Inverse Time, Directional Overcurrent Elements 67-Toc, 67N-Toc - Siemens SIPROTEC 7SJ62 Manual

Multi-functional protective relay with local control
Hide thumbs Also See for SIPROTEC 7SJ62:
Table of Contents

Advertisement

Functions
2.3 Directional Overcurrent Protection 67, 67N
Figure 2-24
Logic of the dropout delay for 67-1
2.3.4

Inverse Time, Directional Overcurrent Elements 67-TOC, 67N-TOC

Inverse time elements are dependent on the variant ordered. They operate either according to the IEC- or the
ANSI-standard or to a user-defined characteristic. The characteristics and associated formulas are identical
with those of the non-directional overcurrent protection and are given in the Technical Data. When the inverse
time curves are configured, the definite time relay elements (67-2, 67-1) are also available.
Pickup Behavior
For each element an individual pickup value 67-TOC PICKUP or 67N-TOC PICKUP is set, which can be mea-
sured as Fundamental or True RMS. Each phase and ground current is separately compared with the
common pickup value 67-TOC PICKUP or 67N-TOC PICKUP of each element. When a current value exceeds
the corresponding setting value by a factor of 1.1, the corresponding phase picks up and a message is signaled
phase-selectively assuming that the fault direction is equal to the direction configured. If the inrush restraint
feature is used, either the normal pickup signals or the corresponding inrush signals are issued as long as
inrush current is detected. If the 67-TOC element picks up, the time delay of the trip signal is calculated using
an integrating measurement scheme. The calculated time delay is dependent on the actual fault current flowing
and the selected tripping curve. Once the time delay elapses, a trip signal is issued assuming that no inrush
current is detected or inrush restraint is disabled. If the inrush restraint feature is enabled and an inrush condi-
tion exists, no tripping takes place but a message is recorded and displayed indicating when the overcurrent
element time delay elapses.
For ground current element 67N-TOC the characteristic may be selected independently of the characteristic
used for phase currents.
Pickup values of the67-TOC (phases) and 67N-TOC (ground current) and the associated time multipliers may
be set individually.
Dropout Behavior
When using an IEC or ANSI curve select whether the dropout of an element is to occur instantaneously after
the threshold has been undershot or whether dropout is to be performed by means of the disk emulation. "In-
stantaneously" means that pickup drops out when the pickup value of approx. 95 % of the set pickup value is
undershot. For a new pickup the time counter starts at zero.
The disk emulation evokes a dropout process (time counter is decrementing) which begins after de-energiza-
tion. This process corresponds to the reset of a Ferraris-disk (explaining its denomination "disk emulation"). In
case several faults occur in succession the "history" is taken into consideration due to the inertia of the Ferraris-
disk and the time response is adapted. Reset begins as soon as 90% of the setting value is undershot, in ac-
cordance to the dropout curve of the selected characteristic. In the range between the dropout value (95% of
the pickup value) and 90% of the setting value, the incrementing and the decrementing processes are in idle
state.
Disk emulation offers advantages when the overcurrent relay elements must be coordinated with conventional
electromechanical overcurrent relays located towards the source.
102
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008

Advertisement

Table of Contents
loading

Table of Contents