ABB Relion 670 series - Page 1393

Also the reset time of the delayed function can be controlled. There is the possibility to choose
between three different reset time-lags.
• Instantaneous Reset
• IEC Reset
• ANSI Reset.
If instantaneous reset is chosen the timer will be reset directly when the current drops below the
set pickup current level minus the hysteresis.
If IEC reset is chosen the timer will be reset after a set constant time when the current drops
below the set pickup current level minus the hysteresis.
If ANSI reset time is chosen the reset time will be dependent of the current after fault clearance
(when the current drops below the pickup current level minus the hysteresis). The timer will reset
according to equation
236.
[ ]
2
1
r
t
t s td
i
pickupn
= ×
-
æ ö
ç ÷
ç ÷
ç ÷
æ ö
ç ç ÷ ÷
è è ø ø
ANSIEQUATION1197 V1 EN-US (Equation 236)
where:
The set value t
r
is the reset time in case of zero current after fault clearance.
The possibility of choice of reset characteristics is to some extent dependent of the choice of time
delay characteristic.
For the definite time delay characteristics the possible reset time settings are instantaneous and
IEC constant time reset.
For ANSI inverse time delay characteristics all three types of reset time characteristics are
available; instantaneous, IEC constant time reset and ANSI current dependent reset time.
For IEC inverse time delay characteristics the possible delay time settings are instantaneous and
IEC set constant time reset).
For the programmable inverse time delay characteristics all three types of reset time
characteristics are available; instantaneous, IEC constant time reset and ANSI current dependent
reset time. If the current dependent type is used settings pr, tr and cr must be given, see
equation
237:
[ ]
r
pr
t
t s td
i
cr
pickupn
= ×
-
æ ö
ç ÷
ç ÷
ç ÷
æ ö
ç ç ÷ ÷
è è ø ø
ANSIEQUATION1198 V1 EN-US (Equation 237)
1MRK 502 066-UUS B Section 26
Inverse time characteristics
1387
Technical manual