Siemens Siprotec 7VK61 Manual page 76

Functions
2.3 Overcurrent protection (optional)
The set times are mere additional delays for the independent stages, which do not include the inherent oper-
ating time of the protection. If only the phase currents are to be monitored, set the pickup value of the earth
fault stage to ∞.
The parameter I> Telep/BI (address 2624) defines whether the time delays T Iph> (address 2621) and
T 3I0> (address 2623) can be bypassed by the binary input „>O/C InstTRIP". The binary input (if allocat-
ed) is applied to all stages of the time-overcurrent protection. With I> Telep/BI = YES you define that the I>
stages trip without delay after pickup if the binary input was activated. For I> Telep/BI = NO the set delays
are always active.
If the I> stage, when switching the line on to a fault, is to trip without delay or with a short delay, SOTF Time
DELAY (address 2680, see above under margin heading „General"), the parameter I> SOTF (address 2625)
is set to YES. We recommend, however, not to choose the sensitive setting for the switch on to a fault function
as energizing of the line on to a fault should cause a large fault current. It is important to avoid that the selected
stage picks up due to transients during line energization.
Overcurrent StagesI , 3I
P
In the case of time inverse overcurren stages, various characteristics can be selected, depending on the order-
ing version of the device and the configuration (address 126), with IEC characteristics (address 126 Back-Up
O/C = TOC IEC) the following options are available in address 2660 IEC Curve:
Normal Inverse (inverse, type A according to IEC 60255-3),
Very Inverse (very inverse, type B according to IEC 60255-3),
Extremely Inv. (extremely inverse, type C according to IEC 60255-3), and
LongTimeInverse (longtime, type B according to IEC 60255-3).
For the setting of the current thresholds Ip> (address 2640) and 3I0p PICKUP (address 2650) the same
considerations as for the overcurrent stages of the definite time protection (see above) apply. In this case, it
must be noted that a safety margin between the pickup threshold and the set value has already been incorpo-
rated. Pickup only occurs at a current which is approximately 10°% above the set value.
The above example shows that the maximum expected operating current may directly be applied as setting
here.
Primary: Set value IP = 630 A,
Secondary: Set value IP = 5.25 A, i.e. (630 A/600 A) X 5 A.
The time multiplier to be set T Ip Time Dial (address 2642) results from the grading coordination chart
created for the system.
The time multiplier setting T 3I0p TimeDial (address 2652) can usually be set smaller according to a sep-
arate earth fault grading plan. If only the phase currents are to be monitored, set the pickup value of the earth
fault stage to ∞.
In addition to the current-dependent delays, a time fixed delay can be set, if necessary. The settings T Ip Add
(address 2646 for phase currents) and T 3I0p Add (address 2656 for earth currents) are in addition to the
time delays resulting from the set curves.
The parameter I(3I0)p Tele/BI (address 2670) defines whether the time delays T Ip Time Dial (ad-
dress 2642), including the additional delay T Ip Add (address 2646), and T 3I0p TimeDial (address
2652), including the additional delay T 3I0p Add (address 2656), can be bypassed by the binary input „>O/C
InstTRIP" (No. 7110). The binary input (if allocated) is applied to all stages of the time-overcurrent protection.
With I(3I0)p Tele/BI = YES you define that the IP stages trip without delay after pickup if the binary input
was activated. For I(3I0)p Tele/BI = NO the set delays are always active.
If the IP stage, when switching the line on to a fault, is to trip without delay or with a short delay, SOTF Time
DELAY (address 2680, see above under margin heading „General"), the parameter I(3I0)p SOTF (address
2671) is set to YES. We recommend, however, not to choose the sensitive setting for the switch on to a fault
76
for inverse time overcurrent protection with IEC characteristics
0P
SIPROTEC, 7VK61, Manual
C53000-G1176-C159-3, Release date 05.2009