ABB Relion 670 Series RES670, Техническое руководство

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9.1.7 Operation principle
Two-step undervoltage protection (UV2PTUV ,27) is used to detect low power system
voltage. UV2PTUV (27) has two voltage measuring steps with separate time delays. If
one, two or three phase voltages decrease below the set value, a corresponding PICKUP
signal is generated. UV2PTUV (27) can be set to PICKUP/TRIP based on
1 out of 3 , 2 out
of 3 or 3 out of 3 of the measured voltages, being below the set point. If the voltage remains
below the set value for a time period corresponding to the chosen time delay, the
corresponding trip signal is issued. To avoid an unwanted trip due to disconnection of the
related high voltage equipment, a voltage controlled blocking of the function is available,
that is, 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.
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:
(%) ( )
3
Vpickup VBase kV
< ×
EQUATION1606 V1 EN
(Equation 48)
and operation for phase-to-phase voltage under:
Vpickup (%) VBase(kV)
< ×
EQUATION1991-ANSI V1 EN
(Equation 49)
When phase-to-ground voltage measurement is selected the function
automatically introduces division of the base value by the square root of
three.
9.1.7.1 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.
Section 9
1MRK 511 365-UUS A
Voltage protection
274 Phasor measurement unit RES670 2.1 ANSI
Technical manual