Measurement Principle; Time Delay - ABB RET650 Technical Manual

Section 9
Voltage protection
9.1.7.1
9.1.7.2
206
U (%) UBase kV ( )
< ⋅
EQUATION1429 V2 EN
and operation for phase-to-phase voltage under:
< ×
U (%) UBase(kV)
EQUATION1990 V1 EN
When phase-to-earth voltage measurement is selected the function
automatically introduces division of the base value by the square root
of three.

Measurement principle

Depending on the set ConnType value, UV2PTUV measures phase-to-earth or phase-
to-phase voltages and compare against set values, U1< and U2<. The parameters
OpMode1 and OpMode2 influence the requirements to activate the START outputs.
Either 1 out of 3, 2 out of 3, or 3 out of 3 measured voltages have to be lower than the
corresponding set point to issue the corresponding START signal.
To avoid oscillations of the output START signal, a hysteresis has been included.

Time delay

The time delay for step 1 can be either definite time delay (DT) or inverse time delay
(IDMT). Step 2 is always definite time delay (DT). For the inverse time delay two
different modes are available; inverse curve A and inverse curve B.
The type A curve is described as:
k
=
t
æ ö
< -
U U
n
ç ÷
<
U
è ø
n
EQUATION1431 V2 EN
The type B curve is described as:
×
k 480
=
t
æ
< -
U U
n
× -
32 0.5
ç
<
U
è
n
EQUATION1432 V2 EN
3
+
0.055
2.0
ö
÷
ø
1MRK 504 135-UEN A
(Equation 67)
(Equation 68)
(Equation 69)
(Equation 70)
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