Table of Contents
Advertisement
2.22.2
Setting Notes
General
Overvoltage protection is only effective and available if this function was set during protective function config-
uration (Section 2.4, address 141, OVERVOLTAGE is set to Enabled. If the function is not required Disabled
is set. Address 4101 OVERVOLTAGE serves to switch the function ON or OFF or to block only the trip command
(Block relay).
Settings
Address 4107 VALUES serves to specify the measured quantities used by the protection feature. The default
setting (normal case) is specified for phase-to-phase voltages (= U-ph-ph). The phase-earth voltages should
be selected for low-voltage machines with grounded neutral conductor (= U-ph-e). It should be noted that even
if phase-earth voltages are selected as measured quantities, the setting values of the protection functions refer
to phase-to-phase voltages.
The setting of limit values and time delays of the overvoltage protection depends on the speed with which the
voltage regulator can regulate voltage variations. The protection must not intervene in the regulation process
of the faultlessly functioning voltage regulator. For this reason, the two-stage characteristic must always be
above the voltage time characteristic of the regulation procedure.
The long-time stage 4102 U> and 4103 T U> must intervene in case of steady-state overvoltages. It is set to
approximately 110 % to 115 % U
In case of a full-load rejection of the generator, the voltage increases first in relation to the transient voltage.
Only then does the voltage regulator reduce it again to its nominal value. The U>> stage is set generally as a
short-time stage in a way that the transient procedure for a full-load rejection does not lead to a tripping. For
example, for 4104 U>> about 130% U
All setting times are additional time delays which do not include the operating times (measuring time, dropout
time) of the protective function.
The dropout ratio can be adapted at the address 4106 DOUT RATIO in small stages to the operating conditions
and used for highly precise signalizations (e.g. network infeed of wind power stations).
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
and, depending on the regulator speed, to a range between 1.5 s and 5 s.
N
with a delay 4105 T U>> of zero to 0.5 s are typical values.
N
2.22 Overvoltage Protection (ANSI 59)
Functions
179
Advertisement
Table of Contents
