DPO System Components & Functions 3 — Questions and Answers
Question 1: In a DP power plant, what is the purpose of bus-tie breakers?
- Connect different power distribution busbars together or isolate them (Correct answer)
- Protect individual generators from overload
- Step down high voltage to usable ship voltage levels
- Monitor harmonic distortion in the power network
Correct answer: Connect different power distribution busbars together or isolate them
Bus-tie breakers allow operators to connect or isolate separate power busbars, enabling flexible power distribution configurations that support redundancy requirements.
Question 2: What is the primary advantage of a Voith-Schneider Propeller (VSP) in DP operations?
- High efficiency at transit speeds
- Ability to produce thrust in any direction without rotation delay (Correct answer)
- Low noise output suitable for research vessels
- Simple mechanical design requiring minimal maintenance
Correct answer: Ability to produce thrust in any direction without rotation delay
The VSP can instantaneously redirect thrust through 360 degrees by adjusting blade pitch, providing extremely fast and precise force vectoring ideal for DP applications.
Question 3: Which reference system uses acoustic transponders placed on the seabed to determine vessel position?
- Taut Wire
- Laser-based FANBEAM
- Hydroacoustic Position Reference (HPR) (Correct answer)
- Inertial Navigation System (INS)
Correct answer: Hydroacoustic Position Reference (HPR)
Hydroacoustic Position Reference systems such as USBL, SBL, and LBL use acoustic transponders on the seabed and transducers on the hull to calculate the vessel's position relative to the seabed.
Question 4: What does the term 'capability plot' represent in DP system assessment?
- A log of thruster maintenance intervals
- A diagram showing maximum environmental conditions the vessel can hold position in (Correct answer)
- A graph of fuel consumption versus engine load
- A record of position excursions during operations
Correct answer: A diagram showing maximum environmental conditions the vessel can hold position in
A capability plot is a polar diagram showing the maximum wind, current, and wave conditions from each direction in which the vessel can maintain DP position with its available thrusters.
Question 5: In DP terminology, what is 'environmental feedforward' used for?
- Displaying wind and current data on the operator console
- Pre-compensating thruster forces based on measured environmental loads (Correct answer)
- Alerting the operator when environmental limits are approached
- Logging weather conditions for post-operation reporting
Correct answer: Pre-compensating thruster forces based on measured environmental loads
Environmental feedforward uses measured wind and current forces to proactively apply counteracting thruster forces before the vessel is displaced, reducing position excursions.
Question 6: What is the consequence of operating a tunnel thruster at very low RPM for extended periods?
- Increased thrust due to reduced cavitation
- Poor cooling of the motor windings leading to overheating (Correct answer)
- Enhanced maneuverability due to laminar flow
- Reduced wear on the propeller blades
Correct answer: Poor cooling of the motor windings leading to overheating
Many tunnel thruster motors rely on adequate flow through the tunnel for cooling; operating at very low speed reduces this flow and can cause motor windings to overheat.
Question 7: Which component prevents reverse power flow from the busbars back into a generator when it trips offline?
- Automatic Voltage Regulator (AVR)
- Generator Circuit Breaker (GCB)
- Reverse Power Relay (Correct answer)
- Load-sharing controller
Correct answer: Reverse Power Relay
A reverse power relay detects when a generator starts absorbing power from the busbar rather than supplying it, and trips the generator circuit breaker to protect the prime mover.
DPO System Components & Functions 3
In a DP power plant, what is the purpose of bus-tie breakers?