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Functional description short white paper
ASDS for Main Breaker Control, Mud-Pump, Drawworks, Top Drive and Cement Pump
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Document No. 1 of 23
1 Contents
1 Contents... 2
2 Figure list ... 3
3 General ... 4
4 Definitions and Abbreviations... 5
5 General Arrangement Description ... 6
5.1.1 Overview ... 6
5.2 MAIN COMPONENTS ... 6
5.2.1 Module connection ... 6
5.2.2 Control cabinet ... 6
5.3 RECTIFIER MODULE, WITH BRAKE CHOPPER ... 7
5.4 MAIN SUPPLY ... 8
5.4.1 Pre-charge system ... 8
5.5 DC-BUS ... 8
5.5.1 DC-bus load sharing ... 9
5.5.2 DC-bus current control ... 9
5.5.3 DC-bus tie breakers ... 9
5.6 THE ELECTRONIC DC-BREAKER ... 9
5.7 AC-BREAKER ... 9
5.8 BRAKE CHOPPER ... 10
5.9 BRAKE RESISTOR ... 10
5.10 SHORT CIRCUIT PROTECTION. ... 10
6 Cooling system description ... 11
6.1 VSD COOLING SYSTEM ... 11
6.1.1 Requirements for cooling water system ... 11
6.1.2 Monitoring of cooling water pressure and temperature ... 11
6.1.3 Leakage detector. ... 12
7 System functions PLC ... 12
7.1 SPEED ENCODER ... 12
7.1.1 General ... 12
7.2 PLC ... 13
7.2.1 ICS connection... 13
7.2.2 Mud pump ... 13
7.2.3 Drawwork ... 15
7.2.4 DDM/top drive... 16
7.2.5 Cement pump ... 17
7.2.6 Drive changeover example ... 18
8 ASDS Power Management ... 19
8.1 GENERAL INTRODUCTION ... 19
8.2 PMDESCRIPTION ... 19
8.2.1 ASDS PM Topology for two ASDS buses ... 20
8.2.2 ... 20
8.3 ASDSPMSIGNAL INTERFACE. ... 20
8.3.1 Signal Description. ... 20
8.4 DRIVE GROUPS ... 21
8.5 ASDSPMPOWER /CURRENT CONTROL. ... 21
8.5.1 Logic 1 ... 21
8.5.2 Logic 2 ... 22
8.5.3 Logic 3 ... 22
2 Figure list
Figure 5-1 Rectifier module with brake chopper ... 7
Figure 5-2 Transitor short circuit protection ... 10
Figure 6-1 Temperature limits ... 12
Figure 7-1 Mud pump internal interface ... 13
Figure 7-2 Drawwork internal interface ... 15
Figure 7-3 DDM internal interface ... 16
Figure 7-4 Cement pump internal interface ... 17
Figure 7-5 Profibus interface, cement pumps. ... 17
Figure 8-1 ASDS System typical power limit functionality ... 23
3 General
The purpose/objective of this document is to short describe the functions and facilities of the frequency converters, also known as the variable speed drives (VSD) and also the ASDS system.
The document covers:
General arrangement description
Frequency Converter cooling system
System / Electrical arrangement
Interface to other systems
Control system
Display
PLC
Local panel
Main board
Failure modes
ASDS PM system
Unless it is stated otherwise all alarms and faults mentioned in this document is displayed in the frequency converter display and transferred to the drilling system/view.
Alarms and faults can be collected into common alarms and faults in drilling view but will always be described in detail in the display.
4 Definitions and Abbreviations
Definitions
AI Analogue Input
AO Analogue Output
CP Cement Pump
DCMS Drilling Control and Monitoring System
DDM Derrick Drilling Machine
DECS Drilling Equipment Control System
DFB Derived Function Block
DI Digital Input
DICS Drawwork Integration Control System
DO Digital Output
DP Dynamic Positioning
DW Drawwork
EMC Electromagnetic Compability
E-DCB Electronics DC breaker
ESD Emergency Shut Down
FS Fail Safe
HK Main board (Hovedkort) see also HKA
HKA Main board (Hovedkort)
IAS Integrated Automation System
ICS Integrated Control System
IO Input / Output
LLC Low Loss Concept
LT Low temperature
MCT Multi Cable Transit
MP Mud Pump
MPCS Mud pump control system.
MPMP Mud Pump Maintenance Panel
NC Normally Closed
NO Normally Open
PDO Process Data Object
PLC Programmable Logic Controller
THD Total Harmonic Distortion
UPS Un-interruptible Power Supply
VSD/ VFD Variable Speed Drive/ Variable Frequency Drive
VSDS Variable Speed Drive System, i.e. a set of several VSD’s
FPGA Field Programmable Gate Array
Power Modules –The transistor modules.
Fault – An alarm signal that will give a trip of the VSD Local control panel – Push buttons for local control
Local display – Local touch display showing the alarms, limits and faults of the VSD
5 General Arrangement Description
5.1.1 Overview
The ASDS system is several power/rectifier modules connected to the same DC-bus. This means that one frequency converter can use regenerated power from another frequency converter.
If the total regenerated power is more than the consumed power the voltage on the DC-bus will increase and a brake chopper will automatically connect the DC-bus to a brake resistor and discharge the regenerated power. When the voltage on the DC-bus has decreased the brake chopper will disconnect the brake resistor.
The transformers must be of 12, 18 or 24 pulse type transformers with 4 secondary windings.
The frequency converters are directly water cooled with no external fans. Internal air-to-water fans are mounted to reduce the internal power cabinet temperature.
5.2 Main components
The cabinets are manufactured in stainless steel. Vibration dampers are used between cabinets and foundation. All power cable entries are located in the bottom, and the cabinets are
accessible from behind to terminate power cables. MCT’s with 360degr. EMC shielding is used. All cabinets have an effectively EMC shielding, by utilising stainless steel enclosure, conductive gaskets and EMC shielded MCT’s.
5.2.1 Module connection
The rectifier modules and the inverter modules are extractable modules, equipped with heavy- duty plug connectors. The plug connectors are self-aligning.
5.2.2 Control cabinet
The control cabinets will be placed next to the power cabinets.
The following cables are connected between the control cabinet and the power cabinet:
Leakage detector cables.
Fibre cables.
ESD signals.
Pre-charge cables
Motor breaker status cables
DC bus tie breaker status cables
Only optical fibres are passing through from the control cabinet to the power cabinets. The control cabinet also contain a separate enclosure, housing the pre-charge transformer,
auxiliary transformer, isolation monitor, and some protection equipment related to these units.
The enclosure is designed as a separate EMC shielded compartment.
5.3 Rectifier module, with brake chopper
The drawing below shows the topology of a rectifier module with brake chopper.
The brake resistor is connected between DC+ and DC- via the brake chopper. The chopper consists of 3 transistors in parallel. Current sharing is controlled by the gate driver card that they share.
Figure 5-1 Rectifier module with brake chopper
Note that each rectifier module has two diode rectifier bridges in parallel.
One bridge for one of the delta windings from the transformer and one bridge for one of the star windings from the transformer are connected to the rectifier module via plug connectors.
The brake resistor arrangement and breaker for disconnecting the resistor is not shown in Figure 5-1 Rectifier module with brake chopper.
5.4 Main supply
All signal monitoring of the transformer is done by the ASDS.
Highest transformer temperature is transferred to the ASDS and then to the Drilling control.
The ASDS breaker PLC will have the high and high-high alarms and will perform a power reduction according to the logic/settings inside the ASDS power Management system.
The ASDS power Management system is described in 8 ASDS Power Management.
5.4.1 Pre-charge system 5.4.1.1 ASDS-Bus
In order to limit the inrush current into the capacitor banks located on the DC-bus, a pre- charge arrangement is included. Prior to closing the main breakers, a transformer supplied from a dedicated breaker in the 690V switchboard is connected to the rectifiers. This transformer limits the inrush current to a desired level, and the voltage is being built up gradually. When the voltage level reaches a parameter defined value, the main breaker is closed. The pre-charge sequence is aborted if the voltage on DC bus has not reached 682 V DC (parameter adjustable) within 2 seconds. Normally pre-charge sequence takes 1.2 seconds.
If there is a fault in the transformer, rectifier or DC-bus, the Pre-charge transformer will not be able to energize the DC-bus and the main breaker will not get a close signal.
It will be given a pre-charge fault signal from the ASDS after 3 faulty attempts to perform a pre-charge. If a faulty pre-charge sequence has occurred, there is no automatic reattempts.
The pre-charge circuit is protected by fuses, located at the secondary side of the pre-charge transformer.
Using a transformer instead of resistors gives a higher operating frequency of the pre-charge system.
The transformer has a greater mass and uses longer time to heat up then resistors.
An earth fault monitoring instrument is also located in the pre-charge circuit.
5.4.1.2 Power Modules
Each power module has two inbuilt capacitors between DC+ and DC- on the module.
Before a power module is connected to the DC-bus, it has to be pre-charged in the same manner as the whole ASDS system.
The pre-charge of the individual power modules is handled by the corresponding DC-breaker.
The pre-charge sequence of the individual power modules is a pre-programmed functionality inside the drive software. It will be a part of the start sequence of the respective power module.
5.5 DC-bus
There is an interlock in the ASDS system that will prevent closing a drilling transformer feeder breaker in case one of the other transformer feeder breakers is closed and a DC bus tie is also closed. Parallel operation with two drilling transformers on a common interconnected DC bus (bus tie closed) is not allowed.
5.5.1 DC-bus load sharing
All three of the ASDS systems is powered from both sides. With approximately equal voltage level into the two rectifiers, the power supply will be equal/symmetrical from both sides. This means that at full load, half of the power is coming from the left side supply and the other half is coming from the right side supply.
5.5.2 DC-bus current control
In order to prevent over load of the DC-bus, current control algorithms is implemented in the drives. All drives are connected to the same communication network. See section 8 for detailed description over this functionality.
5.5.3 DC-bus tie breakers
The ratings of the DC-bus tie breakers that are normally used are 3200A.
The ASDS power management function will control/limit the current through the bus-tie breakers in order to prevent tripping.
5.6 The Electronic DC-breaker
For each inverter module in the ASDS system, there is an electronic DC-breaker. The main task for this electronic DC-breaker is to connect the inverter module to the DC-link and disconnect it if a critical fault occurs on the inverter module. The E-DCB will disconnect a module with a critical fault within 6µs and it will not have any influence on the other VSDs.
The other VSDs will not even notice that there have been a critical fault in the system.
The electronic DC-breaker is found in the lower part of the cubical. It consists of a mechanical breaker and an electronic breaker.
Even though the mechanical breaker is engaged this does not mean it has connected the inverter module to the common DC-link, there is a transistor which has to be triggered to connect the inverter module. The mechanical breaker only makes it possible for the inverter to be connected to the DC-link. The mechanical breaker also makes it possible to isolate the transistor module completely from the DC-bus.
It is the associated VSD local control panel or remote operation which triggers the electronic DC-breaker when “close breaker” is engaged.
The electronic DC-breaker communicates with the control cabinet through fibre-optic cables.
Note that this solution is patented by Wärtsilä.
5.7 AC-breaker
There is installed AC-breakers between the power module and the motor on all drives.
The breaker is mounted in the back panel of the VSD as shown in Appendix.
The AC breaker is normally closed and operated locally.
Trip of the breaker is controlled via an external ESD system.
ESD trip will stop the VSD immediately and an emergency stop alarm will appear in the VSD display.
The breaker is not used as a short-circuit or over-load protection. These protections are handled by the VSDs themselves.
5.8 Brake chopper
Brake choppers are used when there is a possibility of power being generated from the motors and returned to the DC-bus. Winch, drawwork and DDM are applications where this is a possibility.
The regenerated power can be used by all other inverters connected to the bus.
Brake choppers are physically mounted inside the rectifier module on a standard diode cooling flange. This can be seen on the figures below.
The brake chopper is an autonomous device. It has no external control. It is connected to a maincard via a fibre cable for monitoring and viewing of current, voltage and power only.
Alarms and faults on the brake chopper and brake resistor will be transferred to drilling control system and can be viewed in local display.
5.9 Brake resistor
Water cooled resistors that are connected to the ASDS systems can be used to remove re- generated power.
Brake resistor can be manually disconnected via a breaker inside the ASDS cabinet.
This allows for maintenance of the brake resistor while the ASDS is energized.
The breaker is not used as a short-circuit or over-load protection. These protections are handled by the VSDs themselves.
5.10 Short circuit protection.
C
E V
C
E V
VCE Sat
A
Short circuit protection
Figure 5-2 Transitor short circuit
protection
The motor is protected via Vce sat protection on the GateDriver board with a response time 6us. Also over current protection with response time approximately 6us implemented on the GateDriver board. These protections are used for both motor inverter and brake chopper.
The main board also has current limits. The FPGA has over current protection with 10ms response, and the DSP on the main board has over current protection with response time 667us. The two on the main board are changeable via parameter settings and are adjusted according to motor cables, and motor size. These protections are only used for motor inverter.
6 Cooling system description 6.1 VSD cooling system
Each VSD cabinet has a cooling distribution block located at the bottom of the cabinet. This block distributes two branches of cooling water, one for the upper unit and one for the lower unit where the DC-breaker for each power module is placed. The block is arranged with internal ball valves that can be operated by small handles. It is possible to shut off water circulation to each of the two branches in each cabinet.
The water circulation to each module can be handled individually.
6.1.1 Requirements for cooling water system
Medium Fresh water with corrosion inhibitors
Design pressure 4.0 bar, max 2 bar pressure drop between input and output.
Test pressure 6.0 bar
Inlet temperature Max. 38 °C, min. 22 °C, or above condensation level
Flow Ref Data sheet
Losses to water Ref Data sheet
6.1.2 Monitoring of cooling water pressure and temperature
The VSD as well as the ASDS transformer are all cooled by the LT fresh water system. The cooling system and the central cooling pumps are monitored by the ICS system.
Loss of cooling water pressure will not cause any shut down or start inhibition.
The VSD has a built in, self- protecting function, based on monitoring of the IGBT transistor temperature. If the VSD is started without any cooling water flow, the IGBT transistor temperature will rise above defined limit values and cause a linear current limitation, and if temperature continues to rise, a trip. Starting the VSD without cooling water will not cause any damage to the equipment. The IGBT transistor temperature is presented at the local display. Alarms and faults are presented in local display and sent to ICS.
The following limit values are valid:
Table 6-1 IGBT Transistor temperatures
Temperatures Limit
IGBT transistor temperature, high alarm 66 °C
IGBT transistor temperature, current limitation activated, start 68 °C IGBT transistor temperature, current limitation activated, stop 71 °C
IGBT transistor temperature, trip value 72 °C
IGBT transistor temperature, trip value HW 83 °C See Figure 6-1 Temperature limits for explanation of what the limits are.
Loss of cooling water flow in a load condition will also cause alarm, current limitation and finally trip of VSD. At higher load levels the temperature will rise rapidly, and time to trip will be short.
When cooling water flow is restored, the VSD can be started after a reset of trip.
The Gate Drivers also have temperature surveillance that can be reached if the cabinet coolers have a fault.
The following temperature limits are valid:
Table 6-2 GDA Temperature limits
Temperatures Limit
Temp Limit GDA Alarm 80 °C
Temp Limit GDA Start 83 °C
Temp Limit GDA Stop 85 °C
Temp Limit GDA Trip 87 °C
Temp Limit GDA HW Trip 90 °C
See Figure 6-1 Temperature limits for explanation of what the limits are.
Figure 6-1 Temperature limits
Figure 6-1 Temperature limits explain how and what the current reduction limits are when the different temperature limits are reached.
Current Rated Inverter HD is an adjustable.
6.1.3 Leakage detector.
All cabinets except the control cabinets and DC-bus tie cabinets are equipped with a leakage detector. The cabinet without leakage detector do not have any water cooling installed.
The leakage sensors in the VSD power cabinets are mounted from below, and any water leakage will be drained through a hole in the bottom plate and on to the detector. The detector will give alarm in local display and ICS when the sensor tip comes in contact with water.
7 System functions PLC
7.1 Speed Encoder
The use of encoder is needed in low speed applications to ensure accurate torque and speed.
Without the encoder the motor drive will run at the minimum speed selected in the database.
For DDM and DW the drive is not allowed to run without encoder.
Similarly to the direction of rotation, the direction of the encoder readout can also be changed by a simple parameter change
The speed encoder is mounted on the motor shaft and has to be hardwired to Wärtsilä Power Drive control system.
7.2 PLC
The main task of the PLC is to interface with external equipment like:
Control system
Transformer
Motor
PMS system
ICS
7.2.1 ICS connection
The different PLC’s for the different VSD’s are connected to each other so that the all information from the different frequency converters is available for the ICS.
Losing the overall switch will not have any kind of operational impact to the system, since this network is made only for distribution of alarms/status to ICS. Control of the frequency converters from the drilling control are not done in this ring, there are dedicated connections for each group of PLC’s as shown in later chapters.
7.2.2 Mud pump
7.2.2.1 Mud pump internal interface example
Schneider Premium PLC MUD 1 and 2
=U12
Ethernet HW Profibus Fibre
Schneider Premium PLC MUD 3 and 4
=U15
Wago PLC Mud 1
=U12
Wago PLC Mud 4
=U15 Wago PLC
Mud 3
=U12 Wago PLC
Mud 2
=U15 To Drilling
control
To Drilling control
Figure 7-1 Mud pump internal interface example
7.2.2.2 Mud Pump Displaced Synchronisation
Normally one of the Premium PLC’s is master and the other is slave, this is controlled by parameter settings inside the PLC. Master and slave are used for controlling displaced synchronisation of the mud pumps.
If communication between the different Premium PLC’s are lost they will both be working as master and communicate with drilling control. In this case displaced synchronisation can only be guaranteed between MP1 and MP2 , and between MP3 and MP4. Alarm will be sent to drilling control system.
When more than one mud pump are used together they may be synchronised with the appropriate angular displacement in order to avoid discharge pressure pulsation (hammer effect). Synchronisation applies to two, three and four pumps when allocated to a group function. When allocated, the pumps acts as a single unit by running at a common speed with the stroke of each piston evenly displaced for each collective revolution of the cranks.
A dedicated proximity switch is fitted to each mud pump and connected directly to the VSD's in order to achieve pump displaced synchronisation. On selection of pump synchronisation from the pump control the transmitted speed reference signals for each pump are made from a single common control interface (i.e. the operator selects a single speed from the screen). The VSD ensures that all pumps run at a constant speed with a crankshaft displacement difference of 60 degrees (two pumps), 40 degrees (tree pumps) or 30 degrees (four pumps). The control algorithm controls the individual speed set points by temporarily reducing the speed reference to a pump until the crankshaft displacement is at correct level. When displacement is correct, the speed set points to all pumps will be identical again.
7.2.3 Drawwork
7.2.3.1 Drawwork internal interface example
The interface topology will be according to drilling control system.
Figure 7-2 Drawwork internal interface
All motors are speed controlled with an internal droop factor to ensure proper power sharing.
There is one fibre optic network between drawwork control and the VSD. The OLM’s in each end are set up as “redundant ring” with 2 pairs of fibres
Communication failure on one pair will not have any impact on the system and it will generate alarm to drilling control system
Schneider Premium PLC
Drawwork
=U16
To Drilling control
Ethernet
Profibus, 2x2 FO
Wago PLC DW 1
=U11
Wago PLC DW 2
=U16
Wago PLC DW 3
=U13 DP/DP
OLM
Profibus, Copper
7.2.4 DDM/top drive
7.2.4.1 DDM internal interface example
The interface topology will be according to drilling control system
Figure 7-3 DDM internal interface
There are two redundant fibre optic networks between drilling control and the VSD.
Communication failure on one line will not have any impact on the system and it will generate alarm to drilling control system
Schneider Premium PLC
DDM
=U13 To Drilling
control
Wago PLC DDM 1
=U13
Wago PLC DDM 2
=U16 DP/DP
OLM
DP/DP
Ethernet
Profibus, 4x2 FO Profibus, Copper
OLM
7.2.5 Cement pump
7.2.5.1 Cement pump interface example
Figure 7-4 Cement pump internal interface
There are one fibre optic network between cement pump control and the VSD’s. The OLM’s in each end are set up as “redundant ring” with 2 pairs of fibres on each pump/VSD.
Communication failure on one pair will not have any impact on the system. See figure below for details.
Figure 7-5 Profibus interface, cement pumps.
PP3 is a fibre optic patch box.
Wago PLC Cement 1
=U17
Wago PLC Cement 2
=U18 To Cement control
Ethernet Profibus, 2x2 FO on each pump
DP/DP OLM
Profibus, Copper
DP/DP OLM
7.2.6 Drive changeover example
A drive can be shared by two different applications with different parameters.
For example a changeover between a mud pump and a cement pump.
Changeover can be with other applications also. Winch and cement for instance.
It must be selected which motor that has priority and what motor the drive shall be initialized with after a power black out.
Each motor will have a separate interface PLC and will share local display, local control panel, motherboard and inverter module.
In local it is possible to change application with a local switch.
In remote the drilling control needs to do the application change.
8 ASDS Power Management 8.1 General introduction
Each ASDS system (A, B and C) is equipped with one PLC that calculates and controls the amount of consumed power on each ASDS system. This is an internal ASDS Power Management (ASDS PM) function which comes in addition to the vessel PMS.
All PLC’s communicate with all three ASDS systems. If one of them fails, one of the other will take over the control. All PLC’s will have motor load inputs from all drives and all three PLC’s will send individual available power signals to all drives.
The ASDS A-bus PM functionality is placed in the PLC for Breaker 1(A).
This is defined as master.
The ASDS B-bus PM functionality is placed in the PLC for Breaker 2(B).
This is defined as back-up.
The ASDS C-bus PM functionality is placed in the PLC for Breaker 3(C).
This is defined as back-up for the back-up.
The ship overall PMS will send available power signals to each ASDS power management (PM) system. The internal ASDS PM will distribute the overall available power to the individual drives based on the logic described later in this document.
The ASDS PM will take into consideration regenerated power from DW/DDM and current capacity on DC busbars and DC-bus-ties.
8.2 PM Description
There are three ASDS systems.Each ASDS system is powered via rectifiers from both sides. Due to approximately equal voltage level into the two rectifiers, the power supply will be equal/symmetrical from both sides. This means that at full load, half of the power is coming from the left side supply and the other half is coming from the right side supply.
8.2.1 ASDS PM Topology for two ASDS buses
The system is redundant. There is two PLC’s that performs the same task. One of them is defined as master(A), the other is defined as backup(B).
The figure below shows the topology. All signals are HW 4-20mA.
8.3 ASDS PM Signal Interface.
Each of the 3 ASDS PM PLC’s has analogue inputs and analogue outputs to/from the individual drives and the vessel PMS. This is hardwired signals with signal range 4-20 mA.
The PLC’s are galvanic isolated from each other by signal splitters.
Based on this interface, all ASDS PM PLC’s will be able to calculate the total amount of consumed power on all three ASDS systems.
8.3.1 Signal Description.
Converter Signal Type From To Range Description
Available Power From Vessel PMS
AI Vessel
PMS
ASDS PM
4-20 mA.
4 mA(0%) = 0 kW, 18 mA(100%) = x kW Motor Load From
Drive(s)
AI Drives ASDS
PM
4-20 mA.
4 mA(0%) = 0%, 18 mA(100%) = 100%
Total Motor Load To Vessel PMS
AO ASDS
PM
Vessel PMS
4-20 mA.
4 mA(0%) = 0 kW, 18 mA(100%) = x kW Available Power To
Drive(s)
AO ASDS
PM
Drives 4-20 mA.
4 mA(0%) = 0 %, 18 mA(100%) = 100%
ASDS A-Bus PM
ASDS B-Bus PM
ASDS A-Bus Drives
ASDS B-Bus Drives
Max Power = 6080kW
Max Power = 6080kW
Redundant ASDS PM
Av. Power signals from Vessel PMS A+B
Av. Power signals to Drives
Figure 8-1 Redundant ASDS PM
8.4 Drive Groups
The available power signals from PM A and PM B to the drives is bundled together into drive groups inside the software. Primarly, this is done in order to reduce the complexity of the system. Secondly it is necessary to have the same available power to motors connected to the same shaft, e.g DDM and DW.
Groups:
1. DDM 2. DW
3. Mud group A 4. Mud group B 5. Mud group C 6. CP
8.5 ASDS PM Power /Current Control.
The internal topology for each of the ASDS PMs is divided into 3 modules as shown in figure below. The modules are called “LOGIC 1”, “LOGIC 2” and “LOGIC 3”.
8.5.1 Logic 1
The input to this module is analogue signals from vessel PMS and all digital signals from breakers and fuses.
The output of this box is 3 different temporary available power limits:
1. LIM 1
Available power limit based only on vessel PMS signals.
2. LIM 2
Available power limit based only on Transformer fuse signals.
3. LIM 3
Available power limit based only on breaker status signals. Main breaker and bus-
LOGIC 1
Signals FROM Vessel PMS A+B
LOGIC 2 LOGIC 3
Signals FROM Transformer Fuses
Signals FROM Main/bus-tie breakers and "Rectifier Status" selector
LIM 1
LIM 2
LIM 3 LIM
Drive 1
Drive 10
Av. Pow
Mot. Load
ASDS PM
tie breakers.
8.5.2 Logic 2
The input to this module is the 3 output from previous module. This module selects the lowest limit of the 3 inputs and sends that to the output.
8.5.3 Logic 3
This module controls the power reduction of the individual drives based on priorities. The consumers are reduced in the following order:
1. MP’s/CP’s 2. DDM 3. DW
This means that the DDM will not be limited until MP/CP is reduced to its minimum value.
DW will not be limited until both MP/CP and DDM are both at their minimum values. The table and figures below presents this in a graphical way. The constants MP_min , CP_min and DDM_min will be configured during commissioning. The minimum value of power limit for each ASDS system is recommended to be 30 %.
LIM MP CP DDM DW
100%
90% X X - -
40% MP_min CP_min X -
30% MP_min CP_min DDM_min X
Figure 8-2 ASDS System typical power limit functionality
Y- axis is individual drilling machine power limit (MP, CP , DDM , DW)
If one high prioritized drive is not loaded up to its available power limit, this drive will give back the unused power capacity and share it with the other drives.
If the high prioritized drives some time later need all its available power, it will take it back from the drives that have “borrowed” the unused power capacity and the lower prioritized drive will be limited.
8.6 Operation
The individual ASDS systems are powered from their separate transformer and the DC bus-tie breakers are open.
ASDS PM A, ASDS PM B and ASDS PM C has status feedback from the DC bus-tie breakers and the main feeders for the ASDS system A, B and C.
The “Av Power“ signals from ASDS PM A, ASDS PM B and ASDS PM C to the respective drives will be equal from the three systems.
The PLC program on ASDS PM A, ASDS PM B and ASDS PM C is identical.
The individual drives has internal logic that compares the three different available power signals and always select the one with highest analogue value.
