motor bus transfer

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


Motor Bus Transfer

Excerpts from ANSI 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


MMM

Motor Bus



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



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


MMM

Motor BusG


-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


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



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



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


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



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.


Motor Bus 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



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


▪ “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



Motor Bus Transfer

Open Transition

MMM

Motor Bus



Motor Bus Transfer

External Trip

Open Transition

MMM

Motor Bus



Motor Bus Transfer


▪ “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


MMM

Motor Bus



Motor Bus Transfer


MMM

Motor Bus



Motor Bus Transfer

External Close


MMM

Motor Bus



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



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.



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

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 System

Motor Bus Transfer

M-5802 Syncrotran® 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


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


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


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


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


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.


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


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.


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


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.


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


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.


Motor Bus Transfer

System SetupThe System Setup consists of defining all pertinent information regarding the connection environment.


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.


Motor Bus Transfer

System SetpointsThe System Setpoints screen consists of defining all Common, Automatic and Manual Transfer settings, and Function settings.


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


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


Motor Bus Transfer

System SetpointsCommon Function Settings, Inputs and Outputs


Motor Bus Transfer

System SetpointsCommon Function Settings Inputs


Motor Bus Transfer

System SetpointsCommon Function Settings Outputs


Motor Bus Transfer

System SetpointsAutomatic Transfer Settings


Motor Bus Transfer

System SetpointsManual Transfer Settings


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).


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.


Motor Bus Transfer

System Setpoints60FL Bus VT Fuse Loss Input/Output Selection


Motor Bus Transfer

System Setpoints27 Bus Phase Under Voltage


Motor Bus Transfer

System Setpoint27 Bus Phase Under Voltage initiate Input/Output Selection


Motor Bus Transfer

System Setpoints50BF #1 Source 1 Breaker Failure


Motor Bus Transfer

System Setpoints50BF #1 Source 1 Breaker Failure Input/Output Selection


Motor Bus Transfer

System Setpoints50BF #1 Source 1 Breaker Failure Initiating Input/Output Selection


Motor Bus Transfer

System SetpointsTrip Circuit Monitor


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


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


Motor Bus Transfer

ISSlogicTM Setup Screen


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


Motor Bus Transfer

Metering and StatusSecondary Metering and Status Screen


Motor Bus Transfer

Metering and StatusPrimary Metering Screen


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.


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.


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.


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


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


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


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.


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)



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



Motor Bus Transfer

Transfer Event Log (Detail)


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


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.

motor bus transfer

Engineering