High Voltage Trainng - virtual.bstc-training.com

High Voltage Awareness Training

E-Learning TrainingBSTC

Course Outlines 1. An understanding of electrical systems2. Legislation and standards3. High voltage terminology4. Electrical hazards and risk management5. Safe Working System in a high voltage area6. Permit procedures7. Safety Precautions of working with High Voltage

Electrical Systems Onboard Marine Vessel

• The electrical power system onboard is designed to provide asecure supply to all loads withadequate built-in protection forthe equipment and operatingpersonnel.

• Most MV have a 3-phase A.C., 3-wire, 60Hz, 440V supply beinggenerated and distributed onboard.

Electrical Systems Onboard Marine Vessel –contd.

• MV with very large electrical loads have generators operating athigh voltages (HV) of 3.3KV, 6.6KV, and even 11KV.

• Any Voltage used on board if less than 1kV (1000 V) then it iscalled as LV (Low Voltage) system and any voltage above 1kV istermed as High Voltage

IEC Voltage Range AC DC Defining Risk

High voltage system > 1Kv > 1.5Kv Electrical arcing

Low voltage system < 1Kv < 1Kv Electrical shock

Extra-low voltage system < 50V < 120V Low risk

Legislation & Standard• The International Electro-technical Commission and its

National counterparts (IET, IEEE, VDE etc) define highvoltage as above 1000 V for AC, and at least 1500 V for DC.

• In the USA 2005 National Electrical Code (NEC), highvoltage is any voltage over 600 V (Article 490.2)

• British Standard BS 7671:2008 defines high voltage as anyvoltage difference between conductors that is higher than1000 V AC or 1500 V ripple-free DC or any voltagedifference between conductor and Earth that is higherthan 600 V AC or 900 V ripple-free DC.


High Voltage Vs Low Voltage System• High voltage systems are more extensive with complex networks

and connections.• Isolation procedures are more involved in HV.• Isolated equipment required earthed down process.• Access to high voltage areas is strictly limited and controlled.• Switching strategies are formulated and recorded.• Specific high voltage test probes and instruments are used.• Diagnostic insulation resistance testing is necessary.• High voltage systems are usually earthed neutral and use current

limiting resistors.• Special high voltage circuit breakers are installed.


Why is High Voltage system is commonly used in Marine Vessels or in Offshore Installations?

• Higher power requirements on board vessels is theforemost reason for the evolution of HV in MV.

• Most MVs have large electrical power demand, it isnecessary to utilise the benefits of a high voltage (HV)installation.


The distribution of different electrical system components on board include; • Generator consisting of prime mover and

alternator – Electrical generator (AC/DC) & motors.

• Main switch board which is a metal enclosure taking power from the diesel generator and supplying it to different machinery.

• Busbars which acts as a carrier and allow transfer of load from one point to another.


• Circuit breakers which act as a switch and in unsafe condition can be tripped to avoid breakdown and accidents.

• Fuses as safety device for machinery.• Transformers to step up or step down

the voltage.• The distribution system is three wires

and can be neutrally insulated or earthed. Insulated system is more preferred as compare to earthed system


Emergency Power System• The emergency power supply ensures that the essential

machinery and system continues to operate such as:a) Fire fighting system.b) Navigation lights and emergency lights.c) Communication and alarm system.d) Accommodation lighting


High Voltage Terminology • ARC: A disruptive discharge of electricity through an insulator, typically a

gas, normally characterized by a voltage drop. This can be a single event, intermittent or continuous. Same as Flashover.

• BREAKDOWN VOLTAGE: The voltage level which causes insulation failure. Same as Dielectric Withstand Voltage.

• CORONA: A luminous discharge due to the ionization of the gas surrounding a conductor caused by a voltage gradient exceeding a certain critical value. It does not greatly heat the conductor, and it is limited to the region surrounding the conductor. While corona is a low energy process, over long periods of time, it can degrade insulators, causing a system to fail due to dielectric breakdown.

• CORONA EXTINCTION VOLTAGE: The highest voltage at which continuous corona of specified pulse amplitude no longer occurs as the applied voltage is gradually decreased from above the corona inception value.

• CORONA INCEPTION VOLTAGE: The lowest voltage at which continuous corona of specified pulse amplitude occurs as the applied voltage is gradually increased.

High Voltage Terminology – Contd.

• CREEPAGE: Current flowing between two conductors along a surface that is in contact with both conductors. Generally this can be neglected up until the voltage where corona or flashover occurs.

• CREEPAGE DISTANCE: The shortest distance separating two conductors as measured along the surface touching both conductors. Along the surface of most materials, flashover can occur at distances much shorter than the flashover distance in air. Therefore, it is extremely important in high voltage designs to look for places where creepage can occur.

• DIELECTRIC: An insulating material between two conductors.• DIELECTRIC WITHSTANDING VOLTAGE or DIELECTRIC WITHSTAND

VOLTAGE: Voltage an insulating material will withstand before flashover (arcing) or puncture. Same as Breakdown Voltage. This is a greater value than working voltage. The difference depends on how much design margin the designer wants between the failure point and the operating point


• FLASHOVER: A disruptive discharge of electricity through an insulator, normally characterized by a voltage drop. Also, a discharge around or over a liquid or solid material. This can be a single event, intermittent or continuous. Same as Arc.

• HI-POT TEST: A test performed by applying a dc or ac high voltage for a specified time to determine adequacy of insulating materials in an assembly. Short for high potential test.

• HIGH VOLTAGE: High voltage starts at the point where designers have to consider additional technical issues, and where there are significantly fewer component suppliers to choose from.

• ISOLATION: The electrical separation between two conductors or two circuits.

• ISOLATION VOLTAGE: The maximum dc or ac voltage that may be continuously applied between two isolated conductors or two circuits.


• PRIMARY CIRCUIT: A circuit electrically connected to the input or source of power to the device. See also Secondary Circuit.

• SAFETY GROUND: A conductive path to earth that is designed to protect persons from electrical shock by shunting away any dangerous currents that might occur due to malfunction or accident.

• SECONDARY CIRCUIT: A circuit that is electrically isolated from the input or source of power to the device. See also Primary Circuit.

• STANDOFF: A mechanical support insulator used to support a wire or component away from its mounting surface.

• TRACKING: Marks made on a surface that experienced flashover.• WITHSTAND VOLTAGE: See Dielectric Withstand Voltage.• WORKING VOLTAGE: The specified or actual operating voltage

applied between two conductors, circuits or a component.

High Voltage Safety & Rules

• Personnel who are required to routinely test and maintain HV equipment should be trained and certified as qualified for this duty.

• PPE requirement includes; safety clothing, footwear, eye protection and hard hat should be worn where danger may arise from arcs, hot surfaces and high voltage etc.

• Use of safety equipment which includes; insulated rubber gloves and mats. Safety equipment must be tested regularly to ensure it is still protecting the user.

• Access to HV switchboards and equipment must be strictly controlled using electrical permit-to- work system, isolation procedures together with live-line tests and earthing-down before any work starts.

• Equipment that is considered by an Authorised Person (HV) to be in a dangerous condition should be isolated elsewhere and action taken to prevent it from being reconnected to the electricity supply.

• All works or testing activities of high voltage equipment connected to a system should be covered by electrical permit-to-work system or a sanction-for-test procedures.

• No hand or tool (unless the tool has been designed for the purpose) shall in contact with any high voltage conductor unless that conductor has been confirmed dead by an Authorised Person (HV) in the presence of the Competent Person (HV).

High Voltage Safety & Rules – Contd.

• Voltage Test Indicators should be tested immediately before and after each use against a test supply designed for the purpose.

• Where the procedures involve the application of Circuit Main Earths (CME), unauthorised removal of such earths should be prevented by the application of safety lock & tag system.

• Where the procedures involve the removal of Circuit Main Earths (CME) and testing under a sanction-for-test is required, the earths will be secured using locks. The keys to these locks will be retained by the Duty Authorised Person (HV), who will remove and replace the earths as requested.

High Voltage Safety & Rules – Contd.

High Voltage Test ActivityTesting at high voltage:• Where high voltage tests are to be undertaken, a sanction-for-test

form should be issued to the Competent Person (HV) who will be present throughout the duration of the tests.

• The areas containing exposed live conductors, test equipment and any high voltage test connection should be regarded as high voltage enclosures.

High voltage test enclosures:• An access to a high voltage test enclosure should be barricaded and

high voltage danger signs must be put on displayed. An accompanying Safety Person (HV) or Duty Authorised Person (HV) should be present throughout the duration of the tests, and the area should be continually watched while testing is in progress.

HV Electrical Hazards

1. The general hazards of electricity include, • Electrocution• Burns• Fire or Arc or Explosion, maybe present at high

voltage2. Burns & fire can happen as high voltage conductors

are likely to carry high currents and therefore run at higher temperatures than low voltage conductors.

3. Most electrical shock and fire hazards are posed by a condition at high voltages , electric current can arc or “jump” (like lightning) across significant spaces —1000V (1kV) can bridge an air gap of 1cm and 25kV can bridge a distance of 25cm. A person does not need to be in direct contact with an electrical conductor to be electrocuted or for a fire to start from the discharge.


4. Electrical arc at HV overhead power distribution lines can occur at minimum clearance distance range from 5.2m at 11kV to 7.3m at 400kV. For the purpose of rescuing someone from the high power lines, the safe distance to approach should be at least 18 meters away until the power line is made safe.

5. During HV maintenance work, accidental short circuit of the system or an unintentional application of power can happen and result in fire and explosion.


HV Risk AssessmentA risk assessment, which includes a review of theelectrical hazards, the associated foreseeable tasks, andthe protective measures that are required in order tomaintain a tolerable level of risk. A risk assessmentshould be performed before work is started.

HV Risk AssessmentRisk Assessment Steps 1. Identify the electrical hazards associated with the task

and the electrical system, or electrical process involved (example: shock hazard risk; arc flash hazard risk).

2. Identify the electrical work to be performed within the electrical system or process.

3. Define the possible failure modes that result in exposure to electrical hazards and the potential resultant harm.

4. Assess the severity of the potential injury from the electrical hazards.

HV Risk Assessment5. Determine the likelihood of the occurrence for each

hazard. 6. Define the level of risk for the associated hazard. 7. If the level of risk is not acceptable, identify the

additional measures or corrective actions to be taken. Example: wear appropriate PPE and if the risk too great, do not perform the task.

The risk related to an identified hazard may be thought of as being composed of the severity of the injury and the likelihood of occurrence of that injury

Because it is possible to suffer a shock or burn without touching live voltage parts, the dead working procedure as outlined below must be followed

HV Risk Assessment

Additional precautions for high voltage work include:• Application of LOTO system while work is in progress to

avoid inadvertent re-energisation of the apparatus.• Application of electrical permit-to-work system and

sanction-for-test.• Putting in place measures to prevent people approaching

dangerously close to uninsulated high voltage conductors.

HV Risk Assessment

Emergency proceduresEmergency involving high voltage, the following procedures should be carried out.• Get help immediately — contact the authorized personnel

and disconnect the power.• Do not attempt to rescue someone in contact with or

closer than 18m to a high voltage source until the power has been disconnected and the system made safe.

• Do not attempt to use a water-based hose or portable extinguisher to fight any flames present until the power has been disconnected and made safe.

HV Risk Control

• When working in HV area and the risks involved are significantly high, there should always be at least two people present during high voltage work, with both being aware of the responsibilities they hold and the emergency procedures which may need to be carried out.

• The physical risk controls required for working on high voltage work station or equipment must be explicitly specified by the authorised person in the permit to work.

• Isolation (by means of a device) that has a safe isolating gap between live parts and those that have been made dead for work to be carried out. Earthing conductors at the point where the supply is disconnected are essential and additional earths may be necessary at the place of work.

HV Risk Control

• General physical risk controls include:§ Isolation of the work station or equipment being

worked on using the locking off system to ensure this remains isolated until the work is completed.

§ Discharge of conductors and equipment to remove any residual electrical charge that could be present.

§ Earthing of the part of the electrical system being worked on to ensure that a dangerous voltage cannot occur on it.

HV Risk Control

Safe Working System in a High Voltage AreaFire Protection System• Most electrical high voltage switchgear rooms have automatic

fire protection, often a gaseous flood system. • Any work in these areas must take note of the precautions

and must be made safe for the workers undertaking the tasks in that area. This may require rendering the fire extinguishing system temporarily inactive, or placing it in manual-only control.

Safe Working System in a High Voltage Area

Lighting• It is a requirement that there is sufficient space and light at the

point of the work to ensure that it can be undertaken safely.• If lighting is provided, care must be taken to ensure that the

lighting does not introduce hazards by altering the colours of signs or labels. The ability to discriminate between colour-coded hazards or controls should not be impaired by the lighting.


Access and egress• Access to and egress from the work area must be suitable and safe

for the workers during the work. If there could be difficulties, egawkward access or confined space working, there must be suitable rescue equipment available and ready to use.

Working practices• Additional procedures will be necessary to adequately cover shift

changes or work extending over long periods. It may also be necessary to have special rules or procedures for particular items of equipment and for particular working practices such as testing (eg it may be necessary to remove earths to facilitate testing under a clearly defined sanction-to-test procedure).


Testing• Any test equipment necessary to verify the safety of

any conductor must be available and verified as correctly functioning immediately before and after every test to confirm its indication.

LOTO System• In some circumstances there could be more than one

source of power supply to the work station or equipment, eg emergency back-up supplies, therefore it is necessary to identify any other possible paths that could supply the work station or equipment and ensure that they are not only isolated but also prevented from being inadvertently reapplied. This is best achieved by locking off with a proprietary LOTO system.

Permit-To-Work Procedures• High voltage work should be carried out only under a

permit-to-work system.• The permit to work should explicitly state:

§ the task to be carried out.§ defined persons who will carry out the work.§ the controls necessary to ensure the safety of the people

undertaking the work.§ the duration of time for which the permit is valid.

Permit-To-Work Procedures – Contd.

• The written permit should be issued by a person competent to understand the hazards and risks involved and to check that all the control measures are correct and in place. This person is known as the authorised person.

• No work other than that stated on the permit to work should be undertaken, and no areas other than the safe working area indicated in the permit should be occupied or approached. If any changes in work are necessary it must be agreed with the authorised person or a specifically nominated deputy.

• There should be no ambiguity regarding the risk controls, the location of the actual work or any safe distances or safe working areas described in the permit. To avoid this, it is preferable to include diagrams, and for the authorised person and the competent person to discuss the risk controls, isolation, earthing points and safe working areas.

• The person signing to accept the permit to work is the person with whom the responsibility for compliance with the permit lies. This person is responsible for ensuring that all the risk controls and safety precautions contained within it are complied with and that work is restricted to only that which is allowed for in the permit and only within the safe working areas given.


• The permit-to-work system must be regularly checked to ensure that it is being followed and is functioning correctly and should be fully audited occasionally. The results of these checks and audits will be necessary to ensure that the higher levels of risk controls implemented by the permit to work will reduce the risk to workers so far as is reasonably practicable to prevent incidents relating to work with electricity as required by legislation.

• While the actual equipment being worked on is made dead, there may be work station, equipment nearby that are still live. This must be considered and a safe working area noted on the permit to work. In some organisations this is placed explicitly on a separate document, often known as a “Limitation of Access” document.


When the job has been completed, supervisor should ensure that:• They receive notification that the task has been completed,

signed by the competent person with date and time.• There is acceptance that the task has been completed, signed

by the authorised person with date and time.• Any notes, relevant comments or requests for an extension of

the permit are reviewed.


Additional Procedures for HV System

Sanction-for-Test SystemFollowing work on a high voltage system, it is often necessary to perform various tests. testing should only be carried out after the circuit main earth (CME) has been removed.A sanction-for-test declaration should be issued in an identical manner to a permit to work provided and it should not be issued on any apparatus where a permit to work or where another sanction-fortest is in force. Note: A sanction-for-test is not a permit to work.

Additional Procedures for HV System – Contd.

Limitation of Access Form When carrying out high voltage maintenance, it may be dangerous to allow anyone to work adjacent to high voltage equipment, as workers may not be familiar with the risks involved when working on or nearby high voltage equipment. The limitation of access form states the type of work that is allowed near high voltage equipment and safety precautions. the form is issued and signed by the chief engineer AND electrical officer, and countersigned by the persons carrying out the work

Earthing Down Earthing down is a very important concept to understand when working with high voltage systems. It is important to ensure that any stored electrical energy in equipment insulation after isolation is safely discharged to earth. Earthing down ensures that isolated equipment remains safe

Additional Procedures for HV System – Contd.

1. Know the riskDamaging effects which can be induced in the body by electric shock or contact with live electrical systems include:• Ventricular fibrillation - This is a potentially fatal condition where

the heart muscle quivers rather than beats, eliminating blood flow and causing death.

• Cardiac asystole - where the heart stops beating. Combined with ventricular fibrillation this constitutes cardiac arrest.

• Respiratory arrest.• Burns from arc flash and resistive heating of body tissues.• Radio frequency burns if radio or microwave frequencies are used.

Safety Precautions Working on High Voltage

2. Know What High Voltage Is• AC High Voltage• DC High Voltage • Pulsed High Voltage

3. Know the Components • Capacitors• Transmission Lines• Inductors(and transformers)• Diodes and Switches


4. Know Your Ground • Good Ground• Ground Conductors• What to Ground• Grounding Sticks

5. Know When to Work, and When Not to Work • Always work on a circuit that is de-energized if at all

possible.• Always work with at least one other person who is

familiar with the equipment, its hazards, and emergency procedures.


• Use test instruments and components only at their rated conditions.

• Always discharge capacitors with a grounding stick before working on a circuit.

• Don't perform work if you are mentally compromised.• Keep stored energies, currents and voltage as low as possible

at the design stage.• Never assume a circuit is safe just because it is powered off.


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High Voltage Trainng - virtual.bstc-training.com