News

17.02 2011

Why use BOS in according to international standards?

Questions and Answers

why DC 1000V?	The designers of PV installations like to go for a higher voltage to have lower energy losses. (P=U x I and Pv=I2 x R)
why UL94-V0?	UL94 is a American standard for switchgear suitable for use directly connected to the power grid. This standard demands for switches with larger air- and creeping distances than the Standard for normal Industrial Control Equipment UL508. Because of the special characteristics of PV panels (low short circuit current) UL and CSA accepted the application of switches designed according to UL 508 as safety switches for the use between the PV panel and the Inverter.
Why IEC 60629?	This international Standard is intended for application to all kinds of installation accessories for use in domestic and similar installations, such as socket-outlets, switches, push-buttons, pilot or signaling lights, etc. May also be applied to related equipment, which is intended to be used in conjunction with common installation accessories, such as dimmers, buzzers, telephone or signaling contacts, etc.
WHY EC RoHS?	Working in partnership with the policy lead at the new Department for Business, Innovation and Skills (BIS), NMO is the UK Enforcement Authority for the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment Regulations 2008 (the “RoHS Regulations”). These Regulations implement EU Directive 2002/95 which bans the placing on the EU market of new electrical and electronic equipment containing more than agreed levels of lead, cadmium, mercury, hexavalent chromium, polybrominated biphenyl (PBB) and polybrominated diphenyl ether (PBDE) flame retardants. Santon switchgear complies to these regulations.
Why UL508?	UL508 is the American Standard for Industrial Control Equipment and used also for PV switch disconnectors (our switches).
Why IEC 60695, 960℃?	It is only for switch design. Isolating materials in switches have to fulfill certain criteria. One of them is flammability. The international standard IEC 60695 describes the way to determine the flammability of a material.
Why IEC60715?	international standard IEC 60715 Dimensions of Low-Voltage Switchgear and Control gear, Standardized Mounting on Rails for Mechanical Support of Electrical Devices
WHY IEC 60269-4?	international standard IEC 60269-4 Low-voltage fuses – Part 4: Supplementary requirements for fuse-links for the protection of semiconductor devices.
Why IEC60364-7-712?	international standard IEC 60364-7-712 Electrical Installations of Buildings - Part 7-712: Requirements for Special Installations or Locations - Solar Photovoltaic (PV)         This is the Standard that tells you that you have to use a safety switch-disconnector between the panel and the inverter. (A mandatory component)
Why VDE0636?	German Standard DIN VDE 0636-201 Low-voltage fuses - Part 2-1: Supplementary requirements for fuses for use by authorized persons (fuses mainly for industrial application)
Why  DIN43620?	German Standard for Semi conductor fuses
why DIN43623?	German Standard for dimensions of fuses
WHY IEC 60947-1	International standard IEC 60947-1 {Ed.5.0}. Low-voltage switchgear and control gear - Part 1: General rules. The purpose of this standard is to harmonize as far as practicable all switchgear
WHY IEC 60947-3	international standard IEC 60947-3 Low-voltage switchgear and controlgear – Part 3: specific for: Switches, disconnectors, switch-disconnectors and fuse-combination units
WHY DC21	DC21 is a utillization category for switches and switch-disconnectors (switching resistive dc loads including moderate overloads) as defined in IEC 60947-3, table 2, according to which a switch-disconnector will be tested and certified. The PV safety switch-disconnectors application is accepted to fit in this utilization category.
Why IEC61643-1	international standard IEC 61643-1 Low-voltage surge protective devices – Part 1: Surge protective devices connected to low-voltage power distribution
WHY UL1449	American standard: requirements cover Surge Protective Devices (SPDs) designed for repeated limiting of transient voltage surges as specified in the standard on 50 or 60 Hz power circuits not exceeding 1000 V

 

 

With the DC250V rating value, series connection of two AC electrodes will not increase the rated DC voltage when an AC disconnector is used for direct current.

 

 

It is a typical AC breaker which seems totally not suitable for high voltage DC applications. Apparently the system voltage stays under the (very low) 250Volt. Also, it is not likely the AC residual current measurement works for DC since (almost) all AC residual current measurement systems work with coils, which are not suitable for DC. So, in short this product seems a standard AC breaker, is totally not suitable for high voltage DC systems and with a AC residual current measurement that doesn’t work at all for DC.

 

The IEC60364-7-712 says that it is obliged to have a DC switch in the PV system.

In the past some people used only fuses and no DC switch. That has changed, now a DC switch for PV systems is by law prescribed (in Europe).

 

For the switch selection the following is at hand:

The sun irradiation can go up to 1300W/m2. The PV module suppliers give the rating Inom, Isc, Vnom of the modules at 1000W/m2. When the sun power goes up to 1300W/m2 the current goes up to 1,3xInom. Therefore we advise to take 1,3 x the Isc of the modules for selecting the switch.

 

For both UL508 and IEC the test current for certification is 1,5 of the nominal current rating of the switch. Also the test voltage is somewhat higher than the nominal voltage rating of the switch.

 

IEC 60364‐7‐712 – prescribes the use of a DC switch between PV modules and the inverter in Europe.

 

In USA for PV installations the switches must be UL508 certified.

In Europe for all electrical switches the IEC 60947‐3,table 2 is mandatory. The category in table 2 is dependent on the application, for PV (resistive) DC21 applies.