To gather and protect the control and protective devices together with electrical and mechanical connections against external influences.
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
It is a question of balance between:
It is a question of balance between:
the needs of safety and availability
the constraints of reliability and maintenability of the installation.
One general standard :
One general standard :
IEC 60439-1 type-tested assemblies (TTA) and partially type-tested assemblies (PTTA)
Four related standards:
IEC 60439 -2 busbar trunking systems (busways)
IEC 60439 -3 distribution boards (<250A, unskill people)
IEC 60439 -4 assemblies for construction sites (ACSs)
IEC 60439 -5 cable distribution cabinets (CDCs)
Scope : Low-voltage switchgear and controlgear assembly, TTA or PTTA, whose rated voltage is 1000 Vac or 1500 Vdc.
Scope : Low-voltage switchgear and controlgear assembly, TTA or PTTA, whose rated voltage is 1000 Vac or 1500 Vdc.
TTA : type-tested assemblies conforming to an established type or system without deviations likely to significantly influence the performance, from the typical ASSEMBLY verified to be in accordance with this standard. A full range of representative configurations have been tested.
PTTA : partially type-tested assemblies, containing both type-tested and non type-tested arrangements provided that the latter are derived (e.g. by calculation) from type-tested arrangements which have complied with the relevant tests. Some limited configurations may be tested.
Definition : A combination of one or more low-voltage switching devices together with associated control, measuring, signalling, protective, regulating equipment, etc., completely assembled under the responsibility of the manufacturer with all the internal electrical and mechanical interconnections and structural parts
Meeting IEC 60439-1 requirements means :
Meeting IEC 60439-1 requirements means :
a minimum level of safety for people and equipment
to include the low-voltage switchgear and controlgear assemblies for the power distribution and control
precise requirements for
- service conditions (temperature...)
- construction requirements (IP, IK, forms,...)
precise test procedures
IEC 60439-1: one worldwide standard for all the professionals of switchboards.
external design (open-type, dead front, enclosed, busway)
external design (open-type, dead front, enclosed, busway)
place of installation (indoor - outdoor)
conditions of installation with respect to mobility (stationary - movable)
degree of protection (for outdoor IP 3X)
type of enclosure (e.g metallic or plastic)
method of mounting (fixed or removable)
measures of protection of persons
form of internal separation (to be detailed, agreement between customer and manufacturer)
types of electrical connections of functional units (to be detailed, agreement between customer and manufacturer)
IEC 60439-1 : Functional unit
Definition : Part of an assembly, comprising all the electrical and mechanical elements that contribute to the fulfilment of the same function
Example : drawer in a Motor Control Centre switchboard .
In most installations, no particular partitioning is needed, electrical switchboard of the form 1 type is acceptable.
In most installations, no particular partitioning is needed, electrical switchboard of the form 1 type is acceptable.
However this is no longer true without a front plate or other equivalent mean. The user shall not access to living parts.
Following forms 2, 3 and 4 introduce additional partitioning within the switchboard
Form 2: partitioning of busbars
Form 3a and 3b:
functional units separated from each other and separated from the busbars
connecting terminals separated from busbars
Form 4a and 4b:
functional units separated from each other and separated from the busbars
connecting terminals separated from each other and separated from busbars.
Types of electrical connections of functional units (FU)
F = Fixed
D = Disconnectable
W = Withdrawable
Identification
connections are codified with these 3 letters referring to :
1st : main incoming circuit
2nd : main outgoing circuit
3rd: auxiliary circuits
There are two type of tests:
7 type tests are performed by the manufacturer on one or several configurations:
n°1 temperature rise limits
n°2 dielectric properties
n°3 short-circuit withstand
n°4 protective circuit effectiveness
n°5 clearances and creepage distances
n°6 mechanical operation
n°7 degree of protection.
3 routine tests are performed by the panelbuilder on each particular switchboard:
n°8 general inspection
n°9 insulation/dielectric test
n°10 protection measures.
The aim of these tests is to confirm the switchboard
The aim of these tests is to confirm the switchboard
characteristics.
The 7 type tests are carried out on the most difficult and unfavourable system configurations. The assembled and cabled switchboards are made up of their usual components, connection system…, equipped with switchgear and assemblied and installed according to industrial standards.
The tests are conducted either in approved laboratories (Asefa, Kema, Lcie,…), or in a manufacturer laboratory.
Guarantees the safety and reliability of the switchboard, by avoiding problems such as:
Guarantees the safety and reliability of the switchboard, by avoiding problems such as:
connection damages
reduction in insulation performances
risk of burn for maintenance operators
electronic components damages
faulty operation of the devices: inopportune release.
How to proceed:
to measure the temperature of each equipment, after a delay allowing a stabilized temperature, when each circuit is used at its rated power and when the complete switchboard is loaded with an appropriate diversity factor
Result to be obtain
temperature rise shall not exceed what the different equipment can withstand
the temperature of accessible surfaces has to be checked
Guarantees the switchboard safety and reliability, to avoid problems such as:
Guarantees the switchboard safety and reliability, to avoid problems such as:
electrical arc generation
insulation performance decreasing
connection damages
Withstand impulse voltage test and an ac test are performed
This test simulates an incident which could occur on site.
This test simulates an incident which could occur on site.
Withstanding the short-circuit currents is:
to avoid danger (rupture and projections of components, arc generation and propagation outside the switchboard,...)
it also means the installation can be quickly put back into operation after the incident.
The effectiveness of the protective circuit is verified by two tests:
The effectiveness of the protective circuit is verified by two tests:
resistance measurement of the connection between the exposed conductive parts and the protective circuits
short-circuit withstand performed between the protective conductor and the nearest phase conductor.
Clearance control: shortest distance between two conductive parts.
Clearance control: shortest distance between two conductive parts.
Creepage distance control: shortest distance along the surface of an insulating material between two conductive parts.
Endurance of material, guaranteeing the longevity of the various mechanisms.
Endurance of material, guaranteeing the longevity of the various mechanisms.
The standard requires 50 operating cycles.
The tests carried out define the capacity of an equipped switchboard to:
The tests carried out define the capacity of an equipped switchboard to:
protect persons against contact with live parts
protect equipment against penetration of solid objects and liquids
3 routine tests performed by the panelbuilder:
3 routine tests performed by the panelbuilder:
n°8 general inspection
n°9 insulation/dielectric test
n°10 protection measures.
Check of mechanical actuating elements, interlocks,... effectiveness.
Check of mechanical actuating elements, interlocks,... effectiveness.
Check of proper laying of conductors and cables and proper mounting of device.
Check of connections adequate contact, especially screwed and bolted connections.
No arc flash-over or insulator perforation must be observed between the live parts each other and between the live parts and the conductive structural parts.
No arc flash-over or insulator perforation must be observed between the live parts each other and between the live parts and the conductive structural parts.
Checking of protective measures and of the electrical continuity of the protective circuits for metallic assemblies.
Checking of protective measures and of the electrical continuity of the protective circuits for metallic assemblies.
Specifiers/consultants:
Specifiers/consultants:
the certainty to prescribe a switchboard which ensures the level of safety required by the user
Panel-builder / Installer:
confidence in products and swichboards systems, following the standard
