Measurement Principle - ABB Relion Technical Manual

1MRK 502 048-UUS A
9.2.7.1
9.2.7.2
Technical manual
When phase-to-ground voltage measurement is selected the function
automatically introduces division of the base value by the square root of
three.

Measurement principle

All the three voltages are measured continuously, and compared with the set values,
Pickup1 for Step 1 and Pickup2 for Step 2. The parameters OpMode1 and OpMode2
influence the requirements to activate the PICKUP outputs. Either 1 out of 3, 2 out of 3 or
3 out of 3 measured voltages have to be higher than the corresponding set point to issue the
corresponding PICKUP signal.
To avoid oscillations of the output PICKUP signal, a hysteresis is included.
Time delay
The time delay for step 1 can be either definite time delay (DT) or inverse time overvoltage
(TOV). Step 2 is always definite time delay (DT). For the inverse time delay three
different modes are available:
• inverse curve A
• inverse curve B
• inverse curve C
The type A curve is described as:
TD
=
t
− >
V Vpickup
>
Vpickup
EQUATION1625 V2 EN
The type B curve is described as:
⋅
TD 480
= −
t
− >
V Vpickup
⋅ −
32 0 5 .
>
Vpickup
ANSIEQUATION2287 V2 EN
The type C curve is described as:
⋅
TD 480
= +
t
− >
V Vpickup
⋅ −
32 0 5 .
>
Vpickup
ANSIEQUATION2288 V2 EN
0 035 .
0 035 .
Section 9
Voltage protection
(Equation 81)
(Equation 82)
(Equation 83)
291