GE Industrial Solutions MX350 Instruction manual - Manual (Page 91)

CHAPTER 5: SETPOINTS CONTROL
MX350 AUTOMATIC TRANSFER CONTROL SYSTEM – INSTRUCTION MANUAL 5–17
• Manual S1-S2, S2-S1 (S12): In this mode, the controller will not automatically initiate a
transfer of the load from one source to the other. It will always wait for an operator
input before automatically transferring the load.
• Manual S2-S1 Only (S5): In this mode, the controller will automatically transfer the
load from S1 to S2, e.g. when a power outage occurs. However, it will only start the re-
transferring from S2 to S1 after it receives an operator input, or upon Source 2 failure.
Commit transfer to S2
(S13)
Depending on empirical data, a customer may want to assume that a brief outage is an
isolated event or that it is likely to be followed by another outage.
If the former is the case, the user should set the 'Commit Transfer to S2' to OFF. This will
start the generator, but the ATS will not transfer to the alternate source unless the outage
is still present the generator power has reached its nominal voltage and frequency and
when the 'Delay - Transfer to Nonpreferred Source' timer (W timer) has expired.
If the latter is the case, the user should set the 'Commit Transfer to S2' to ON. This will
ensure that the ATS will transfer to the alternate source if the outage is still present when
the generator power has reached its nominal voltage and frequency and the 'Delay -
Transfer to Nonpreferred Source' timer (W timer) has started timing.
Transition mode
select
NOTE
NOTE: Applicable only to Closed Transition types of ATS
If a power outage occurs, the MX350 controller will transfer the load to the alternate
source, once that source has become available. An interruption of power cannot be
avoided in this case. However, after the utility has returned and the T time has expired,
another brief power interruption due to the load transfer from one source to the other may
be undesirable.
If this is the case, the switch needs to be operated in Closed Transition mode. The
controller will then ensure that power to the load is not interrupted during the re-transfer
process.
Closed Transition may also be desirable for testing and exercising the switch so that power
interruptions to the switch load can be avoided during the transfer.
Alternatively, the user can select Delayed Transition mode as the normal mode of
operation.
Auto load shed Auto load shed
Range: Enabled, Disabled
Default: Disabled
Source 2 (normally the generator source) can be protected with the Auto Load Shed
feature.
By factory default this feature is disabled. If desired, it can be activated by changing the
parameter ‘S2 Auto Load Shed Underfrequency Set’ on the Settings > Operations > S2
Set screen from OFF to a valid frequency set point. For example, the user could enter a
value of 59.0 Hz as the trigger point for the Auto Load Shed feature.
Once a valid set point has been entered, the user will be presented with three more entry
fields. For example, the parameters could be set up as follows:
S2 Auto Load Shed Underfrequency Set (Hz) 59.0
S2 Auto Load Shed Underfrequency Delay (s) 3
S2 Auto Load Shed Undervoltage Set (%) 95
S2 Auto Load Shed Overpower Set (%) 103