Proven Measurement PrinciplesUp To Date Technology

Fields of applicationPXLC 3000 is a static switch distanceprotection capable of detecting alltypes of faults. It is used as mainprotection in high voltage networks upto 225 kV with solidly earthed neutralor using impedance earthing(reactance or Petersen coil). This unitis particularly suitable for overheadlines and can also be used forprotecting underground cables. It iscapable of detecting faults withcurrent far below the rated linecurrent.

Main characteristics- Circular form under impedancestarting with off set capability.- Three forward zones, one reversezone.- Four tripping steps.- Reactance type zone measurementfor eliminating the influence of faultresistance and load current.- Electronic voltage memory slavedonto the network frequency permittingdirectional operation even in theevent of close-up three-phase faults.- Fuse failure detection.- Instantaneous tripping in the event ofclosing onto fault.- Locking device in event of powerswing detection.- All signalling schemes available :• step acceleration,• permissive overreach,• blocking,

• zone extension,• direct inter-tripping.- Programming of single phase orthree-phase tripping modes forvarious steps.- Built-in single phase/three-phaseauto-recloser.

OperationThe three voltages and three currentsfrom the measurement reducers feedtransformers ensuring galvanicinsulation and reducing levels tovalues compatible with the electronics.In block 1, the signals from thetransformers are added to generatezero sequence quantities Vo, Io, Ko.Block 2 includes three under-impedance relays and their settings.These relays serve to start theprotection.Block 3 includes the optional voltagememory circuit.Block 4 ensures bandpass filtering ofinput quantities, thus eliminating allsignals which are harmful formeasurement : aperiodic component,line oscillation, CVT transients,harmonics... It also ensures electronicswitching of significant quantities ofthe faulty loop.Block 5 carries out zone setting.Block 6 carries out measurement.Block 7 receives measurement data,processes it, dialogues with the steptime delay and generates outputsignals (tripping and indication).

Block 8 represents the protectionpower supply DC-DC converter.Block 9 includes step time delays.Block 10 represents opticalindications.Block 11 includes indication andtripping contacts.Block 12 receives data from theoutside (fuse failure, line closing, ...).Block 13 includes an optional powerswing detection circuit.

StartingFor each of the three starting elements,the protection generates twodifferential voltages whose phase shiftis measured. The impedance pointfalls within starting when themeasured phase shift is greater than90°.

Distance measurementA differential voltage is generated forthe faulty loop detected by phaseselection, itself generated from starting.In the same way as for starting, thephase-shift of this voltage is measuredwith respect to a current imagevoltage. The impedance point is withinthe zone in question when the phase-shift is greater than 90°. For earthfaults, distance measurement in thefirst zone is carried out when thevoltage drop in the fault resistance iszero (zero instantaneous residualcurrent), rendering this measurementparticularly insensitive to faultresistance. It is also insensitive tofrequency, aperiodics and loads.

Direction measurement without deadzoneTo obtain directional sensitivity for alltypes of faults, two bias voltages areused :- Healthy voltageThe voltage representing the directionof fault current flow is compared withthe opposite healthy phase voltage,phase-shifted by 60°.- Positive sequence stored voltageIn the event of a three-phase close-upfault, a voltage stored in electronicform is used, preserving the frequencyand phase of the voltage existingbefore the fault. This type of

Modular And Compact Presentation

directional principles does not includeany dead zones, whatever theposition or type of fault encountered.

Fault on secondary side of voltagereducerA logic checking the presence ofresidual voltage and the absence ofresidual current detects the blowing ofone of the fuses across the secondaryof the VT or the breaking of one of theconnection circuits. This detectioninstantly blocks the protection andtriggers an alrm by contact after atime delay has elapsed. Blocking canalso be controlled by an externaldevice (protection of reducers byminiature circuit-breaker).

Closing on to faultIn the event of a circuit-breakerclosing on a faulty line, the protectiontrips on a starting criterion.

SignallingOn the front panel of the protection,there are indicator lamps whichindicate the faulty phase or phasesand the tripping step. The indicationis stored (bistables) even in the eventof auxiliary supply loss. Manypolarity-free contacts are provided topermit remote signalling.

TrippingIn its basic version, the protection

includes six tripping contacts (two perphase), providing direct control of thecircuit-breaker coils. To prevent anydeterioration, the contacts are held aslong as the current conducted throughthem is greater than 0.2 A.

Complementary modules- Voltage memoryA memory voltage module can beincluded in the protection toguarantee good directional sensitivityin the event of a nearby three-phasefault.- Power swing detectionThe module measures the speed ofvariation of the impedance point

between two circular characteristics,one of which is the startingcharacteristic. After initial detection,the protection is blocked for onesecond and blocking is rearmed aftereach further passage through thepower swing band. In the event of asimultaneous single phase fault, theprotection is unlocked immediately.- Auto-recloserThe protection can incorporate asingle phase/three-phase auto-reclosermodule. It includes a six positionselector for choosing the desiredoperating mode.

3I

3U

Operation block diagram

12

10

13

1ΣU, ΣI

(Vo, Io, Ko)

3V

memoryD

11

2 4

Logical

5 7

9 8CC

CC

6

A Single Standardized Presentation

PresentationPXLC 3000 is a modular rangeprotection. It is built in the form of a 4 U 19’’ standardized rack, whateverthe model. All these models includethe following basic parts :- transformer unit,- card for low level testing,- starting, zone measurement andtime delay modules,- indication modules,- input-output and tripping module. Atall stages of manufacture, fromcomponent incoming checking to finalinspection, protection is put through asevere quality control plan designedto ensure optimum reliability. Toeliminate faults in the early stage, theprotection undergoes ovendebugging for a period of 168 hours.

Adaptation for chassis

Testing and maintenanceIn the same way as all the modularrange protections, PXLC 3000 can betested at low level by means of acard interfacing with the DLF 3000device. During testing, all the trippingsignals can be inhibited to preventany inadvertent tripping.

DocumentationOn request :- descriptive leaflet : ND 1.6866- commissioning leaflet : MS 1.6866- maintenance leaflet : M 1.6866

Simplified diagram of PXLC 3000 connections

3L

Common

Common

Auto-recloser lock 2Auto-recloser lock 1

2L 1L

Phase C selection (from P3)

Phase A selection (from P4)Phase A selection (from P3)

Phase B selection (from P4)Phase B selection (from P3)

Phase C selection (from P4)

Step 1 indication (from P3)Step 2 indication (from P4)

Earth fault (from P3)Earth fault (from P4)

Step 3 indication (from P4)

+ P3Step 4 indication (from P4)

+ P4 (from P4)

(from P4)Fuse failureindication

Auxiliary supplyfailure

Tripping indication

Tripping indication

Starting indication

Starting indication

HF transmission

Phase A tripping indication

Phase B tripping indication

Phase C tripping indication

Auto-recloser lockingcontrol

Auto-recloser lockingcontrol

Remote control commonAuto-recloser outAuto-recloser in

Tripping commonTripping C inputTripping B inputTripping A input

Fuse failure inputProtection locking + inputProtection locking + inputHF presence + inputReception common and HFReception + inputRemote clearing - / inputClosing - pulseRemote clearing + / inputClosing + pulse

Phase A tripping (P1)Phase B trippingPhase C tripping

+ P1

Circuit-breaker closing

Power swing indicator

Three-phase cycleSingle phase cycleBlocking indication

Common

Single phase cyclein progress

Three-phase standardization

Three-phase standardization Phase A tripping (P2)Phase C tripping (P2)Auxiliary supply + PPhase B tripping (P2)Auxiliary supply - P

+ P2

Technical Characteristics

Input circuits

Rated voltage Un 100 to 130 V(or 200 to 260 V for non-standard model)

Constantly permissible voltage 2 UnBurden 0.1 VAFrequency 50 or 60 HzRated current In 1 or 5 AConstant overload current 4 InOverload current for 10 s 30 InOverload current for 1 s 100 InBurden measured across rack terminal 0.1 VA (1 A) ; 0.5 VA (5 A)

Auxiliary supply

Inaudible DC/DC converter 48,110, 125, 220, 250 V DCTolerance -20%, +20%

except for 250 V DC : -20%, +10%Standby state consumption 30 WFault state consumption 55 W

Settings

Forward supervision limit : X4 X4 = 10 x Fn ohms/phaseN4 + 1 In

N4 adjustable from 0 to 99 onthumbwheels switches

Table of X4 limits (in ohms/phase)

In Fn 50 Hz 60 Hz

1 A 5 to 125 6 to 505 A 1 to 25 1.2 to 30

Reverse supervision limit : X5 X5 = K5 x X4 with K5 = 1, 1/2, 1/4, 1/8

First zone limit : X1 X1 = a1 x 0.4 x Fn ohms/phaseN1 +1 In

a1 = 1, 5, 25, 100 thumbwheel switchesN1 = 0 to 99

Second zone limit : X2(same equation as for X1 with index 2) Table of X1 limits

(in steps equal or less than 5%)The settings for the two zones areindependent In Fn 50 Hz 60 Hz

1 A 0.2 to 100 0.24 to 1205 A 0.04 to 20 0.048 to 24

Setting from 0 to 1.5 in steps of 0.1Earth coefficient : Ko = Xo - Xd (thumbwheel switch)

3 Xd

Reference impedance characteristic F = 50 Hz : 45° to 86° in 16 stepsangle : ϕ F = 60 Hz : 50° to 87° (thumbwheel

switch)

X

R

First zone forward

X1

X

R

Second zone forward

X2

X

R

Third zone forward

X4

X

R

Fourth zone reverse

X5

SettingsTime delays : step 1 T1 0 to 495 ms in steps of 5 ms

step 2 T2 0 to 990 ms in steps of 10 msor 0 to 9.9 s in steps of 0.1 s

step 3 T3 0 to 9.9 s in steps of 0.1 sstep 4 T4 0 to 9.9 s in steps of 0.1 s

Sensitivity : phase current threshold 0.2 InEarth current threshold 0.2 to 3.2 In step

or percentage relay (thumbwheel switch)Directional sensitivity unlimited for all unbalance faults

unlimited for 0.5 s for nearby three-phasefaults (memory voltage)

Power swing blocking bandwidth ∆ X4 with X4 : forward zone value∆ : setting : 0.1 ; 0.2 ; 0.4 ; 1

AccuracyDistance measurements for 1st and 2nd zone for an SIR from 0.1 to 30 andcurrent from 0.25 to 30 In 5% of set valueStarting 10% of set valueTime delays 2% of set value Operating timeMinimum value 30 mstypical value 35 msAuto-recloserSingle phase cycle 0.1 to 9.9 s in steps of 0.1 sFast three-phase cycle 0.05 to 4.95 s in steps of 0.05 sSlow three-phase cycle 1 to 9 s in steps of 1 sReclaim time 1 to 99 s in steps of 1 sTripping circuits 2 tripping contacts per phase, self-held for current greater than 0.2 AContacts • Tripping :

Max service voltage 250 VMaking current (0.5 s) 30 APermanent current 5 ABreaking capacity (L/R = 40 ms) 0.75 A at 48 VDC

0.30 A at 125 VDC0.15 A at 220-250 VDC

• Indication :Max service voltage 250 VPermanent current 5 ABreaking capacity (L/R = 40 ms) 0.75 A at 48 VDC

0.30 A at 125 VDC0.15 A at 220-250 VDC

Environment In operation -10° C to +55° CStorage -40° C to +70° CRelative humidity less than 95% without condensationInsulation (International standard IEC 255)Dielectric strength 2 kV, 50 Hz, 1 mnImpulse wave withstand 5 kV, 1.2/50 µs, 0.5 JHigh frequency perturbation 2.5 kV, 1 MHzPresentation Size : one 19’’ rack, 4 UWidth 483 mmHeight 177 mmDepth 304 mmWeight of complete model 10 kg

thumb-wheelswitches

Complete EquipmentIn Its Basic Version

Auto-recloser module

A Z1A

Z1B

Z2A

Z2B

B

AZ2AZ1A or

Z2BZ1B or

B

AZ2AZ1A or

Z2BZ1B or

B

(1)

Z4B

Z4A

(2)

A

Z2A

Z1A

Z2A

Z1A

B

VariantsDepending on the built-incomplementary modules, the

protection is codified as follows :

Signalling schemesBy means of internal selectors, the following signalling schemes can be selected :- step acceleration,- permissive overreach,- blocking,- intertripping.The zone extension scheme, which does not require any transmission means, isalso available.

Step accelerationB detects the fault in zone 1 and sends a signal to A which switches itsmeasurement reach in zone 2 without waiting for the second step. Thus, a faultnear B, normally eliminated at T2 by A, will be eliminated at T1.

Permissive overreachA sees the fault in extended zone 1 and sends the signal to B which trips if it hasdetected the fault in its extended zone 1.

Blocking(2) : B detects the reverse fault and sends a signal to A, inhibiting it fromtripping.(1) : A and B both detect the fault in extended zone 1 and trip after a slightwaiting delay for a possible blocking order.

Zone extensionInitially, the protection is set to a supervision reach in zone 2. During a trippingand reclosing cycle, the supervision reach is brought to the value of Z1 to obtainthe best possible selectivity in the event of a permanent fault.

Code P/S Memory Auto-recloserblocking

3001

3002 •

3003 •

3004 • •

3005 •

3006 • •

3007 • •

3008 • • •

Overall dimensions

482.6

466.7

31640 465.1

(19'')

177

(4 U

)

177

(4 U

)

101.

6

37.7

450 min.

101.

6

37.7

4 holes M6

Information required when ordering• Code 3 0 0 (see table on page 6)• Rated current 1 A 5 A• Rated voltage 100 200

• Frequency 50 Hz 60 Hz• Auxiliary 48 Vcc 110 Vcc 125 Vcc 220 Vcc 250 Vcc

supply

Note : on leaving the works, and unless the above information is given, modelconfiguration will be as follows :• Basic model : 3001• Rated current : 5 A (transformable to 1 A)• Rated voltage : 100/ V• Rated frequency : 50 Hz (transformable to 60 Hz)

130 2603 3

3

3 3

Saturation Of Current TransformersThe PXLC Solution

Current measurement transformers aresubject to saturation, which can comefrom an increase of TC’s load or fromsevere short circuit conditions. Thesesaturation conditions interfere withconventional protections by distortingthe start-up, direction indication andzone computation functions. Thisresults in accidental trip-outs or indelays of several hundreds milli-seconds.The solution sought could consist in anincrease in the size of the magneticcircuit of the transformer. In additionto the fact that the remanenceacquired with TPX transformers duringa fault can last a substantial period oftime and produce subsequentsaturations, this solution represents amajor overcost.The PXLC version with MTS moduleprovides an efficient solution bylimiting computation to the momentswhere the signal is not saturated.

Description of MTS moduleThe start-up, phase selection anddistance measurement functions areachieved by detecting the sign of thecosine of the phase shift between theelectrical values. The MTS moduleperforms these measurements withoutinterference by the moments duringwhich the cycles are saturated.

Let A and B be the electrical valuesA = a sin wtB = b sin (wt + ϕ)

and let :P = A.B - (dA/dt) Bdt

Therefore :A.B = (a.b/2).(cos ϕ - cos (2wt + ϕ))(dA/dt) Bdt = - (a.b/2).(cos ϕ + cos

(2wt + ϕ))

This results in :P = a.b.cos ϕ

Detection of the sign is achieved byintegrating the expression in time.

OptionsPXLC options comprising the MTSmodule and memory voltage :

Operation with saturationThe curve (I) represents the faultvoltage.The curve (II) represents the faultcurrent seen by the protection whensaturation of a line transformeroccurs.The areas without hachure representthe portions during which the currentand voltage are linear, and can beused by the algorithms.The hachure areas represent themoments of saturation.During these moments, the currentbeing near-null, the product P is alsonull.Therefore, by integrating all theseareas, the average power sign (cos ϕ)remains true.

(I)

(II)

Code Power-swing Recloserdetection

3011

3014 •

3015 •

3016 • •