400kV OHL Protection En

Siemens PTD EA Applications for SIPROTEC Protection Relays 2005 1

Line Protection in Transmission Systems

1. IntroductionThis application example will guide the readerthrough all the steps required to set the distanceprotection functions for a typical transmissionline. Standard supplements such as teleprotection,power swing, switch onto fault, directional earth-fault protection, etc. are also covered.

2. Key functions applied: Distance protection (ANSI 21):

Quadrilateral characteristic Teleprotection for ANSI 21:

POTT Earth fault O/C (ANSI 67N):

IEC curves, directional Teleprotection for ANSI 67N:

Directional comparison Power swing blocking Weak infeed:

Echo and trip Overcurrent protection:

Emergency mode Auto-reclose:

1 and 3-pole, 1 cycle Synchronism check:

Sync. and async. closing Fault locator:

Single-end measurement

3. Single line diagram and power systemdata

The required time graded distance protectionzones are:

400 kV OverheadTransmission LineProtection

Fig. 2 Single line diagram of protected feeder

Zone number Function Reach Time delay

Zone 1 Fast underreach protection for Line 1 80 % Line 1 0 s

Zone 2 Forward time delay backup, overreach 20 % less than Z1 reach on Line 3 1 time step

Zone 3 Reverse time delay backup 50 % Z-Line 1 2 time steps

Zone 4 Not applied

Zone 5 Non-directional 120 % Line 2 3 time steps

Table 1 Notes on setting the distance protection zones

Fig. 1 Universal protection for OHL

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Siemens PTD EA Applications for SIPROTEC Protection Relays 20052

Parameter Value

System data Nominal system voltage phase-phase 400 kV

Power system frequency 50 Hz

Maximum positive sequence source impedance 10 + j100

Maximum zero sequence source impedance 25 + j200

Minimum positive sequence source impedance 1 + j10

Minimum zero sequence source impedance 2.5 + j20

Maximum ratio: Remote infeed / local infeed (I2/I1) 3

Instrument transformers Voltage transformer ratio (LINE) 380 kV / 100 V

Voltage transformer ratio (BUS) 400 kV / 110 V

Current transformer ratio 1000 A / 1 A

Current transformer data 5P20 20 VA Pi = 3 VA

CT secondary connection cable 2.5 mm2 50 m

CT ratio / VT ratio for impedance conversion 0.2632

Line data Line 1 length 80 km

Maximum load current 250 % of full load

Minimum operating voltage 85 % nominal voltage

Sign convention for power flow Export = negative

Full load apparent power (S) 600 MVA

Line 1 positive seq. impedance per km Z1 0.025 + j0.21 /km

Line 1 zero seq. impedance per km Z0 0.13 + j0.81 /km

Line 2 total positive seq. impedance 3.5 + j39.5

Line 2 total zero seq. impedance 6.8 + j148

Line 3 total positive seq. impedance 1.5 + j17.5

Line 3 total zero seq. impedance 7.5 + j86.5

Maximum fault resistance, Ph - E 250

Power data Average tower footing resistance 15

Earth wire 60 mm2 steel

Distance: Conductor to tower/ground (midspan) 3 m

Distance: Conductor to conductor (phase-phase) 5 m

Circuit-breaker Trip operating time 60 ms

Close operating time 70 ms

Table 2 Power system and line parameters

Based on the source and line impedance, the fol-lowing minimum fault current levels can be calcu-lated for faults on Line 1:

IU

Zfault

source

tot3=

with Usource = 400 kV

If fault resistance is neglected then for 3-phasefaults:

Ztot = sum of positive sequence source and lineimpedance (as only current magnitudes are beingcalculated, only the magnitude of the impedanceis relevant)

|Ztot| = |(10 + 80 0.025) + j(100 + 80 0.21)||Ztot| = |12 + j116.8|

|Ztot| = 117.4

The minimum three-phase fault current is there-fore:

I 3400

3 117 4ph min

kV=

.

I 3 1967ph min A=



If fault resistance is neglected then for single-phase faults:

Ztot = 1/3 (sum of positive, negative and zero se-quence source and line impedance)

The minimum single-phase fault current withoutfault resistance is therefore:

I1400

167 31380ph min

kV

3A=

=

.

If fault resistance is included then for single-phasefaults:

Ztot_R = Ztot + RF

|Ztot_R| = |RF + Ztot|

|Ztot| = |250 + 19.8 + j166.1|

|Ztot| = 316.8

The minimum single-phase fault current withhigh resistance is therefore:

I1400

3 316 8729ph min_ R

kVA=

=

.

4. Selection of device configuration(functional scope)

After selection and opening of the device in theDIGSI Manager, the first step when applying thesettings is entering the functional scope of the de-vice. A sample screen shot showing the selectionfor this example is given below:

The available functions displayed depend on theordering code of the device (MLFB). The selectionmade here will affect the setting options duringthe later stages. Careful consideration is therefore

required to make sure that allthe required functions are se-lected and that the functionsthat are not required in thisparticular application are dis-abled. This will ensure thatonly relevant settingalternatives appear later on.

103 Setting Group Change Option:Only enable this function, if more than onesetting group is required. In this exampleonly one setting group is used; therefore thisfunction is disabled.

110 Trip mode:On OHL applications, single-pole tripping ispossible if the circuit-breaker is capable ofthis. The advantage is that during a single-pole dead time the OHL can still transportsome power and reduce the risk of systeminstability. In this example both one andthree-pole tripping is used so the setting is1-/3-pole.

112 Phase Distance:As distance protection for phase faults is re-quired, Quadrilateral must be selected. Insome cases (depending on the ordering code)a MHO characteristic can also be selected.

113 Earth Distance:Here the earth fault distance protection char-acteristic is selected as for 112 above. There-fore set Quadrilateral.

120 Power Swing detection:If power swing conditions can occur in thevicinity of the applied relay, the power swingdetection must be enabled. It is required forblocking of the distance protection duringpower swings. At 380 kV it is common prac-tice to Enable the power swing detection.

121 Teleprotection for Distance prot.:To achieve fast tripping for all faults on thecircuit a teleprotection scheme must be ap-plied.

| || [( . ) ( . )] ( .

Zj

tot = + + + + + 2 10 80 0 025 100 80 0 21 25 80 013 200 80 0 81

3

) ( . )|+ + j

|Ztot| = |19.8 + j166.1|

|Ztot| = 167.3

Fig. 3 Selected scope of functions

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Parameter PUTT POTT Blocking Unblocking

Short line Not suitable as theZone 1 operation is es-sential and Zone 1 set-ting in X and Rdirection must besmall on short lines

Suitable as the Z1b set-ting may be substan-tially larger than theline impedance so thatsignal transmission issecure for all faults onthe line

Suitable as reversereach setting is inde-pendent of line length

Suitable as the Z1b set-ting may be substan-tially larger than theline impedance so thatsignal transmission issecure for all faults onthe line

Weak infeed Not suitable as theZone 1 operation is es-sential at both ends for100 % line coverage

Suitable as the strongend detects all linefaults with overreach-ing Z1b. The weakinfeed end then echosthe received signal

Partially suitable as thereverse fault is also de-tected at the weakinfeed end but no tripat weak infeed end

Suitable as the strongend detects all linefaults with overreach-ing Z1b. The weakinfeed end then echosthe received signal

Amplitude modulatedpower line carrier

Not suitable as the sig-nal must be transmit-ted through the faultlocation which attenu-ates the signal


Suitable as the signal isonly sent when the lineis not faulted


Frequency or phasemodulated power linecarrier

Suitable as the signalcan be transmittedthrough the fault loca-tion


Suitable as the signalcan be transmitted un-der all conditions


Communication inde-pendent of power line

Suitable Suitable Suitable Suitable

Table 3 Selection of teleprotection scheme

In this case the selection is POTT

122 DTT Direct Transfer Trip:If external inputs must be connected to initi-ate tripping via binary input, this functionshould be activated. The trip will then auto-matically be accompanied by the minimumtrip command duration (trip circuit seal in)and event and fault recordings. In this exam-ple this function is not required and there-fore Disabled.

124 Instantaneous High Speed SOTFOvercurrent:When closing onto bolted faults extremelylarge currents arise that must be switched offas fast as possible. A special overcurrent pro-tection stage is provided for this purpose. Inthis example it will not be used and is there-fore Disabled.

125 Weak Infeed:When weak infeed conditions exist (perma-nently or temporarily) at one or both ends,the weak infeed function must be Enabled.Refer also to Table 3.

126 Backup overcurrent:When the distance protection is in service, itprovides adequate backup protection for re-mote failures. The overcurrent protection inthe distance relay is usually only appliedwhen the distance function is blocked due to,for example, failure of the measured voltagecircuit (VT-fuse fail). This will be done inthis example, so the function must be acti-vated. The selection of the response curve

standard is Time Overcurrent Curve IEC inthis application.

131 Earth Fault overcurrent:For high resistance earth faults it is advisableto not only depend on the distance protectionas this would demand very large reach settingsin the R direction. The directional (and non-directional) earth-fault protection is very sen-sitive to high resistance earth faults and istherefore activated in this example. Here TimeOvercurrent Curve IEC is selected.

132 Teleprotection for Earth fault Overcurr.:To accelerate the tripping of the earth-faultprotection (activated under 131 above) ateleprotection scheme can be applied. In thisexample a Directional Comparison Pickupscheme will be applied.

133 Auto-Reclose Function:Most faults on overhead lines are of a tran-sient nature so that the line can be energisedsuccessfully after fault clearance. For thispurpose an automatic reclosure function canbe implemented to minimise the line outageby reclosing with a set or flexible dead time.In this application 1 AR-cycle will be applied.



134 Auto-Reclose control mode:If, as in this example, single and three-poletripping is used, the auto-reclose function istriggered by the trip command. If the trip isdue to a backup protection operation (e.g.Zone 2) then reclosure is normally not de-sired. By application of an action time whichmonitors the time between fault detectionand trip, reclosure can be prevented for timedelayed tripping (longer than set actiontime). In this example the auto-recloser willbe triggered with Trip and Action time mon-itoring.

135 Synchronism and Voltage Check:Before closing a circuit-breaker it is advisableto check that the system conditions on bothsides of the circuit-breaker are suitable forbeing connected. For this purpose the Syn-chronism and Voltage Check function is En-abled in this example.

138 Fault Locator:Following fault clearance an inspection of thefault location may be needed to check thatthere is no permanent damage or risk of fur-ther faults at the fault location. Particularlyon longer lines it is very helpful to have anindication of the fault location to allow fasteraccess by the inspection team. For this pur-pose the fault locator is Enabled in this ex-ample.

140 Trip Circuit Supervision:The monitoring done by the relay can be ex-tended to include the trip circuit and tripcoils. For this purpose a small current is cir-culated in the monitored circuits and routedvia binary inputs to indicate a failure. In thisexample this function is not used and there-fore set to Disabled.

5. Masking I/O (configuration matrix)The configuration matrix is used to route and al-locate the information flow in the device. All theassignments of binary inputs and outputs, as wellas LEDs, sequence of event records, user definedlogic, controls etc. are made in the matrix.

6. User defined logic CFCIf any special logic is required in the application,the CFC task can be used for this purpose.

7. Settings for power system data 17.1 Instrument transformersUnder this heading power system parameters areapplied. Place a Tick in the box Display addi-tional settings to include advanced settings (des-ignated by A, e.g. 0214A) in the displayed list.

The advanced settings can in most cases be lefton the default setting value.

201 CT Starpoint:In this application the CTs are connected asshown below in Figure 5. The polarity of theCT connection must be selected correctly toensure correct response by the protection.For this purpose the position of the starpoint

connection is indicated: In this example itmust be set towards line.

203 Rated Primary Voltage:The VT ratio must be set correctly to ensureaccurate measured value output. It is alsopossible to set the protection parameters inprimary quantities. For correct conversionfrom primary to secondary the VT and CTdata must be set correctly. In this applicationthe VT primary voltage is 380 kV.

204 Rated Secondary Voltage (ph-ph):Set to 100 V as per VT data.

205 CT Rated Primary Current:Set to 1000 A as per CT data.

Fig. 4 Configuration of CT and VT circuits

Fig. 5 Relay connections

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19"



206 CT Rated Secondary Current:Set to 1 A as per CT data. Note that this set-ting must correspond to the jumper settingson the measurement module (printed circuitboard). If this is not the case, the relay willblock and issue an alarm. Refer to devicemanual for instructions on changing jumpersettings.

210 U4 voltage transformer is:The 4th voltage measuring input may be usedfor a number of different functions. In thisexample it is connected to measure busbarvoltage for synchronising check (set Usynctransformer) as shown in Figure 6.

211 Matching ratio Phase-VT to Open-delta-VT:If in setting 210 the 4th voltage measuring in-put is selected to measure the open-deltavoltage (3 U0) then this setting must be usedto configure the transformation ratio differ-ence between the phase VT and the open-delta VT. As sync. check is applied this set-ting has no relevance.

212 VT connection for sync. voltage:If the setting 210 for the 4th voltage measur-ing input is selected to measure the voltagefor sync. check this setting must be applied todefine which voltage is used for sync. check.In this example, the voltage connected to U4is the phase-phase voltage L3-L1 as shown inFigure 6.

214A Angle adjustment Usync-Uline:If there is a phase angle difference betweenthe voltage Usync and Uline, for example dueto a power transformer with phase shiftingvector group connected between the meas-uring points, then this phase shift must beset here. In this example the busbar is con-nected directly to the line so that there is0 phase shift.

215 Matching ratio Uline-Usync:If the transformation ratio of the VT forline voltage and sync. voltage measurementis not the same, then the difference must beset here. In this application:

Ratio correction

prim Line

sec Line

prim BUS

sec

=

U

UU

U BUS

= =

380

01400

011

105.

.

.

The required setting is therefore 1.05.

220 I4 current transformer is:The 4th current measurement may be usedfor a number of different functions. In thiscase it is used to measure the Neutral Cur-rent (of the protected line) by means of aHolmgreen connection. See Figure 5.

221 Matching ratio I4/Iph for CTs:If the CT connected to I4 has a different ra-tio, for example a core balance CT, to theratio of the CT measuring the phase cur-rents of the protected circuit, this differ-ence must be set here. In this applicationthe ratio is the same so the setting must be1.00.

7.2 Power system data

207 System Starpoint is:The condition of the system starpointearthing must be set here. If the systemstarpoint is not effectively earthed, isolatedor resonant earthed, then the distance pro-tection response to simple earth faults willbe stabilised to prevent operation on tran-sient earth fault currents. In this exampleSolid Earthed applies.

Fig. 6 VT connections

Fig. 7 Power system data

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230 Rated Frequency:Set the rated system frequency to 50 Hz or60 Hz.

235 Phase Sequence:The phase sequence of the system is usuallypositive, L1 L2 L3. If the system has nega-tive phase sequence this can be set here. Inthis example the phase sequence is positive(L1 L2 L3).

236 Distance measurement unit:The distance measurement unit for thefault locator and certain line parameterscan either be in km or in miles. In this ex-ample km is used.

237 Setting format for zero seq. comp.:The distance protection includes a zerosequence compensation so that the samereach settings apply to phase and earthfaults. The zero sequence compensationcan either be set as RE/RL and XE/XL pa-rameters (standard format used by Siemensin the past) or as the complex ratio KO bymeans of a magnitude and angle setting. Inthis example the setting will be applied asZero seq. comp. factors RE/RL and XE/XL.

7.3 Breaker

239 Closing (operating) time of CB:This setting is only relevant if synchrocheck with asynchronous switching is con-figured. Under asynchronous closing, thesync. check function will determine the in-stant for issuing the close command so thatthe primary CB contacts close when theswitched voltages are in phase. For thispurpose the time that expires after applica-tion of the close command to the close coiluntil the primary contacts of the CB makemust be set here. From Table 2 the re-quired setting is 0.07 s.

240A Minimum TRIP Command Duration:The trip command to the circuit-breakermust have a minimum duration to ensurethat the CB responds and to prevent pre-mature interruption of the current in thetrip coil which may cause damage to thetrip contact which is not rated to interruptsuch a large inductive current.

When primary current flow is detected(measured current > pole open current:Parameter 1130) then the trip command issealed in by the current flow and will onlyreset once the current flow is interrupted(refer to Figure 9). When the trip com-mand is issued and no current flow is de-tected, the minimum trip command dura-tion set here will apply. It must be setlonger than the maximum time taken forthe CB auxiliary contacts to open and in-terrupt the current in the trip coil follow-ing the start of the trip command. The re-set conditions for the trip command can beset with parameter 1135 RESET of TripCommand. From Table 2 the given circuit-breaker operating time is seen to be 60 ms.A safety margin of 50 ms is sensible so thata setting of 0.11 s is applied.

241A Maximum Close Command Duration:The close command must also have a mini-mum duration to ensure that the circuit-breaker can respond and that the auxiliarycontacts can interrupt the current flowthrough the close coil. If, following a closecommand, a trip is issued due to switch onto fault, the close command is reset imme-diately by the new trip command. Theclose command maximum durationshould be set at least as long as the maxi-mum time required by the CB auxiliarycontact to interrupt the close coil currentafter start of the close command. From Ta-ble 2 the given circuit-breaker operatingtime is seen to be 70 ms. A safety margin of50 ms is sensible so that a setting of 0.12 sis applied.

242 Dead Time for CB test-autoreclosure:One of the test features in DIGSI is the CBtest-autoreclosure. For this test the circuit-breaker is tripped and reclosed under nor-mal load conditions. A successful testproves that the trip and close circuits andthe CB are in a fully functional state. As thetest causes a disruption to the power flow(either single phase or three phase), thedead time should be as short as possible.While a normal dead time must allow forthe time required by the fault arc to dissi-pate (typically 0.5 s for three-pole trip and1s for single-pole trip), the test cycle mustonly allow for the circuit-breaker mecha-nism to open and close. Here a dead timeof 0.10 s is usually sufficient.

Fig. 8 Breaker parameters

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8. Settings for Setting Group AThe setting blocks that are available in SettingGroup A depend on the selections made duringthe selection of the device configuration (Heading4). If the setting group changeover had been acti-vated, a total of 4 setting groups would have beenavailable.

9. Settings for Power System Data 2Further power system data, in addition to PowerSystem Data 1, is set here. As these parameters areinside Setting Group A, they can be modified be-tween the setting groups if setting group change-over is activated.

9.1 Power system1103 Measurement: Full Scale Voltage (100 %):

For the indication and processing of meas-ured values it is important to set the fullscale value on the primary side. This doesnot have to correspond to the VT rated pri-mary voltage. When the primary value cor-responds to this setting the percentagemeasured value will be 100 %. Other per-centage measured values that also dependon voltage, such as for example power (P)will also have the full scale indication de-pendant on this setting. In Table 2 the sys-tem rated voltage is given and therefore setat 400 kV.

Fig. 9 Trip command seal in

Fig. 10 Setting blocks available in Setting Group A forthis application

Fig. 11 Power system settings in Power System Data 2

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1104 Measurement: Full Scale Current (100%):For the indication and processing of mea-sured values it is important to set the fullscale value on the primary side. This doesnot have to correspond to the CT rated pri-mary current. When the primary value cor-responds to this setting the percentagemeasured value will be 100 %. Other per-centage measured values that also dependon current, such as for example power (P)will also have the full scale indication de-pendant on this setting. In Table 2 therated apparent power of the line is stated at600 MVA:

Full scale currentRated MVA

3 Full scale voltage

Fu

=

ll scale current A=

=

600

3 400866

The measurement: Full scale current(100 %) is therefore set to 866 A.

1105 Line Angle:The line angle setting is calculated from thepositive sequence line impedance data. Inthis example:

Z1 = 0.025 + j0.21

Line angle arctanX

RL

L

=

Line angle = 83

1211 Angle of inclination, distance charact.:This is usually set the same as the line an-gle. In this manner the resistance coveragefor all faults along the line is the same(Fig. 12). Therefore set for this applicationthe angle of inclination of the distancecharacteristic equal to the line angle whichis 83.

1107 P,Q operational measured values sign:The measured values P and Q are desig-nated as positive when the power flow isinto the protected object. If the oppositesign is required, this setting must bechanged so that the sign of P and Q will bereversed. In Table 2 the sign convention forpower flow states that exported power(flowing into the line) is designated as neg-ative. The setting here must therefore bereversed.

1110 x-Line Reactance per length unit:The line reactance per length unit (in thisexample per km) is required for the faultlocator output in km (miles) and percent.In Table 2 this is given as 0.21 /km pri-mary. The setting can therefore be appliedas primary value 0.2100 /km, or it can beconverted to a secondary value:

x'CT ratio

VT ratiox'secondary primary= =

1000

1380

01.

=

0 21

0 0553

.

.x'secondary

The setting in secondary impedance is0.0553 /km.

1111 Line Length:The line length setting in km (miles) is re-quired for the fault locator output. FromTable 2 set 80.0 km.

1116 Zero seq. comp. factor RE/RL for Z1:The zero sequence compensation setting isapplied so that the distance protectionmeasures the distance to fault of all faulttypes based on the set positive sequencereach. The setting is applied as RE/RL andXE/XL setting; here RE/RL for Zone 1 withthe data for Line 1 from Table 2.

R

R

R

RE

L

=

=

=

1

31

1

3

013

0 0251 140

1

.

..

Apply setting RE/RL for Z1 equal to 1.40.

Fig. 12 Polygon and line angle



1117 Zero seq. comp. factor XE/XL for Z1:The same consideration as for parameter1116 above applies:

X

X

X

XE

L

=

=

=

1

31

1

3

0 81

0 211 0 950

1

.

..

Apply setting XE/XL for Z1 equal to 0.95.

1118 Zero seq. comp. factor RE/RL for Z1BZ5:As the overreaching zones cover the pro-tected line as well as adjacent circuits, thezero sequence compensating factor musttake the impedance parameters of the pro-tected line as well as the adjacent lines intoaccount. The Zone 2 reach has to beco-ordinated with the protection on theshortest adjacent feeder (Line 3) so that theZone 2 reach will be used to determine thissetting. The other zone reaches are largelyinfluenced by other system conditions suchas parallel and intermediate infeeds:

If the Zone 2 reach is set to 80 % of the to-tal impedance up to the Zone 1 reach onLine 3 (shortest adjacent line) then the to-tal positive sequence impedance at theZone 2 reach limit is:

X X X

XLine1 Line32 0 8 0 8

2 0 8 80 0 21 0 8 171

1

= +

= +

. ( . )

. ( . . . ) .5 24 64=

R RX X

XR

R

Line1Line1

Line3

Line322

2 80 0 02524

1

1

= +

= +

( )

.. .

.. .

64 80 0 21

17 515 2 672

=

The corresponding zero sequence imped-ance is calculated as follows:

X XX X

X

X

Line1Line1

Line3

Line32 02

0

2 80 0 812

0

0

= +

= +

( )

.

X

4 64 80 0 21

17 586 5

2 10340

. .

..

.

=X

R RX X

XR

R

Line1Line1

Line3

Line32 02

0

2 80 0132

0

0

= +

= +

( )

.4 64 80 0 21

17 57 5

2 13760

. .

..

.

=R

This is graphically shown for the X valuesin Figure 13. A similar drawing can also bemade for the R values. Always use the Zone2 setting in the X direction as a reference.Now apply the derived values, X21, R21,X20 and R20 to the following equation:

R

R

R

RE

L

=

=

=

1

31

1

3

1376

2 6721 1 380

1

.

..

Apply setting RE/RL for Z1B...Z5 equal to1.38.

1119 Zero seq. comp. factor XE/XL for Z1BZ5:This is the XE/XL setting corresponding tothe RE/RL setting 1118 above. Thereforeapply the derived values, X21, R21, X20 andR20 to the following equation:

X

X

X

XE

L

=

=

=

1

31

1

3

1034

24 641 1070

1

.

..

Apply setting XE/XL for Z1B...Z5 equal to1.07.

Fig. 13 Positive and zero sequence line impedanceprofile



9.2 Line status1130A Pole Open Current Threshold:

For a number of functions in the relay theswitching state of the circuit-breaker is animportant logical information input. Thiscan be derived via auxiliary contacts or bymeasuring the current flow in the circuit.With this parameter the current thresholdis set to determine the pole open conditionof the circuit-breaker. If the phase currentmeasured by the relay is below this thresh-old this condition for pole open detectionis true.

This setting should be as sensitive as possi-ble (setting equal to or lower than thesmallest current pick-up threshold of aprotection function). Stray induced cur-rents during a true open pole conditionmay however not cause incorrect pick-up.

In this example no special conditions haveto be considered, so the default setting of0.10 A is maintained.

1131A Pole Open Voltage Threshold:As was described for the pole open currentabove (1130A), the pole open voltage set-ting determines the threshold below whichthe voltage condition for pole open is true.

As single-pole tripping will be applied hereand the voltage transformers are located onthe line side of the circuit-breaker, the set-ting should be large enough to ensure thatthe voltage induced on the open phase isbelow this setting. Apply a setting that is atleast 20 % below the minimum operatingphase to earth voltage.

In this example the minimum operatingvoltage is 85 % of nominal voltage:

Setting< 0.8 0.85 400 kV/380 kV 100/ 3 < 41

Therefore apply a setting of 40 V.

1132A Seal-in Time after ALL closures:When the feeder is energised the switch onto fault (SOTF) protection functions areactivated. The line closure detection condi-tions are set with parameter 1135 below.This seal-in time setting applies to all lineclosure detections other than the manualclose binary input condition. This directdetection of circuit-breaker closing re-sponds almost at the same instant as theprimary circuit-breaker contact closing. Afairly short seal in time can therefore be sethere to allow for pick-up of the desiredprotection functions.

In this application only the distance pro-tection will be used for switch on to faultso that a setting of 0.05 s is sufficient.

1134 Recognition of Line Closure with:As stated above (1132A) the recognition ofline closure is important for the switch onto fault protection functions. If the manualclose binary input is assigned in the matrix,it will be one of the line closure detectioncriteria. If other circuit-breaker closingconditions such as auto-reclose or remoteclosing are applied then it is advisable toapply additional criteria for line closure de-tection. In the table below the prerequisitesfor application of the individual conditionsare marked with X.

In this example, the manual close binaryinput and CB aux contacts are not allo-cated in the Matrix, so the conditions Volt-age and Current flow must be used for lineclosure detection. As the voltage trans-formers are on the line side, the settingCurrent or Voltage or Manual Close BI isapplied. Note that the inclusion of ManualClose is of no consequence because the bi-nary input is not allocated in the Matrix.

Line status settings in Power System Data 2

1134 Recognition ofLine Closure with:

Manual Close BI al-located in Matrix

CB aux allocated inMatrix

VT on line sideof CB

Manual Close BI X

Voltage X

Current flow Always valid Always valid Always valid

CB aux X

Table 4 Prerequisites for application of individual conditions in Parameter 1134LSP2

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1135 RESET of Trip Command:The trip command duration must alwaysbe long enough to allow the circuit-breakerauxiliary contacts to interrupt the currentflowing through the trip coil. The most re-liable method for sealing in the trip com-mand is the detection of current flow in theprimary circuit through the CB. The auxil-iary contact status may be used as an addi-tional condition. This is helpful when tripcommands are issued in the absence of pri-mary current flow, e.g. during testing or byprotection functions that do not respondto current flow such as voltage or fre-quency protection. In this example, theauxiliary contacts are not allocated in theMatrix so that the trip command is resetwith Pole Open Current Threshold only.

1140A CT Saturation Threshold:CT saturation is normally detected bymonitoring of harmonic content in themeasured current. This is not possible forprotection response below 1 cycle as atleast one cycle of recorded fault current isrequired to determine the harmonic con-tent. Below one cycle the CT saturationcondition is therefore set when the currentexceeds this threshold. The following cal-culation gives an approximation of thiscurrent threshold:

CT Sutaration Threshold N= n

I'

5

with

n nP P

P P'

'=

+

+=

N i

i

actual overcurrent factor

P = the actual burden connected to thesecondary CT relay burden + CTsecondary connection cable burden

In this example only the 7SA relay isconnected to the CT, so that the relay bur-den is 0.05 VA per phase. Due to theHolmgreen connection, the maximumburden for earth currents is therefore twice0.05 VA =0.1 VA.

The CT secondary cable connection bur-den is calculated as follows:

Rl

acable

cable CU

cable

=

2

lcable = 50 mCU = 0.0179 mm2/macable = 2.5 mm

2

therefore:

R

R

cable

cable 0.72

=

=

2 50 0 0179

2 5

.

.

at 1 A nominal secondary current, this re-lates to:

P' = Rcable IN CT2 +PrelayP' = 0.72 12 + 0.1P' = 0.82 VA

From Table 2, the CT data is 5P20 20 VA,therefore:

n'.

=

+

+=20

20 3

0 82 3120

with this value, the setting can then be cal-culated:

CT Sutaration Threshold A = 24 A= 120

51

The applied setting in this case is therefore24.0 A.

1150A Seal-in Time after MANUAL closures:This setting is only applicable when themanual close binary input is allocated inthe Matrix (refer to setting 1134 above).The time applied here should allow for thecircuit-breaker response and any addi-tional delays such as sync. check releasewhich can occur between the initiation ofthe binary input and closure of the CB pri-mary contacts. In this example, the manualclose binary input is not allocated so thissetting is of no consequence and thereforeleft on the default value of 0.30 s.

1151 Manual CLOSE COMMAND generation:If the manual close binary input is allo-cated, it may be used to generate a closecommand to the circuit-breaker in the re-lay. Alternatively the input may be usedonly to inform the relay that a manualclose has been issued externally to the cir-cuit-breaker. If the relay has to generate aclose command following the initiation,this can be done with or without sync.check if the internal sync. check function isavailable. In this example the manual closebinary input is not allocated so this settingshould be set to NO.



1152 MANUAL Closure Impulse afterCONTROL:If the internal control functions are used,either via front keypad or system interface,the issued control-CLOSE command to thecircuit-breaker can be used to activate theprotection functions in the same manneras the manual-close binary input would.The setting options provided consist of allthe configured controls in the device. Inthis example, the internal control functionsare not used, so this setting is left on thedefault value:

9.3 Trip 1/3-poleAs 1 and 3-pole tripping is applied in thisexample, the following settings must be applied:

1155 3 pole coupling:When single-pole tripping is applied therelay must select the faulted phase and tripsingle pole selectively. In the event of 2 si-multaneous faults, e.g. inter-circuit faulton double circuit line, the relay detects twofaulted phases, but only one of the two isinside a tripping zone. To ensure single-pole tripping under these conditions, set3-pole coupling to with Trip.

1156A Trip type with 2phase faults:Phase to phase faults without ground, canbe cleared by single-pole tripping. On cir-cuits where such faults occur frequently,e.g. conductor clashing due to conductorgalloping with ice and wind conditions,single-pole tripping for 2-phase faults canimprove availability of the circuit. The set-ting at both line ends must be the same. Ifsingle-pole tripping is selected, either theleading or lagging phase will then be trip-ped at both line ends. In this example 2-phase faults will be tripped 3-pole.

10. Distance protection, general settings Setting Group A

10.1 General

1201 Distance protection is:If the distance protection must be switchedoff in this setting group, it can be done sowith this setting.In this example, only one setting group isused and the distance protection functionis required so this setting is left on the de-fault value which is ON.

1202 Phase Current threshold for dist. meas.:Although the distance protection respondsto the impedance of the faulted loop, alower limit must apply for the current flowbefore the distance protection responds. Ifthe system conditions can not ensure thatthis minimum current flows during all in-ternal short-circuit faults, special weakinfeed measures may be required (seechapter 14). It is common practice to applya very sensitive setting here so that theback-up functionality of the distance pro-tection for remote faults on other circuitsis effective. The default setting of 10 % istherefore commonly applied.In this application, no special conditionsexist, so the default setting of 0.10 A is ap-plied.

1211 Angle of inclination, distance charact.:This setting was already discussed and ap-plied in chapter 9.1 Power system, whereits association with the line angle was de-scribed. It is set to 83.

1208 Series compensated line:On feeders in the vicinity of series capaci-tors, special measures are required for di-rection measurement.This application is without series capaci-tors on the protected or adjacent feeders,so the setting applied is NO.

Fig. 15 Trip 1/3-pole settings in Power System Data 2

Fig. 16 General settings for distance protection

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1232 Instantaneous trip after SwitchOnToFault:When the protected circuit is switched off,a permanent fault (e.g. working earth orbroken conductor on ground) may bepresent. After switching on the circuit,such faults must be cleared as fast as possi-ble. It is common practice to activatenon-selective stages with fast tripping forswitch on to fault conditions. In the dis-tance protection a number of alternativesexists:

It is recommended to use the distance pro-tection for SOTF conditions. In many casesthe setting with pickup (non-directional)would result in a reach that operates due toheavy load inrush, e.g. when large machinesand transformers are connected to thefeeder so that the energising current ismore than twice the full load current. Inthese cases the Zone Z1B can be applied asits reach is typically only between approx.120 % and 200 % of the protected feeder.Of special interest is the application ofZone Z1B undirectional. If the local busbarcan be energised from the remote end viathe protected feeder, then SOTF conditionsfor busbar faults can be provided by appli-cation of this setting. Note that the line clo-sure detection should not be with thevoltage condition in this case, as the liveline voltage prior to energising the busbarwould prevent the SOTF release.In this example, the local bus will not beenergised via the feeder so the setting withZone Z1B is applied.

1241 R load, minimum Load Impedance (ph-e):The settings 1241 to 1244 determine theload encroachment area for the distancerelay setting characteristic. The distancezone settings must exclude the load area inthe impedance plane so that operation isonly possible under fault conditions. For

this purpose, the smallest load impedanceand the largest load impedance angle mustbe determined (refer to Fig. 17).

The load encroachment area is set forphase to earth loops (parameter 1241 and1242) and for phase to phase loops (para-meter 1243 and 1244) separately. Normallyload conditions will not cause earth faultdetection as no zero sequence current ispresent in the load. In the event of single-pole tripping of adjacent circuits, an earth-fault detection and increased load currentflow may be present at the same time. Forsuch contingencies, the load encroachmentmust also be set for earth-fault characteris-tics.

RI

load minoperation min

load max

=

U

3

From Table 1, the minimum operatingvoltage is 85 % of nominal system voltage,and the maximum load current is 250 % ofthe full load apparent power.

U operation min kV kV= =0 85 400 340.

I load maxMVA

kVA=

=2 5600

3 4002170.

By substituting these values in the aboveequation:

Rload minkV

=

=

340

3 217090 5.

To convert this to a secondary value, mul-tiply it with the factor 0.2632 (Table 2) toobtain the setting 23.8 . As worst caseconditions are assumed, a safety factor isnot required. If the parameters for calcula-tion are less conservative, a safety factor,e.g. 10 to 20 % may be included in the cal-culation.

1242 PHI load, maximum Load Angle (ph-e):To determine the largest angle that the loadimpedance may assume, the largest anglebetween operating voltage and load currentmust be determined. As load current ide-ally is in phase with the voltage, the differ-ence is indicated with the power factorcos . The largest angle of the load impe-dance is therefore given by the worst,smallest power factor. From Table 2 theworst power factor under full load condi-tions is 0.9:

load max minarc power factor = cos( ) load max arc = = cos( . )0 9 26

Setting Distance protection during SOTF

Inactive No special measures

With pickup (non-directional) All distance zones are released forinstantaneous tripping

With Zone Z1B The Zone Z1B is released for in-stantaneous tripping and will oper-ate with its set direction if a polaris-ing voltage is available

Zone Z1B undirectional The Zone Z1B is released for in-stantaneous tripping and will oper-ate as a non-directional zone.(MHO characteristic as forward andreverse zone)

Table 5 Setting alternatives for SOTF with distanceprotection



The power factor under full load condi-tions should be used for this calculation, asunder lightly loaded conditions the VARflow may dominate, but under these condi-tions the load impedance is not close to theset impedance reach. In this case the settingfor PHI load, maximum Load Angle (ph-e)is 26.

1243 R load, minimum Load Impedance(ph-ph):No distinction is made in this example be-tween the maximum load during phase toearth pickup (adjacent circuit single-poleopen) and phase to phase pickup, e.g. whenparallel circuit is three-pole tripped. There-fore the same setting as for 1241 is appliedhere, being 23.8 .

1244 PHI load, maximum Load Angle (ph-ph):Again the same setting as for the phase toearth loop is applied here, being 26.

1317A Single pole trip for faults in Z2:For special applications, single-pole trip-ping by Zone 2 can be applied. However,time delayed protection stages are usuallyapplied with 3-pole tripping.In this example, 3-pole tripping in Zone 2is desired so the default setting of NO is leftunchanged.

1357 Z1B enabled before 1st AR (int. or ext.):In this example a teleprotection scheme(POTT) is applied. The controlled ZoneZ1B operation is therefore subject to thesignals from the teleprotection scheme.In an application where no teleprotectionscheme is applied or in the case of a recep-tion failure of the teleprotection scheme,the Zone Z1B can also be controlled by theauto-reclose function.

This achieves fast tripping for all faults onthe feeder although some non-selectivetrips can also occur. This is tolerated insuch a scheme because following all fasttrips there is an automatic reclosure. In thisexample, the Z1B will only be controlled bythe teleprotection, the setting NO is there-fore applied.

10.2 Earth faults

1203 3I0 threshold for neutral current pickup:The distance protection must identify thefaulted loop to ensure correct response. Ifan earth-fault is present, this is detected bythe earth-fault detection. Only in this casewill the three earth loop measurements bereleased subject to further phase selectioncriteria. The earth current pickup is themost important parameter for the earth-fault detection. Its threshold must be setbelow the smallest earth current expectedfor faults on the protected feeder. As thedistance protection is also set to operate asbackup protection for remote externalfaults, this setting is set far more sensitivethan required for internal faults. In chapter3 the minimum single-phase fault currentfor internal faults neglecting fault resis-tance was calculated to be 1380 A.To allow for fault resistance and reach intoadjacent feeders for back-up, the settingapplied here should be substantially lowerthan this calculated value. In this example,the default value of 0.10 A secondary(100 A primary) is maintained.

Fig. 17 Load encroachment characteristic

Fig. 18 Earth-fault settings for distance protection

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1204 3U0 threshold zero seq. voltage pickup:A further criteria for earth-fault detectionis the zero sequence voltage. In an earthedsystem, zero sequence voltage is alwayspresent during earth faults and it decreasesas the distance between the measuringpoint and the fault location increases. Thisthreshold setting is therefore also used forearth-fault detection as shown in the logicdiagram, Fig. 19. When the zero sequencesource impedance is large, the zero se-quence current component in the faultcurrent may become small. In such anevent, the zero sequence voltage will how-ever be relatively large due to the small zerosequence current flowing through the largezero sequence source impedance.For secure earth-fault detection the defaultsetting of 5 V is maintained. If system un-balance during unfaulted conditions causeslarger zero sequence voltages then this set-ting should be increased to avoid earth-fault detection under these circumstances.

1207A 3I0> pickup stabilisation (3I0>/Iph max):In the event of large phase currents, thesystem unbalance (e.g. non-transposedlines) and CT errors (e.g. saturation) cancause zero sequence current to flow via themeasuring circuit of the relay although noearth fault is present. To avoid earth-faultdetection under these conditions, the zerosequence current pickup is stabilised bythis set factor.Unless extreme system unbalance or excep-tionally large CT errors are expected, thedefault setting of 10 % i.e. 0.10 can bemaintained, as is done for this example.

1209A Criterion for earth fault recognition:For the settings 1203 and 1204 above, andin Fig. 19, the method and logic of theearth-fault detection were explained. Withthis setting the user has the means to influ-ence the earth-fault detection logic. Inearthed systems it is recommended to usethe very reliable OR combination of zerosequence current and voltage for the earth-fault detection. As mentioned before, thesetwo criteria supplement each other so thatsmall zero sequence current is often associ-ated with large zero sequence voltage atweak infeeds and the other way around atstrong infeeds. The AND setting is only forexceptional conditions when, for example,the zero sequence voltage or current ontheir own are not a reliable indicator forearth faults.In this example, the default setting OR ismaintained for the reasons stated above.

Fig. 19 Earth-fault detection logic

Fig. 20 Stabilised zero sequence pickup threshold



1221A Loop selection with 2Ph-E faults:If some fault resistance (arc voltage) ispresent, then the measured fault loop im-pedances are affected by this additionalvoltage drop in the short-circuit loop. Inthe case of 2Ph-E faults this is most severeas the current in the fault resistance stemsfrom 3 different short-circuit loops. Theo-retical analysis and simulations show thefollowing distribution of the measuredloop impedances for a 2Ph-E fault:The influence of load (remote infeed andload angle) can increase or decrease the ro-tation of the measured fault resistances.The leading phase to earth loop will how-ever always tend to produce an overreach.For this reason, the default setting of blockleading Ph-E loop will be used in this ex-ample. If the application is on a double cir-cuit line where simultaneous earth faultson both lines can occur, the setting onlyphase-earth loops or all loops should beused to avoid blocking of the internal faultloop by this setting. Of course additionalgrading margin must be applied for Zone 1in this case to avoid an overreach during anexternal 2Ph-E fault.

10.3 Time delays1210 Condition for zone timer start:

During internal faults, all time delayedzones pickup unless there is substantialfault resistance and very strong remoteinfeed.Although the fault in Fig. 23 is an internalfault it is measured only by Zone Z4 due tothe fault resistance and strong remote in-feed. If all zone timers are started by thedistance pickup, the fault will be cleared bythe relay with the set Zone 2 time afterfault inception because the measured im-pedance moves into Zone 2 as soon as theremote, strong infeed trips the breaker onthe right hand side.From the timing diagram in Fig. 24 the in-fluence of this setting can be seen. If thezone timers are started with distancepickup, the trip signal is issued with Zone 2time delay (250 ms) after fault inception(distance pickup) although the Zone 2 onlypicks up some time later when the remoteend has opened the circuit-breaker on theright hand side. The timing of the trip sig-nals is therefore as if the fault had been in-side the Zone 2 all along. For external faultback-up tripping similar operation byhigher zones is achieved. This mode of op-eration will be applied in this example, sothe setting with distance pickup is applied.

Fig. 21 Impedance distribution for 2ph-E fault with fault resistance

Fig. 22 Time delay setting for the distance zones

Fig. 23 Influence of fault resistance and remote infeed onmeasured impedance

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If co-ordination with other distance orovercurrent protection is required, the set-ting with zone pickup can be applied.For the scenario described in Fig. 23 and 24this will however result in additional timedelay (t in Fig. 24). During external faultswith backup protection operation this timedelay may become very long, often a fulltime grading step so that reach and timegrading must be applied more conserva-tively.

1305 T1-1phase, delay for single phase faults:The Zone 1 is usually operated as fast trip-ping (instantaneous) underreach zone. Forthe fastest tripping all Zone 1 times are setto 0.00 s. For special applications, the triptime of single-phase faults may be set hereto differ from that for multi-phase faultswhich is set below with parameter 1306.

1306 T1 multi-ph, delay for multi phase faults:Also here the zone 1 is usually operated asfast tripping (instantaneous) underreachzone. For the fastest tripping all Zone 1times are set to 0.00 s. Refer also to setting1305 above.

1315 T2-1phase, delay for single phase faults:For the Zone 2 and higher zones the co-or-dination time must be calculated. Thistime must ensure that time graded trippingremains selective.In Fig. 25 the parameters that need to beconsidered for the time grading margin areshown. The values entered apply for thisexample and correspond to the worst caseconditions. The required time gradingmargin is therefore 250 ms. The Zone 2 isgraded with the Zone 1 at the remote feed-ers so that a single time grading step is re-quired (refer to Table 1). Set this time forsingle-phase faults to 0.25 s. For special ap-plications, the trip time of single-phasefaults may be set here to differ from thatfor multi-phase faults which is set belowwith parameter 1316.

1316 T2 multi-ph, delay for multi phase faults:As the Zone 2 will only trip three-pole inthis example, and no special considerationis given to single-phase faults, this time isset the same as 1315 above to 0.25 s.

1325 T3 delay:From Table 1, the required time delay forthis stage is two time steps = 0.50 s.

1335 T4 delay:From Table 1, this stage is not required sothe time delay can be set to infinity, s.

1345 T5 delay:From Table 1, the required time delay forthis stage is three time steps = 0.75 s.

1355 T1B-1phase, delay for single ph. faults:The zone Z1B will be used for theteleprotection in a POTT scheme. For thisapplication no time delay is required so thesetting here is 0.00 s. For special applica-tions, the trip time of single-phase faultsmay be set here to differ from that formulti-phase faults which is set below withparameter 1356.

Fig. 24 Timing diagram for fault in Fig. 23

Fig. 25 Time chart to determine time step for gradedprotection



1356 T1B-multi-ph, delay for multi ph. faults:As stated above the Zone Z1B will be usedfor the teleprotection in a POTT scheme.For this application no time delay is re-quired so the setting here is 0.00 s.

11. Distance zones (quadrilateral) SettingGroup A

11.1 Zone Z11301 Operating mode Z1:

In the case of quadrilateral distance pro-tection zones, the user may select the oper-ating mode for each zone as either for-ward, reverse, non-directional orinactive. When the zone is inactive, itdoes not produce any pickup signals ortrip. The other options can be seen in theadjacent diagram where Z1, Z1B, Z2 andZ4 are set in the forward direction. Z3 is setin the reverse direction and Z5 is set non-directional. In this example, Zone 1 mustbe set in the forward direction.

1302 R(Z1), Resistance for ph-ph faults:As the distance protection is applied withpolygonal (quadrilateral) tripping charac-teristics, the zone limits are entered as re-sistance (R) and reactance (X) settings. Aseparate resistance reach setting is availablefor ph-ph measured loops and ph-e meas-ured loops. This setting is for the ph-phloops. With setting 1211 Angle of inclina-tion, distance charact. the polygonR-reach is inclined such that it is parallel tothe line impedance (refer to Figure 12).The resistance settings of the individualzones therefore only have to cover the faultresistance at the fault location. For theZone 1 setting only arc faults will be con-sidered. For this purpose the arc resistancewill be calculated with the following equa-tion:

RU

Iarc

arc

F

=

The arc voltage (Uarc) will be calculated us-ing the following rule of thumb which pro-vides a very conservative estimate (theestimated Rarc is larger than the actualvalue):

U larc arcV= 2500 whereby larc is thelength of the arc.

The length of the arc is greater than thespacing between the conductors (ph-ph),because the arc is blown into a curve due tothermal and magnetic forces. For estima-tion purposes it is assumed that larc is twicethe conductor spacing.

To obtain the largest value of Rarc , which isrequired for the setting, the smallest valueof fault current must be used (calculated inChapter 3):

RarcV m

A=

=

2500 2 5

196712 7.

By addition of a 20 % safety margin andconversion to secondary impedance (factorfrom Table 2) the following minimum set-ting is calculated (division by 2 because Rarcappears in the loop measurement while thesetting is done as phase impedance or posi-tive sequence impedance):

R Z( ). . .

. ( )11 2 12 7 0 2632

22 01=

= sec.

This calculated value corresponds to thesmallest setting required to obtain the de-sired arc resistance coverage. Dependingon the X(Z1) reach calculated (see nextpage), this setting may be increased to ob-tain the desired Zone 1 polygon symmetry.

Fig. 26 Distance zone settings (Zone 1)

Fig. 27 Quadrilateral zone diagram

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Therefore, looking ahead at the setting re-sult for 1303 X(Z1), Reactance below, wesee that 3.537 Ohm are applied. For over-head line protection applications, the fol-lowing rule of thumb may be used for theR(Z1) setting:

0.8 X(Z1) < R(Z1) < 2.5 X(Z1)

In this example the lower limit applies, sothe setting for R(Z1) is:

R(Z1) = 0.8 3.537 = 2.830 (sec.)

This setting is then applied, 2.830 .

1303 X(Z1), Reactance:The reactance reach is calculated based onthe distance reach that this zone must pro-vide. In Table 1 the reach of Zone 1 is spec-ified as 80 % of Line 1. Therefore:

X(Z1) = 0.8 XLine 1

X(Z1) = 0.8 80 0.021 = 13.44 (prim.)

This is converted to a secondary value bymultiplying with the conversion factor inTable 2:

X(Z1) = 13.44 0.2632 = 3.537 (s)

This setting is then applied, 3.537 .

1304 RE(Z1), Resistance for ph-e faults:The phase to earth fault resistance reach iscalculated along the same lines as the 1302R(Z1) setting for ph-ph faults. For theearth fault however, not only the arc volt-age must be considered, but also the towerfooting resistance. From the graph in Fig-ure 29 it is apparent that although the indi-vidual tower footing resistance is 15 (Table 2) the resultant value due to theparallel connection of multiple tower foot-ing resistances is less than 1.5 .

From Fig. 28 it can be seen that the remoteinfeed (I2) will introduce an additionalvoltage drop across the effective towerfooting resistance which will be measuredin the fault loop by the relay (this effect isalso shown in Figure 23).

To compensate for this influence, the max-imum value (for practical purposes) of theratio of I2/I1 is required. This is given inTable 2 as the value 3. The maximumtower footing resistance that is measuredby the relay in the fault loop is therefore:

RI

ITF effective tower footing R= +

1

2

1

RTF = (1 + 3) 1.5 = 6 (prim.)

The arc voltage for the earth faults is calcu-lated as follows using the conductor totower/ground spacing given in Table 2:

Uarc = 2500 V larc

Uarc = 2500 V 2 3 m = 15 kV

To obtain the largest value of Rarc , which isrequired for the setting, the smallest valueof fault current must be used (calculated inChapter 3):

RarckV

= =

15

138010 9

.

The total resistance that must be coveredduring earth faults is the sum of Rarc andRTF . A safety factor of 20 % is included andthe result is converted to secondary values(division by factor (1 + RE/RL), becauseRarc and RTF appear in the loop measure-ment while the setting is done as phase im-pedance or positive sequence impedance):

RE Z sec.( ). ( . ) .

( . ). ( )1

1 2 10 9 6 0 2632

1 142 22=

+

+=

This calculated value corresponds to thesmallest setting required to obtain the de-sired resistance coverage. Depending onthe X(Z1) reach calculated above, this set-ting may be increased to obtain desiredZone 1 polygon symmetry. The setting re-sult for 1303 X(Z1), Reactance is3.537 . For overhead line protection ap-plications, the following rule of thumb maybe used for the RE(Z1) setting; note thatthe lower limit is the same as for ph-phfaults this ensures fast Zone 1 tripping,while the upper limit is based on the loopreach this avoids overreach:Fig. 28 Combination of arc voltage and tower footing

resistance



0 8 1 11

12 5 1. ( ) ( ) . ( ) < stage

2610 Iph>> Pickup:This high set stage is required to trip withsingle time step grading. It should there-fore have a reach equivalent to the Zone 2setting. The setting should therefore beequal to the maximum 3-phase fault cur-rent for a fault at the Zone 2 reach setting.

Based on the source and line impedances,the following maximum fault current levelcan be calculated for faults at the Zone 2reach limit:

IU

faultsource

totZ=

3with Usource = 400 kV

Ztot = sum of minimum positive sequencesource and line impedance up to Zone 2reach (as only current magnitudes are be-ing calculated, only the magnitude of theimpedance is relevant)

Fig. 41 General settings, backup overcurrent

Fig. 42 I>> stage settings, backup overcurrent

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The maximum three-phase fault current atthe Zone 2 reach limit therefore is:

I 3400

3 34 86636ph Z2

kVAmax

.=

=

As a secondary value, the setting applied forI>> is therefore 6.64 A.

2611 T Iph>> Time delay:This high set stage is required to trip withsingle time step grading. Therefore set 0.25 swhich is one time step (refer to Fig. 25).

2612 3I0>> Pickup:This high set stage is required to trip earthfaults with single time step grading. Itshould therefore have a reach equivalent tothe Zone 2 setting. The setting should there-fore be equal to the maximum single-phasefault current for a fault at the Zone 2 reachsetting.

Based on the source and line impedances,the following maximum fault current levelcan be calculated for faults at the Zone 2reach limit:

IU

faultsource

totZ=

3with Usource = 400 kV

Ztot = 1/3 of the sum of minimum positive,negative and zero sequence source and lineimpedance up to Zone 2 reach (as only cur-rent magnitudes are being calculated, onlythe magnitude of the impedance is relevant)

For the 3-phase fault level used in setting2610, the total positive sequence impedancewas calculated. As the negative sequenceimpedance equals the positive sequencevalue, the Ztot for this setting can be calcu-lated as follows:

| | |( . ( . ))Z j(Xtot source_ min ine1 Line2 s= + + +R R RL0 8 0 8 ource_ min Line1 Line2X X+ + 0 8 0 8. ( . ))|

| | |( . ( . . . )) . ( .Z j(tot = + + + + + 1 0 8 80 0 025 0 8 15 10 0 8 80 0 21 0 8 17 5+ . . ))|

| | . .Z jtot = +356 34 64

| | .Z tot = 34 8

|Z |Z

tottot source_ min Line1

=

+ + +| ( . ( ._2 0 0 8 0 0 82610 R R + + + R s0 0 0 8 0 0 8 0Line2 ource_ min Line1 Line2j(X X X)) . ( . ))|

3

|Z |j(

tot =+ + + + +|( . . . ( . . . )) .712 2 5 0 8 80 013 0 8 7 5 69 28 20 0 8 80 0 81 0 8 86 5

3

+ + . ( . . . ))|

|Z tot| = |7.58 + j65.49|

|Z tot| = 65.9



The maximum single-phase fault current atthe Zone 2 reach limit therefore is:

I 3400

3 65 93504ph Z2

kVAmax

.=

=

As a secondary value, the setting appliedfor 3I0>> is therefore 3.50 A.

2613 T 3I0>> Time delay:This high set stage is required to trip withsingle time step grading. Therefore set 0.25 swhich is one time step (refer to Fig. 25).

2614 Instantaneous trip via Teleprot./BI:The backup overcurrent is only activewhen the distance protection is blockeddue to failure of the secondary VT circuit(refer to setting 2601 in Chapter 15.1). Ifunder these conditions a teleprotection sig-nal is received from the remote end, thetripping of the overcurrent protection maybe accelerated. This may be safely appliedfor this stage, because its reach is less thanthe set Z1B. Therefore apply the settingYES. Note that for this function to work,the binary input function 7110 >O/CInstTRIP must be assigned in parallel tothe teleprotection receive binary input ofthe distance protection.

2615 Instantaneous trip after SwitchOnToFault:This function is not applied (refer to set-ting 2680 in Chapter 15.1). Therefore NOis set.

15.3 I> stage

2620 Iph> Pickup:This stage is required to trip with time de-lay equal to Zone 5. It may not pick up dueto load (permissible overload). The per-missible overload is twice the full load,therefore:

Iph PickupRated MVA

Full scale voltage>

2

3

Iph Pickup A>

=

2 600

3 4001732

As a secondary value, the setting appliedfor I> is therefore 1.74 A.

2621 T Iph> Time delay:This stage is required to trip with the sametime delay as Zone 5, three time gradingsteps. Therefore set 0.75 s which is threetime steps (refer to Fig. 25).

2622 3I0> Pickup:This stage is required to trip with time de-lay equal to Zone 5. It should detect earthfaults with similar sensitivity as Zone 5.Therefore, with the weakest infeed accord-ing to Table 2, an earth fault at the X reachlimit of Zone 5 will have the following cur-rent magnitude:

3

3 1

IU

0 Z5_ minnom_ sec

source_ max Z5_ settX XXE

XL

=

+ +( )

3100

3 100 0 2632 17 782 1 1 38I0 Z5_ min =

+ +( . . ) ( . )

3 0 55I0 Z5_ min A= .

As a secondary value, the setting appliedfor 3I0> is therefore 0.55 A.

2623 T 3I0>> Time delay:This high set stage is required to trip withthree time grading steps. Therefore set0.75 s which is three time steps (refer toFig. 25).

2624 Instantaneous trip via via Teleprot./BI:The I>> stage is applied for this purpose,refer to setting 2614 in Chapter 15.2.Therefore set NO for this stage.


Fig. 43 I> stage settings, backup overcurrent

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15.4 Inverse stage

2640 Ip> Pickup:The co-ordination of inverse time gradedprotection can be applied effectively to ob-tain reasonably fast and sensitive selectiveprotection. In this application, the inversestage is not used, so the setting here is in-finity, A.

2642 T Ip Time Dial:As the setting of 2640 above is infinity (),this setting is not relevant and left on thedefault value of 0.50 s.

2646 T Ip Additional Time Delay:This stage may also be used as a furtherdefinite time delay stage by using this set-ting. As the setting of 2640 above is infinity(), this setting is not relevant and left onthe default value of 0.00 s.

2650 3I0p Pickup:The co-ordination of inverse time gradedprotection can be applied effectively to ob-tain reasonably fast and sensitive selectiveprotection. In this application, the inversestage is not used, so the setting here is in-finity, A.

2652 T 3I0p Time Dial:As the setting of 2650 above is infinity (),this setting is not relevant and left on thedefault value of 0.50 s.

2656 T 3I0p Additional Time Delay:This stage may also be used as a furtherdefinite time delay stage by using this set-ting. As the setting of 2650 above is infinity(), this setting is not relevant and left onthe default value of 0.00 s.

2660 IEC Curve:During the device configuration (Chapter4) the standard of the curves was selectedwith parameter 0126 to be IEC. Here thechoice is made from the various IECcurves. As the stage is not applied in thisapplication the setting is not relevant andleft on the default value of Normal inverse.

2670 Instantaneous trip via Teleprot./BI:The I>> stage is applied for this purpose,refer to setting 2614 in Chapter 15.2.Therefore set NO for this stage.


15.5 I STUB stage

2630 Iph> STUB Pickup:This stage may be used as a normal definitetime delay stage. In addition to this, it pro-vides for blocking or release via binary in-put. For certain applications (e.g.1 CB) aSTUB exists when the line isolator is open.By releasing this overcurrent stage via thementioned binary inputs, a fast selectivefault clearance for faults on the STUB canbe obtained. In this application, no suchSTUB protection is required, so this stageis disabled by applying an infinite pickupvalue with the setting A.

2631 T Iph STUB Time delay:As the setting of 2630 above is infinity (),this setting is not relevant and left on thedefault value of 0.30 s.

2632 3I0> STUB Pickup:This stage may be used as a normal definitetime delay stage. In addition to this, it pro-vides for blocking or release via binary in-put. For certain applications (e.g.1 CB) aSTUB exists when the line isolator is open.By releasing this overcurrent stage via thementioned binary inputs, a fast selectivefault clearance for faults on the STUB canbe obtained. In this application, no suchSTUB protection is required, so this stageis disabled by applying an infinite pickupvalue with the setting A.

2633 T 3I0 STUB Time delay:As the setting of 2632 above is infinity (),this setting is not relevant and left on thedefault value of 2.00 s.

Fig. 44 Inverse stage settings, backup overcurrent

Fig. 45 I STUB stage settings, backup overcurrent

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2634 Instantaneous trip via Teleprot./BI:The I>> stage is applied for this purpose,refer to setting 2614 in Chapter 15.2.Therefore set NO for this stage.


16. Measurement supervision SettingGroup A

16.1 Balance / Summation

2901 Measurement Supervision:Only in exceptional cases will the measure-ment supervision not be activated. There-fore this setting should always be ON.

The advanced settings 2902A to 2909A can beused to modify the parameters of the monitoringfunctions. Generally, they can all be left on theirdefault values.

16.2 Measured voltage failure

2910 Fuse Failure Monitor:Only in exceptional cases will the fuse fail-ure monitor not be activated. Thereforethis setting should always be ON.

For the voltage failure detection, the default pa-rameters can be applied for the advanced settings.

2915 Voltage Failure Supervision:In the event of energising the primary cir-cuit with the voltage transformer second-ary circuit out of service, an alarm 168Fail U absent will be issued and the emer-gency mode activated. This monitoringtask can be controlled with this parameter2915. As no auxiliary contacts of the cir-cuit-breaker are allocated, it is only con-trolled with current supervision.

16.3 VT mcb

2921 VT mcb operating time:If an auxiliary contact of the mcb is utilised(allocated in the matrix), the operatingtime of this contact must be entered here.Note that such an input is not required inpractice as the relay detects all VT failures,including the operation of the mcb viameasurement. This set time will delay alldistance protection fault detection so itshould in general not be used. In this appli-cation, it is also not required and thereforeleft on the default setting of 0 ms.

17. Earth-fault overcurrent Setting Group A17.1 General

3101 Earth Fault overcurrent function is:For the clearance of high resistance earthfaults this function provides better sensitiv-ity than the distance protection. As high re-sistance earth faults are expected in thisapplication, this function is activated bysetting it ON.

3102 Block E/F for Distance protection:As the distance protection is more selective(defined zone reach) than the earth-faultprotection and has superior phase selectionit is set to block the E/F protection withevery pickup.

Fig. 46 Balance/Summation settings, measurementsupervision

Fig. 47 Measured voltage fail settings, measurementsupervision

Fig. 48 VTmcb settings, measurement supervision

Fig. 49 General settings, earth fault overcurrent

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3174 Block E/F for Distance Protection Pickup:As fast single-pole tripping is only donewith Zone 1 and Zone 1B with the distanceprotection, the earth-fault protection isonly blocked when the distance protectionpicks up in Zone Z1/Z1B.

3103 Block E/F for 1pole Dead time:During 1-pole dead times, load current canflow via the zero sequence path. To preventincorrect operation of the earth-fault pro-tection as a result of this it should beblocked. Therefore set YES.

3104A Stabilisation Slope with Iphase:When large currents flow during faultswithout ground, CT errors (saturation)will cause current flow via the residualpath. The earth-fault protection, having avery sensitive pickup threshold for high re-sistance faults, could pick up due to thisCT error current. To prevent this, a stabi-lising characteristic is provided to increasethe threshold when the phase currents arelarge. The characteristic is shown below inFigure 50. The default setting of 10 % issuitable for most applications.

3105 3I0-Min threshold for Teleprot. schemes:For directional comparison protection, inparticular for the weak infeed echo func-tion, a teleprotection send or echo blockcondition must be more sensitive than theteleprotection trip condition. This thresh-old determines the minimum earth currentfor teleprotection send and is set to 80 % ofthe most sensitive teleprotection trip stage.Set

3 0 8 30 0I TP I_ .= >>

3 0 8 0 580I TP_ . .=

3 0 460I TP_ .= A

Therefore apply the setting of 0.46 A.

3109 Single pole trip with earth flt. prot.:The distance protection is set to cover allarc faults on the line. High resistance faultsusually are due to mechanical defects (bro-ken conductors or obstructions in the line)so that an automatic reclosure is not sensi-ble. Therefore, set earth fault only forthree-pole tripping by application of NO.

3170 2nd harmonic for inrush restraint:When energising the line, connected trans-formers and load may cause an inrush cur-rent with zero sequence component. Thisrush current can be identified by its 2ndharmonic content. In this application in-rush blocking is not required and not ap-plied in the individual stages. The setting isof no consequence, so leave the defaultvalue of 15 %.

3171 Max. Current, overriding inrush restraint:If very large fault currents flow, CT errorsmay also cause some 2nd harmonic. There-fore the rush blocking is disabled whencurrent is above this threshold. As statedfor parameter 3170 above, the inrush re-straint is not applied in this example. Thissetting is of no consequence, so leave thedefault value of 7.50 A.

3172 Instantaneous mode after SwitchOnToFault:The earth-fault protection may be acti-vated with a set time delay (parameter3173) in the case of line energising (SOTF).In this application, only the distance pro-tection function is used for SOTF so thatthis setting is of no consequence, so leavethe default value of with pickup and direc-tion.

3173 Trip time delay after SOTF:As stated for parameter 3172 above, thistimer defines the delay of the SOTF trip byearth-fault protection. As it is not applied,the default value of 0.00 s is left unchanged.

Fig. 50 Stabilisation of 3I0 pickup threshold



17.2 3I0>>>

3110 Operating mode:A total of 4 stages are available, one ofwhich may be applied as inverse stage. Inthis application only three stages will beused, the 3I0>>> stage for fast (single timestep) directional operation and the 3I0>>stage for time delayed directional opera-tion and fast directional comparison aswell as the 3I0> stage for non-directionalbackup operation. This stage must there-fore be set to Forward.

3111 3I0>>> Pickup:This stage must operate with the same sen-sitivity as the backup (emergency)overcurrent stage 3I0>> (refer to setting2612). Therefore apply the setting 3.50 Ahere. Note that this stage is only activewhen distance protection is not picked up,and it is directional (no reverse fault opera-tion) whereas the backup O/C stage onlyoperates in the emergency mode when dis-tance protection is not available.

3112 T 3I0>>> Time delay:This stage must operate with single timestep delay. Therefore set 0.25 s here.

3113 Instantaneous trip via Teleprot./BI:The stage 3I0>> will operate withteleprotection, so the setting here is NO .

3114 Instantaneous trip after SwitchOnToFault:As stated above, only the distance protec-tion operates with SOTF, so set NO here.

3115 Inrush Blocking:As stated above, inrush blocking is not ap-plied, so set NO here.

17.3 3I0>>

3120 Operating mode:In this application only three stages will beused, the 3I0>>> stage for fast (single timestep) directional operation and the 3I0>>stage for time delayed directional opera-tion and fast directional comparison aswell as the 3I0> stage for non-directionalbackup operation. This stage must there-fore be set to Forward.

3121 3I0>> Pickup:This stage must operate for all internalhigh resistance faults, use a 20 % margin.

3 0 80I I>> = Pickup 1ph min_ R.

3 0 8 729 5830I >> = =Pickup A.

In secondary values therefore set 0.58 A.

3122 T 3I0>> Time delay:This stage must operate with two time stepdelays. Therefore set 0.50 s here.

3123 Instantaneous trip via Teleprot./BI:The stage 3I0>> will operate withteleprotection, so the setting here is YES .



Fig. 51 3I0>>> stage settings, earth fault overcurrent

Fig. 52 3I0>> stage settings, earth fault overcurrent

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17.4 3I0>

3130 Operating mode:In this application only three stages will beused, the 3I0>>> stage for fast (single timestep) directional operation and the 3I0>>stage for time delayed directional opera-tion and fast directional comparison aswell as the 3I0> stage for non-directionalbackup operation. This stage must there-fore be set to Non-Directional.

3131 3I0> Pickup:This stage must operate for all internalhigh resistance faults, the same as 3I0>>,but non-directional and with longer timedelay. In secondary values therefore set0.58 A.

3132 T 3I0> Time delay:This stage must operate with four time stepdelays. Therefore set 1.00 s here.

3133 Instantaneous trip via Teleprot./BI:The stage 3I0>> will operate withteleprotection, so the setting here is NO.



17.5 3I0 Inverse time

3140 Operating mode:This stage is not required so it is set toInactive.

Because this stage is inactive, the settings 3141 to3151 are of no consequence and left on their de-fault values.

17.6 Direction

3160 Polarization:Because both applied stages of the earth-fault overcurrent protection are directional(forward), the choice of polarising signalmust be carefully considered. If both nega-tive and zero sequence infeed are present atthe relay location polarisation with U0 +IY or U2 provides excellent results. Theearth current from a star connected andearthed transformer winding is only in-cluded, when the 4th current input of therelay is connected as such. In this applica-tion, this current input measures the resid-ual current of the protected line, (parame-ter 220 in Chapter 7.1). Therefore only thezero sequence or negative sequence voltageare used as polarising signal with this set-ting. The choice is automatic (the larger ofthe two values is chosen individually dur-ing each fault).

Fig. 53 3I0> stage settings, earth fault overcurrent

Fig. 54 3I0 Inverse time stage settings, earth fault overcurrent

Fig. 55 Direction settings, earth fault overcurrent

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3162A ALPHA, lower angle for forward direction:The default direction limits have been opti-mised for high resistance faults and are leftunchanged at 338 here.

3163A BETA, upper angle for forward direction:The default direction limits have been opti-mised for high resistance faults and are leftunchanged at 122 here.

3164 Min. zero seq. voltage 3U0 for polarizing:The zero sequence voltage is one of the val-ues for directional polarising. Under highresistance fault conditions, this value maybecome very small. For the setting it is cal-culated using the minimum single-phasefault current under high resistance faultconditions and the smallest zero sequencesource impedance (this includes a safetymargin as these two conditions will not co-incide):

3I I Z0 min 1 ph min_ R 0 source_ min=

3 729 20 14 58I0 min kV= = .

As secondary value this is:

3 3100

380U U0 min_ sec 0 min

V

kV=

3 14 58100

38038U 0 min_ sec kV

V

kVV= =. .

Therefore apply the setting 3.8 V.

3166 Min. neg. seq. polarizing voltage 3U2:Although a similar calculation as done for3164 would return a smaller value (50 %),this is not applied, as an automatic selec-tion of the larger of the two voltages wasset (parameter 3160). The setting appliedhere therefore is the same as that for thezero sequence voltage. Therefore apply thesetting 3.8 V.

3167 Min. neg. seq. polarizing current 3I2:Apply here the minimum negative se-quence current flowing for high resistancefaults with a 20 % margin.

3 0 8I I2 min 1 ph min_ R= .

3 0 8 729 583 2I2 min A= =. .

Therefore apply the setting 0.58 A.

3168 Compensation angle PHI comp. for Sr:This setting is only relevant for directiondecisions based on zero sequence power. Inthis application it is of no consequence andleft on default value of 255.

3169 Forward direction power threshold:This setting is only relevant for directiondecisions based on zero sequence power. Inthis application it is of no consequence andleft on default value of 0.3 VA.

18. Teleprotection for earth faultovercurrent Setting Group A

3201 Teleprotection for Earth Fault O/C:In this application the teleprotection is re-quired and applied as Directional Com-parison Pickup, refer to parameter 132 inChapter 4. This function is therefore acti-vated by setting it ON.

3202 Line Configuration:The line is a two terminal line.

3203A Time for send signal prolongation:As the same type of communication withthe same channel delay time is used for dis-tance teleprotection and earth-fault tele-protection, the same setting considerationas for parameter 2103A in Chapter 13 ap-plies here. Therefore in this example a set-ting of 0.05 s is applied.

3209A Transient Block.: Duration external flt.:As the same type of communication withthe same channel delay time is used for dis-tance teleprotection and earth-fault tele-protection, the same setting considerationas for parameter 2109A in Chapter 13 ap-plies here. Therefore in this example a set-ting of 0.04 s is applied.

3210A Transient Block.: Blk. T. after ext. flt.:As the same type of communication withthe same channel delay time is used for dis-tance teleprotection and earth-fault tele-protection, the same setting considerationas for parameter 2110A in Chapter 13 ap-plies here. Therefore in this example a set-ting of 0.05 s is applied.

Fig. 56 Teleprotection for earth fault overcurrentsettings

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19. Automatic reclosure Setting Group A19.1 General

3401 Auto-Reclose function:In this application the automatic reclosurefunction is required and applied with 1Cycle and with Trip and Action Time,refer to parameters 133 and 134 in Chap-ter 4. This function is therefore activatedby setting it ON.

3402 CB ready interrogation at 1st trip:Before a reclosure is attempted the circuit-breaker status must be checked. This canbe done before the reclose cycle is started(prior/at time of initiation) or before thereclose command is issued. In this applica-tion the breaker status is checked beforethe close command is issued by the reclo-ser, so this setting must be NO.

3403 Reclaim time after successful AR cycle:If the reclose is successful, the reclosermust return to the normal state which ex-isted prior to the first fault. The time sethere is started by each reclose commandand must take the system conditions intoaccount (also the circuit-breaker recoverytime may be considered). Here a setting of3.00 s is applied.

3404 AR blocking duration after manual close:If the manual close binary input is as-signed, then the AR should be blocked for aset time after manual close to prevent ARwhen switching onto a fault. In this appli-cation the manual close binary input is notassigned, SOTF is recognised by currentflow and AR is not initiated in this case.This setting is not relevant here as themanual close binary input is not assigned,the default setting of 1.00 s is left un-changed.

3406 Evolving fault recognition:If during the single-pole dead time a fur-ther fault is detected (evolving fault), theAR function can respond to this in a de-fined manner. The detection of evolvingfault in this application will

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