ABB Relion 670 Series RES670, Technical Manual

Page: 281 / 888

9.1.7.2 Time delay
The time delay for the two steps can be either definite time delay (DT) or inverse time
undervoltage (TUV). For the inverse time delay three different modes are available:
• inverse curve A
• inverse curve B
• customer programmable inverse curve
The type A curve is described as:
TD
t
Vpickup V
Vpickup
=
< -
<
ANSIEQUATION1431 V1 EN
(Equation 50)
where:
Vpickup
<
Set value for step 1 and step 2
V Measured voltage
The type B curve is described as:
2.0
480
0.055
Vpickup < -V
32 0.5
Vpickup
TD
t
×
= +
× -
<
æ ö
ç ÷
è ø
EQUATION1608 V1 EN
(Equation 51)
The customer programmable curve can be created as:
P
TD A
t D
Vpickup V
B C
Vpickup
×
= +
< -
× -
é ù
ê ú
ê ú
ê ú
æ ö
ê ú
ç ÷
è ø
ë û
EQUATION1609 V1 EN
(Equation 52)
When the denominator in the expression is equal to zero the time delay will be infinity.
There will be an undesired discontinuity. Therefore a tuning parameter
CrvSatn is set to
compensate for this phenomenon. In the voltage interval Vpickup< down to Vpickup< ·
1MRK 511 365-UUS A
Section 9
Voltage protection
Phasor measurement unit RES670 2.1 ANSI 275
Technical manual