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Metering or Relaying: Select the type of CT. Selection of the type of CT affects the performance
of the excitation test. Typically a metering class CT will saturate and thus have a knee point of
less than 30V. So in order to gather enough data points to calculate the knee point, if the type
of CT is set to “Metering” the MRCT will increment the voltage during the excitation by ½ V
increments. Conversely a relaying/protection class CT will saturate at much higher voltage
levels. So if the type of CT is set to “Relaying” the MRCT will increase voltage increment with
each subsequent step until the knee point is reached. This allows the MRCT to reduce the
number of data points and thus the testing time of relaying class CT. Please note that if the type
of CT is unknown then it is best to omit this selection. For if the type of CT is unknown then the
MRCT will increment the voltage by ½ V up to 30 V and then begin increasing the voltage
increment until the knee point is reached.
Accuracy Class: Use the drop down menu to select the CT accuracy class from available options
such as
a
a)
C10
h)
T10
b)
C20
i)
T20
c)
C50
j)
T50
d)
C100
k)
T100
e)
C200
l)
T200
f)
C400
m)
T400
g)
C800
n)
T800
VA
Burden
Buried CT in Delta Connection: The CT ratio is measured as ratio = Vx/Vh. However since the
induced voltage measured through the H terminals of a Delta winding is V = 2/3Vh. Thus the
measured ratio is 3/2 higher than actual ratio. By checking this box when the CT under test is in
a delta configuration, the MRCT will display the correct ratio by reducing measured ratio by 2/3
Ratio: For a multi- tap CT, different tap ratios can be obtained from nameplate and can be
entered in nameplate screen. By entering these four ratios the MRCT will auto-determine all
interior ratios and use these values when calculating ratio errors
User Descriptions and Values are used to fill out the optional testing information such as
1.
Technician name,
2.
Company information,
3.
Substation location,
4.
Position and phase of CT
5.
type of CT - Bar Type or Window Solid Core
6.
Other relevant testing data.
Note
: All the information in Nameplate screen is optional. It is not required to perform a test on CT.
However by inputting proper data a more complete report can be generated.
