart fuse,” but it is much better to call it a “smart switch”

HOW IS THE OPERATION OF A SECTIONALIZER SIMILAR TO THAT OF A FUSE?

Like a fuse, the sectionalizer is intended to operate in conjunction with a source-side recloser or with the substation FCB

Like a fuse, it isolates (sectionalizes) the faulted portion of the line from the main line

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HOW IS THE OPERATION OF A SECTIONALIZER DIFFERENT FROM THAT OF A FUSE?Main advantage is that it has no time-current characteristics that must be coordinated with another device

Can discriminate between temporary and permanent faults

Can be used over the full range of available fault currents

Will not operate due to cold-load pickup

Can be used in close-in taps where high available fault current prevents fuse coordination

Cannot acquire “pre-damage” problems

Like a fuse, it isolates (sectionalizes) the faulted portion of the line from the main line

Recloser -- Sectionalizer Coordination

Reclosers

Sectionalizer(Set to 3 Counts)

Three-PhasePrimary

AFCB

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Quiz on Sectionalizers

1. Explain the function of the sectionalizer in the figure below:

Reclosers

Sectionalizer(Set to 3 Counts)

FCB

Quiz on Sectionalizers

1. Explain the function of the sectionalizer in the figure below:

Ans. • If a permanent fault occurs downstream of the sectionalizer, the

sectionalizer counts the number of times that fault current flows, followed by an interruption.

• At the count of “3” (i.e., the recloser has operated twice on its fast curve and once on its delay curve), the sectionalizer drops out and therefore isolates the faulted branch of the circuit. The recloser then re-energizes the rest of the circuit.

• If the fault is a temporary fault, the recloser will trip and reclose, and the fault will be gone.

• The sectionalizer will have counted to “1”, but since the fault has disappeared and the circuit is restored, it will time out after 25 seconds and return its count to zero.

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2. What is the main advantage of sectionalizers over fuses?

Ans. The sectionalizer has no time-current curve to coordinate with other devices --thus making coordination easier.

32 line protection.pdf

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