ABB Relion REQ650, Руководство по применению

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High impedance earthed systems
In high impedance earthed systems, earth-faults cause a voltage increase in the non-
faulty phases. OV2PTOV can be used to detect such faults. The setting must be above
the highest occurring "normal" voltage and below the lowest occurring voltage during
faults. A metallic single-phase earth-fault causes the non-faulted phase voltages to
increase a factor of √3.
The following settings can be done for Two step overvoltage protection
GlobalBaseSel : Selects the global base value group used by the function to define
( IBase ), ( UBase ) and ( SBase ).
ConnType: Sets whether the measurement shall be phase-to-earth fundamental value,
phase-to-phase fundamental value, phase-to-earth RMS value or phase-to-phase
RMS value.
Operation: Off/On .
OV2PTOV measures the phase-to-earth voltages, or phase-to-phase voltages as
selected. The function will operate if the voltage gets higher than the set percentage of
the global set base voltage
UBase . This means operation for phase-to-earth voltage
over:
( )
(%)
3
UBase kV
U
> ×
IEC09000054 V1 EN
(Equation 69)
and operation for phase-to-phase voltage over:
U (%) UBase(kV)
> ×
EQUATION1993 V1 EN
(Equation 70)
Characteristic1 : This parameter gives the type of time delay to be used. The setting
can be. Definite time/Inverse Curve A/Inverse Curve B/Inverse Curve C . The choice
is highly dependent of the protection application.
OpModen : This parameter describes how many of the three measured voltages that
should be above the set level to give operation for step n (n=step 1 and 2). The setting
can be
1 out of 3, 2 out of 3 or 3 out of 3 . In most applications it is sufficient that one
phase voltage is high to give operation. If the function shall be insensitive for single
phase-to-earth faults
3 out of 3 can be chosen, because the voltage will normally rise
in the non-faulted phases at single phase-to-earth faults.
Un> : Set overvoltage operating value for step n (n=step 1 and 2), given as % of the
global parameter UBase . The setting is highly dependent of the protection application.
Here it is essential to consider the Maximum voltage at non-faulted situations.
Normally this voltage is less than 110% of nominal voltage.
tn : time delay for step n (n=step 1 and 2), given in s. The setting is highly dependent
of the protection application. In many applications the protection function has the task
Section 7
1MRK 505 291-UEN A
Voltage protection
160
Application manual