Basler BE1-11g Instruction Manual page 108

96
Unbalance Mode
Unbalance mode provides unbalanced current protection. Two methods are available to calculate
unbalanced current. The first method is based on the negative-sequence current divided by the positive-
sequence current while the second method is based on the average current. The calculation method must
be specified on the System Parameters, Sensing Transformers screen in BESTCOMSPlus. Refer to the
Configuration chapter for more information.
CT Source
The CT Source setting configures an inverse overcurrent element to monitor CT circuit 1 or CT circuit 2
on protection systems equipped with two sets of CTs. CT circuit 1 terminals are designated D1 (IA1)
through D8 (IG1) and CT circuit 2 terminals are designated F1 (IA2) through F8 (IG2). For an illustration,
refer to the Terminals and Connectors
Direction
An inverse overcurrent element can be configured for forward or reverse tripping. Refer to the
Overcurrent (67) Protection
Timings
Each inverse overcurrent element has a Curve setting. The following paragraphs describe the available
timing curves. The user can select integrating reset timing to make the protective element use integrated
reset and emulate an electromechanical induction disk reset characteristic.
Standard Curves
There are 22 standard curves available including standard inverse, short inverse, moderately inverse,
long inverse, very inverse, and extremely inverse. Refer to the
specific information on each curve.
Programmable Curves
An available programmable curve can be used to create a custom curve by selecting coefficients in the
inverse time characteristic equation. When inverse time overcurrent characteristic curve P is selected, the
coefficients used in the equation are those defined by the user. Inverse overcurrent characteristics for trip
and reset programmable curves are defined by Equation 6 and Equation 7. These equations comply with
IEEE Std C37.112-1996 - IEEE Standard Inverse-Time Characteristic Equations for Overcurrent Relays.
Definitions for these equations are provided in Table 33. The curve-specific coefficients are defined for
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the standard curves as listed in the �� =
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Equation 6. Time OC Characteristics for Trip
Parameter Description
T Time to trip
T
D Time dial setting
M Multiple of pickup
Coefficient specific to
A
selected curve
Coefficient specific to
B
selected curve
C Coefficient specific to
Inverse Overcurrent (51) Protection
chapter.
chapter for more information.
+ ���� + �� Time Curve Characteristics
Table 33. Definitions for Equation 6 and Equation 7
Time that the 51-x function will take to time out and trip.
Time dial setting for the 51-x function.
Measured current in multiples of pickup. The timing algorithm
has a dynamic range of 0 to 40 times pickup.
Affects the effective range of the time dial.
Affects a constant term in the timing equation. Has greatest
effect on curve shape at high multiples of tap.
Affects the multiple of PU where the curve would approach
Time Curve Characteristics
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chapter. �� =
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2
Equation 7. Time OC Characteristics for Reset
Explanation
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Directional
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BE1-11g