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The function is divided into two parts. The SOTF function will give operation from

step 2 or 3 during a set time after change in the position of the circuit breaker. The

SOTF function has a set time delay

. The under time function, which has 2

harmonic

restrain blocking, will give operation from step 4. The 2nd harmonic restrain will

prevent unwanted function in case of transformer inrush current. The under time

function has a set time delay.

Below the settings for switch on to fault logics are described.

SOTF: This parameter can be set: Disabled/SOTF/Under Time/SOTF+Under Time.

SOTFSel: This setting will select the signal to activate SOTF function; CB position

open/CB position closed/CB close command.

StepForSOTF: If this parameter is set on step 3, the step 3 pickup signal will be used as

current set level. If set on step 2, the step 2 pickup signal will be used as current set

level.

HarmBlkSOTF: This is used to On/Off harmonic restrain during SOTF conditions.

tSOTF: Time delay for operation of the SOTF function. The setting range is 0.000 -

60.000 s in step of 0.001 s. The default setting is 0.100 s

t4U: Time interval when the SOTF function is active after breaker closing. The setting

range is 0.000 - 60.000 s in step of 0.001 s. The default setting is 1.000 s.

ActUndrTimeSel: Describes the mode to activate the sensitive undertime function. The

function can be activated by Circuit breaker position (change) or Circuit breaker

command.

tUnderTime: Time delay for operation of the sensitive undertime function. The setting

range is 0.000 - 60.000 s in step of 0.001 s. The default setting is 0.300 s

8.4.3.5 Settings for each step (x = 1, 2, 3 and 4)

M15282-9 v12

Operation: Sets the protection to Enabled or Disabled.

DirModeSelx: The directional mode of step x. Possible settings are Disabled/Non-

directional/Forward/Reverse.

Characteristx: Selection of time characteristic for step x. Definite time delay and

different types of inverse time characteristics are available.

Inverse time characteristic enables fast fault clearance of high current faults at the same

time as selectivity to other inverse time phase overcurrent protections can be assured.

This is mainly used in radial fed networks but can also be used in meshed networks. In

meshed networks, the settings must be based on network fault calculations.

1MRK 511 401-UUS A Section 8

Current protection

Bay control REC670 2.2 ANSI 175

Application manual

ABB rec670 Applications Manual

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