ABB Relion 650 Series Technical Manual page 612

Section 21
Time inverse characteristics
twenty times the set current pickup value. Note that the operating time value is dependent on the
selected setting value for time multiplier k.
In addition to the ANSI and IEC standardized characteristics, there are also two additional inverse
curves available; the RI curve and the RD curve.
The RI inverse time curve emulates the characteristic of the electromechanical ASEA relay RI. The
curve is described by equation 102:
æ
ç
[ ]
ç
s
=
t
ç
ç
0.339
è
EQUATION1647 V1 EN-US
where:
Pickupn is the set pickup current for step n
td
i
The RD inverse curve gives a logarithmic delay, as used in the Combiflex protection RXIDG. The
curve enables a high degree of selectivity required for sensitive residual ground-fault current
protection, with ability to detect high-resistive ground faults. The curve is described by
equation 103:
[ ]
s =
t 5.8 1.35 ln
EQUATION1648 V1 EN-US
where:
Pickupn is the set pickup current for step n,
td
i
The timer will be reset directly when the current drops below the set pickup current level minus the
hysteresis.
21.3 Inverse time characteristics
606
ö
÷
td
÷
Pickupn
÷
÷
- ×
0.235
ø
i
is set time multiplier for step n
is the measured current
æ ö
i
- ×
ç ÷
è × ø
td Pickupn
is set time multiplier for step n and
is the measured current
When inverse time overcurrent characteristic is selected, the operate time of the
stage will be the sum of the inverse time delay and the set definite time delay.
Thus, if only the inverse time delay is required, it is of utmost importance to set the
definite time delay for that stage to zero.
© Copyright 2011 ABB Power Grids. All rights reserved
1MRK 506 326-UUS B
(Equation 102)
(Equation 103)
IP15797-1 v2
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Line distance protection REL650
Technical manual