4_7UT6 low imp REF

Energy Automation

7UT6: Low impedance Restricted Earth Fault Forum Schutztechnik

s Global network of innovation

Power Transmission and Distribution

Internal single pole fault’s close to transformer star point No. 1 with Energy Automation

400kV

230kV

Example: Autotransformer 500MVA , 400/230kV, uk12 = 15.8% Inductivity L ? winding2 ; RF = fault resistance

X ? ? ?L ; I F LV ? w1

f ?U LV / 3

?f

2

?

2

?X ? R 2F

; I F HV ? I FLV

f ?w2 w1 ? w2 ?(1 ? f)

IF [p.u.] IF HV [p.u. HV side] 1

IF LV [p.u. LV side] IF tot [p.u. LV side]

w2 f

0

Short circuited winding part f L2 L3

PF ? I 2Ftot ?R F ; Energy : WF ? I 2Ftot ?R F ?t Trip

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PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

Limits of the differential protection No. 1 with Energy Automation

(1 of 2)

Earth fault current limited by RE to IEmax = 2000A ; R E >> XTr 20 MVA ; YNd5 ~

1L1

Side 1: 132kV

100/1A

…/1A

~ 1L2 ~

Side 2: 13.8kV 2L1 2L2 0

1L3

InO1 = 87.5A

1

f

2L3

InO2 = 837A

RE …/1A

IF ? f

?U

?

?

?

?

/ 3 f ? U 2N / 3 U / 3 ? f ?I Emax and I K ? I F ? f 2 ?I Emax 2N RE U1N U1N

2N

?

Will the differential protection detect the fault (setting IDiff> = 0.25I/InO , slope 1 = 0.25) ? (fault location 20% from the star point)

I F ? 0.2 ?2000A ? 400A ;

I K ? 0.2 2 ?2000A

132kV I ? I F /I nO2 ? 400A/837A ? 0.478 ; I ? I K /I nO1 ? 4.82A/87.5A ? 0.055 1 Io - Elimination : I D Elim ? 0 ? I*K ? I*K ? 1.154 ?I*K ? 0.063I/InO 3 1 1 0.478 Io ? Correction : I D Corr ? 0 ? I *K ? I*K ? I*F ? 0.063I/InO ? I/InO ? 0.222 I/I nO 3 3 3 * F

? ?

s

?13.8kV/ 3 ? ? 4.82A ;

* K

? ?

PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

Limits of the differential protection No. 1 with Energy Automation

(2 of 2)

With the above setting the differential protection (with Io-correction) would only just fail to pick up! IF,ID,IK [p.u.]

IF [p.u. 13.8kV side] ID Cor Io-correction ID Elim Io-elimination IK [p.u. 132kV side]

Diff. pickup at nom. load Diff. pickup at no load REF Example

Short circuited winding part f

In the example at hand, it is therefore advisable to connect a CT with earth current relay (pick up threshold 200A) in the earth connection of the star-point, to increase the range of protection coverage to 90%. This protection however requires a large time delay setting as the earth current relay in the system must trip faster to maintain selectivity.

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PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

7UT6: Restricted Earth Fault Protection (General) No. 1 with Energy Automation

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The REF measures the Neutral current of the object ( ISP = 3I0’ ) and, depending on the angle (? f ) between 3I0’ and the also measured sum of the phase currents ( 3I0’’ = IL1 + IL2 + IL3 ), decides for internal or external fault. The sensitivity of the REF is almost independent from the load of the object. (The sensitivity of the “Differential Function” especially for high ohm faults will be reduced by the load due to the slope of its “Tripping Characteristic” ). The REF can be stetted to 0.1 I/INO and is therefore more sensitive as the “Differential Protection” (even without load).

PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

7UT6: Tripping Characteristic of REF No. 1 with Energy Automation

(1 of 3)

IREF> = Setting value (Trip Threshold) IRest = Restraint current IREF = ¦ 3I0’¦ 1) for basic Trip-Area (0° = ? f = 90°): Characteristic_1):

IREF = ¦ 3I0’¦

and must be = IREF>

IREF / I REF> = 1 (no restraining current IRest effective)

2) for extended Trip-Area (90° = ? f = 180°): IREF = IREF> + k·IRest

where IRest = (¦ 3I0’-3I0’’¦ -¦ 3I0’+3I0’’¦ )

IRest includes the direction

I REF ? I REF ? ? k ??3Io'? 3Io' ' ? 3Io'? 3Io' ' ?? 3Io' ' ? reference, ? (3Io' ' ) ? 0

?

I REF ? I REF ? ? k ? 3Io'?e j? ? ? 3Io' ' ? 3Io'?e j? ? ? 3Io' ' 1?

?

? I REF ? 3Io' ' 3Io' ' ? ?? ? I REF ? 3Io' ? 3Io' ? k ??? 1?e j? ? ? ? 1 ?e j? ? ? 3Io' 3Io' 3Io' ? ?

I REF ? ? 3Io' ' 3Io' ' ? ?? ? 1 ? k ??? 1?e j? ? ? ? 1?e j? ? ? I REF 3Io' 3Io' ? ?

Characteri stic_2) :

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I REF ? I REF ?

? 1 ? k ?? 1?e j? ? ?

1 3Io' ' 3Io' ' ? ? ? 1?e j? ? ? ? 3Io' 3Io' ?

for 7UT612 : k ˜ 2 for 7UT613/63 k ˜ 4

PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

7UT6: Tripping Characteristic of REF No. 1 with Energy Automation

(2 of 3)

Figure 2: 7UT6 REF tripping characteristic I REF

Char. for ? f = 180°

I REF ? 4

Tripping 3

2

1

Blocking -0.3

-0.2

-0.1 180° = ? f > 90° Characteristic_2)

s

0.0

+0.1

+0.2

90° = ? f = 0° Characteristic _1)

3I '0' 3I '0

+0.3

PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

7UT6: Tripping Characteristic of REF No. 1 with Energy Automation

Figure 3 ?f > 90° 3I0’-3I0’’

(3 of 3) Figure 5 ?f < 90°

Figure 4 ?f =90°

-3I0’’

+3I0’’ -3I0’’

IRest

+3I0’’ -3I0’’

3I0’

+3I0’’

3I0’+3I0’’

3I0’ IRest

3I0’

3I0’-3I0’’

3I0’+3I0’’ 3I0’-3I0’’

3I0’+3I0’’

? f = 45° 3I0’’

? f = 135°

3I0’’

3I0’’

IRest = (¦ 3I0’-3I0’’¦ -¦ 3I0’+3I0’’¦ ) = 0

IRest = (¦ 3I0’-3I0’’¦ -¦ 3I0’+3I0’’¦ ) > 0

IRest = (¦ 3I0’-3I0’’¦ -¦ 3I0’+3I0’’¦ ) < 0 (neg. values will be set to 0)

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PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

7UT6: REF CT saturation at star point CT No. 1 with Energy Automation

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(1 of 2)

The star point CT can or even should be weaker designed than the phase Ct’s ! In case of an external fault and saturation on this CT there will be no false trip.

PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

7UT6: REF CT saturation at star point CT

(2 of 2)

No. 1 with Energy Automation

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PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

Comparison of sensitivity between Differential Protection and REF No. 1 with Energy Automation

38.1 MVA ; Vector group: YNd5 Side 2: 11kV Side 1: 110kV 2000/1A

200/1A

2L1

1L1

2L2

1L2

2L3

1L3 200/1A

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PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

Settings No. 1 with Energy Automation

Io-Correction

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PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

Fault 1: Internal high ohm Fault L1-E Side 1, without Load (1 of 3) No. 1 with Energy Automation

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PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

Fault 1: Internal high ohm Fault L1-E Side 1, without Load (2 of 3) No. 1 with Energy Automation

With Io-Correction

With Io-Elimination

Idiff ? 0.11 I/InO

Only Ires, no Idiff for L2,L3

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PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

Fault 1: Internal high ohm Fault L1-E Side 1, without Load (3 of 3) No. 1 with Energy Automation

Trip Area

Block Area

Iref = actual current, IREF = Setting I REF>, K s=1, IoL = I0’’, IoSt = I0’

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PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

Fault 2: Internal high ohm Fault L1-E Side 1, with Load (1 of 3) No. 1 with Energy Automation

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PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

Fault 2: Internal high ohm Fault L1-E Side 1, with Load (2 of 3) No. 1 with Energy Automation

Iref = actual current, IREF = Setting I REF>, Ks = 1, IoL = I0’’, IoSt = I0’

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PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

Fault 2: Internal high ohm Fault L1-E Side 1, with Load (3 of 3) No. 1 with Energy Automation

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3I0’’ = 3·6.49mA = 19.47mA, ? 3I0’/ 3I0’’ = 19.47/140 = 0.139 InO = 200A ? 1000mA, IRef = 140mA, IRef> = 0.1 ? IRef/IRef> = 1.4 PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

7UT6: REF settings No. 1 with Energy Automation

proposed value

InS = nominal side current Increasing the pickup value

I Ref InO 0.3

1313A slope = 0.1

0.2 IRef> 0.1

0

0

0.5

1.0

1.5

2.0

? I = ¦ IL1¦ + ¦ IL2¦ + ¦ IL3¦ + ¦ ISP¦

2.5

3.0

3.5 ? I InO

nominal load

(to be handled with care) !!!

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PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

Setting the direction of the Star point CT No. 1 with Energy Automation

Transformerwinding L1 Setting for “CT-Strpnt in Direct. Of Object”

must be correct !

L2 L3

Q7 Q8 7UT612

0230 Earthing Electrode versus

Terminal Q7

Q7 Q8 7UT612

0230 Earthing Electrode versus

Terminal Q7

Q7

0230 Earthing Electrode versus

Terminal Q8

0230 Earthing Electrode versus

Terminal Q8

Q8

7UT612 Q7

Q8

7UT612

Secondary earthing of Star point CT has no influence on the direction

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PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

7UT6: versions No. 1 with Energy Automation

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7UT612 Version 4.0

7UT613/63. 7UT613/63. Version 4.0 Version 4.6 (Jan. 2006)

Number of 1 Low impedance REF

1

2

REF for Autotransformer

No

Yes

No

PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

Application Device Configuration

No. 1 with Energy Automation

0105 0112 0113

M1 S1 Main protect. object

7UT613

Y S2

M2 Starpointbilder X2

Sides: S1 High voltage side (HV) S2 Low voltage side (LV) Measuring locations 3-phase , assigned M1 assigned to the main protected object (side 1) M2 assigned to the main protected object (side 2) Auxiliary measuring locations 1-phase X1 assigned to the main protected object (side 1) X2 assigned to the main protected object (side 2) X3 not assigned to the main protected object

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3 phase Transformer Enabled Enabled

Power System Data 1

X1

?

Protected Object Differential Protection REF Protection

CT-Numbers 0211 No. of connected Meas. Loc. 0212 No. of assigned Meas. Loc. 0213 No. of sides CT-Assign 0222 Assignment at 2 assig. Meas.Loc./2 sides 0251 Auxiliary CT IX1 is used as 0252 Auxiliary CT IX2 is used as Transf. …. 0313 Starpoint of Side 1 is 0314 Transf. Winding Connection Side 1 …. 0323 Starpoint of Side 2 is 0324 Transf. Winding Connection Side 2 0325 Vector Group Numeral of Side 2 Funct. 0413 REF assigned to 0420 DMT/IDMT Phase assigned to

2 2 2

S1:M1, S2:M2 Side 1 earth Side 2 earth Solid Earthed Y (Wye) Solid Earthed (!!) D (Delta) 11 Side 2 Side 1

Setting Group A Differential Protection-Settings Group A 1211A Diff-Prot. with meas. Earth Curr. S1 1212A Diff-Prot. with meas. Earth Curr. S2

Yes (Io- correct. Side 1) No

PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

7UT6: REF Interturn fault / terminal earth fault No. 1 with Energy Automation

38.1 MVA ; Vector group: YNd5 Side 2: 11kV Side 1: 110kV 2000/1A 2L1

200/1A

1L1

~

2L2

1L2

~

2L3

1L3

~

1L1

~

2L2

1L2

~

2L3

1L3

~

200/1A

(-)

(+)

? ? = 180° ? no Trip by REF

38.1 MVA ; Vector group: YNd5 Side 2: 11kV Side 1: 110kV 2000/1A 2L1

200/1A

200/1A

ISP

ISP = 0 ? no Trip by REF

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PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

7UT6: REF, testing the characteristic No. 1 with Energy Automation

(1 of 3)

Configuration: Winding 1: 80MVA,110kV

500/1A

500/1A

In ?

S NTr ?I NCTSec 3 ?U NTr ?I NCT Pr im

?

80000kVA ?1A ? 0.839 A 3 ?110kV ?500 A

(In this case for Io’ and Io’’, because all ct’s are primary 500A)

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PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

7UT6: REF testing the characteristic No. 1 with Energy Automation

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(2 of 3)

Test point 1: Io’ = 2 IREF> = 2?0.1?0.839A = 0.168A = constant. Io’’: at the begin approximate 0.4?0.168A ej180°=0.067A, than reducing step by step until trip? Result: -21mA/168mA = -0.125 Test point 2: Io’ = 4 IREF> = 4?0.1?0.839A = 0.336A = constant. Io’’: at the begin approximate 0.4?0.336A ej180°=0.134A, than reducing step by step until trip? Result: -60mA/336mA ? 0.18

-0.18 TP 2

-0.125 TP 1

PTD EA13 N.M. 7UT6: REF 07/2005

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Power Transmission and Distribution

7UT6: REF testing the characteristic No. 1 with Energy Automation

Test point 1:

Test point 2:

?-21mA

168mA

s

(3 of 3)

?-60mA

336mA

PTD EA13 N.M. 7UT6: REF 07/2005

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