e_t_line traps

7/26/2019 E_T_Line Traps

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Line Tra ps


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Ba sic Functio n o f Line Tra ps

Pow er Line C arrier (PLC ) is acom m on m ethod of Pow er SystemC om m unication, such as telepro-tection, voice and data com m uni-cation, etc. It has developed the

reputation of being one of them ost econom ical and reliable form sof com m unication and versatile inits application. Fig.2 show s a basicPLC system consisting of threedistinct com ponents:

signal carrying m edium (H Vtransm ission line)

com m unication apparatus(transm itters, receivers andassociated com ponents)

coupling/blocking equipm entsuch as coupling capacitors, linetuners (coupling devices) andLine Traps.

Line Traps are connected in seriesw ith H V transm ission lines. Them ain function of the Line Trap is topresent a high im pedance at thecarrier frequency band w hileintroducing negligible im pedanceat the pow er frequency. The high

im pedance lim its the attenuationof the carrier signal w ithin thepow er system by preventing thecarrier signal from being:

dissipated in the substation

grounded in the event of a faultoutside the carrier transm issionpath

dissipated in a tap line or abranch of the m ain transm issionpath.

Line Tra ps

Introduction

W ith over 40 years of successfulfield experience Trench is therecognized w orld leader in thedesign and m anufacture of air-core dry-type inductors for electric

utility applications. The uniquecustom design approach, alongw ith fully integrated engineeringand m anufacturing facilities inboth N orth A m erica and Europehave enabled Trench to becom ethe technical leader for highvoltage inductors w orld w ide.

Line Traps for Pow er Line C arrier(PLC) com m unication system srepresent a significant application

segm ent for high voltageinductors.

Fig. 1

Post moun ted

Lin e Traps


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Desig n a nd Construction

Line Traps are designed to m eetA N SI standard C 93.3, IEC stan-dard 353 or other internationalstandards.

The m ajor com ponents of a LineTrap are the m ain coil, tuningdevice and protective device(see Fig. 3).

Fig. 4

Suspension mounted

Line Traps

Fig. 2

Prin ciple scheme of a

PLC system

Tun ing

Device

Term ina l

Main

Coil

Pedes ta l

(Optional)

Lightning

Arrester

Bird Ba rrier (Optio na l)

Since Line Traps are series connec-ted w ith the H V transm ission line,they m ust be designed to w ith-stand the high m echanical forcesgenerated by the short circuit (s/c)current associated w ith the H Vtransm ission system .

Fig. 3

Line Trap

components

1 C oupling Capacitor 2 Line Tuner 3 Transm itter/Receiver

Line Trap Line Trap

Station A Station B


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Ma in Co il

The m ain coil of a Line Trap is anair-core dry-type pow er inductor.

Trench offers Line Traps w ith eitherof tw o w ell established w inding

technologies:

Encapsulated design (E-design)

O pen style design (O -design).

Both technologies fully com plyw ith pow er system and PLCrequirem ents and are thereforeapplied over the full range of com -m only specified m ain coil ratings.H ow ever, in the upper lim its ofinductance and current ratings the

encapsulated design is thepreferred concept (see Fig.5).

The w inding of the encapsulateddesign utilizes alum inum w ire orcable, w hereas the open stylew inding em ploys alum inum flat-bar conductor. A ll pow er currentcarrying com ponents utilizew elded connections.

H igh m echanical strength of thew inding is either achieved by resinim pregnated, fiberglass reinforcedencapsulation (E-design) or byfiberglass spacers w hich are resin

bonded betw een turns (O -design).

The w inding is term inated at bothends on a system of alum inumbars, denoted as the spiders w hichare tensioned together by fiber-glass ties (E-design) or fiberglassrods (O -design). These spiders areadditionally used for

the electrical connection to theLine Trap by term inal pads orstuds

providing the hardw are forlifting (lugs), m ounting (pede-stals) and corona protection (bells,rings)

connecting the tuning andprotective device across them ain coil.

Trench can provide the com pleterange of standard ratings(inductance, continuous and s/c

current ratings, system voltage) inaccordance w ith IEC 353 or A N SIC 93.3 standards (see Fig.5).C ustom ized units are also availableto m eet specific custom er require-m ents, such as specific inductance,current (s/c or continuous), lowloss requirem ents, etc.

a


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Ra ted Current s Ra ted Induct a nce

IEC 353 IEC 353

C ontinuous Short-tim eA Series 1 m H at 100 kH z

kA /1sec

100 2,5 0,2 0,25 0,315 0,4 0,5 1,0 2,0

200 5 0,2 0,25 0,315 0,4 0,5 1,0 2,0

400 10 0,2 0,25 0,315 0,4 0,5 1,0 2,0

630 16 0,2 0,25 0,315 0,4 0,5 1,0 2,0

800 20 0,2 0,25 0,315 0,4 0,5 1,0 2,0

1000 25 0,2 0,25 0,315 0,4 0,5 1,0 2,01250 31,5 0,2 0,25 0,315 0,4 0,5 1,0 2,0

1600 40 0,2 0,25 0,315 0,4 0,5 1,0 2,0

2000 40 0,2 0,25 0,315 0,4 0,5 1,0 2,0

2500 40 0,2 0,25 0,315 0,4 0,5 1,0 2,0

3150 40 0,2 0,25 0,315 0,4 0,5 1,0 2,0

4000 63 0,2 0,25 0,315 0,4 0,5 1,0 2,0

C ontinuous Short-tim eA Series 2 m H at 100 kH z

kA /1sec

100 5 0,2 0,25 0,315 0,4 0,5 1,0 2,0

200 10 0,2 0,25 0,315 0,4 0,5 1,0 2,0

400 16 0,2 0,25 0,315 0,4 0,5 1,0 2,0

630 20 0,2 0,25 0,315 0,4 0,5 1,0 2,0

800 25 0,2 0,25 0,315 0,4 0,5 1,0 2,0

1000 31,5 0,2 0,25 0,315 0,4 0,5 1,0 2,0

1250 40 0,2 0,25 0,315 0,4 0,5 1,0 2,0

1600 50 0,2 0,25 0,315 0,4 0,5 1,0 2,0

2000 50 0,2 0,25 0,315 0,4 0,5 1,0 2,0

2500 50 0,2 0,25 0,315 0,4 0,5 1,0 2,0

3150 50 0,2 0,25 0,315 0,4 0,5 1,0 2,0

4000 80 0,2 0,25 0,315 0,4 0,5 1,0 2,0

Ra ted Current s Ra ted Induct a nceANSI C93.3 ANSI C93.3

C ontinuous Short-tim e

A kA /2secm H at 100 kH z

400 15 0,265 0,53 1,06 1,59 2,12 2,65

800 20 0,265 0,53 1,06 1,59 2,12 2,65

1200 36 0,265 0,53 1,06 1,59 2,12 2,65

1600 44 0,265 0,53 1,06 1,59 2,12 2,65

2000 63 0,265 0,53 1,06 1,59 2,12 2,65

3000 63 0,265 0,53 1,06 1,59 2,12 2,65

4000 80 0,265 0,53 1,06 1,59 2,12 2,65

5

N ote:

A ll ratings availablew ith E-design

Shaded ratings notavailable w ith O -design

Fig. 5

Values of contin uou s

curr ent, short time curr ent

and i nductance


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Tun ing De vice

The tuning device, connectedacross the m ain coil, form s ablocking circuit w hich provideshigh im pedance over a specifiedPLC -frequency range.

D epending on the type of tuning(see below ) the tuning deviceconsists of capacitors, inductorsand resistors, all having relativelylow pow er ratings, com pared tothe m ain coil. For environm entalprotection these com ponents arem ounted in one or m ore fiberglasshousings. The tuning device isinstalled inside the m ain coil.To m eet changing PLC frequencyrequirem ents the tuning device iseasily accessible for replacem entor field adjustm ent (if applicable).

The bandw idth of a Line Trap isthat frequency range over w hichthe Line Trap provides a certainspecified m inim um blocking im pe-dance or resistance. M inim umblocking resistance should bespecified if the potential exists forthe reactive com ponent of theLine Trap im pedance to resonatew ith the substation im pedance.

The achievable bandw idth can beexpanded by increasing the m aincoil inductance.D ifferent types of tuning m ay beexpanded by increasing the m aincoil inductance.

D ifferent types of tuning m ay besupplied.

Single Frequency Tuning

If narrow blocking bands arerequired single frequency tuning isthe sim plest and m ost econom icaltype of tuning available. Fig.6show s a typical schem atic andblocking characteristic. W ithin thisnarrow band, how ever, highblocking im pedance can be provi-ded, resulting in excellent PLCsignal isolation.

D ouble Frequency Tuning

The double frequency tuningarrangem ent blocks tw o relativelynarrow bands of frequencies.O therw ise, the blocking characte-ristic is sim ilar to single frequencytuning.

For proper operation and isolationof the tuned bands a m inim umfrequency separation m ust bem aintained betw een the peaktuning frequencies. This is 25 kH z

or 25 % of the upper tuningfrequency peak, w hichever isgreater. Fig.7 show s a typicaldouble frequency schem atic andblocking characteristic.

Fig.6

Sin gle frequency tun in g

Fig.7

Double frequency tun in g

Fig.8

Wideband tunin g

b

Z Blocking im pedance

R Resistive com ponent

f C arrier frequencyf m Resonant frequency

(G eom etric M ean Frequency

G M F)

f 1 f 2 Frequency lim its of

blocking im pedance

f 1 f 2 Frequency lim its of

resistive blocking im pedance


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Fig.10

Selftun ed Lin e Trap

blocking characteristics

W ideband Tuning

W ideband tuning is the m ostcom m on type of tuning as itefficiently utilizes the m ain coilinductance. W ideband tuned LineTraps are suitable for m ulti-chan-

nel applications, since relativelyconstant im pedance is obtainedover a broad frequency range. Thistype of tuning provides high band-w idth flexibility for future changesor expansion of PLC frequencies.PLC channels can be placedanyw here w ithin the blockedbandw idth.Fig.8 show s a typical w idebandfrequency Line Trap schem atic andblocking characteristic.

Selftuned Line Traps

Selftuned Line Traps do not requirethe use of tuning devices. Theblocking characteristic as show n inFig.10 is achieved by sim ply utili-zing the self-capacitance of the

m ain coil w inding. The inductanceof a selftuned Line Trap is higherthan that of a tuned Line Trap.

Fig. 9

Suspension mounted 380 kV,

1.0 mH, 2100 A Line Trap


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Prot ective Device

The protective device is a surgearrester connected in parallel w iththe m ain coil and the tuningdevice. It protects the m ain coiland the tuning device by reducing

the transient overvoltages to levelscorresponding to distributionvoltage class insulation.

The insulation level of the m aincoil and tuning device is coordinatedw ith the surge arrester protectivecharacteristics.

Trench Line Traps are equippedw ith advanced m etal-oxide typesurge arresters having a discharge

current rating of 10kA . Surgearresters w ith higher dischargecurrent or high energy dissipationarrangem ents are also available onspecific request.

Mount ing a nd Connection

Trench Line Traps can be m ountedin several configurations. Suspen-sion m ounted Line Traps areavailable w ith either single pointorm ulti-point suspension brackets.Line Traps can also be pedestalm ounted directly onto couplingcapacitors (CCs), capacitive voltagetransform ers (C VTs) or station postinsulators. Trench offers severaltypes of m ounting pedestals:

single insulator support pedestal

m ulti-insulator support pedestal

insulated pedestal

O ther than the insulated pedestal,all pedestals are electricallyconnected to the low er term inalof the Line Trap, and as such canbe used as both the electrical and

m echanical connection to the C Cor C VT (see Fig.11a). Should it benecessary to utilize the upper LineTrap term inal as the connection tothe C C or C VT, a pedestal insulatedfrom the bottom end (bottomspider) of the Line Trap m ust beused in conjunction w ith a specialinsulated connection rod suppliedby Trench (see Fig.11b).A ll pedestals can be custom m adeto suit custom er requirem ents.

Term inals supplied on the Line Trapscan be either pad or stud type.Each type is m anufactured tom eet the applicable IEC or N EM Astandards.In addition, term inals can belocated on virtu ally any spider arm, ensu-

rin g total flexibi lity to meet ind ividu al re-

quir ements. Term in al details and term i-

nal ori entati on ar e shown in Fig.12 and

Fig.13.

c

Fig. 11a Fig. 11b

Station

Station

Line

Line

C ouplingC apacitor

C ouplingC apacitor

Line Trap conn ection


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Fig.12

Fig. 12Term inal orientation(by special request m ay be situatedat any spider arm location.N um ber of spider arm s is obtainedfrom actual quotation draw ing,

typically 4, 6 or 8)Et: is used to define the topterm inal location, at centre or atany of the spiders.Eb: is used to define the bottomterm inal location; at centre or atany of the spider arm s.

Fig. 13Standard term inal types plated orbare alum inum

N ote:U nless otherw ise specified, flatterm inal pads w ill be verticallyoriented to reduce eddy currentheating. (ie. term inals oriented sothat the coils axis is in the planeof the term inal.)

Fig.13

Top view


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C alculation of tapping loss (A t)

and blocking attenuation (A b)

Z1 = C haracteristic im pedance of

the line

The im pedance of substation Zsis

assum ed to be 0 O hm s.

Center Frequency (fc)

fc is the m ean frequency of

the blocked bandw idth lim itfrequencies (f1, f2).

Definiton of Blocking

Term s

The blocking requirem ent of aLine Trap is dependent on thecharacteristic im pedance of the

transm ission line w here Pow erLine C arrier is to be applied. TheLine Trap blocking requirem ents

can be specified in term s of:

Blocking Im pedance (Zb):

Zb is the com plex im pedance of

the com plete Line Trap w ithin aspecified PLC frequency range.

Blocking Resistance (Rb):

R

b

is the value of the resistive

com ponent of the blockingim pedance, w ithin a specifiedPLC frequency range.

Tapping Loss (A t)

A t, also know n as Insertion

Loss, is a m easure of the lossof pow er sustained by a carrierfrequency signal due to thefinite blocking ability of the LineTrap. The tapping loss of an

ideal Line Trap should be verylow and approach zero.

Blocking A ttenuation (A b)

A b is a m easure of the relative

transm itted carrier frequencysignal w hich enters the trappedcircuit section of netw ork. Theblocking attenuation of an idealLine Trap should be infinitelyhigh.

Equ.I A t (dB) = 20 log 10 (1+ ___)Z12Zb

Equ.II A b (dB) = 20 log 10 (1+ ___)Zb

Z1

fc=f1xf2


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1,0 m H Line Tra p

0,315 m H Line Tra p0,2 m H Line Tra p

0,5 m H Line Tra p


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