Siemens siprotec 7SA6 User Manual page 369

Adaptive
Dead Time (ADT)
7SA6 Manual
C53000-G1176-C133-1
earth,above which the line is considered to be fault-free. It must be set smaller than
the smallest expected operating voltage. The setting is applied in Volts secondary.
This value can be entered as a primary value when parametrizing with a PC and
®
4. Address  7 8VWDEOH determines the measuring time available for
DIGSI
determining this voltage. It should be longer than any transient oscillations resulting
from line energisation. Address  is irrelevant here.
When operating with adaptive dead time, it must initially be ensured that one end per
line operates with defined dead times and has an infeed. The other (or the others in
multi-branch lines) may operate with adaptive dead time. It is essential that the voltage
transformers are located on the line side of the circuit breaker. Details about this
function can be found in section 6.12.1 under subtitle "Adaptive Dead Time (ADT)" on
page 6-176.
For the line end with defined dead times the number of desired reclose cycles must be
set during the configuration of the protective functions (section 5.1) under address
 $XWR 5HFORVH. For the devices operating with adaptive dead time $XWR
5HFORVH = $GDSWLYH 'HDG 7LPH $'7 must be set during the configuration of
the protective functions (section 5.1) under address . Only the parameters
described below are interrogated in the latter case. No settings are then made for the
individual reclosure cycles. The adaptive dead time implies functionality of reduced
dead time.
The adaptive dead time may be controlled by return voltage or by the remote–
CLOSE–command. Both is possible at the same time. In the first case reclosure takes
place as soon as the return voltage, after reclosure at the remote end, is detected. For
this purpose the device must be connected to voltage transformers located on the line
side of the circuit breaker. In the case of remoteCLOSE, the device waits until the
remoteCLOSE command is received before issuing the reclose command.
The action time 7$&7,21 $'7 (address ) is the time after a pick-up by a
protection function which is able to activate the automatic reclosure within which the
trip command must occur. If the command does not appear until after the action time
has expired, there is no reclosure. Depending on the configuration of the protection
functions (see section 5.1) the action time may also be omitted; this particularly
applies when an initiating protection function has no fault detection signal (only trip
signal).
The dead times are determined by the reclosure command of the device at the line
end with the defined dead times. In cases where this reclosure command does not
appear, e.g. because the reclosure was in the mean time blocked there, the readiness
of the local device must return to the quiescent state at some time. This takes place
after the maximum wait time 70$; $'7 (address ). This must be long enough
to include the last reclosure of the remote end. In the case of single-shot reclosure,
the sum total of maximum dead time plus reclaim time of the other device is sufficient.
In the case of multiple reclosure the worst case is that all reclosures of the other end
except the last one are unsuccessful. The time of all these cycles must be taken into
account. To save having to make exact calculations, it is possible to use the sum of all
dead times and all protection operating times plus one reclaim time.
Under address  $'7 S DOORZHG it can be determined whether single-pole
tripping is allowed (on condition that single-pole tripping is possible). If 1R, the
protection trips three-pole for all fault types. If <HV the tripping capability of the
initiating protection functions is decisive.
Under address  $'7 &%" &/26( it can be determine whether circuit-breaker
ready is interrogated before reclosure after an adaptive dead time. If set to <HV the
dead time may be extended if at the end of the dead time the circuit-breaker is not
Functions
6-187