motor bus transfer
TRANSCRIPT
M M M
IntroductionTo maintain plant operation and process continuity, motor buses may require transfer from a present (old) source to a new source:
- Power plants- Industrial facilities
Motor Bus Transfer (MBT) schemes and systems are employed to maintain process continuity in processes served by large motors or aggregates of smaller and large motors.
Larger motors, of both the synchronous and induction variety, may require comprehensive, integrated source transfer strategies in order to avoid mechanical damage.
Motor Bus Transfer
The coast down period and resultant voltage and frequency decay may take seconds, and unsupervised source transfer may cause damage.
During improper transfer, mechanical damage may occur in the motor, the coupling to the load or the load itself, and is primarily caused by excessive shaft torque.
The total mission of a MBT system is not only to maintain process continuity but also to effect source transfers so as not to causeany damage to the motors and connected loads.
Introduction
Motor Bus Transfer
Why Transfer Motor Load Sources?
Fault on present supply
Interruption on present supply
For power supply security, transfer to on-site source when storm approaches
Plant Start Up and Shut Down
Maintenance
Motor Bus Transfer
Unit-Connected Generator Motor Bus
MMM
Motor Bus
Unit AuxTransformer
StartupTransformer
G
GSUTransformer
OtherLoadMOTOR BUS VT
MAIN VT STARTUP VT
NONC
Motor Bus Transfer
VT-M VT-SU
VT-B52M
STATION BUS SYSTEM
STARTUP SOURCE
N.C.
M
CT-M
N.O. 52SU
CT-SU
UNIT AUXILIARYTRANSFORMER
STATION SERVICETRANSFORMER
MAIN SOURCE
M
M-4272
Two-Breaker Configuration
Motor Bus Transfer
Combined Cycle Plant Motor Bus
Motor Bus Transfer
Typical Industrial Plant One-Line
MMM
Bus 1Supply Source
(Bus 2 Backup Source)
Bus 2Supply Source
(Bus 1 Backup Source)
M M M
UtilitySupply SystemIncoming 1 Incoming 2
NC NC
NO
Bus TieBus 1 Bus 2BUS 1 VT BUS 2 VT
INCOMING 1 VT
INCOMING 2 VT
Motor Bus Transfer
STATION BUS SYSTEM
N.C.52M1
VT-B1
NORMAL SOURCE (Main 1 )
N.C. 52M2
VT-M2
ALTERNATE SOURCE (Main 2)
BUS 1 BUS 2
VT-B2
52T
N.O.
BUS-TIE
VT-M1
CT-M1 CT-M2
CT-B1 CT-B2
TRANSFORMERNORMAL SOURCE ALTERNATE SOURCE
TRANSFORMER
M-4272 M-4272
M M M M
Three-Breaker Configuration(Main-Tie-Main)
Motor Bus Transfer
Conditions across Normally Open Startup or Bus Tie Breaker?
Immediately prior to Transfer Initiate- Effects of a Fault - System faults can cause the internal electrical
angles of motors to differ from new source (i.e., single-phase faults)
- System Separation between Transmission or Distribution Incoming Supply Sources
- Supply Source Transformer Winding Phase Shift
Immediately after Transfer Initiate, but prior to closure of Startup Source Breaker- Transient Effects upon Disconnect of Motor Loads
Motor Bus Transfer
Motor Bus Transfer
G
MM
MM
MM
M MM
MM
MM
MMM
M M M MM
500kVTransmissionSystem
230kVTransmissionSystem
NC NC NC NC NO NO NO NO
Unit Aux.Transformer
StartupTransformer
Unit 3
3-phase fault
NuclearPowerPlant
29°angular differencewith a 3-phase faultat CR3 500kV BusG
RCP RCP RCP RCP
32Miles
Unit 5
Motor Bus Transfer
G
Load Load
802 MVA22.5 kV50 Hz
Standing angleof at least 30°
786 MVA525 kV / 22.5 kV
W2 (525 kV)
W1 (22.5 kV)
Ynd11 (YΔ )AB
W1 W154 MVA
22.5 kV / 10.5 kV54 MVA
22.5 kV / 10.5 kV
W2 W2
Dyn11 Dyn11 (D Y )AC
30°W1 (22.5 kV)
W2 (525 kV)
30°W2 (10.5 kV)
W1 (22.5 kV)
60°W1 (10.5 kV)
525 kV 525 kVW2 (525 kV)
W2 (525 kV)W1 (10.5 kV)
Motor Bus Transfer
Load
YnYno
115 kV New
115 kV / 6.9 kV30 MVA
Load
YnYno
Angle = 23°
69 kV / 6.9 kV15 MVA
69 kV
Petrochemical Plant
Transient Effects upon Disconnect of Motor Loads
Essentially instantaneous phase shift upon disconnect of Motor.- Simulation based on 7,860 hp Induction Motor operating at full
load supplied from 11,550 Vac bus.
- Instantaneous phase shift of 9 to 10 degrees in the slow direction calculated upon disconnect.
- Effect is additive to conditions occurring due to other causes.
- Effect is followed by subsequent frequency decay, the speed of which is dependent on inertia and loading of motor.
Same effect occurs upon disconnect subsequent to a bus fault.
Motor Bus Transfer
Phase Angle and Motor Bus Voltage Characteristics
Phase angle rate of change (caused by deceleration of the motors during transfer) and the rate of voltage decay determined by the type of motors in use and the type of loads being driven.
Motor Bus Transfer
Coast Down of Low Inertia Load on a Large Induction Motor
Motor Bus Transfer
Motor & Load Characteristics:Effects on MBT
Motor Size: The larger the motor, the longer the time the voltage will take to decay on an induction motor.
Loading: The higher the load on the motors, the faster the motor bus frequency will decay.
Inertia: The higher the inertia of the aggregate motor loads on the motor bus, the more slowly the motor bus frequency will decay during the disconnected coast down period. That has a direct impact on how fast the phase angle changes.
- Low inertia loads will cause the phase angle to change quickly, as the frequency of motor bus decays quickly, and the slipfrequency between the motor bus and the new sourcequickly increases.
Motor Bus Transfer
Mix of Synchronous and Induction Motors:
- Voltage will tend to decay much more rapidly on a motor bus with all induction motors
- On a motor bus with a mix of synchronous and induction motors, the synchronous motors will attempt to hold up the voltage during the transfer interval
Motor & Load Characteristics:Effects on MBT
Motor Bus Transfer
Resultant V/Hz
Pursuant to phase angle and voltage, and their effect on resultant V/Hz, some generalizations can be made:
- Phase Angle: As the phase angle increases between the two sources, assuming the two source voltages are the same, theV/Hz will increase
- Voltage: As the voltage difference between the two sources increases, assuming the phase angle between the sourcesremains the same, the V/Hz will increase
Motor Bus Transfer
V/Hz Resultant from ES and EMANSI STANDARD C50.41-2000
Motor Bus Transfer
C50.41 is an American National Standard Institute standard only found under NEMA.
ANSI C50.41-2000Status is Current.
C50.41 originally was a combined ANSI/IEEE standard, however it is no longer under the IEEE. Four NEMA representatives were included as part of the Working Group for the 2000 Standard. The standard is now available on the NEMA website and it is still active as an ANSI Standard.
The link is:http://www.nema.org/stds/results.cfmsrchString=c50.41&UserSel
ectedSubSites=12
V/Hz Resultant from ES and EMANSI STANDARD C50.41-2000
Motor Bus Transfer
Excerpts from ANSI C50.41-2000
V/Hz Resultant from ES and EMANSI STANDARD C50.41-2000
Motor Bus Transfer
Excerpts from ANSI C50.41-2000
V/Hz Resultant from ES and EMANSI STANDARD C50.41-2000
Motor Bus Transfer
Excerpts from ANSI C50.41-2000
V/Hz Resultant from ES and EMANSI STANDARD C50.41-2000
θcos222MSMSR EEEEE −+=
ES = 1 pu @ 0 degrees
EM = 0.81 pu @
-95 degrees
ER = 1.33 pu
θ
Motor Bus Transfer
Motor Bus Transfer Classification▪ Closed Transition
- Hot Parallel Transfer
▪ Open Transition - Methods
- Fast Transfer
- In-Phase Transfer
- Residual Voltage Transfer
- Fixed Time Transfer
▪ Open Transition - Modes
- Sequential
- Simultaneous
Motor Bus Transfer
Closed Transition – Hot Parallel Transfer▪ New source connected to the motor bus before the old source
is tripped. Transfers sources without interruption.
▪ Voltages and phase angle between the motor bus and the new source must be evaluated prior to the transfer to assure that the motor bus and the new source are in synchronism and that the new source voltage is within acceptable limits.
▪ Auto Trip provisions must be incorporated such that, if the new source breaker is closed but the old source breaker remains closed, the transfer system must immediately trip the old source breaker. This allows parallel transfer but prohibits inadvertent parallel operation.
▪ Alternatively, Auto Trip provisions can be programmed to trip the new source breaker that may have been inadvertently closed.
Motor Bus Transfer
Closed Transition – Hot Parallel Transfer
MMM
Motor Bus
Source 1(Old Source)
Source 2(New Source)
Motor Bus Transfer
Closed Transition – Hot Parallel Transfer
MMM
Motor Bus
Source 1(Old Source)
Source 2(New Source)
Motor Bus Transfer
Closed Transition – Hot Parallel Transfer
MMM
Motor Bus
Source 1(New Source)
Source 2(Old Source)
Motor Bus Transfer
Closed Transition - Hot Parallel TransferAdvantages- No disruption of plant process- Simple to implement with sync-check relay supervision across
new source breaker- No transient torque on motors during the transfer
Disadvantages- Will not work during transient (emergency) conditions Do not
want to connect “good” source to new source that is having problems.
- Exposure to double-fed motor faults during parallel operation may violate the interrupt rating for the circuit breakers and the short term withstand ratings source transformers and damage bus-connected equipment
- Design must ensure that a parallel condition is temporary- The two sources may not be derived from the same primary
source and a large standing phase angle may be present between them, precluding a hot parallel transfer
Motor Bus Transfer
Open Transition
▪ Open Transition - Methods
- Fast Transfer
- In-Phase Transfer
- Residual Voltage Transfer
- Fixed Time Transfer
▪ Open Transition - Modes
- Sequential Mode
- Simultaneous Mode
Motor Bus Transfer
Open Transition
MMM
Motor Bus
Source 1(Old Source)
Source 2(New Source)
Motor Bus Transfer
Open Transition
MMM
Motor Bus
Source 1(Old Source)
Source 2(New Source)
Motor Bus Transfer
Open Transition
MMM
Motor Bus
Source 1(New Source)
Source 2(Old Source)
Motor Bus Transfer
Open Transition - Methods- Fast Transfer- In-Phase Transfer- Residual Voltage Transfer
Bus Transfer Zones
-π
-2π
Motor Bus Transfer
Fast Transfer MethodThe new source breaker will be closed by the Fast Transfer Method if the phase angle between the motor bus and the new source is within or moves into the phase angle limit during the Fast Transfer Enable (Time) Window.One-cycle phase angle response is required.Closing is also supervised by an Upper and Lower Voltage Limit check on the new source.
Motor Bus Transfer
In-Phase Transfer MethodThe new source breaker will be closed using the In-Phase Transfer Method by predicting movement through zero phase coincidencebetween the motor bus and the new source during the In-Phase Transfer Enable Window.
Closing is also supervised by an Upper and Lower Voltage Limit check on the new source and a Slip (ΔF) Frequency Limit between the motor bus and the new source.
The calculation of the predicted phase coincidence shall be compared with the breaker closing time setting for the new source breaker for the In-Phase Transfer method.
In order to accurately predict phase coincidence, considering the decaying motor bus frequency, the phase angle, slip frequency and rate-of-change of frequency between the motor bus and the new source must be calculated and inserted in the following second order partial differential equation to solve for the precise breaker closing advance angle (Φ) to compensate for the breaker closing time (TB). One-cycle response is required.
Motor Bus Transfer
In-Phase Transfer MethodMotor Bus Transfer
Unit-Connected Generator Motor Bus
MMM
Motor BusG
OtherLoadMOTOR BUS VT
-30deg
+30deg 0deg
Motor Bus Transfer
In typical applications, a wye-wye or delta-delta Startup Transformer connection is used, resulting in a net phase shift of zero between the Unit Auxiliary and Startup Transformers. In this case Hot Parallel Transfers are possible and Open Transition Fast Transfers are permitted given sufficiently fast sync check supervision and breaker speeds.
Wye-Wye Startup Transformer
Unit-Connected Generator Motor Bus
Motor Bus Transfer
In some plants, a delta-wye Startup Transformer has been specified, creating a 30 deg phase shift between the Unit Auxiliary and Startup Transformers.
Delta-Wye Startup Transformer
MMM
Motor BusG
OtherLoadMOTOR BUS VT
Unit-Connected Generator Motor Bus
Motor Bus Transfer
The Startup Transformer source leads the Unit Auxiliary Transformer source by 30 deg. Hot parallel transfers are NOT possible. After the Startup Transformer breaker opens, the Motor Bus will begin slowing which moves the Bus voltage towards the Unit Aux Transformer voltage.
Startup to Unit Aux TransferFast Transfer Possibilitywith Hi-Speed Sync Check
MMM
Motor BusG
OtherLoadMOTOR BUS VT
Unit-Connected Generator Motor Bus
Motor Bus Transfer
The Unit Auxiliary Transformer source lags the Startup Transformer source by 30 deg. After the Unit Auxiliary Transformer breaker opens, the Motor Bus will begin slowing which moves the Bus voltage away from the Startup Transformer voltage.
Unit Aux to Startup TransferIn-Phase Transfer Possibility
MMM
Motor BusG
OtherLoadMOTOR BUS VT
Residual Voltage Transfer MethodThe new source breaker will be closed by the Residual Voltage Transfer Method if the motor bus voltage drops below the Residual Voltage Transfer limit during the Residual Voltage Transfer Enable Window.
Since this is otherwise unsupervised, this must prevent closure of the new source breaker until the bus voltage drops below a predetermined voltage limit (usually < 0.25 pu).
Setpoint accuracy MUST measure correctly and operate down to 4 Hz.
Undervoltage settings must be coordinated with motorundervoltage relays to prevent motor drop-out.
Residual Voltage Transfer Method may be disableddepending on the application.
Motor Bus Transfer
Open Transition – Sequential ModeTransfer Timing Sequence
Motor Bus Transfer
If the Sequential Mode is selected, the old source breaker shall be tripped immediately, but closure of the new source breaker shall be attempted only upon confirmation by the breaker status contact that the old source breaker has opened. Upon receipt of this confirmation, all three methods of transfer are immediately enabled to supervise closure of the new source breaker.
Closure of the new source breaker will then occur when permitted by the Fast, In-Phase or Residual Voltage Transfer criteria, whichever occurs first.
Open Transition – Sequential ModeTransfer Timing Sequence
Motor Bus Transfer
(4 msec Delay w/M-4272)
(Window Adjustable w/M-4272)
Open Transition – Simultaneous ModeTransfer Timing Sequence
Motor Bus Transfer
If the Simultaneous Mode is selected, all three methods of 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.
Thus, the commands for the old source breaker and the new source breaker to trip and close could be sent simultaneously if and only if the phase angle between the motor bus and the new source is within the phase angle limit immediately upon transfer initiation.
Otherwise, the old source breaker will be tripped but closure of the new source breaker must wait until permitted by the Fast, In-Phase or Residual Voltage Transfer criteria, whichever occurs first.
Open Transition – Simultaneous ModeTransfer Timing Sequence
Motor Bus Transfer
Delays Eliminated
(4 msec Delay w/M-4272)
Window Adjustable w/M-4272)
Fast TransferSequential Trip and Close of Old
and New Source Breakers (“early b” breaker status contact)Advantages
- Fast (5 to 7 cycles)- Transient torques are reduced due to speed of transfer- Transfer of complete bus with reduced interrupting of process- Rapid supervision of the phase angle just prior and just after old
source interruption is mandatory and possible with high-speed sync-check relays
- Avoids parallel transfer operation- Avoids exposure to breaker failure effects
Motor Bus Transfer
COMMENT: Presently, the majority of fast transfer systems are NOT supervised by high-speed sync-check relays.
Simultaneous Trip and Close of Oldand New Source Breakers
Advantages- REALLY Fast - minimum dead time for bus (2 to 3 cycles)- Least exposure to transient torque in motors if system operates
as expected- Transfer of complete bus with minimum interrupting of process- Rapid supervision of the phase angle just prior and just after
old source interruption is mandatory and possible with high-speed sync-check relays
- Avoids “intentional” parallel transfer operationConsiderations – Breaker Failure Scheme is a MUST !- Failure of old source breaker to trip back feeds generator from
new source- AND exposes equipment to double-fed faults for which it was
not designed- Presently, the majority of fast transfer systems are NOT
supervised by high-speed sync-check relays
Fast Transfer
Motor Bus Transfer
Open Transition – Simultaneous ModeBreaker Failure
Motor Bus Transfer
FailedTo Open
Fast Transfer
Motor Bus Transfer
Presently, the majority of fast transfer systems are NOT supervised by high-speed sync-check relays !
Fast transfer CANNOT be correctly performed without a high-speed sync check relay
Modern solid-state or microprocessor-based sync check elements have a minimum time delay of 0.1 second or 100 milliseconds. By the time they respond to the phase angle of a decaying motor bus, the possibility of a successful transfer is long gone.
Worse yet, the contacts may be still closed and permit transfers at excessive angles and damage critical motors.
Fast Transfer
Motor Bus Transfer
Fast Transfer
Motor Bus Transfer
Dropout Test
-23.5-28.2-170.6104 V ac/sec31 Hz/secLow Inertia
-23.2-24.1-58.694 V ac/sec20 Hz/secMedium Inertia
-22.5-24.4-5275 V ac/sec8.33 Hz/secHigh Inertia
M-4272DigitalMotor Bus TransferDegrees @ Dropout
M-3410ADigitalSync CheckDegrees @ Dropout
M-0388AnalogSync CheckDegrees @ Dropout
Voltage Decay (Vac/sec)
Frequency Decay (Hz/sec)
Motor Bus
Fast Transfer
Motor Bus Transfer
Pickup Test
17.913.3No Close104 V ac/sec31 Hz/secLow Inertia
18.114.5No Close94 V ac/sec20 Hz/secMedium Inertia
19.815475 V ac/sec8.33 Hz/secHigh Inertia
M-4272DigitalMotor Bus TransferDegrees @ Pickup
M-3410ADigitalSync CheckDegrees @ Pickup
M-0388AnalogSync CheckDegrees @ Pickup
Voltage Decay (Vac/sec)
Frequency Decay (Hz/sec)
Motor Bus
Fast Transfer
Motor Bus Transfer
Presently, the majority of fast transfer systems are NOT supervised by high-speed sync-check relays !
Synchronism-Check Relay TestGeneral Electric Type IJS52
The purpose of this test was to determine the blocking characteristics of the IJS Relay set for 20° and minimum time delay. Tests were run for the following conditions:
With the initial phase angle at 0° and both inputs at 60Hz, increase the line frequency to create a slip frequency (ΔF) and measure the blocking time and blocking angle.
TEST DATA
Fast Transfer
Motor Bus Transfer
Sync Check Relay TestThe purpose of this test is to determine the blocking characteristics of Sync Check Relays set for 20° and minimum time delay. With the initial phase angle at 0°and both inputs at 60Hz, the line frequency is increased to create a slip frequency (ΔF) and the blocking angle is measured.
26.3531063.01825.747992.751725.246932.51624.935872.251524.63379.92.01423.632721.751322.931671.51222.33059.81.2511222951.81.01021.82640.10.75921.62536.773.620.58212328.754.000.25720.520.623.840.320.162020.322.127.180.0552020.221.40.02542020210.013202020.80.0052202020.60.0011
M-4272DigitalMotor Bus TransferDegrees
M-3410ADigitalSync CheckDegrees
M-0388AnalogSync CheckDegrees
GE IJSElectromechanicalSync CheckDegrees
Delta Frequency (Hz)
Advantages
- May operate significantly faster than residual voltage transfer
- Significantly reduces the pre-closure V/Hz due to synchronous closing
- Permits bus transfer for out-of-synchronism initial conditions or where large initial standing angles prevent fast transfer
- Provides an excellent backup to fast transfer systems
In-Phase Transfer
Motor Bus Transfer
Advantages
- Familiar technique that is widely used
- Simple to implement (undervoltage relays – but mustoperate correctly to low frequencies and with significant rate of change in voltage decay)
- Works properly during transient conditions
loss of synchronismangular differencesvoltage transients
Residual Voltage Transfer
Motor Bus Transfer
Disadvantages- Slower- Process is interrupted due to load shedding (new source cannot re-
accelerate all bus motors simultaneously)- Analysis of plant process is required to determine effects of
transfer- Certain motors loads may cause rapid stalling and may necessitate
a restart of the motors on the bus- Cannot be used to transfer from new source to present source
during unit startup- Risk of transfer to dead source unless new source is monitored- Properly sequenced motor restart required to prevent excessive
voltage dip- Effect of transient torque on motors during restart should be limited
to starting torque (analysis may be required depending on length of motor supply interruption)
- Motor contactors drop out unless designed to stay in at residualtransfer voltage.
Residual Voltage Transfer
Motor Bus Transfer
Residual Voltage Transfer
Motor Bus Transfer
25.4 V (0.21 pu)24.2 V (0.20 pu)14 V (0.12 pu)104 Vac/sec31 Hz/secLow Inertia
27.9 V (0.23 pu)26 V (0.22 pu)22.4 V (0.19 pu)94 Vac/sec20 Hz/secMedium Inertia
30 V (0.25 pu)27.5 V (0.23 pu)23.7 V (0.20 pu)75 Vac/sec8.33 Hz/secHigh Inertia
M-4272Under VoltageV ac @ Operate
M-3410AUnder VoltageV ac @ Operate
M-0388Under VoltageV ac @ Operate
Voltage Decay (Vac/sec)
Frequency Decay (Hz/sec)
Motor Bus
Under Voltage Operate Test
Fixed Time TransferDesigned to wait for a predetermined time, usually greater than 30 cycles, after a bus power source is removed before connecting the bus to new source. Voltage relays do not supervise the transfer.
Motor Bus Transfer
Advantages
- Familiar technique that is widely used
- Simple to implement (time delay relays)
- Works properly during transient conditions
loss of synchronismangular differencesvoltage transients
Fixed Time Transfer
Motor Bus Transfer
Disadvantages- Slowest- Process is interrupted due to total loss of power (new source
cannot reaccelerate all bus motors simultaneously)- Analysis of plant process is required to determine effects of
transfer- Cannot be used to transfer from new source to present source
during unit startup -- parallel transfer required- Risk of transfer to dead source unless new source is monitored- Properly sequenced motor restart required to prevent excessive
voltage dip- Effect of transient torque on motors during restart should be
limited to starting torque (analysis may be required depending on length of motor supply interruption)
Fixed Time Transfer
Motor Bus Transfer
Transfer InitiateNOTE: For each of the following, transfers may be bi-directional or may be programmed to only transfer in one direction.
▪ Protective Relay Initiate
▪ External Initiate
▪ Bus Phase Undervoltage (Auto Transfer) InitiateWhen enabled, this automatically initiates transfer whenever the motor bus
voltage drops below an under voltage limit for a set time delay. MUST be set to ride through normal bus voltage dips.
▪ Auto Close InitiateIf both breaker status contacts are in the open state, due to an external
operation that opens the old source breaker while leaving the new source breaker open, an Open Transition, Sequential Mode Transfer is initiated.
▪ Manual Initiate
- Local
- Remote
Motor Bus Transfer
Load Shed During TransferNOTE: For each of the following, Load Shed may be enabled or disabled.
▪ Load Shed Coincident with Fast TransferEXAMPLE: This may be used to disconnect motor loads from the aggregate bus,
coincident with the command to trip the old source breaker, if the new source is not designed to pick up the full motor bus load.
▪ Load Shed After Fast Transfer Window and Before In-Phase Attempt
EXAMPLE: This may be used to disconnect large synchronous motors from the aggregate bus prior to In-Phase Transfer which may close in sync but at a high slip rate.
▪ Load Shed Coincident with Residual Voltage TransferEXAMPLE: This may be used to disconnect motor loads from the aggregate bus just
prior to Residual Voltage Transfer so the remaining motors may re-accelerate.
Motor Bus Transfer
LockoutsNOTE: The old source breaker SHALL NOT BE TRIPPED whenever any transfer initiate is blocked by any of the lockout conditions described below or if the new source voltage is outside the upper voltage limit and lower voltage limit .
▪ Motor Bus Voltage LockoutDetects Motor Bus VT loss-of-potential (i.e. fuse loss) and may be programmed to
block transfer or if a transfer is required, can be programmed to proceed with a fixed time transfer.
▪ External LockoutExternal contact input blocks transfer.
▪ Incomplete Transfer (Auto) LockoutBlocks the completion of any transfer initiated if, after the old source breaker
opens, the new source breaker fails to close after a set time delay.
▪ Transfer In Process LockoutOnce a transfer is in process, all other transfer initiate inputs are ignored.
▪ Lockout After TransferSubsequent transfers are blocked for a set time after any transfer occurs.
Motor Bus Transfer
LockoutsNOTE: The old source breaker SHALL NOT BE TRIPPED whenever any transfer initiate is blocked by any of the lockout conditions described below or if the new source voltage is outside the upper voltage limit and lower voltage limit .
▪ “Both Breakers” LockoutIf both breaker status contacts end up in the open state, due to an
external operation that opens the old source breaker while leaving the new source breaker open, no transfer sequence shall be initiated. Furthermore, any subsequent initiation of a transfer sequence while the breakers are in this state shall be blocked. May alternatively be programmed to initiate an Auto Close Transfer.
If both breaker status contacts are closed due to an external operation that closes the new source breaker while leaving the old source breaker closed, and if Auto Trip is not enabled, no transfer sequence shall be initiated.
Motor Bus Transfer
Open Transition
MMM
Motor Bus
Source 1(Old Source)
Source 2(New Source)
Motor Bus Transfer
Open Transition
MMM
Motor Bus
Source 1(Old Source)
Source 2(New Source)
Motor Bus Transfer
External Trip
Open Transition
MMM
Motor Bus
Source 1(New Source)
Source 2(Old Source)
Motor Bus Transfer
LockoutsNOTE: The old source breaker SHALL NOT BE TRIPPED whenever any transfer initiate is blocked by any of the lockout conditions described below or if the new source voltage is outside the upper voltage limit and lower voltage limit .
▪ “Both Breakers” LockoutIf both breaker status contacts end up in the open state, due to an
external operation that opens the old source breaker while leaving the new source breaker open, no transfer sequence shall be initiated. Furthermore, any subsequent initiation of a transfer sequence while the breakers are in this state shall be blocked. May alternatively be programmed to initiate an Auto Close Transfer.
If both breaker status contacts are closed due to an external operation that closes the new source breaker while leaving the old source breaker closed, and if Auto Trip is not enabled, no transfer sequence shall be initiated.
Motor Bus Transfer
Closed Transition – Hot Parallel Transfer
MMM
Motor Bus
Source 1(Old Source)
Source 2(New Source)
Motor Bus Transfer
Closed Transition – Hot Parallel Transfer
MMM
Motor Bus
Source 1(Old Source)
Source 2(New Source)
Motor Bus Transfer
External Close
Closed Transition – Hot Parallel Transfer
MMM
Motor Bus
Source 1(New Source)
Source 2(Old Source)
Motor Bus Transfer
Bus transfer Acceptance TestingVerify scheme operation
Perform “Ring Down” test of load bus and record
Determine relay settings by analysis of ring down
Verify continuity of switching operation
Examine transients
Difficult to simulate running conditions of plant
Used to verify computer models (if available)
Motor Bus Transfer
Bus transfer Acceptance TestingInitial Steps: Dry Run, Dead Bus
• Connect transfer system and monitoring equipment• Simulate inputs to transfer system from test equipment
(main, auxiliary, bus)• Rack out breakers and operate on umbilical cords (at
test position)• Test system to ensure proper operation of transfer
system, breakers, monitoring equipment• Verify breaker times• Simulate all types of transfer appropriate for bus
– Fast Transfer– In-Phase Transfer– Residual Voltage Transfer
Motor Bus Transfer
Bus transfer Acceptance TestingFinal Running Test
• All equipment in normal operating state• Initiate transfer and monitor for each transfer type
– Fast Transfer– In-Phase Transfer– Residual Voltage Transfer
• Verify acceptable operations
Motor Bus Transfer
Ringdown AnalysisA bus ringdown involves- operation of the motor bus at expected nominal conditions- then disconnecting the source from the bus, recording the
waveform and observing the frequency decay and voltage decay characteristics as the motors coast down
- Computer analysis and field testing is necessary to ensure a successful transfer – Fast and In-Phase
- Determine if motors and loads on bus have sufficient inertia to limit the rate of change of angle (frequency decay) – Fast and In-Phase
A tool for recording and analyzing the ringdown is an oscillograph- Older technology offered lightwave oscillography - Newer technology offers digital oscillography
May be included as part of newer digital metering, protection and bus transfer packagesStand-alone digital fault and event recorders (DFR)
Motor Bus Transfer
Simultaneous Transfer Mode Selected: 10 ms after a transfer initiate, the trip command signal is sent directly to the old source breaker, and the three methods of transfer are immediately enabled to supervise closure of the new source breaker.The new source breaker close time starts only when the permissive close signal is generated by either the Fast, In-Phase or Residual Voltage Transfer Method. Sequential Transfer Mode Selected: 10 ms after a transfer initiate, the trip command signal is sent directly to the old source breaker. 4 ms after the 52a or 52b breaker status aux contact indicates the old source breaker has opened, the three methods of transfer are enabled to supervise closure of the new source breaker. For Fast Transfer, depending on the status of the initial phase angle across the new source breaker (in or out of phase limits),the 4 ms reaction time of the supervising high-speed sync check must be taken into account, although this occurs simultaneously with other delays.
Ringdown Analysis ConsiderationsMotor Bus Transfer
For fast transfers, the fast transfer phase angle limit setting is calculated, using the resultant V/Hz calculation shown earlier, such that the actual V/Hz at the point of closure is far less than the 1.33 pu V/Hz limit or, in the worst case, is not more than this limit.
The phase angle limit setting on the fast transfer high-speed sync check supervision relay must be set so it blocks before the phase angle becomes prohibitively large, and the angle setting must include the effect of the new source breaker closing time.
Ringdown Analysis Considerations
Motor Bus Transfer
The in-phase transfer must be initiated at an advance angle before the first phase coincidence.
- The advance angle is calculated for in-phase transfer by a specialized high-speed automatic synchronizing relay capable of predicting the advance angle, based on the new source breaker closing time and the rapidly increasing slip frequency.
- The ΔF Limit setpoint is calculated using the resultant V/Hz calculation shown earlier, such that the actual V/Hz at the point of closure is far less than the 1.33 pu V/Hz limit or, in the worst case, is not more than this limit.
The residual and fixed time transfers only need to take into account that the motor bus voltage has fallen to 0.25 pu or less.
- The new source breaker closing time does not have to be considered, as the angle is now not important, since the resultant V/Hz cannot exceed 1.33 V/Hz
Motor Bus Transfer
Ringdown Analysis Considerations
Ringdown Oscillograph Representation
52 TripFast TransferPossible
In-PhaseTransferPossible
Residual & Long Time Transfer Possible
52a opens52b closes
Window of AcceptablePhase Angle
Present Source Breaker
New Source
Motor Bus
Motor Bus Transfer
Ring Down Digital WaveformMotor Bus Transfer
45.6 VRMS
BREAKER OPEN
ZERO CROSSING
Ring Down Digital Waveform without fansMotor Bus Transfer
ZERO CROSSING
28.4 VRMS
BREAKER OPEN
Sequential Fast Transfer Digital WaveformMotor Bus Transfer
91.8 VRMS
BREAKER S2 OPENS BREAKER S1 CLOSES
Delayed In-Phase Transfer Digital WaveformMotor Bus Transfer
BREAKER S1 OPENS
BREAKER S2 CLOSES
Ringdown Analysis
Motor Bus Transfer
CASE STUDY
Central Ciclo CombinadoLa Laguna II
Torreon, Coahuila de ZaragozaMexico
Ringdown Analysis
Motor Bus Transfer
Spin down Testing
The waveforms of spin down test show that the bus decay lasted for almost one second. The high inertia of the motor bus load provides a stable and uniform decay, this gives an excellent opportunity to perform a smooth motor bus transfer. Measurements and calculations for the Phase angle and Delta Frequency settings for the MBT equipment are derived from these results.
Spin Down TestMotor Bus Transfer
Ringdown Analysis
Motor Bus Transfer
Volts per Hertz Calculations for Sequential Fast Transfer
The maximum volts per hertz across the breaker that is closing is defined in the ANSI C50.41-2000 Paragraph 14 as 1.33V/Hz. Refer to figures below for how the measurements were taken on the waveform. The equation for the pre-closure volts per hertz is as follows:
Where:
EPU is the per unit volts per hertz across the open breaker.
EREFPU is the per unit volts per hertz of the reference, which is the new source to which the bus is being transferred. (1pu volts/1pu hertz) = 1
EBUSPU is the per unit volts per hertz of the bus.
Cos θ is the cosine of the phase angle between the reference and the bus.
Measurements and Calculations at breaker closing time for Sequential Fast Transfer, refer to following figures.
Phase angle = 29.8 degrees
Bus voltage pu = 101/121 rms = 0.8347pu (voltage readings X 10)
Bus frequency = 58.82/60 = 0.9804pu (Frequency = 1/time period; 1/17.0ms)
EBUSPU = 0.8347/0.9804 = 0.8514
EPU = 0.497pu
θCosEBUSPUEREFPUEBUSPUEREFPUEPU ×××−+= 222
Spin Down Estimated Sequential Fast Transfer Breaker Closing Time(Measured from breaker trip = 78.5ms, breaker close time 57.5ms+10ms+8.3ms)
Motor Bus Transfer
Spin Down Estimated Sequential Fast Transfer Voltage and Phase Angle at Closing
Motor Bus Transfer
Spin Down Estimated Sequential Fast Transfer Frequency at Closing
Motor Bus Transfer
Ringdown Analysis
Motor Bus Transfer
Spin Down Measurements and Calculations for the Fast Transfer Phase Angle Setting
Phase angle at 2.5 cycles: 10ms +8.3ms+25ms (1.5 cycle worst case error) after breaker opens = 15.7 degrees (See next slide.)
In this application add 6 degrees to phase measurement. Phase angle setting is 16 plus 6 degrees for total of 22 degrees.
Ringdown Analysis
Motor Bus Transfer
Ringdown Analysis
Motor Bus Transfer
Volts per Hertz Calculations for In-Phase Transfer
The maximum volts per hertz across the breaker that is closing is defined in the ANSI C50.41-2000 Paragraph 14 as 1.33V/Hz. Refer to figures below for how the measurements were taken on the waveform. The equation for the pre-closure volts per hertz is as follows:
Where:
EPU is the per unit volts per hertz across the open breaker.
EREFPU is the per unit volts per hertz of the reference, which is the new source to which the bus is being transferred. (1pu volts/1pu hertz) = 1
EBUSPU is the per unit volts per hertz of the bus.
Cos θ is the cosine of the phase angle between the reference and the bus.
Measurements and Calculations at breaker closing time for Sequential Fast Transfer, refer to following figures.
Phase angle = 0 degrees
Bus voltage pu = 77.8/120 rms = 0.6483pu (voltage readings X 10)
Bus frequency = 55.87/60 = 0.9311pu (Frequency = 1/time period; 1/17.9ms)
EBUSPU = 0.6483/0.9311 = 0.6963
EPU = 0.3038pu
θCosEBUSPUEREFPUEBUSPUEREFPUEPU ×××−+= 222
Spin Down Estimated Sequential In-phase Transfer Voltage
Motor Bus Transfer
Spin Down Estimated Sequential In-phase Transfer Frequency
Motor Bus Transfer
Ringdown Analysis
Motor Bus Transfer
Spin Down Measurements and Calculations for the In-Phase Transfer Slip Frequency (ΔF) Setting
The frequency at time of breaker closure is 56.18HZ (1/17.8ms, see next slide); the delta frequency at breaker closure is 3.82 HZ. In this application, set the in-phase slip frequency (ΔF) limit setting to 4.5HZ.
Spin Down Estimated Sequential In-Phase Frequency 4 cycles Before In Phase (Breaker time + ½ cycle)
Motor Bus Transfer
Motor Bus Transfer Application-The Need for SpeedProject Background
The following example shows actual data from commissioning tests at the Laguna II station in Mexico. This plant consists of two combustion turbines (154MW) and one heat recovery steam plant (279MW). The plant auxiliary loads are below:
Bus A (4KV)3600HP High pressure boiler feed pump3600HP High pressure boiler feed pump1100HP Condensate pump
620HP Closed circuit Cooling pump1500HP Gas compressor
450HP Auxiliary cooling pump480V Service Transformers
Note that these loads are centrifugal pumps and compressors. There are no fans or other high inertia loads in this application. In addition, the breakers are not particularly fast, 35mSec trip and 60mSec to close.
Bus B (4KV)3600HP High pressure boiler feed pump3600HP High pressure boiler feed pump1100HP Condensate pump
620HP Closed circuit Cooling pump1500HP Gas compressor1500HP Gas compressor
450HP Auxiliary cooling pump480V Service Transformers
Motor Bus Transfer
Closing Voltage9.82/12.00
Closing Angle=11.7deg
Main Position(Open)
Startup Position(Closed)
Trip Main
Close Startup
Motor Bus Transfer Application-The Need for SpeedSimultaneous Transfer Mode
•Note that the trip and close commands occur together.
•Transition time (old source breaker open to new source closed) is about 1 cycle
Motor Bus Transfer
Closing Voltage
Closing Angle=38.24deg
Main Position(Open)
Startup Position(Closed)
Trip Main
Close Startup
Motor Bus Transfer Application-The Need for SpeedSequential Transfer Operation
•Note that the close command to the new source occurs after the old source breaker indicates open.
•Transition time (old source breaker open to new source closed) is about 4 cycles
Motor Bus Transfer
Simultaneous ModeTransfer Time: 24.2mSec(both breakers open)Transfer Angle: 11.7degBus Voltage at Transfer: 98.2/120VBus Frequency at transfer: 58.4HzV/Hz per C50.41-2000 0.246pu
Sequential ModeTransfer Time: 79.1mSec(both breakers open)Transfer Angle: 38.2degBus Voltage at Transfer: 77.8/120VBus Frequency at transfer: 57.8HzV/Hz per C50.41-2000 0.629pu
The sequential transfer was slower which allowed the motor bus frequency and voltage to decay further, however the V/Hz quantities are far below the 1.33pu limit.
Even in this application, which has less than ideal mechanical inertia, the sequential mode offers significantly more security without compromising the transfer.
In applications with faster vacuum breakers, there will be even less difference between sequential and simultaneous operating modes.
Motor Bus Transfer Application-The Need for SpeedTransfer Data Analysis
Motor Bus Transfer
Using traditional synch check relays, measurement time is a very slow (up to 100msec). This long measurement time could prevent the traditional scheme from detecting unacceptable conditions which could result in an improper transfer. •In an attempt to minimize this effect, traditional transfer systems are set to operate at the highest possible speed (simultaneous mode).•The safety of the simultaneous mode relies on a fast and reliable breaker failure scheme. Frequently, these schemes are assembled from auxiliary relays and wiring that are rarely tested. High speed measurements allows the LUXURY of waiting until the old source breaker is open before issuing the close command to the new source.
Motor Bus Transfer Application-The Need for SpeedBus Transfer Application
Simultaneous ModeTransfer Time: 24.2mSec(both breakers open)Transfer Angle: 11.7degBus Voltage at Transfer: 98.2/120VBus Frequency at transfer: 58.4HzV/Hz per C50.41-2000 0.246pu
Sequential ModeTransfer Time: 79.1mSec(both breakers open)Transfer Angle: 38.2degBus Voltage at Transfer: 77.8/120VBus Frequency at transfer: 57.8HzV/Hz per C50.41-2000 0.629pu
Motor Bus Transfer
It should be noted that in some applications, very little back-EMF and inertia is present and therefore operation in simultaneous mode is required. •A reliable breaker failure scheme is mandatory •High speed measurement provides the ability to rapidly detect unacceptable bus voltage changes caused by the fault and block the transfer.
Simultaneous ModeTransfer Time: 24.2mSec(both breakers open)Transfer Angle: 11.7degBus Voltage at Transfer: 98.2/120VBus Frequency at transfer: 58.4HzV/Hz per C50.41-2000 0.246pu
Sequential ModeTransfer Time: 79.1mSec(both breakers open)Transfer Angle: 38.2degBus Voltage at Transfer: 77.8/120VBus Frequency at transfer: 57.8HzV/Hz per C50.41-2000 0.629pu
Motor Bus Transfer Application-The Need for SpeedBus Transfer Application
Motor Bus Transfer
CASE STUDY
Central Ciclo CombinadoFelipe Carrillo PuertoValladolid, Yucatan
Mexico
Motor Bus Transfer
Motor Bus Transfer
Motor Bus Transfer
GERENCIA REGIONAL DE PRODUCCIGERENCIA REGIONAL DE PRODUCCIÓÓN SURESTEN SURESTESUBGERENCIA REGIONAL DE GENERACISUBGERENCIA REGIONAL DE GENERACIÓÓN TERMOELECTRICA PENINSULARN TERMOELECTRICA PENINSULAR
CENTRAL FELIPE CARRILLO PUERTOCENTRAL FELIPE CARRILLO PUERTO
GERENCIA REGIONAL DE PRODUCCIGERENCIA REGIONAL DE PRODUCCIÓÓN SURESTEN SURESTESUBGERENCIA REGIONAL DE GENERACISUBGERENCIA REGIONAL DE GENERACIÓÓN TERMOELECTRICA PENINSULARN TERMOELECTRICA PENINSULAR
CENTRAL FELIPE CARRILLO PUERTOCENTRAL FELIPE CARRILLO PUERTO
Punto 2.- Problemática
2.1 DEFINICIÓN DE LA PROBLEMÁTICA
ESTANDO ENLAZADOS LOS AUXILIARES DE LA TURBINA DEVAPOR A UNA TURBINA DE GAS, ANTE UN EVENTO DEDISPARO DE LA TURBINA DE GAS SE GENERA UN COMANDODE INICIACION POR PROTECCION AL MODULO DETRANSFERENCIA.
REALIZÁNDOSE EN UN TIEMPO DE TRANSFERENCIA DE 140MILISEG, LO QUE OCASIONA EL DISPARO DE LOS EQUIPOSAUXILIARES DE LA TURBINA DE VAPOR POR PROTECCIÓN DEBAJO VOLTAJE DERIVANDO EN EL DISPARO DE LA UNIDAD 3.
Punto 2.- Problemática
UnidadDisponibilidad Factor de Planta
Real RealPropia
Meta Real Meta
2.1 DEFINICIÓN DE LA PROBLEMÁTICA
Since the auxiliaries for the steam turbine and the gas turbine are interconnected, before a gas turbine trip, the protection generates an initiate command to the transfer module.
The transfer time of 140 milliseconds causes a trip of the steam turbine auxiliary equipment by undervoltage protection resulting in the trip of Unit 3 (the steam turbine).
Motor Bus Transfer
Motor Bus Transfer
Motor Bus Transfer
Motor Bus Transfer
Motor Bus Transfer
Motor Bus Transfer
Motor Bus Transfer
Motor Bus Transfer
Motor Bus Transfer
Motor Bus Transfer System
Motor Bus Transfer
M-5802 Syncrotran® Bus Transfer System
Motor Bus Transfer
M-4272Digital Motor Bus Transfer System
Motor Bus Transfer
M-4272Digital Motor Bus Transfer System
Motor Bus Transfer
Hot Parallel Transfer (Manual Only)Supervision of Parallel Transfer:Sync Check– Accurate phase angle, delta voltage and delta frequency measurement – Fast blocking response– Time delay for tripping adjustable
Timers– Time window for transfer (1 to 50 cycles)
M-4272 Motor Bus Transfer System Functionality Provided
Motor Bus Transfer
Fast Transfer (Manual or Automatic)Supervision of Fast Transfer:High Speed Sync Check– Accurate phase angle, delta voltage and delta frequency measurement – Instantaneous blocking and pickup (<1 cycle) if phase moves at the time
of transfer
Voltage Level Check – New Source– Verify voltage integrity of new source
Timers– Time window for transferLoad shedding– Programmable Load shedding with no time delay
M-4272 Motor Bus Transfer System Functionality Provided
Motor Bus Transfer
In-Phase Transfer (Manual or Automatic)Supervision of In-Phase Transfer: High Speed Synchronizer– Predictive advance angle calculation that compensates for circuit breaker
closing time– Frequency and voltage difference supervision– Two breaker time settings available for bi-directional transfers
Voltage Level Check - New Source– Over/under voltage level supervision for new source verification
Timers– Time window for transferLoad shedding– Programmable Load shedding with no time delay
M-4272 Motor Bus Transfer System Functionality Provided
Motor Bus Transfer
Residual Voltage Transfer (Manual or Automatic)Voltage Level Check - Motor Bus– Undervoltage relay applied on motor bus to sense safe level for reclosing.
– Voltage measurement accuracy independent of frequency from 4 to 67 Hz
Voltage Level Check - Motor BusOver/under voltage level supervision for new source verification
Load shedding– Programmable Load shedding with no time delay
M-4272 Motor Bus Transfer System Functionality Provided
Motor Bus Transfer
Fixed Time Transfer (Automatic)A transfer has been initiated when the motor bus voltage drops below the bus undervoltage relay (27B) limit setting, but it is not possible to monitor the motor bus voltage due to Bus VT fuse loss during a transfer operation.
The close command to new source breaker is issued after a selectable fixed time delay (30 to 1000 cycles)
Load shedding– Programmable Load shedding with no time delay
M-4272 Motor Bus Transfer System Functionality Provided
Motor Bus Transfer
Bus Phase Undervoltage (27B) for transfer initiate and/or load sheddingFrequency (81) and Rate of Change of Frequency (81R) for load sheddingBreaker Failure (50BF), Source 1 and Source 2Sixteen Output Contacts
– Four output contacts (two trip and two close) for Present Sourceand New Source
– One lockout/blocking output contact– Eleven programmable output contacts (ten Form 'a' and one Form
'c')Two RS-232 ports (front and rear) and one RS-485 port (rear)IRIG-B time synchronization
M-4272 Motor Bus Transfer System Functionality Provided
Motor Bus Transfer
Eighteen Control Status Inputs – Six Breaker Status inputs (a, b, and sp (service position) for the
Present Source and New Source breakers
– Twelve programmable digital inputs.
All functions can be enabled or disabled, except those listed as"Common Function Settings”
Four trip and close circuit monitoring inputs
Remote/Local control selection
M-3931 Human-Machine Interface (HMI) Module
M-3972 Target Module (24 status LEDs and 8 output LEDs)
There are additional 4 status LEDs, 8 output LEDs and 12 input LEDs located on the front panel.
M-4272 Motor Bus Transfer System Functionality Provided
Motor Bus Transfer
OptionsRJ45 Ethernet Port Utilizing MODBUS over TCP/IP Protocol
5 A or 1 A models available
60 and 50 Hz models available
M-4272 Motor Bus Transfer System Functionality Provided
Motor Bus Transfer
M-4272 Motor Bus Transfer SystemAutomatically attempts the following transfer types in order:
- Fast transfer- In-phase transfer- Residual voltage transfer- Fixed time transfer
Offers Sequential (break-before-make) and Simultaneous break and make operation modesProvides five methods to initiate transfer
- Protective relay initiate (one-way or bi-directional)- Bus phase undervoltage initiate (one-way or bi-directional)- Auto close initiate (bi-directional)- Manual initiate via Front Panel, contact input or communication
Provides trip and close to old and new source breakersProvides programmable load shedding for Fast, In-Phase, ResidualVoltage and Fixed Time Transfers
Motor Bus Transfer
Standard Features
Circuit Breaker Control :
Control of two circuit breakers with two individual programmablebreaker closing timesThree-breaker configuration can be provided by two M-4272 devicesBreaker failure monitoring
M-4272 Motor Bus Transfer System
Motor Bus Transfer
Lockout/BlockingA transfer is blocked when any of the following lockout/blockingconditions described below is active:Voltage Blocking – If prior to a transfer, the new source voltage exceeds the Upper or Lower voltage limits, all transfers are blocked as long as the voltage remains outside these limits.
External Blocking – When this control input contact is closed, all transfers are blocked.
Incomplete Transfer Lockout – Blocks any transfer initiated by a protective relay initiate or an automatic initiated transfer or manual transfer if the last transfer has not been completed within the time delay. A time delay can be set from 50 to 3000 Cycles. The MBTS remains in the lockout condition until manually reset.
M-4272 Motor Bus Transfer System
Motor Bus Transfer
M-4272 Motor Bus Transfer SystemCommunicationsM-3872 ISScom™ Communications Software package for setpoint interrogation/modification, metering, monitoring, and downloading oscillographic records.
Metering of all measured inputs, measured and calculated quantitiesPhasor diagramsSynchroscope displaySingle line diagram mimic displaySequence of Event logs and Transfer Event logsOscillograph recording
ISSplotTM Oscillographic Analysis Software graphically displays waveforms to facilitate analysis, and also prints captured waveformsModbus,Modbus/TCP Communications
RS-232, RS-485, EthernetIRIG-B Time Synchronization
Motor Bus Transfer
M-4272 Motor Bus Transfer SystemPower Source
Two power supplies Power Input - Flexibility and Range
110/120/230/240 V ac or 110/125/220/250 V dcAC Range 85 – 265 V ac or DC Range 80 – 312.5 V dc24/48 V dcDC Range 18 – 56 V dc
Motor Bus Transfer
M-4272 Motor Bus Transfer System
Can accommodate two and three-breaker configurations
Multiple setpoint profiles for various application requirements
Integrated control, supervisory functions, sequence of events, Transfer Event Log and oscillographic recording in one device
Extensive commissioning tools, including “ring-down” analysis
Motor Bus Transfer
Standard Features Initiating Automatic Transfer:
Transfer initiated by protective relay external to the MBTS system
Transfer initiated through ISSLogic
Automatic Transfer after a loss of the motor bus Source 1 supplybased on the internal programmable undervoltage element. This provides a selectable backup feature if a manual or protective relay transfer is not initiated.
M-4272 Motor Bus Transfer System
Motor Bus Transfer
Standard FeaturesTypes of Automatic Transfer:
Fast Transfer with adjustable Δ θ , Δ V and Δ F limitsSequential and Simultaneous break-before-make operation modesDelayed In-Phase Transfer at the first phase coincidence if Fast Transfer is not possibleResidual Voltage Transfer at an adjustable low residual voltage limit if Fast Transfer and Delayed In-Phase Transfer are not possibleFixed Time Transfer after an adjustable time delayProgrammable Load Shedding with Fast, Delayed in-phase, Residual voltage and Fixed time Transfer
M-4272 Motor Bus Transfer System
Motor Bus Transfer
Standard FeaturesManual Transfer:
Make-before-break (Hot Parallel) operation mode with Sync Check function.
Break-before-make operation with Fast, Delayed In-Phase, Residual Voltage.
Programmable Load Shedding.
Transfer initiated manually by contact input, front panel HMI orthrough serial communication.
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System SetupThe System Setup consists of defining all pertinent information regarding the connection environment.
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System SetpointsThe MBTS System Setpoints consists of entering the following:
Common settings
Automatic, Manual and Auto Trip Transfer settings
Enabling the functions and entering the desired settings
Designating the output contacts each function will operate, and which control/status inputs will enable or block the transfer.
The programmable output/input choices include 11 programmable output contacts (OUT5–OUT16) and six breaker status inputs (IN1–IN6) for Source 1 and Source 2, plus 12 other programmable inputs. A block or fixed time transfer choice for bus fuse loss logic operation.
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System SetpointsThe System Setpoints screen consists of defining all Common, Automatic and Manual Transfer settings, and Function settings.
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System SetpointsThe Display All feature of the System Setpoints screen contains the settings for each MBTS function within a single window to allow scrolling through all MBTS setpoint and configuration values
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System SetpointsThe Configure feature of the System Setpoints screen contains a chart of programmed input and output contact configuration settings for each MBTS function within a single window to allow scrolling through all MBTS configuration values
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System SetpointsCommon Function Settings, Inputs and Outputs
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System SetpointsCommon Function Settings Inputs
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System SetpointsCommon Function Settings Outputs
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System SetpointsAutomatic Transfer Settings
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System SetpointsManual Transfer Settings
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System SetpointsAuto Trip SettingsWhen the Auto Trip is enabled, the MBTS will trip the breaker that was originally closed within an adjustable time delay (0 to 10 Cycles in increments of 1 Cycle) after the other breaker is closed by external means (breaker control close switch for example).
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System Setpoints60FL Bus VT Fuse Loss SettingsA Bus VT Fuse-Loss condition is implemented by comparing the voltage on both sides of the closed breaker.
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System Setpoints60FL Bus VT Fuse Loss Input/Output Selection
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System Setpoints27 Bus Phase Under Voltage
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System Setpoint27 Bus Phase Under Voltage initiate Input/Output Selection
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System Setpoints50BF #1 Source 1 Breaker Failure
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System Setpoints50BF #1 Source 1 Breaker Failure Input/Output Selection
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System Setpoints50BF #1 Source 1 Breaker Failure Initiating Input/Output Selection
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System SetpointsTrip Circuit Monitor
M-4272 Motor Bus Transfer System
Motor Bus Transfer
ISSlogicTM
ISSlogic is programmed utilizing the M-3872 ISScom Communications Software. ISScom takes the control/status input status, system status and function status, and by employing (OR, AND, NOR and NOT) boolean logic and timers, can activate an output, change setting profiles, initiate transfer, or block transfer. An ISSlogic Function can not be used to initiate itself.
Since there are six ISS Logic Functions per setting profile, depending on the number of different MBTS settings defined, the scheme can provide up to 24 different logic schemes.
There are six initiating input sources:
– Initiating Outputs
– Initiating Function Time Out
– Initiating Function Pickup (including the ISSlogic functions themselves)
– Initiating System Status
– Initiating Inputs
– Initiation using the communication port
M-4272 Motor Bus Transfer System
Motor Bus Transfer
ISSlogicTM
There are three blocking input sources:
– Blocking Inputs (contacts)
– Blocking through system status conditions
– Blocking using the communications port
The activation state of the input function selected in the Initiating Function can be either timeout (trip) or pickup.
The desired time delay for security considerations can be obtained in the ISS Logic Function time delay setting.
The ISS Logic Function can be programmed to perform any or all of the following tasks:
– Change the Active Setting Profile
– Close an Output Contact
– Be activated for use as an input to another ISS Logic Function
– Initiate a Transfer
– Block a Transfer
M-4272 Motor Bus Transfer System
Motor Bus Transfer
ISSlogicTM Setup Screen
M-4272 Motor Bus Transfer System
Motor Bus Transfer
ISSlogicTM Setup Screen SelectionsM-4272 Motor Bus Transfer System
Motor Bus Transfer
ISSlogicTM Setup Screen SelectionsM-4272 Motor Bus Transfer System
Motor Bus Transfer
ISSlogicTM Setup Screen SelectionsM-4272 Motor Bus Transfer System
Motor Bus Transfer
ISSlogicTM Setup Screen SelectionsM-4272 Motor Bus Transfer System
Motor Bus Transfer
Metering and StatusThe Digital Motor Bus Transfer System provides metering of voltage, current, and frequency of the Source 1, Source 2, and the Motor Bus.
Metering accuracies are:
Voltage: ± 0.5 V or ± 0.5%, whichever is greater
Current: 5 A rating, ± 0.1 A or ± 3%, whichever is greater
1 A rating, ± 0.02 A or ± 3%, whichever is greater
Frequency: ± 0.02 Hz (from 57 to 63 Hz for 60 Hz models; from 47 to 53 Hz for 50 Hz models)
Phase Angle: ± 0.5 degree or ± 0.5%, whichever is greater
M-4272 Motor Bus Transfer System
Motor Bus Transfer
Metering and StatusSecondary Metering and Status Screen
M-4272 Motor Bus Transfer System
Motor Bus Transfer
Metering and StatusPrimary Metering Screen
M-4272 Motor Bus Transfer System
Motor Bus Transfer
Metering and StatusThe Phasor Diagram provides the user with the ability to evaluate a selected reference Phase Angle to Phase Angle data from other sources. The Phasor Diagram also includes a Freeze capability to freeze the data displayed on the Phasor Diagram.
M-4272 Motor Bus Transfer System
Motor Bus Transfer
Metering and StatusThe Sync Scope screen provides the user with the ability to observe the Delta Frequency relationship between the Bus and the New Source, illustrated in a Fast or Slow direction based on Delta Frequency.
M-4272 Motor Bus Transfer System
Motor Bus Transfer
Metering and StatusThe Single Line Diagram provides the user with the ability to observe the Delta Phase Angle, Delta Voltage and Delta Frequency relationship between the Bus and the New Source. The Single Line Diagram also displays the metering, the status of S1 and S2 breakers and the status of Manual Transfer Ready, Lockout/Blocking, Remote/Local and Device On/Off.
M-4272 Motor Bus Transfer System
Motor Bus Transfer
Oscillographic RecorderSamples at 16 or 32 (50 or 60 Hz) Samples/Cycle.
The Oscillographic Recorder can be triggered by a control/status inputs or output contact signals.
Supports COMTRADE file format
User-defined, post-trigger delay period
M-4272 Motor Bus Transfer System
Motor Bus Transfer
Oscillographic RecorderThe following parameters are captured by the Oscillographic Recorder:
– MBTS start (initiate) signal. It can be manual transfer initiate, protective relay initiate, internal bus undervoltage initiate or external bus undervoltage initiate.
– Source 1 and Source 2 breaker status (Closed or Open)
– Trip and close commands to the Source 1 breaker
– Trip and close commands to the Source 2 breaker
– Source 1 voltage waveforms, single-phase or three-phase
– Source 2 voltage waveforms, single-phase or three-phase
– Source 1 current waveforms, single-phase if available
– Source 2 current waveforms, single-phase if available
– Bus voltage waveforms, single-phase or three-phase
M-4272 Motor Bus Transfer System
Motor Bus Transfer
Oscillographic RecorderThe following parameters are also captured by the OscillographicRecorder:
– Delta Phase Angle
– Delta Frequency
– Trip Circuit Monitor (TCM) or Close Circuit Monitor (CCM) open signal
– Inputs 1-18
– Outputs 1-16
M-4272 Motor Bus Transfer System
Motor Bus Transfer
Oscillographic Recorder Setup ScreenM-4272 Motor Bus Transfer System
Motor Bus Transfer
Oscillographic Recorder Retrieve Record ScreenM-4272 Motor Bus Transfer System
Motor Bus Transfer
M-4272 Motor Bus Transfer SystemOscillographic Recorder Record Opened in ISSplotTM
Motor Bus Transfer
Transfer Event LogEach transfer event log (total of 4) includes the following parameters:
– Start Signal. The signals that can trigger a transfer are an external protective relay initiate, external undervoltage relay initiate, internal automatic bus undervoltage relay initiate, and manual initiate (either local, remote or through serial communications).
– Source 1 RMS value of voltage and current at time of trip (or close)
– Source 2 RMS value of voltage and current at time of close (or trip)
– Bus RMS value of voltage at time of close (or trip)
– Positive and Negative Sequence values
– Delta Voltage between bus and new source* at time of close command (or trip command)
– Delta Voltage between bus and new source* at the time of actual breaker close (or breaker open)
* The 'new source' is defined as the source to which the bus is being transferred.
M-4272 Motor Bus Transfer System
Motor Bus Transfer
Transfer Event Log (cont.)– Bus frequency, at time of close (or trip)
– Resultant Volts/Hertz at time of actual breaker close
– Element(s) operated, for example: 27B, 81, 81R, 50BF, TCM and CCM Functions
– Element(s) picked up, for example: 27B, 81, 81R, 50BF, TCM and CCM Functions
– Input/output contact status changes
– Trip and close commands
– Delta Phase Angle between bus and new source* at time of close command (or trip command)
– Delta Phase Angle between bus and new source* at time of actual breaker close (or breaker open)
– Delta Frequency between bus and new source* at time of close command (or trip command)
* The 'new source' is defined as the source to which the bus is being transferred.
M-4272 Motor Bus Transfer System
Motor Bus Transfer
Transfer Event Log (cont.)– Delta Frequency between bus and new source* at time of actual breaker close (or
breaker open)
– Breaker closing time (time from when the close command is issued to when the new source breaker status contact closes
– Breaker opening time
– Open transition time (time from when the old source breaker status contact opens to when the new source* breaker status contact closes)
– Close transition time in Hot Parallel Transfer only (time from when the new source* breaker status contact closes to when the old source breaker status contact opens)
– Type of transfer completed: Fast, Delayed In-Phase, Residual Voltage, Fixed Time or Hot Parallel
* The 'new source' is defined as the source to which the bus is being transferred.
M-4272 Motor Bus Transfer System
Motor Bus Transfer
Transfer Event Log (Detail)
M-4272 Motor Bus Transfer System
Motor Bus Transfer
System Status and Transfer Start Signal Status ScreenM-4272 Motor Bus Transfer System
Motor Bus Transfer
M-4272 Motor Bus Transfer SystemSequence of Events RecorderIn addition to the Transfer Event Log the Digital Motor Bus Transfer System provides Sequence of Events Recording.
The Sequence of Events Recording stores every change in the input status, trip commands, close commands, any signal to initiate a transfer, type of transfer, change in any breaker status, change in setpoint and status reset.
Each of these Running Events are time stamped with the date and time in 1 ms increments whether the IRIG-B is present or not.
The Running Event Log stores the last 512 events, when a new event occurs the oldest event is removed.
A reset feature is provided to clear this log through the serialcommunications.
Motor Bus Transfer
Sequence of Events Setup Screen
M-4272 Motor Bus Transfer System
Motor Bus Transfer
Sequence of Events File Details ScreenM-4272 Motor Bus Transfer System
Motor Bus Transfer
Conclusions
The fast transfer requires a ringdown or simulation analysis to determine the phase angle limit at the instant of connection to the new source.
Worst case scenarios should be considered that include rapid external system changes, changes in loading that include inertia, and mixture of synchronous and induction machines.
The sync check equipment to be used for supervising fast transfers must be able to detect a phase angle pickup or block very rapidly if the angle moves in or out of the desired range.
Sync check relays used for traditional applications do not have the required speed of operation to effectivelypickup or block if required.
Conclusions
Motor Bus Transfer
The in-phase transfer offers an opportunity to synchronize a motor bus on the first available slip cycle- This type of transfer will enable process continuity as the
motors are still spinning and the resultant V/Hz for an in-phase close is well below the 1.33 pu maximum
Specialized high speed synchronizing equipment permits in-phase transfer that can determine the deceleration of the motor bus and effect a new source breaker closure at phase coincidence.
Undervoltage relays classically used for residual voltage transfer exhibit setpoint error at low frequency that could permit an out-of-phase transfer well above the maximum acceptable resultant V/Hz standard of 1.33 pu.
Undervoltage relays must be selected exhibitingsetpoint accuracy down to low frequencies.
Motor Bus Transfer
Conclusions
©2008 Beckwith Electric Co., Inc.