Basler Electric BE1-11m - Manual (Page 80)

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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 chapter.
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
Time Curve Characteristics chapter for
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 1 and Equation 2. 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 23. The curve-specific coefficients are defined for
the standard curves as listed in the
Time Curve Characteristics chapter.
𝑇
𝑇
=
𝐴𝐷
𝑀 𝑁 − 𝐶 + 𝐵𝐷 + 𝐾
Equation 1. Time OC Characteristics for Trip
𝑇
𝑅
=
𝑅𝐷
|𝑀 2 − 1|
Equation 2. Time OC Characteristics for Reset
Table 23. Definitions for Equation 1 and Equation 2
Parameter Description Explanation
T
T
Time to trip Time that the 51-x function will take to time out and trip.
D Time dial setting Time dial setting for the 51-x function.
M
Multiple of pickup Measured current in multiples of pickup. The timing algorithm
has a dynamic range of 0 to 40 times pickup.
A
Coefficient specific to
selected curve Affects the effective range of the time dial.
B
Coefficient specific to
selected curve Affects a constant term in the timing equation. Has greatest
effect on curve shape at high multiples of tap.
C
Coefficient specific to
selected curve Affects the multiple of PU where the curve would approach
infinity if allowed to continue below pickup. Has greatest effect on
curve shape near pickup.
N
Exponent specific to
selected curve Affects how inverse the characteristics are. Has greatest effect
on curve shape at low to medium multiples of tap.
K Constant Characteristic minimum delay term.
T
R
Time to reset Relevant if 51-x function is set for integrating reset.
R
Coefficient specific to
selected curve Affects the speed of reset when integrating reset is selected.
Inverse Overcurrent (51) Protection BE1-11m