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M-4272 Digital Motor Bus Transfer System
* NOTE: The 'new source' is defined as the source to which the bus is being transferred.
The M-4272 Digital Motor Bus Transfer System provides Automatic and Manual Transfers. The Fast Transfer,
Delayed In-Phase Transfer, and Residual Voltage Transfer methods are activated at the same time, if enabled. If
the conditions for the Fast Transfer are not met, then the Delayed In-Phase Transfer or the Residual Voltage
Transfer will be attempted. The Fixed Time Transfer is also provided if during a transfer operation, it is not
possible to monitor the motor bus voltage (due to Bus VT fuse loss, for example). The Delayed In-Phase
Transfer, Residual Voltage Transfer, and Fixed Time Transfer methods can be selectively disabled. The
Automatic or Manual Transfer operation can be blocked by control/status input or remote serial communications.
See Figure 2 for Typical Application of Motor Bus Transfer Systems.
Automatic Transfer
Automatic Transfer can be initiated by an external protection trip signal (86P) or an external undervoltage function
(27) using control/status input to the Motor Bus Transfer System (MBTS) device or triggered by a sudden loss of
motor bus supply voltage using the internal bus undervoltage relay (27B Function). Automatic Transfer allows
transfer operation in both directions: from Source 1 to Source 2, and vice-versa. The Automatic Transfer provides
Fast Transfer, Delayed In-Phase Transfer, Residual Voltage Transfer and Fixed Time Transfer. The Automatic
Transfer is blocked when any lockout/blocking condition occurs. The MBTS will not respond to any transfer
command and will not send the trip command while in the lockout/blocking condition.
Manual Transfer
Manual transfer can be initiated by using the local Human-Machine Interface (HMI), from a control/status input or
through remote serial communications. The Manual Transfer allows transfer operation in either direction: from
Source 1 to Source 2, and vice versa. Manual Transfer provides Hot Parallel Transfer or a combination of Fast
Transfer, Delayed In-Phase Transfer and Residual Voltage Transfer. The Manual Transfer is blocked when any
lockout/blocking condition occurs. The MBTS will not respond to any transfer command and will not send the trip
command while in the lockout/blocking condition.
Transfer Modes
There are two transfer modes, Sequential and Simultaneous, in the open transition transfer operation.
Sequential Transfer Mode
Once a transfer is initiated, and if the Sequential Mode is selected, the old source breaker is tripped within 10 ms
and closure of the new source* breaker is attempted only upon confirmation by the breaker status contact that the
old source breaker has opened. Within 4 ms of receipt of this confirmation, all three methods, Fast, Delayed In-
Phase and Residual Voltage Transfer are enabled to supervise closure of the new source* breaker, and the Fixed
Time Transfer is enabled 30 cycles later. The new source* breaker is then closed by the Fast Transfer Method if
the phase angle between the motor bus and the new source* is within the delta phase angle limit immediately
after the old source breaker opens.
If the phase angle between the motor bus and the new source* is not within the delta phase angle limit, the old
source breaker is still tripped. When the four methods of transfer are enabled, the new source* breaker then
closes either as a result of a subsequent movement into the delta phase angle limit within the Fast Transfer Time
Window, a movement through a predicted zero phase coincidence within the Delayed In-Phase Transfer Time
Window, or by a drop in the motor bus voltage below the Residual Voltage Transfer limit, or after the fixed time
delay of the Fixed Time Transfer. Transfer is completed and the new source* breaker is closed by any of the
above methods whose criteria is first satisfied.
Refer to Figure 3 for Timing Sequence of Transfer Logic in Sequential Transfer Mode.
Simultaneous Transfer Mode
Alternatively, once a transfer is initiated, and if the Simultaneous Mode is selected, within 10 ms of transfer
initiate, all three methods of transfer, Fast, Delayed In-Phase and Residual Voltage Transfer are immediately
enabled to supervise closure of the new source* breaker without waiting for the breaker status contact
confirmation that the old source breaker has opened. At the same instant, the commands for the old source
breaker and the new source* breaker to trip and close are sent simultaneously if and only if the phase angle
between the motor bus and the new source* is within the delta phase angle limit for the Fast Transfer Method
immediately upon transfer initiation. However only the Fixed Time Transfer is enabled 30 cycles after the old
source breaker has opened.
If the phase angle between the motor bus and the new source* is not within the delta phase angle limit, the old
source breaker is still tripped. When the four methods of transfer are enabled, the new source* breaker then
Содержание M-4272
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