19b_KRUEGER-Onsite measure CT and VT.pdf

 A New App Ap p r o ac ach h f o r On On-Si -Sitt e Cali Cal i b r at atii o n o f Vol oltage tage Trans ransfo form rmers ers

Content > Me Measurement asurement Methods •

Con onve vent ntio iona nall Mea Measu surrem emen entt Meth Method od

•

Alter Alt erna nativ tive e Meas easur urem ement ent Meth ethod od (U (Usin sing g a Mo Mode del) l)

> Ca Case se Studies Stud ies •

Onsi On site te Mea easu sure reme ment nt on a 66k 66kV V Ref Refer eren ence ce VT

•

Mea easu surremen entt on a 66 66kV CVT

Conve onv entio nt ional nal Mea Measurement su rement Me Method th od

Source: IEC 61869-3

Mea Measurement su rement Procedur ro cedure e

• 1. Meas Measure uremen mentt of sho shortrt-cir circui cuitt imped impedan ance ce • 2. Measure Measurement ment of secondary secondary windin winding g resistanc resistance e • 3. Measu Measuremen rementt of secondary secondary short-circ short-circuit uit impeda impedance nce (only (only ifif more than one secondary winding) • 4. Meas Measure uremen mentt of init initia iall magne magnetiz tizati ation on curve curve • 5. Meas Measure uremen mentt of turns turns rati ratio o corre correcti ction on • 6. Calcul Calculatio ation n of voltage voltage ratio ratio error error and phase phase displ displaceme acement nt based based on the equivalent circuit diagram

1. Me Measurement su rement of o f Short-C hor t-Cir ircu cuit it Impedance Impedance Inductiv Induc tiv e Volt Volt age Transfo rmer

1. Me Measurement su rement of o f Short ho rt--Circu ir cuit it Impedance Impedance Capacitive Voltage Transformer

2. Me Measurement su rement of Secondary co ndary Windi in ding ng Resistance

4. Me Measurement su rement of o f the th e Ma Magnetisati gneti sation on Curve ur ve

4. Me Measurement su rement of the th e Ma Magnetiza gneti zati tion on curv cu rve e

BR    ]    T    [    B   y    t    i   s   n   e    d   x   u    l    F

HC

Magnetic Magnetic Force H [A/m] [A/ m]

V C  = 4,44 ⋅ n ⋅ B ⋅  f  ⋅  A

⇒  Bˆ =

ˆ V  C 

n ⋅ 2π   f  ⋅  A

⇒ V  ↑  B ↑ or  f  ↓  B ↑

5. Me Measurement su rement of Turns ur ns Ratio ti o Correcti or recti on

5. Measur Measure ement of o f Capaci Capaciti tive ve Ratio Ratio

1st step:

2nd step:

5. Me Measurement su rement of Turns ur ns Ratio ti o Correcti or recti on • Measu Measure remen mentt of capaci capacitiv tive e ratio ratio in in two step steps: s: • 

=







=

 

• Ratio of Ktotal to Kind is equal to capacitive ratio: • 

=

 

=1+

 

• The total total voltag voltage e ratio ratio of a capacitiv capacitive e volta voltage ge transf transform ormer er is is equal equal to the product of capacitive ratio and inductive ratio obtained at higher voltages (3kV): • 

=

 ∗  @3

5. Me Measurement su rement of Turns ur ns Ratio ti o Correcti or rection on Example for turns ratio correction correct ion from a 10kV reference VT (inductive VT)

Ratio Ratio Error (V) (V) [%] [%] 0.2

0

   %   n    i   r   o   r   r   e   o    i    t   a   r   e   g   a    t    l   o    V

-0.2

-0.4 Reference -0.6 Ratio Error without turns ratio correction correction -0.8 Ratio error with turns ratio correction -1 0

1000

2000

3000

4000

5000

6000

Primary vol tage in V

7000

8000

9000

10000

Cas Cas e Stud Stu d y 66kV Refer Referenc ence e VT Nameplate data

Secondary terminal box

Cas Cas e Stud Stu d y 66kV Refer Referenc ence e VT Obtained voltage ratio error of class ±0.03% ±1.5min reference VT Power

Voltage ratio error in % of rated voltage

VA

VA [%]

cos phi

80%

100%

120%

1,0000

100,0%

1,0000

-0,0064%

-0,0038%

-0,0019%

0,0000

0,0%

1,0000

-0,0052%

-0,0025%

-0,0006%

Cas Cas e St St udy ud y 66k 66k V r eference eferenc e VT VT Obtained phase displacement of class ±0.03% ±1.5min reference VT Power

Phase Pha se disp laceme lacement nt table (min)

VA

VA [%]

cos phi

80%

100%

120%

1,0000

100,0%

1,0000

-2,5727

-2,5655

-2,5576

0,0000

0,0%

1,0000

-2,3296

-2,3225

-2,3146

Cas Cas e Stud Stu d y 66kV Refer Referenc ence e VT Conclusions:

• Results Results have have prov proven en to be very very stabl stable e over over frequency frequency range range of 50Hz to 60Hz and for all successive measurement conducted • The bigg biggest est absol absolute ute varia variance nce betwe between en all success successive ive tests was ±0.001% in regards to the voltage ratio error and ±0.03min in regards to the phase displacement

• Voltage oltage ratio error error results results were were within within the requi requiremen rements ts of ±0.0 ±0.03% 3% • Phase Phase displa displacemen cementt results results were were off off the specs by -1min -1min (still (still acceptible for calibrating class 0.1 metering VTs)

Cas Cas e St St udy ud y Capaciti Capaci tive ve VT 66k 66k V Capacitive Ca pacitive Voltage Tr ansfor mer (CV CVT) T) VA 25 100

fu [%] Reference   0,08   -0,22

fu [%] VOTANO 0, 0,11 -0,20

phi [min] Reference -0,50 1,00

Conclusions:

• Voltage oltage ratio ratio error error results results are are within within ±0.03 ±0.03% % • Phase Phase displ displace acemen mentt resul results ts were were ± 1min 1min

phi [min] VOTANO -0,43 1,41

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Questions uesti ons and Re Remarks? marks ?