Functions
2.17 Flexible Protection Functions
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
292
Note
With single-phase voltage protection, the configured voltage threshold is always interpreted as voltage at the
terminal. The parameterization in 213
VT Connect. 3ph
(see Power System Data 1) is ignored here.
The forward direction of power (P forward, Q reverse) is the direction of the line. Parameter (
1108
P,Q sign
)
for sign inversion of the power display in the operating measured values is ignored by the flexible functions.
Via parameter
PICKUP WITH
it is determined whether the function must be triggered on exceeding or under-
shooting of the set threshold value.
Settings
The pickup thresholds, delay times and dropout ratios of the flexible protection function are set in the „Settings“
dialog box in DIGSI.
The pickup threshold of the function is configured via parameter
P.U. THRESHOLD
. The OFF-command delay
time is set via parameter
T TRIP DELAY
. Both setting values must be selected according to the required ap-
plication.
The pickup can be delayed via parameter
T PICKUP DELAY
. This parameter is usually set to zero (default
setting) in protection applications, because a protection function should pick up as quickly as possible. A setting
deviating from zero may be appropriate if a trip log is not desired to be started upon each short-term exceeding
of the pickup threshold, for example, with power protection or when a function is not used as a protection, but
as a monitoring function.
When setting the power threshold values, it is important to take into consideration that a minimum current of
0.03
I
N
is required for power calculation. The power calculation is blocked for lower currents.
The dropout of pickup can be delayed via parameter
T DROPOUT DELAY
. This setting is also set to zero by
default (standard setting) A setting deviating from zero may be required if the device is utilized together with
electro-magnetic devices with considerably longer dropout ratios than the digital protection device (see Chapter
2.2 for more information). When utilizing the dropout time delay, it is recommended to set it to a shorter time
than the OFF-command delay time in order to avoid both times to "race".
Parameter
BLK.by Vol.Loss
determines whether a function whose measured variable is based on a voltage
measurement (measured quantities voltage, P forward, P reverse, Q forward, Q reverse and power factor),
should be blocked in case of a measured voltage failure (set to
YES
) or not (set to
NO
).
The dropout ratio of the function can be selected in parameter
DROPOUT RATIO
. The standard dropout ratio
of protection functions is 0.95 (default setting). If the function is used as power protection, a dropout ratio of at
least 0.9 should be set. The same applies to the utilization of the symmetrical components of current and volt-
age. If the dropout ratio is decreased, it would be sensible to test the pickup of the function regarding possible
"chatter".
The dropout difference of the frequency elements is set under parameter
DO differential
). Usually, the
default setting of 0.02 Hz can be retained. A higher dropout difference should be set in weak systems with
larger, short-term frequency fluctuations to avoid chattering of the message.
The frequency change element (df/dt) works with a fixed dropout differential.
Renaming Messages, Checking Configurations
After parameterization of a flexible function, the following steps should be noted:
• Open matrix in DIGSI
• Rename the neutral message texts in accordance with the application.
• Check configurations on contacts and in operation and fault buffer, or set them according to the require-
ments.
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