DNV Electrical: OS-D201 Instrumentation: OS-D201

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 ?

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

Ingress protection of enclosures

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

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

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.

Environmental Requirements

Temperature

Humidity

Relative humidity up to 95%.

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.

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

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)

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

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

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.

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.

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

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.

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)

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.

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

Protective Sheaths

Minimum average thickness of insulating walls for power cables with rated voltage 0.6/1.0 kV

Minimum thickness of insulating walls

Control and Instrumentation Cables Rated 150/250 V

Minimum thickness of insulating walls

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

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.

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.

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.

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:

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

Termination

All connections for current-carrying

parts and earthing connections shall be

fixed so that they cannot loosen by vibration.

Conductor Ends (Termination)

All conductor ends shall be provided with suitable pressured sockets or ferrules, or cable lugs.

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

Cables Bending Radius

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

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.

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

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).

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.

Cabinet Cabling

Hinged doors shall be connected to the switchboard or enclosure by a separate, flexible copper earth conductor.

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.

Arrangement of Earth Bus-bar

IE Bar should be isolated from the panel

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.

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!

Equipment Protective Earthing

Terminals for circuits with different system voltages shall be separated, and clearly marked with the system voltage.

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..

Earth Terminations

IEC 61892-6 (2007):4.1.3 quotes: Separate connections shall be used for each individual earth conductor.

Equipment Protective Earthing

Suitable star washers and conductor terminals shall be used, so that a reliable contact is ensured.

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.

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.

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.

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.

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.

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

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

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

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!

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

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

Corresponding Values for NEMA-Type and IP-rating

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

Hazardous areas

Explosion and fire can cause severe damage

Better be safe than sorry

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.