Post on 30-Jun-2020
AN OVERVIEW
OF
TECHOP_ODP_09_(D)
(A METHOD FOR PROVING THE FAULT RIDE-THROUGH CAPABILITY
OF DP VESSELS WITH HV POWER PLANT)
OCTOBER 2014
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
Acknowledgements
• The MTS DP Committee thanks ABS, DNV and the
following companies for their contribution to the
preparation of this Techop:
– ABB
– GE
– Siemens
– AKA
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
CASE FOR ACTION
• There is a need to improve efficiency and reduce
emissions from DP power plants – Operating power
plants with closed busties is a means of achieving this.
• Industries experience of loss of position incidents on
DP vessels operating with closed busties suggests a
lack of sufficient fault ride through capability – Loss of
all thrusters or blackout.
• 18 examples of such incidents are given in the Techop.
• Increasingly difficult to get stakeholder concurrence for
operation with closed busties.
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
PURPOSE OF TECHOP
• Build confidence in common power systems by
testing fault ride-through capability using an
established method.
• Contribute to proof of equivalent station keeping
integrity for DP class 3 vessels IMO MSC 645
Section 3.2.4.
• Communicate experience of doing it successfully.
• Enhance the knowledge of stakeholders.
• NOTE: If there is no intention to carry out DP
operations with closed busties then you don’t need
to prove fault ride through capability.
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
CONTENT OF TECHOP
• Information on one method of proving fault ride-
through that has been carried out safely and
effectively.
• Practical details on how to carry out the testing.
• Details of the power system attributes to be proven.
• Guidance on computer simulation and preparatory
work.
• To provide focus on risk assessment, typical roles
and responsibilities for stakeholders.
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
FAULT RIDE-THROUGH TESTING IS NOT NEW
G
G
G
G
VOLT RISEVOLT DROP
GENERATOR
TERMINAL
VOLTAGE FALLS
A
FAULT CURRENT
BUS VOLTAGE
MAINTAINED
VOLT RISEVOLT DROP
VOLT RISEVOLT DROP
VOLT RISEVOLT DROP
• Fault Ride-Through
Testing on LV DP
DSVs in the 1980s.
• Built to be tested.
• Tested by
application of
bolted short circuit
to 660V feeder.
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
• Requirements for fault ride-though capability have
always existed based on single failure criteria.
• What has changed is that more focus is now placed
on proving this capability by testing.
• Traditional methods inadequate to meet stakeholder
expectations:
– History of too great a reliance on limited analysis only e.g.
short circuit calculations.
– FMEA testing did not create realistic conditions for fault
ride through proof.
FAULT RIDE THROUGH CAPABILITY –
A LOOK BACK
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
SEVEN PILLARS
Ind
ep
en
de
nce
Au
ton
om
y
Diffe
ren
tiatio
n
Fa
ult to
lera
nce
Fa
ult re
sistan
ce
Fa
ult rid
e th
rou
gh
Se
gre
ga
tion
Predictability
Incident Free DP Operations
These pillars
require more
focus when
cross-connections
are introduced.
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
• Expertise - Already available from several
well known sources.
• Qualification and approval – Early
engagement with class.
• Roles and responsibilities – Agree in
advance.
• Action in the event of unsuccessful tests –
Agree in advance.
PRE-REQUISITES FOR CARRYING OUT FAULT RIDE -
THROUGH TESTING
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
INDUSTRY READINESS FOR TESTING
• Recent experiences of successful testing.
• More than 10 tests carried out - plus
experience of real short circuits on DP
vessels.
• Initial apprehension overcome: – Crew safety.
– Test personnel safety.
– Risk assessment.
– Equipment damage – leaving hidden failures (weakness) –
actually helps reveal them.
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
EFFECT ON CIRCUIT BREAKER LIFE
1
20
BREAKING CURRENT (r.m.s. value)
2 510
50
100
1000
100
500
2000
5000
10000
2000030000
50000
10 20 50kA31.5
PE
RM
ISS
IBLE
OP
ER
AT
ING
CY
CLE
S
BUSTIES
TEST FEEDER
You need to check what your circuit breakers are rated for.
Build to test
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
EFFECT ON BUSBARS
• Forces on bus bars are proportional to the
square of the current.
• As peak test current in the example in the
Techop is around 1/3rd of rating.
• Forces are around 1/10th of rating.
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
EFFECT ON GENERATORS
• Generators rated for a defined number of
short circuits – for example 3.
• Generator sees ‘almost’ a full short – there
is some impedance – more could be added
but considered unnecessary on HV systems
by manufacturers – no reports of damage.
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
PRACTICAL CONSIDERATIONS FOR
CARRYING OUT TESTING
1. Advance modelling.
2. Building confidence for the fault ride-
through test – commissioning.
3. Fault ride-through test.
4. Earth fault test.
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
TEST CONDITIONS
• Vessel at sea trials location.
• DP system in full auto DP.
• Two generators online (on different busses).
supplying DP & Hotel.
• All transformers connected.
• All busties closed.
• Instrumentation and logging facilities
operating.
• Carry out test.
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
FAULT RIDE-THROUGH TEST
DG 4
CLOSED
DG 6
CLOSED
LV
RUNNING
DRILLING
RUNNING
LV
RUNNING
DRILLING
RUNNING
CLOSED
CLOSED CLOSED
EARTHINGTRANSFORMER
RUNNING
DRILLING
RUNNING
LV
THIS CABLE MUST BE RATED FOR FULL S/C CAPACITY
THIS CIRCUIT BREAKER IS CLOSED REMOTELY TO APPLY THE TEST FAULT
CLOSED
X3 X3 X3
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
• Test fault applied.
• Busties open to isolate switchboard with
fault.
• All thrusters stay online and selected to DP.
• All DP essential systems continue to
operate without malfunction.
• Feeder removes test fault.
• Both generators remain on line.
• All buses healthy.
EXPECTED RESULT
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
TEST DATA AQUISITION
Signal sources that can be instrumented
(Build to Test) or used to collect data include:
• Generator VTs and protection & measuring CTs.
• Bus VTs and protection & measuring CTs.
• Feeder protection and measuring CTs.
• Serial links from protection relays.
• Serial links from governors and AVRs.
• Serial links from thruster drives.
Vessel management systems, history stations, data
loggers can be used to record any changes in plant
status.
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
POWER SYSTEM ATTRIBUTES TO BE VERIFIED
• This section of the Techop deals with
various functions and features to be verified
as part of the analysis and testing process:
– Fault cleared by busties.
– Voltage dip ride-through.
– No protection operation on plant recovery current.
– No protection operation on plant recovery over
voltage.
– Model mal-synchronisation and inadvertent gen CB
closure.
– Decrement curve and model validated.
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
FAULT CURRENT RECORDINGS
Peak test current 30% of rated
A
B
C
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
MAIN BUS VOLTAGE RECOVERY & OVERSHOOT
Overshoot
Recovery
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
PLANT RECOVERY
Plant recovery current
Fault applied
removed
Voltage dip
Fault Current
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
• Time Domain Modelling – e.g.
MatlabTM SimulinkTM or equivalent.
• Real Time Digital Simulation or similar.
– Protection relays.
– Enhanced generator protection.
– Drive controllers.
• Use test data to validate model
predictions.
COMPUTER SIMULATION
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
EARTH FAULT TEST
DG 4
DG 6
LV
RUNNING
DRILLING
RUNNING
LV
RUNNING
DRILLING
RUNNING
CLOSED
CLOSED
EARTHINGTRANSFORMER
RUNNING
DRILLING
RUNNING
LV
THIS CIRCUIT BREAKER IS CLOSED REMOTELY TO
APPLY THE FAULT
CLOSED
X3 X3 X3
CLOSED CLOSEDCLOSED
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
EFFECT ON LINE TO EARTH VOLTAGE
Increase in line to earth voltage
This phase earthed
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
EARTH FAULT CURRENT
Fault isolated by busties
Fault isolated by test feeder
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
TEST REPORT
INTRODUCTION • Vessel, DP system and power systems description.
• Redundancy design intent and worst case failure design intent.
• Power plant configurations and fault types to be modelled and tested.
APPLICABLE RULES, STANDARDS AND CLASS NOTATION.
TEST METHODOLOGY
• Description of test method with supporting sketches.
DISCUSSION OF SIMULATION METHODOLOGY
• Simulation package, TDS, RTDS, HIL etc. Discussion of any
assumptions made in modelling of configurations which were
not tested. Means by which the worst case conditions were
identified.
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
TEST REPORT - CONT
RESULTS
• Comparison of measured and modelled waveforms.
• Comparison with the results of static studies such as short circuit
calculations.
• Results of RTDS or HIL demonstrating that actual protection and
control systems respond correctly.
• Presentation of worst case conditions and confirmation that the
severity of the failure effect does not exceed the DP system’s worst
case failure design intent.
CONCLUSIONS
• Compliance with the applicable rules & requirements.
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
INSPECTION AFTER TEST
• Removal of test equipment.
• A general inspection of the generators used for
testing could include visual inspection of:
– End winding.
– Auxiliary components, AVRs, CTs etc.
– Cable terminations.
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
CHALLENGES
• Build to Test – Thruster drives may need braking resistors.
• Special cases – HV power plant with limitations which make it more difficult
to test.
– Older power plants – Uncertainty in relation equipment spec.
– LV power plant.
• Complementary methods for periodic testing
where required.
A METHOD FOR PROVING THE FAULT RIDE-THROUGH OF DP VESSELS WITH HV POWER PLANT
CONCLUSIONS
• There is a case for action.
• It is possible to carry out fault ride
through testing with acceptably low risk
when properly executed.
• A combination of design requirements,
computer simulation and testing,
produces common power systems with
comparable integrity to independent
power systems.