Application And Setting Notes - Siemens 7SJ82 Manual

Protection and Automation Functions
6.15 Sensitive Ground-Fault Detection
In many applications, the transient ground-fault stage is used only to indicate the direction. In this case, the
trip logic is not required and remains disabled. However, this stage can also be used to disable a permanent
ground fault. For this, you enable the optional trip logic with the Operate functionality parameter. If
the fundamental-component values V0 and 3I0 exceed the set threshold values, the tripping delay (Operate
delay parameter) starts with the pickup. If the parameter Operate & flt.rec. blocked is set to no, the
stage operates when the tripping delay expires.
An intermittent ground fault has the characteristics of periodical extinction and reignition within one half
period up to several periods. You can find more information in chapter
the tripping delay and the too short fault durations (contact to ground), reliable tripping is not possible. To
ensure reliable tripping under such conditions, the parameter Dropout delay can be used. When the fault
extinguishes, the fundamental values of V0 and 3I0 drop below the threshold values. A dropout can be
delayed for a time specified with the Dropout delay parameter. The tripping delay continues to run. If the
time delay expires within the dropout delay, the stage operates. You can set the Dropout delay according
to the application. The default setting is 0 s. The setting of the dropout delay does not affect the direction
determination. When the fault reignites, a new direction determination takes place if the function has
dropped out before. If the determined direction is opposite to the parameterized direction or is unknown, the
tripping delay is reset immediately.
Blocking the Tripping Delay with Detection of the Fault Extinction
Using the evaluation of the instantaneous value cycle of the zero-sequence voltage, the fault extinction of the
ground fault can be detected faster than via the dropout of the V0 fundamental-component value under the
pickup value. The fast detection of the fault extinction (see function block General information) blocks the
tripping delay after the dropout delay expires. With the parameter Blk. after fault extinction, this
accelerated blocking mechanism can be enabled or disabled.
6.15.5.2

Application and Setting Notes

Parameter: Operate functionality
•
Default setting (_:13021:108) Operate functionality = no
If the transient ground-fault stage is used only to indicate the direction, this optional trip logic is not required
and remains disabled. If the transient ground-fault stage is used to disable permanent faults as well, this
optional trip logic is enabled. Pickup of the stage will initiate the tripping delay.
Parameter: Operate & flt.rec. blocked
•
Default setting (_:13021:2) Operate & flt.rec. blocked = no
You can block the operate indication, the fault recording, and the fault log with the Operate & flt.rec.
blocked parameter. In this case, a ground-fault log is created instead of the fault log.
Parameter: Blk. by meas.-volt. failure
•
Recommended setting value (_:13021:10) Blk. by meas.-volt. failure = yes
You use the Blk. by meas.-volt. failure parameter to control the behavior of the stage when a
measuring-voltage failure is detected.
A measuring-voltage failure can only be detected if one of the following 2 conditions is met:
•
The device-internal supervision function Measuring-voltage failure detection is configured and
enabled.
•
The binary input signal
the voltage-transformer circuit breaker.
Parameter Value
yes
no
582
>Open of the function block Voltage-transformer circuit breaker is linked with
Description
The protection stage is blocked (= default setting). Siemens recommends
using the default setting.
The protection stage is not blocked.
6.14.1 Overview of Functions. Due to
SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017