Reset in inverse-time modes - Arc protection - Motor protection - Feeder protection - Back-up protection - Technical Manual - REX610 Protection and control - 1.2 - IEC - ANSI - 17.02.2023

REX610 Technical Manual

The user can select the reset characteristics by using the Type of reset curve setting.

Table 1. Values for reset mode
Setting name Possible values
Type of reset curve

1=Immediate

2=Def time reset

3=Inverse reset

Immediate reset

If the Type of reset curve setting in a drop-off case is selected as "Immediate", the inverse timer resets immediately.

Definite time reset

The definite type of reset in the inverse-time mode can be achieved by setting the Type of reset curve parameter to “Def time reset”. As a result, the operate inverse-time counter is frozen for the time determined with the Reset delay time setting after the current drops below the set Start value, including hysteresis. The integral sum of the inverse-time counter is reset, if another start does not occur during the reset delay.

Note: If the Type of reset curve setting is selected as “Def time reset”, the current level has no influence on the reset characteristic.

Inverse reset

Note: Inverse reset curves are available only for ANSI and user-programmable curves. If you use other curve types, immediate reset occurs.

Standard delayed inverse reset

The reset characteristic required in ANSI (IEEE) inverse-time modes is provided by setting the Type of reset curve parameter to “Inverse reset”. In this mode, the time delay for reset is given with the following formula using the coefficient D, which has its values defined in the table below.

Figure 1. Equation
t[s] Reset time (in seconds)
k Set Time multiplier
I Measured current
I> Set Start value
Table 2. Coefficients for ANSI delayed inverse reset curves
Curve name D
(1) ANSI Extremely Inverse 29.1
(2) ANSI Very Inverse 21.6
(3) ANSI Normal Inverse 0.46
(4) ANSI Moderately Inverse 4.85
(6) Long Time Extremely Inverse 30
(7) Long Time Very Inverse 13.46
(8) Long Time Inverse 4.6

The delayed inverse reset time depends also on the protection function's start duration value START_DUR. The reset time on the drop-off moment can be calculated by multiplying t[s] with START_DUR.

Figure 2. ANSI extremely inverse reset time characteristics
Figure 3. ANSI very inverse reset time characteristics
Figure 4. ANSI normal inverse reset time characteristics
Figure 5. ANSI moderately inverse reset time characteristics
Figure 6. ANSI long-time extremely inverse reset time characteristics
Figure 7. ANSI long-time very inverse reset time characteristics
Figure 8. ANSI long-time inverse reset time characteristics
Note: The delayed inverse-time reset is not available for IEC-type inverse time curves.

User-programmable delayed inverse reset

The user can define the delayed inverse reset time characteristics with the following formula using the set Curve parameter D.

Figure 9. Equation

The delayed inverse reset time depends also on the protection function's start duration value START_DUR. The reset time on the drop-off moment can be calculated by multiplying t[s] with START_DUR.

t[s] Reset time (in seconds)
k Set Time multiplier
D Set Curve parameter D
I Measured current
I> Set Start value