ABB Relion RES670, Technical Manual

Page: 282 / 934

9.1.7 Operation principle
M15326-3 v9
Two-step undervoltage protection (UV2PTUV ,27) is used to detect low power system
voltage. If one, two or three phase voltages decrease below the set value, a
corresponding START signal is generated. The parameters
OpMode1 and OpMode2
influence the requirements to activate the PICKUP outputs: 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.
UV2PTUV (27) has two voltage-measuring steps with separate time delays. If the
voltage remains below the set value for the chosen time delay, the corresponding trip
signal is issued. To avoid an unwanted trip due to the disconnection of the related high-
voltage equipment, a voltage-controlled blocking of the function is available: if the
voltage is lower than the set blocking level, the function is blocked and no PICKUP or
TRIP signal is generated. The time delay characteristic is individually chosen for each
step and can be either definite time delay or inverse time delay.
To avoid oscillations of the output PICKUP signal, a hysteresis has been included.
9.1.7.1 Measurement principle
M15326-6 v7
Depending on the set ConnType value, UV2PTUV (27) measures either phase-to-
ground voltage or phase-to-phase voltage and compares it against the set values,
Pickup1 and Pickup2 . The voltage-related settings are made in percentage of the base
voltage which is set in kV phase-to-phase voltage. This means operation for phase-to-
ground voltage under:
(%) ( )
3
Vpickup VBase kV
< ×
EQUATION1606 V1 EN-US
(Equation 48)
and operation for phase-to-phase voltage under:
Vpickup (%) VBase(kV)
< ×
EQUATION1991-ANSI V1 EN-US
(Equation 49)
When the phase-to-ground voltage measurement is selected, the
function automatically introduces division of the base value by the
square root of three.
Section 9
1MRK 511 408-UUS A
Voltage protection
276 Phasor measurement unit RES670 2.2 ANSI
Technical manual