Measurement Principle - ABB REL650 series Technical Manual

Section 8
Voltage protection
8.1.7.1
8.1.7.2
296
UV2PTUV (27) can be set to measure phase-to-ground fundamental value, phase-to-
phase fundamental value, phase-to-ground true RMS value or phase-to-phase true RMS
value. The choice of the measuring is done by the parameter ConnType. The voltage
related settings are made in percent of base voltage which is set in kV phase-to-phase
voltage. This means operation for phase-to-ground voltage under:
< ×
Vpickup (%) VBase kV ( )
EQUATION1606 V1 EN
and operation for phase-to-phase voltage under:
< ×
Vpickup (%) VBase(kV)
EQUATION1991-ANSI V1 EN
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

Depending on the set ConnType value, UV2PTUV (27) measures phase-to-ground or
phase-to-phase voltages and compare against set values, Pickup1 and Pickup2. 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 lower than
the corresponding set point to issue the corresponding PICKUP signal.
To avoid oscillations of the output PICKUP signal, a hysteresis has been included.
Time delay
The time delay for step 1 can be either definite time delay (DT) or inverse time
undervoltage (TUV). 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:
TD
=
t
< -
Vpickup V
<
Vpickup
ANSIEQUATION1431 V1 EN
3
1MRK 506 335-UUS A
(Equation 71)
(Equation 72)
(Equation 73)
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