ABB Relion 670 series, Technical Reference Manual

Page: 525 / 1232

8.3.2.1 Measurement principle
The residual voltage is measured continuously, and compared with the set values,
Pickup1 and Pickup2 .
To avoid oscillations of the output PICKUP signal, a hysteresis has been included.
8.3.2.2 Time delay
The time delay for the two steps can be either definite time delay (DT) or inverse time
delay (TOV). For the inverse time delay four different modes are available:
• inverse curve A
• inverse curve B
• inverse curve C
• customer programmable inverse curve
The type A curve is described as:
TD
t
V Vpickup
Vpickup
=
æ ö
- >
ç ÷
>
è ø
ANSIEQUATION2422 V1 EN
(Equation 130)
where:
Un> Set value for step 1 and step 2
U Measured voltage
The type B curve is described as:
2.0
480
0.035
32 0.5
TD
t
V Vpickup
Vpickup
×
= -
æ ö
- >
× -
ç ÷
>
è ø
ANSIEQUATION2423 V1 EN
(Equation 131)
The type C curve is described as:
3.0
480
0.035
32 0.5
TD
t
V Vpickup
Vpickup
×
= +
æ ö - >
× -
ç ÷
>
è ø
ANSIEQUATION2421 V1 EN
(Equation 132)
The customer programmable curve can be created as:
1MRK505222-UUS C
Section 8
Voltage protection
519
Technical reference manual