Siemens siprotec SJ62 User Manual page 154

Pickup Stabilization
(Definite Time)
IEC Curves (Inverse
Time Tripping
Curve)
ANSI Curves (In-
verse Time Tripping
Curve)
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
The following fault currents may be detected at the low side:
If 46-1 PICKUP on the high side of the device is set to = 0.1 A, then a fault current of
· 46-1 PICKUP = 3 · 110/20 · 100 · 0.1 A = 165 A for single-phase
I = 3 · TR · TR
V I
faults and √3 · TR
· TR
V
at the low side. This corresponds to 36 % and 20 % of the transformer nominal current
respectively. It is important to note that load current is not taken into account in this
simplified example.
As it cannot be recognized reliably on which side the thus detected fault is located, the
delay time 46-1 DELAY must be coordinated with other downstream relays in the
system.
Pickup of the definite time elements can be stabilized by means of a configurable
dropout time. This dropout time is set in 4012 46 T DROP-OUT.
The thermal behavior of a machine can be closely replicated due to negative se-
quence by means of an inverse time tripping curve. In address 4006 46 IEC CURVE,
select out of three IEC curves provided by the device the curve which is most similar
to the thermal unbalanced load curve provided by the manufacturer. The tripping
curves of the protective relay, and the formulas on which they are based, are given in
the Technical Data.
It must be noted that a safety factor of about 1.1 has already been included between
the pickup value and the setting value when an inverse time characteristic is selected.
This means that a pickup will only occur if an unbalanced load of about 1.1 times the
setting value 46-TOC PICKUP is present (address 4008). The dropout is performed
as soon as the value falls below 95% of the pickup value.
The associated time multiplier is entered at address 4010, 46-TOC TIMEDIAL.
The time multiplier can also be set to ∞. After pickup the element will then not trip.
Pickup, however, will be signaled. If the inverse time element is not required at all,
address 140 46 should be set to Definite Time during the configuration of protec-
tive functions (Section 2.1.1.2).
Behavior of a machine due to negative sequence current can be closely replicated by
means of an inverse time tripping curve. In address 4007 the 46 ANSI CURVE, select
out of four ANSI curves provided by the device the curve which is most similar to the
thermal unbalanced load curve provided by the manufacturer. The tripping curves of
the protective relay, and the formulas on which they are based, are given in the Tech-
nical Data.
It must be noted that a safety factor of about 1.1 has already been included between
the pickup value and the setting value when an inverse time characteristic is selected.
This means that a pickup will only occur if an unbalanced load of about 1.1 times the
setting value is present. If Disk Emulation was selected at address 4011 46-TOC
RESET, reset will occur in accordance with the reset curve as described in the Func-
tional Description.
The unbalanced load value is set at address 4008 46-TOC PICKUP. The correspond-
ing time multiplier is accessible via address 4009 46-TOC TIMEDIAL.
The time multiplier can also be set to ∞. After pickup the element will then not trip.
Pickup, however, will be signaled. If the inverse time element is not required at all,
address 140 46 should be set to Definite Time during the configuration of protec-
tive functions (Section 2.1.1.2).
·46-1 PICKUP = 95 A can be detected for two-phase faults
I
2.7 Negative Sequence Protection 46
152