MARINE HIGH VOLTAGE TECHNOLOGY

At the Management Level:

The functional, operational and safety requirements for a marine high voltage
system
Assignment of suitably qualified personnel to carry out maintenance and repair of
high voltage switchgear of various types
Taking remedial action necessary during faults in a high voltage system
Producing a switching strategy for isolating components of a high voltage system
Selecting suitable apparatus for isolation and testing of high voltage equipment
Carrying out a switching and isolation procedure on a marine high voltage system,
complete with safety documentation; and
Performing Insulation Resistance (IR) and Polarization Index (PI) tests on high
voltage equipment.
 Course Outline
• International requisites for high voltage knowledge
• Advantages of high voltage systems
• Hazards
• The functional operational
• High voltage equipment on board
• High voltage safety rules
• Safe working procedures
• Protective devices
• Assignment of qualified personnel to carry out maintenance and repairs
• High voltage electrical equipment testing methods
• Performing test of insulation resistance and polarization index
• High voltage equipment maintenance
• Taking remedial actions necessary during faults Carrying out a switching and isolation procedure
on marine high voltage safety documentation.
 Training
High voltage system training is now a part of the Standards of
Training Certification and Watch keeping convention (STCW)
following the 2010 Manila amendments for senior engineering
staff who have responsibility for operating and maintaining
electrical power plants above 1,000 volts. However, existing
officers will not have this training until their certificates are
revalidated. This training includes:
• operational and safety requirements for high voltage systems
• maintenance and repair of high voltage switchgear
• taking appropriate action when dealing with faults in a high
voltage system
 Training

• switching strategies for isolating components of a high voltage

system
• using suitable apparatus for isolation and testing of high voltage
equipment
• switching and isolation procedures on a marine high voltage
system
• understanding safety documentation for high voltage systems
• testing of insulation resistance and polarization index on high
voltage equipment.
 Why high voltage system used on ships ?
The following advantages of high voltage system explain why it is preferred over low
voltage system.
As we mentioned, higher power demand for heavy consumers on ships is the first
reason to choose high voltage on ships. High power bow thruster electric motors,
reefer containers in container ships, cargo cooling machineries in gas carriers, etc.
are examples of such heavy power consumers.
High voltage machineries have much reduced size and weight compared to same
power low voltage counterpart.
Reduced weight and space for machinery means increased space for cargo and
more profit.
Using electric propulsion further reduces engine room size, again more cargo space
and profit.
Ease of installation and reduced installation cost.
 Why high voltage system used on ships ?

Conductor size is reduced due to low current flow in high voltage

system, means reduced copper requirement and low cost.
In high voltage system, copper loss or I²R losses are much
reduced when compared to low voltage system, as the current
flow is less.
Overall estimated 1/3 rd reduction in cost compared to low
voltage system.
What are the disadvantages of high voltage
system on ships ?

Handling high voltage means high class insulation to be used on

conductors. (Generally ‘F’ class and above)
Higher voltages means greater risk and hence require stringent
safety procedures.
Skilled labour required for handling high voltage system.
Danger of arcing, chances of arc flash and arc blast.
Special switch gears are required to preventing arcing.
 Why machinery working in high voltage
system has reduced weight and size ?
Consider an electric motor consuming power of 500 kW

We have the power, P = √3 V I Cos ∅

In low voltage system, power, P = 500 x 1000 Watts, power factor, Cos ∅ = 0.8, Voltage, V =
440
P = √3 V I Cos ∅
Current, I = P / (√3 V Cos ∅)
I = 500000 / (√3 x 440 x 0.8 )
I = 820 Ampere
Next slide
Why machinery working in high voltage
system has reduced weight and size ?
Similarly, In high voltage system, power, P = 500 x 1000 Watts,
power factor, Cos ∅ = 0.8, Voltage, V = 3.3 kV

P = √3 V I Cos ∅

Current, I = P / (√3 V Cos ∅)

I = 500000 / (√3 x 3.3 x 1000 x 0.8 )

I = 109 Ampere
Next slide
Why machinery working in high voltage
system has reduced weight and size ?

So for an electric motor, working in high voltage system draw

very low current compared to that of low voltage system. As
current carrying capacity of conductor reduces, size of the
conductor can also be reduced much. This considerable
reduction in conductor material result in reduced size of
machinery and save space for installation.
Why copper loss and iron loss is less in
high voltage system ?

From the previous (Slide) comparison on current flow between a

high voltage system and low voltage system, it is clear that
current draw with high voltage is much lesser. Hence copper loss
or I²R losses and iron loss are considerably lesser.
What is meant by arcing, arc flash and
arc blast in high voltage system ?
Arcing is the production of unintentional electric arc during opening
circuit breaker, isolator or contactor due to the discharge of electricity
through the medium between the two contacts. (In fact arcing occurs
during closing the breaker also).
Arcing also occurs when heavy current flow to earth during an earth
fault or short circuit fault due to insulation failure.
During arcing temperatures at the arc terminals can go up to 20000 ºC
or more, which is around 4 times the temperature of sun’s surface.
The intense light formed at the point of arc is called as arc flash.
Instant heating of air surrounding the arc occurs and conductors
vaporises, resulting in formation of a high pressure wave. If the
pressure wave is not released, it results in an explosion called arc
blast.
What are the hazards of arc flash and arc
blast ?
Permanent damages to the electrical equipment.
Irreversible damage to the human tissue and incurable burns due to very
high temperatures.
Arc flash produces intense UV light, resulting permanent or severe damages
to the eye vision.
Pressure wave from the arc blast compresses the eyes, resulting permanent
or severe damages to the eye vision.
Heavy noise (above 140 dB) may damage hearing ability, sudden pressure
changes may rupture ear drums also.
Arc blast explodes the equipment, ejecting parts with tremendous force and
velocity. This may result in damages to personnel and property.
Flammable materials present in the vicinity of arc may ignite, causing
secondary fires.
What is the difference between short
circuit and short circuit level ?
A short circuit is a fault which occurs when the current in a
system deviates its normal path and start flowing through an
alternate path.
Since the alternate path offers very low resistance, the
current increases very much above the normal value.
Short circuit level (SCL) is the maximum possible current
that flows through a circuit during a short circuit fault.
What is the effect of short circuit fault in
high voltage system ?

High current flow during a short circuit fault result in

increased temperatures, which damages insulation,
produces high thermal and mechanical stresses in
the system, may cause arcing, arc flash and arc
blast.
What are the methods adopted to prevent
ill effects of short circuit fault ?
Protective relay installed in the system immediately
trips and isolates the equipment during a short
circuit fault within a short time. This prevents the
effects of high current flow through the circuit.
The generators, cables, equipment, switch gears, etc.
associated with the system are designed to
withstand the heavy current during short circuit fault
for this short duration of time.
High Voltage Safety Rules!
Video (Electrical safety Rules)
 ISSUING OF A PERMIT TO WORK OR SANCTION FOR TEST

1. Before a permit-to-work or a sanction-for-test is issued, the

Authorized Person or Electrical Engineer should identify the equipment
on which the work or test is to be undertaken.
2. If the work involves, or may involve, obtaining access to items of
equipment over which confusion could occur, the Authorized Person
(HV)/ Electrical Engineer should identify such items to the Competent
Person (HV) and apply temporary marking to them.
3. Before issuing a permit-to-work or sanction-for- test, the authorized
Person (HV)/ Electrical Engineer should show the Competent Person
(HV) the isolation and earthing diagram and indicate the safety
arrangements at the points-of-isolation and at the point-of-work or
test.
 ISSUING OF A PERMIT TO WORK OR SANCTION FOR TEST

4.The authorized Person (HV)/ Electrical Engineer should ensure

that the Competent Person (HV) understands all the relevant
safety procedures and precautions.
5. If the Competent Person (HV) thereafter accepts the permit or
sanction, that person becomes responsible for the defined work
or test until the permit or sanction is cancelled.
6. Mark the point-of-work.
7. Issue the permit-to-work, isolation and earthing diagram, and
the key to the safety key box to the Competent Person (HV).
ISSUING OF A PERMIT TO WORK OR SANCTION FOR TEST

8. authorized Persons (HV)/ Electrical Engineer undertaking

tasks requiring permits-to-work or sanctions-for-test should issue
the documents to themselves.
9. Adjust mimic diagram and complete the site logbook.
10. All such documents must be countersigned by a site- certified
authorized Person (HV)/ Electrical Engineer before the work or
test starts.
 Undertake the work

The Competent Person (HV) is to undertake or directly

supervise the work and on completion, or when the work
is stopped and made safe, is to return the original of the
permit-to-work, the isolation and earthing diagram and
the Competent Person’s (HV) key to the safety key box to
the Duty Authorized Person (HV)/ Electrical Engineer,
and complete part 3 of the permit retained in the pad.
Check the equipment & Cancel the permit-to-work

Check the equipment:

If the work has been completed, check to ensure it is safe to energize. If
the work has been stopped, check the equipment has been made safe.
Cancel the permit-to-work:
(i) Cancel the permit-to-work by signing the “completion of work” part
and by cancel the permit in the presence of the Competent Person
(HV).
(ii) File the isolation and earthing diagram in the operational procedure
manual and permit-to-work in respective file.
(iii) Return key to key safe.
 Issue the sanction-for-test

(i) The Competent Person (HV) is to be shown the safety

arrangements at all the point/s of isolation and at the locations of
the test, and is to initial the isolation and earthing diagram.
(ii) Issue the sanction-for-test, isolation and earthing diagram,
and the key to the safety key box to the Competent Person (HV).
(iii) Retain working lock keys, and remove and replace earths as
requested.
 Cancel the sanction-for-test

(i) Cancel the sanction-for-test by signing part 4 and by

destroying the sanction in the presence of the Competent
Person (HV).
(ii) File the isolation and earthing diagram in the
operational procedure manual.
(iii) Return key to key safe.