design spec from iec abs dnv lr
DESCRIPTION
DESIGN SPECIFICATION FROM DIFFERENT CLASSESABS, DNV, IEC, LRTRANSCRIPT
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DNV Electrical: OS-D201 Instrumentation: OS-D201
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To gather and protect the control and protective devices together with electrical and mechanical connections against external influences.
To inform the end-user on the state of his installation.
To protect the switchboard user against the main risk of accidents (direct contact protection, indirect contact protection and fire risk).
To evolve with the activity
What is a switchboard used for ?
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The LV electrical switchboard has to be safe
and available
It is a question of balance between:
the needs of safety and availability
the constraints of reliability and maintenability of the installation.
Safety
Maintenability
Reliability Availability
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Ingress protection of enclosures
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Enclosure types in relation to location
Table B1 Enclosure types in relation to location
Location Switchgear and transformers
Engine and boiler rooms
Above the floor IP 22
Dry control rooms and switchboard rooms
IP 21
Closed compartments for fuel oil and lubrication oil separators
IP 44
Deckhouses, forecastle spaces, steering gear compartments and similar spaces
IP 22
Ballast pump rooms, columns below main deck and pontoons and similar rooms below the load Line
IP 44
Open deck, keel ducts
Battery rooms, paint stores, or areas that may be hazardous due to the cargo or processes onboard
IP 56
Dry accommodation spaces IP 20
Galleys, laundries and similar rooms IP 44
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Enclosure
Enclosures shall be resistant to weather, oil and chemicals
shall be made of especially corrosion resistant material or dimensioned with a certain corrosion allowance
Plastics, Light metal alloys as i.e. aluminum shall be avoided as enclosure materials
Flame retardant
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Cable Entrances
Cable entrances into enclosures shall be from below or from the side (except for enclosure IP 20), in order to prevent ingress of water or other liquids.
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Environmental Requirements
Temperature
Humidity
Relative humidity up to 95%.
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Environmental Requirements
Harmonic distortion
Total harmonic content not exceeding 8% of voltage root mean square value
No single harmonic being greater than 5% of voltage root mean square value.
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Power Distribution System
The most common IT-system Limited earth fault current depending on capacitance in the cabling system Alarm in case of an earth fault Ideal for emergency power and important consumers with need for continuous
operation To be used in UPS-systems
Isolated IT-system
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Power Distribution System
The miniature circuit breaker with integrated earth fault tripping is
functioning very well in a fully insulated IT-system!
Isolated IT-system (230 V)
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Power Distribution System
Earth fault current calculated to maximum 100 A
Consumers will be tripped in case of an earth fault
Impedance earthed IT-system
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Power Distribution System
Two voltage levels in one system!
400/230 V are the most common voltages
Separate N- and PE-conductors Consumers will be tripped in case of an earth fault
EMC Performance - Excellent
Directly earthed TN-S system
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Motor Control
Motor Rated 1kW or above:
a multipole circuit breaker
fused circuit breaker or contactor - Each circuit-breaker rated more than 16 A shall be of trip-free type
overcurrent release
if necessary combined with a controller for limiting the starting current
control circuits with undervoltage release (UVR) - Undervoltage and closing coils, including contactor coils, shall allow closing of the switchgear and controlgear when the voltage and frequency are 85 to 110% of nominal value. The undervoltage protection shall release if the voltage is below 70% or absolutely below 35% of nominal voltage.
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Assemblies
Main and emergency switchboards and other switchboards requiring operation shall have handrails with an insulating surface.
The upper limit of the scale of ampere-meters and kilowatt-meters shall be at least 130% of the rated full load of the circuit.
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Emergency Stop
If required:
no single failure will cause loss of duplicated essential or important equipment.
For duplicated equipment, shall be arranged as two separate circuits with separate cables. A common stop button with several contacts (separate for each consumer) will be accepted.
The emergency stop signal shall act independently of any software based control system for the same consumer.
A computer based emergency stop systems shall be independent from other computer based systems with control functions for the same consumers
Alarm for loss of power shall be provided for normally open emergency stop circuits
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Emergency Stop
Emergency stop will not be required for the following:
Fans not capable of supplying outside air to the space such as fans in HVAC temperature control units
Fans for heating coils.
ventilation fans for cabinets and switchboards.
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Signal Classes
Class 1 - Mains power lines, power circuits with a high di/dt, switch-mode converters, powerregulation
Class 2 - Relay contacts. Class 3 - Digital circuits (HF switching). Class 4 - Analogue input/output circuits (low-level
measurements, active sensor supply circuits)
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Cables Construction
Conductor minimum cross section
0.22 mm2 Data communication cables
0.5 mm2 60 V cables and 250 V control and instrumentation cables and control and instrumentation switchboard wires
1.0 mm2 Power circuit switchboard wires
1.0 mm2 250 V and 0.6/1 kV power cables
plain or metal-coated annealed copper low emission of smoke in case of a fire Halogen free cables Braid or armour of lead, bronze or copper shall
not be installed in contact with aluminium alloy structures,
except in dry accommodation spaces.
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Insulating materials
Temperature classes for insulating materials
Material Temperature C
Polyvinyl chloride or (PVC) 70
Hard grade ethylene propylene rubber (HEPR) 90
Halogen free hard grade ethylene propylene rubber (HF HEPR) 90
Halogen free cross linked polyethylene (HF XLPE) 90
Cross linked polyethylene (XLPE) 90
Halogen free cross linked polyolefin (HF 85) 90
The insulation on switchboard wires shall be at least flame retardant
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Protective Sheaths
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Minimum average thickness of insulating walls for power cables with rated voltage 0.6/1.0 kV
Minimum thickness of insulating walls
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Control and Instrumentation Cables Rated 150/250 V
Minimum thickness of insulating walls
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Data Communication Cables
Type
Cat 5 DC cat 6A
Cat 5e DC cat 7
DC cat 6 DC cat 7A
Fiber Optic Cables
Type
QFCI
AICI
AIAI
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Routing of Cables
Cables for control or monitoring circuits below 50 V shall not be run in the same bunch or pipe as cables for circuits emitting a high degree of electromagnetic disturbance, unless means to avoid interference has been provided.
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Routing of Cables
Crossovers or installation of power cables and control cables beside each other are generally not considered a problem if signal cable is screened.
A distance of 50 mm between power and unbraided or unscreened control cables on a cable tray is considered acceptable.
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Routing of Cables
Screens around individual pairs for earthing for EMC purposes in cables for control, electronic, communication and instrumentation equipment, shall normally be earthed at one end only. Cables having both individual screen and common screen (or braiding) shall have these metal coverings separated from each other at the floating end, when earthed at one end only.
Spare cable conductors shall either be terminated or insulated.
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Component Placement
Power and low level apparatus shall be physically separated and cables segregation and distances between power and sensitive cables shall also be respected as shown on the figure:
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Power Circuits
Busbars - The shape, configuration and cross-section shall be such that the temperature rise will not exceed 45C at rated load. The cross-section of busbars for neutral connection on an AC three-phase, four-wire system, and for equaliser connection on a DC system, shall be at least 50% of the cross-section for the corresponding phases (poles).
The maximum permissible load for copper busbars with ambient temperature 45C
With x thickness (mm)
Maximum permissible loading [A] with 50/60 Hz
Painted (matt-black) Bare
Numbers of bars Numbers of bars
2 3 2 3
15 3 390 470 350 445
20 3 485 560 430 535
20 5 690 900 620 855
20 10 1145 1635 1020 1460
25 3 580 650 510 615
25 x 5 820 1040 725 985
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Termination
All connections for current-carrying
parts and earthing connections shall be
fixed so that they cannot loosen by vibration.
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Conductor Ends (Termination)
All conductor ends shall be provided with suitable pressured sockets or ferrules, or cable lugs.
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Conductor Ends (Termination)
Cable terminal lug as per DSB rule
- Cable lugs are to be of the tubular type. (The split-type will not be accepted.)
- Cable lugs 10 mm and larger are to comply with- and tested according to IEC 61238-1
- Cable lugs to be have a inspection hole
- The correct size of the cable lug and the type of the crimping tool have to be used
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Cables Bending Radius
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Cable Selection
YELLOW/GREEN colour code is used, it shall be used
for PROTECTIVE EARTHING only.
Cable temperature class
The temperature class of power cables shall be at least 10C above the ambient temperature
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Protective Earthing and Bonding of Equipment
-Copper
-The connection to the equipment enclosure parts, which shall be earthed, shall be made by corrosion resistant screws or clamps
-All earthing connections of copper shall have sufficient cross-section to prevent the current density exceeding 150 A/mm2 at the maximum earth fault currents that can pass through them.
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Earthing Connections and Conductors
Minimum cross-section of Earthing conductors
Arrangement of earth conductor
Cross-section Q of associated current carrying conductor (one phase or pole) (mm2)
Minimum cross-section of earth conductor
2. Uninsulated earth conductor in cable for fixed installation, being laid under the cable's lead sheath, armour or copper braid and in metal-to-metal contact with this.
Q 2.5 1 mm2
2.5 < Q 6 1.5 mm2
6 < Q Not permitted
3. Separately installed earth conductor for fixed installation
Q < 2.5 Same as current-carrying conductor subject to minimum 1.5 mm2 for stranded earthing connection or 2.5 mm2 for unstranded earthing connection
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Termination and Cable Entrances
Electrical equipment that needs to be connected to protective earth shall be provided with suitable fixed terminal for connecting a protective earth conductor. The terminal shall be identified by a symbol or legend for protective earthing (PE).
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Cabinet Cabling
Each cabinet must be equipped with an earthing bar or a ground reference metal sheet
All shielded cables and external protection circuits must be connected to this point.
Anyone of the cabinet metal sheets or the DIN rail can be used as the ground reference.
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Cabinet Cabling
Hinged doors shall be connected to the switchboard or enclosure by a separate, flexible copper earth conductor.
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Enclosure
Each cabinet must be equipped with an earthing bar or a ground reference metal sheet
All shielded cables and external protection circuits must be connected to this point.
Anyone of the cabinet metal sheets or the DIN rail can be used as the ground reference.
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Arrangement of Earth Bus-bar
IE Bar should be isolated from the panel
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Arrangement of Earth Bus-bar
IEC 61892-6 (2007):4.1.3 quotes: Earth bars, when provided, shall be located in front of equipment and junction boxes to allow for easy access for usage, inspection and maintenance. All earth bars and terminals shall be visible and possible to be checked also after termination of cables.
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Arrangement of Earth Bus-bar for MCC
Install the complete cable right up to the level of the actual starter, and terminate the braiding and/or earth conductor to the vertical sub earth bar at this level!
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Equipment Protective Earthing
Terminals for circuits with different system voltages shall be separated, and clearly marked with the system voltage.
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Single Point Earthing
DNV-OS-D201 (2011): Ch.2 Sec.10 quotes: Single point earthing is permitted for final sub circuits and in those installations (such as for control or instrumentation) where it is required for technical reasons..
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Earth Terminations
IEC 61892-6 (2007):4.1.3 quotes: Separate connections shall be used for each individual earth conductor.
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Equipment Protective Earthing
Suitable star washers and conductor terminals shall be used, so that a reliable contact is ensured.
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Equipment Protective Earthing
The earthing of the cable itself may be carried out by fixing the cable to the hull constructions, or to parts that are welded or riveted to the hull constructions (metal to metal without paint or coating), by corrosion resistant clamps or metal clips.
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Colour-coding in different earthing systems
According to DSB with reference from NORSOK standard Rev. 3 item 12.5.3
Protective earth (PE) bus-bars are to be colour-coded green/yellow and/or with the letters PE.
Instrument earth (IE) bus-bars should be colour-coded green/yellow with additional red marking and/or with the letters IE.
Intrinsically safe earth (IS) bus-bars should be colour-coded green/yellow with additional light blue marking and/or with the letters IS.
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Marking and Signboards
All equipment shall be externally marked
All equipment shall if necessary be marked to ensure correct use
All marking shall be permanently fixed.
All equipment shall be fitted with a rating plate giving information on make, type, current, voltage and power rating
All terminals for connection of external instrumentation and control cables shall be marked.
External instrumentation and control cables shall be marked for identification inside the cabinet.
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Clearance and Creepage Distances
Clearance Clearance is the shortest distance between two conductive parts measured through air. Creepage Creepage is the shortest distance between two conductive parts measured along a surface.
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Type tested assemblies and Partly type tested assemblies
a) Electrical low voltage assemblies constructed and tested in accordance with IEC 60092-302, item 7.1.2.101 (referring to IEC 61439-1) are accepted as long as the following conditions are met: minimum clearance distance shall be 8 mm, minimum creepage distance shall be 16 mm the assembly has been type tested with impulse voltage test in accordance with IEC 61439-1 maximum operating temperature of busbars shall be documented to be acceptable with respect to fixing materials and internal temperature by a full current type test maximum temperature rise at termination points for external cables shall be 60C such assemblies shall not be installed in machinery space category A.
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HAZARDOUS AREAS
Zone 0 Area in which an explosive gas atmosphere is present continuously or for long periods.
Certified safe for Intrinsic safety Ex-ia
Zone 1 Area in which an explosive gas atmosphere is likely to occur in normal operation.
Zone 2 Area in which an explosive gas atmosphere is not likely to occur in normal operation and, if it does occur, is likely to do so infrequently and will exist for a short period only.
certified safe for Zone 1 and Zone 2 application.
Ex-n standard
Minimum of IP45
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Ex Protection According to Zones
Zone 2 Zone 1 Zone 0
Ex d (flameproof) Yes Yes No
Ex e (increased safety) Yes Yes No
Ex i (intrinsic safe) Yes Yes Yes
Ex p (pressurised) Yes Yes No
Ex n Yes No No
Ex s (special protection) Yes Yes Yes
Ex m (moulded) Yes Yes No
Ex q Yes Yes No
Ex o Yes Yes No
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HAZARDOUS AREAS
Ex-e motors (increased safety)
Overload or thermal protection
Frequency Converter
Ex-e and Ex-d motors driven by a Power converter is not accepted
Ex-n motors driven by Frequency Converter needs a conformity declaration
minimum IP44 degree
Ex-p equipment
Automatic shutdown and or isolation of equipment inside enclosures will be required
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HAZARDOUS AREAS
Ex-d Explosion proof (flameproof) enclosure
The part which can ignite an explosive atmosphere are placed in an enclosure which can withstand the pressure caused by an internal explosion and prevents the transmission of the explosion to the explosive atmosphere surrounding the enclosure.
Exd enclosure - Should only be used for arcing (parts of) equipment. Exe junction boxes are more convenient to use and maintain!
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HAZARDOUS AREAS
Ex-i circuits
All intrinsic safe circuits shall have a safety barrier in form of a zener barrier or galvanic isolation certified safe for the application in front of the circuit part going into hazardous areas.
A circuit in which no spark or any thermal effect produced is capable of causing ignition of a given explosive atmosphere
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HAZARDOUS AREAS
Ex-i circuits
All intrinsic safe circuits shall have a safety barrier in form of a zener barrier or galvanic isolation certified safe for the application in front of the circuit part going into hazardous areas.
Exi barrier and circuit(s)
must be sufficiently separated from other circuits
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Corresponding Values for NEMA-Type and IP-rating
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Cable types, Cabling and Termination
All cables installed in hazardous areas shall have an outer non-metallic impervious sheath.
Power and signal cables shall have a metallic braiding or armour between conductors and the non-metallic impervious sheath in the following zones and areas:
zone 0
zone 1
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Hazardous areas
Explosion and fire can cause severe damage
Better be safe than sorry
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The tests of standard IEC 60439-1
There are two type of tests:
7 type tests are performed by the manufacturer on one or several configurations: n1 temperature rise limits n2 dielectric properties n3 short-circuit withstand n4 protective circuit effectiveness n5 clearances and creepage distances n6 mechanical operation n7 degree of protection.
3 routine tests are performed by the panelbuilder on each particular switchboard: n8 general inspection n9 insulation/dielectric test n10 protection measures.