high voltage safety outline

General Safety Instructions for High Voltage Machines

High Voltage SafetyGeneral Safety Instructions for High Voltage Machines

W. Maes

Department of Marine EngineeringAntwerp Maritime Academy

HV, 2015

Willem Maes High Voltage Safety

General Safety Instructions for High Voltage Machines

Outline

1 General Safety Instructions for High Voltage MachinesGeneral Safety Instructions - Machines


General Safety Instructions for High Voltage Machines General Safety Instructions - Machines

General Safety Instructions - Machines

Electric machines have dangerous live and rotating parts andmay have hot surfaces.All operations serving, transport, installation, connection,commissioning, operation and maintenance shall be carried outby responsible skilled people



Electrical Connections - Safety Rules

Figure : De-energize




Figure : Isolate the circuit from the power source




Figure : Provide safeguard against reclosing




Figure : Connect to earth and short




Before starting with the job: The following rules must bestrictly applied:

De-energizeVerify safe isolation from supplyProvide safeguard against reclosingConnect to earth and shortCover or provide barriers against neighbouring live parts




De-energize auxiliary circuits (for example space heaters)!Note rating plate markings and connection diagram in theterminal box!




Figure : safe and permanent electric connection??




Figure : always use cablelugs on flexible cable




The connection must be made in a way that a safe andpermanent electric connection can be maintainedUse appropriate cable terminalsEstablish and maintain safe equipotential bonding




Figure : Establish and maintain safe equipotential bonding




Figure : Air clearance for HV (IACS)




Figure : creepage distances (IACS)




The clearances between High Voltage unisolated live partsand between such parts and earth must not be below thevalues of appropriate standards (minimal) and values givenin the manufacturer’s documentationNo foreign bodies, dirt or moisture is allowed in theterminal boxClose unused cable entrance holes and the box itself in adust- and watertight manner.(maintain its IP rating)Lock the key when the machine is run without coupling




Figure : Lock the key when the machine is run without coupling



Operation - Safety Rules

In case of deviations from normal operation, for example,elevated temperture, noises, vibrations - disconnectmachine, if in doubtEstablish cause and consult manufacturer, if necessary.Do not defeat protective devices, not even in trial run.In case of heavy dirt deposits, clean cooling system atregular intervals.Open blocked condensate drain holes from time to time.



Additional Safety Instructions for Permanent MagnetSynchronous Machines




only qualified personnel familiar with the relevant safetyrequirements are allowed to open and maintain permanentmagnet synchronous machines.it is not allowed to remove the rotor of a permanent magnetsynchronous machine without the special tools designedfor this purposewhen the machine’s shaft is rotating, a permanent magnetsynchronous machine induces a voltage in its terminalsthe induced voltage is proportional to the rotational speed,and can be hazardous even at low speedsprevent any rotation of the shaft before opening theterminal box and or before working at unprotectedterminals




the terminals of a machine with frequency converter supplymay be energized even when the machine is at standstillbeware of revers power when working at the supply systemdo not exceed the maximum allowed speed of the machinesee product specific manualsmagnitic stray fields, caused by an open or disassembledpermanent magnet synchronous machine or by a seperaterotor of such a machine, may disturb or damage otherelectrical or electromagnetic equipment, such as cardiacpacemakers, creditcards and equivalent




loose metallic parts and wast must be prevented fromentering the interior of the permanent magnet synchronousmachine as well as getting in contact with the rotorbefore closing an opened permanent magnet synchronousmachine, wast and any parts not belonging to the machinemust be removedBeware of magnetic stray fields and possible inducedvoltages when rotating the separate rotor of a permanentmagnet synchronous machine as they may cause damageto surrounding equipment.



Rules During any Operation

Disconnect and lock out before working on the machine or thedriven equipment.Ensure no explosive athmosphere is present while the work isin progress.




Starting and Restarting

Figure : The maximum number of sequential starts...




Starting and RestartingThe maximum number of sequential starts has beendeclared in machine’s technical documents.(ex.autotransformator starting)the new starting sequence is allowed after the machinehas cooled down to ambient temperature for a cold startcondition or to operating temperature for a warm startcondition.







Earthing and Equipotential BondingCheck before starting that all earthing and equipotentialbonding cables are effectivly connected.Do not remove any earthing or equipontialing cables,which have been assembled by the manufacturer.




Figure : equipotential bondingWillem Maes High Voltage Safety



Clearances, creepage and separationsDo not make any removal or adjustment in terminal boxes,wich could decrease clearances or creepage distancesbetween parts.Do not install any new equipment to terminal boxes withoutasking for advise from the manufacturer of the originalequipment.Be sure that the air gap between rotor and stator ismeasured after any maintenance on the rotor or bearings.The air gap shall be the same in any point between therotor and the stator.Centralize the fan to the centre of the fan hood or the airguide after any maintenance. The clearance shall be atleast 1 percent of the maximum diameter of te fan and inaccordance with standards.




Connections in terminal boxes (Ex motors)All connections in main terminal boxes must be made withEx-approved connectors, wich are delivered with themachine by the manufacturer.All connections, in auxiliary terminal boxes, as markedintrinsically safe circuits (Ex i or EEx i) must be connectedto proper safety barriers.


Appendix For Further Reading

For Further Reading I

The RulesLloyds register of shipping.

The RulesABS.


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