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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