Output Contact Delay Time; Setting Dtl Times - Siemens 7SG11 Technical Manual

2.3 Output Contact Delay Time

The output relay contacts have a typical close response time of 7ms.This inherent delay is not,
however, the only factor determining the actual contact closure time. The relay has a main software
control loop of 10ms. Any software decision or external interrupt to the microcontroller involves a
maximum possible delay of 10ms while the software completes the loop. This time should be added to
the contact closure time of 7ms to give a maximum response time.
e.g. - if an energisation signal is applied to a status input which is programmed to directly operate an
output relay the following delays should be added:
Status I/P response time (< 5ms) + Status PU delay setting + S/W loop (max. 10ms) + O/P contact
closure (typically 7ms).
This gives a total time of < 22ms + Status PU delay setting.

2.4 Setting DTL Times

When applying a DTL timer with any of the protection elements the instantaneous operate time of the
element will have to be determined so that the overall required time delay can be set.
Total Delay Time = Instantaneous Operate Time + DTL Time
The performance specification - Section 2 of this manual gives typical instantaneous operate times for
all of the different characteristics. The instantaneous operate time of an under voltage element for
example can vary between < 65ms to about 47ms at its fastest. This variation is due to the level of
applied undervoltage and is in fact a function of the method of calculation.
Note that the instantaneous operate time of an undervoltage element is marginally slower than that for
an equivalent overvoltage element. This is because the undervoltage element is deliberately 'slugged'
so that, when nominal voltage is applied, the RMS calculation has time to ramp up to the correct level
without issuing an invalid trip during the ramp up sequence. This is shown in the diagram below:
Nominal Volts
U/V Setting
©2011 Siemens Protection Devices Limited
Volts
V block
Threshold
0V
7SG11 Argus 8 Applications Guide
RMS
ramp-up
Operate
U/V element will
not operate in this
region
time
Chapter 5 Page 3 of 16