The basic principles used are the same in either case. Troubleshooting requires a thorough knowledge of electrical theory and testing equipment, combined with a systematic and methodical approach to finding and diagnosing problems.
The following general tips and principles are intended to help define the troubleshooting process.

Think Before Acting

Electrotechnical Officer (ETO) need study the problem thoroughly, and ask yourself these questions:

● What were the warning signs preceding the trouble?

● What previous repair and maintenance work has been done?

● Has similar trouble occurred before?

● If the circuit, component, or piece of equipment still operates, is it safe to continue operation before further testing?

The answers to these questions can usually be obtained by:

● Questioning the colleague or operator of the equipment.

● Taking time to think the problem through.

● Looking for additional symptoms.

● Consulting troubleshooting charts.

● Checking the simplest things first.

● Referring to repair and maintenance records.

● Checking with calibrated instruments.

● Double-checking all conclusions before beginning any repair on the equipment or circuit components.

The source of many problems is not one part alone, but the relationship of one part to another. For instance, a tripped circuit breaker may be reset to restart a piece of equipment, but what caused the breaker to trip in the first place? It could have been caused by a vibrating “hot” conductor momentarily coming into contact with a ground, or a loose connection could eventually cause overheating, or any number of other causes.

Too often, electrically operated equipment is completely disassembled in search of the cause of a certain complaint, and all evidence is destroyed during disassembly
operations. Check again to be certain an easy solution to the problem has not been overlooked.

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Three-phase power factor meters are installed in switchboards. Many utilities charge large commercial and industrial users a penalty if power factor falls below 90 percent; so these users try to maintain high power factor at all times. A high power factor provides better voltage regulation and stability.

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Item 1 – Multimeter

It is essential that all test instruments be regularly checked for safety, and any connection leads, probes or clips checked to ensure that they are suitable for the voltage levels being tested. Never attempt to test a “LIVE” generator unless there is another competent person present who can switch off the power supply or shut down the engine in an emergency. The Multimeter is a comprehensive test instrument for measuring voltage, current and resistance.

Never expose “LIVE” connections unless you have created a safe working area around you. Make sure you have made all other persons in the immediate area fully aware of what you are doing.

Do not attempt to carry out tests on medium or high voltage generators without using specialised instruments and probes, with suitable protection equipment and procedures for grounding (earthing) the output terminals.

Item 2 – Tachometer or Frequency meter

This instrument is for measuring the shaft speed of the alternator and should be capable of measuring speeds between 0 and 5000 revolutions per minute, (RPM). An alternative to the tachometer is the frequency meter. However the alternator must be generating its normal output voltage for this instrument to be accurate.

Item 3 – Megger (Insulation test meter)

This instrument generates a voltage of 500V or 1000V, and is used to measure the resistance value of the insulation to earth (ground). It may be an electronic push button type, or a hand cranked generator type.

Item 4 – Clip-On Ammeter (Clampmeter)

Used to measure AC current, it consists of a pair of callipers, which are clamped around the conductor, and by means of a transformer action, gives an indication of the amperes flowing in the conductor. Useful ranges to have on this meter are
AC Amps 0-10-50-100-250-500-1000

Item 5 – Kelvin Bridge – low resistance meter

This instrument is used to measure resistance values below 1.0 ohm. They are bulky, and expensive, but are the only means of accurately measuring very low resistances, such as main stator and exciter rotor windings.
However, there are other methods of testing low resistance windings, and these are included in the various test procedures, i.e. Test Method A. This section will enable the main generator windings to be tested while running the generator at normal speed without load.

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The short circuit currents are being reduced, as the DC component decays rapidly, typically with a time constant of 20-100 ms. After 300-500 ms, the transient short circuit current is typically reduced to 3-5 times nominal generator current, and dependent on the system design, this is normally the breaking current for a circuit breaker for a branch.
A sustained short circuit current will after a second or more, reach a stationary value, which according to rules and regulations shall be at least three times nominal current for a generator in order to detect faults reliably, for clearing faulty branches.
The short circuit current is found by numerical simulation or by analytical methods. IEC 61363 is normally applied for short circuit calculations in ships.

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Despite these efforts, the vessel grounded. Although the main engine was soon restarted and propulsion control was transferred back to the bridge, attempts to free the vessel under power were unsuccessful. Two days later the vessel was refloated with the assistance of two tugs and towed to a nearby dock. Subsequent underwater inspection showed there was no apparent damage to the vessel.

The investigation found that the main engine shutdown feature on the touchscreen integrated alarm monitoring and control system had inadvertently been activated. The touchscreen was mounted horizontally in the centre bridge console, close to other controls such as steering and propulsion. At the time of the loss of propulsion, four crew members were within 2m  of the touchscreen.

Tests showed that the touchscreen was reactive to a variety of inputs – including the telephone cord situated next to it. When the main engine shutdown button was activated on the touchscreen, a generic and ambiguous system status message appeared on the screen. The message did not specify that the engine was about to shut down, nor did it indicate how the shutdown was activated or from where (bridge, engine room, emergency stop etc).

Action taken

A plastic cover was placed over the touchscreen to prevent another inadvertent shutdown. After a  thorough review, the equipment manufacturer disabled the main engine shutdown function on the touchscreen and the plastic cover was removed. In case of an emergency, the main engine can  still be shut down from the bridge via the traditional shutdown button.

Lessons learned

In order to use shipboard equipment effectively, crews must know how to operate that equipment during routine and emergency situations. In this case, given that the screen controlled the vessel’s integrated alarm monitoring and control  system, it was especially important for crew members to familiarise themselves with the sensitivity  level of the screen and the lack of any confirmation message after any action was taken using it.

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The pump’s breaker was opened and he proceeded to check the isolation status of the breaker terminals with a multimeter.

As soon as he touched the terminals with multimeter leads, a huge spark emanated from the breaker/multimeter, with a loud explosive sound and black smoke.

The victim sustained burns on his face, neck and hands due to radiant heat. He was given first aid and signed off from the vessel for further medical attention ashore.

The investigation found that he had attempted to check the voltage across breaker terminals with the multimeter selector knob at the Resistance (1 Ohm) setting instead of the Voltage (1000VAC) setting.

The electric charge found its shortest path (through the multimeter), which then exploded. It was also found that the victim had failed to use insulating gloves which would have decreased the severity of the injury.

Lessons learned

• Approved insulated gloves should be used while working on electrical components.
• It is always a good idea to cross-verify your tool and workplace before starting the job;
• Is the guard in place?
• Is the setting correct?
• Is the electrical supply safe?
• Is the lighting adequate?

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Load analysis of the ship’s electrical systems is a complex exercise and covers all operating conditions of the vessel, such as conditions in normal sea-going, cargo handling, harbour manoeuvring, and emergency operations.

Dimensioning the Electrical Network depicts a few considerations to be taken while the entire electrical system is being designed.

It must be understood that there are many constraints to be kept in mind, the main factors being the money involved and of course the ship’s operating profile.

Often the tentative area of operation is also decided; this also determines the vessel’s size. The vessel will also be required to comply with the stipulated safely norms and requirements of a Classification Society and other regulatory bodies.

The power rating of the generators is determined by the power demand of the electrical load. Principle design documents for the ship’s auxiliary services should include a load list, load analysis and short-circuit current analysis.

In consultation with the client, all electrical services on the vessel are identified.

Ship’s Electrical Network Ratings

Approximate horsepower or kilowatt ratings are obtained for motors. Lighting loads are estimated from the ship’s general arrangements and electronic aids are obtained from similar vessels, and then a complete load list compiled. The electrical load analysis uses the load list in order to estimate the expected power demand of the electrical system under specific operating conditions of the ship.

Typical operating conditions would be with the ship, ‘in transit’, ‘at anchor’, ‘manoeuvring’, etc. For special vessels, other operating conditions would be appropriate such as ‘towing’ for a tug, ‘drilling’ for a drill ship.

How determine Ship Load Analysis

Load analysis also helps to calculate the expected power demand by multiplying each service power by a ‘demand’ factor. The demand factor is a combined load factor and diversity factor and is the ratio of the estimated power consumption of a service to its normal full load power consumption.

It is determined by an experienced assessment of toe estimated power during a four to six hour period when loads may be at their maximum utilisation.

For each service, data banks are searched to determine toe service toll-load current and power factor dependent upon the operating voltage.

The information thus derived, is used to determine the ‘services’ kilowatt and kilovar demand from which toe kilovolt-amps required is finally computed. Also, by applying the demand factor to each load (kW and KVAr) and summing all loads for specific operating conditions, toe expected kilowatts, kilovolt-amps and power factor can be computed.

By comparing toe expected load for toe different operating conditions of toe ship, toe number and rating of the main generators can be assessed.

Short-circuit Current Calculations on Ship

Preliminary short-circuit current calculations can be completed once toe load analysis and number and rating of generators have been determined. The principle purpose of short-circuit current calculation is to ascertain toe short-circuit rating of toe systems’ protective devices.
Several types of short-circuit current calculations are applied under different circumstances at various stages of the design process.

The major contributors to short-circuit current are toe generators and motors.
The most simple short-circuit current analysis is based on an assumed value of toe generator’s sub-transient reactance and an approximate estimate of the worst case motor loading can be obtained from toe load analysis.
The ‘second stage’ short-circuit current analysis is completed when toe electrical system’s conceptual one-line diagram is finished. For this calculation actual sub-transient data is used together with cable transformers and other system parameters. This calculation generally results in Iowa- values of short-circuit current.
When complete system information is available, a ‘third-stage’ short-circuit analysis is completed. This is toe most accurate and also determines toe decrements of toe short-circuit current over a 3 and 5 cycle period.

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This is only a proposal how the procedure could look like, procedure must be established by the owner.
It is extremely important of following correct procedures while working with high voltage. An error would most probably be fatal working on a high voltage switchboard.

Like all work with high voltage, two persons are always required, with at least one electrician with a high voltage training course.

High Voltage Working procedure on Ship Bow Thruster

Pull the contactor out in test position by turning the interlock handle with left hand and pulling the operating handle as shown on figure 1. below.

Important! Open the door to make the earthing mechanism to be engaged. No need to unscrew the screws on the front panel.

Do this on all three contactors. Main C, By-Pass B and Star A.

Take out the ground interlock key on all three breakers.

The electrician should keep these keys personally until work is finished.

Open the connection box on the thruster.

Remember that high voltage equipment should be considered live until you have established visible earthing of the work place.

Do a voltage test with proper high voltage tester.

Remember to do a function test of the tester both before and after the actual test.
The work place is now ready to be earthed.

Connect all three phases to ground with proper high voltage earthing equipment designed for the short circuit currents.

The work place is now safe and ready for the needed maintenance.

Tool check list should be made, listing all tools that are being used.

This needs to be checked out when finished the work, making sure that no tools are left behind at the work place.
After finishing the work, disconnect the earthing apparatus again remember that the connections should now be considered “alive” since they are no longer grounded.
Return the keys and push all three breakers back in place.

It’s a good habit to stay away from the switchboard room first time connecting the breakers again in an unlikely case of forgotten tools etc, making a short circuit.

Please remember that this document is only a draft and needs to be reviewed and checked for errors.

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This is only a proposal how the procedure could look like, procedure must be established by the owner.

It is extremely important of following correct procedures while working with high voltage.

An error would most probably be fatal working on a high voltage switchboard.

Like all work with high voltage, two persons are always required, with at least one electrician with a high voltage training course.
Pull the contactor out in test position by turning the interlock handle with left hand and pulling the operating handle as shown on picture below.

Important!

Open the door to make the earthing mechanism to be engaged. No need to unscrew the screws on the front panel.

Take out the ground interlock key on the breaker.

The electrician should keep this key personally until work is finished.

Open the connection box on motor.

Remember that high voltage equipment should be considered live until you have established visible earthing of the work place.
Do a voltage test with proper high voltage tester.

Remember to do a function test of the tester both before and after the actual test.
The work place is now ready to be earthed. Connect all three phases to ground with proper high voltage earthing equipment designed for the short circuit currents. The work place is now safe and ready for the needed maintenance.

 Ballast Pump/DOL High Duty Compressors High Voltage work procedure on Ship

A tool check list should be made, listing all tools that are being used.

This needs to be checked out when finished the work, making sure that no tools are left behind at the work place.
After finishing the work, disconnect the earthing apparatus again remember that the connections should now be considered “alive” since they are no longer grounded.
Return the key and push the breaker back in place.

It’s a good habit to stay away from the switchboard room first time connecting the breaker again in an unlikely case of forgotten tools etc, making a short circuit.

Please remember that this document is only a draft and needs to be reviewed and checked for errors.

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