NDB Technologies CTT Series User Manual page 18

7.2.4 Menu - System
The system menu contains all CTT parameters.
• Date/Time: Set the time and date. Time and date will be used to time-stamp a
test records when it is saved to memory.
• Saturation: The saturation's knee point is the point on the magnetization
curve where a 10% increase in flux density (voltage) causes a 50% increase in
magnetization force (current) (ANSI / IEC 10/50). The saturation knee point is
one of the main health indicators of a CT since it reflects its structural integrity.
A drop in the saturation knee point can indicate a deterioration in the material
of its core (delamination, cracking, etc...) or a defect in the winding (short-
circuit). Several defects arising in a CT can be detected by analyzing the trend
of the saturation knee point over time. To ensure that the trend is reliable,
the saturation knee point measurements must be constantly accurate. The
IEEE 45 and 30 definitions apply to class "C" CTs and refer to the point on the
saturation curve where the tangent is 45° (or 30°) from the abyss.
• Insulation: Allows to select the insulation test voltage, as well as the
stabilization time.
• CT: Select "Normal" for any CT not buried in a delta type transformer. Select
"CT in Delta" for any CT in series with a winding of a delta type transformer
(buried). Error compensation will be applied to correct the reading. Refer to
section 9.2 for more details.
C T T S e r i e s - U s e r M a n u a l
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