Datakom DKG-705 - 7.3 Soft Transfer

DATAKOM DKG-705 User’s Manual
705_USER.doc - 25 -
7.3 Soft Transfer
In this mode, the transfer will be made without interruption like the No Break Transfer mode. But
the load will not be transferred suddenly, instead of this it will be gradually transferred under GOV and
AVR control.
The AVR and GOV control are absolutely necessary to succeed a Soft Transfer.
With the basic DKG-705 unit, only a soft transfer from the genset to the mains is possible. The
transfer from mains to the genset will simply be a No Break Transfer.
With a full version of DKG-705 with mains current inputs, soft transfer in both directions are
allowed.
The Soft Transfer sequence starts like a No Break transfer. But when both contactors are
activated, the unit starts transferring the KW and KVAr load to the mains with predefined ramps. This
ramping is achieved with GOV and AVR control. The duration of the load transfer sequence is controlled
by the Soft Transfer Timer (P_A08).
The unit includes a comprehensive set of protection functions to detect quickly a mains failure
during parallel with mains operation. The protections are enabled after the timeout defined by the
parameter P_A23. These protections will be explained with more detail in the following chapter.
If a mains failure occurs during parallel with mains operation, the mains contactor will immediately
deenergize, a general Parallel Mains Fail warning and a specific protection function warning will be
generated.
At the end of the Soft Transfer Timer (P_A08) the generator contactor will be released. If any
alarm is encountered during the Soft Transfer sequence, the DKG-705 will revert to Interrupted transfer.
The DKG-705 has a set of programmable parameters to define the Soft Transfer operation. All
parameters used in No Break Transfer are also used in Soft Transfer. Additional parameters are:
P_A01 Soft Transfer Enable: This parameter enables/disables the Soft Transfer feature.
P_A08 Soft Transfer Timer: This is the time duration of the Soft Transfer. At the end of this timer one of
the contactors will release to terminate the parallel operation.
P_633 Mains Current Transformers: This parameter enables/disables the Soft Transfer from Mains to
Genset.
P_A18 KW Ramp: The load’s active power (KW) will be transferred to the mains with this rate.
P_A19 KVAr Ramp: The load’s reactive power (KVAr) will be transferred to the mains with this rate.
P_A20 KW Gain: This parameter defines the reaction speed of the KW control during soft transfer.
P_A21 KVAr Gain: This parameter defines the reaction speed of the KVAr control during soft transfer.
P_A23 Parallel Check Timeout: This is the delay after the mains contactor is energized (for parallel to
mains) and before the protections for mains failure are enabled.