Standards for the Load

Overview

This overview on standards for loads connected to solar home systems is an extract of the publication: Photovoltaic Systems in Developing Countries, GTZ 2000

Comment: In the meantime, radios, TV sets, etc. are directly acquired by the users in the conventional appliances market; the associated energy consumption tends to be modest and they are highly standardised products. For these reasons, only light fixtures are reviewed in these specifications, while features of radios and TV sets are entrusted to training and general information activities.

Lighting Fixtures with Fluorescent Lamps and Ballasts

Comment: The standardisation of lighting fixtures with energy-saving fluorescent lamps and electronic DC ballasts is quite well described in IEC 60924 and 60925 “DC supplied electronic ballasts for tubular fluorescent lamps - General and safety requirements and - Performance requirements”. As these kinds of lights are utilised in public transport vehicles, aircraft and emergency lights, as well as in consumer applications like caravans and private cars, there is a much wider market for these products than just for PV solar systems. But there is still a need for standardisation of the special features; such lights must be compatible with PV applications, especially for the operation in Solar Home Systems in developing countries. Therefore, a new standard-proposal was drafted by the CENELEC CLC/BTTF 86-2 committee for "Photovoltaic Lighting Systems, Part 1, 2 and 3", which was also accepted by the IEC TC 82 and is currently circulating among the committee members for discussion and correction. A copy of the current draft version (as of 07/98) was kindly made available by TÜV-Rheinland, a member of the standards committee. The final version of this standard will probably be released by the end of 2000 and will not differ much from this draft.

The draft will be the basis for the following specifications:

Scope of the Standard

The scope of this standard comprises electronic ballasts and fluorescent lamps for use in photovoltaic systems. The electronic ballast and the lamp should be a matching pair, as recommended by the manufacturer or the supplier. If there is no recommendation available, the operation of the fluorescent lamp should at least be in line with the appropriate data sheet of IEC 60081 or IEC 60901.

Definitions

Lighting systems in PV stand-alone systems serve to illuminate dwellings and working areas. They are DC-supplied and thus consist of an electronic ballast, a fluorescent lamp and some kind of fixtures. The rated voltage range (V_R), at which the ballast may be operated and at which the proper and correct start, and operation, respectively, of the fluorescent lamp is safeguarded (IEC 60924) will be 10 V < V_R < 16 V for a 12 V system and 20 V < V_R < 32 V for a 24 V system.

Tests and Documentation

The following technical data have to be submitted by the manufacturer and will be verified during the tests:

• Casing of electronic ballast: material, IP-protection, type of assembly
• Type of lamp, certified according to IEC 60081 (tubular lamps) or IEC 60901 (single capped lamps)
• Terminals (marking, type, for which cable)
• Fuses (type, where is what protected by the fuse)
• Rated voltage range at which the ballast safely starts and operates (10 to 16 V for 12 V system, 20 to 32 V for 24 V system), see IEC 60924
• Design voltage according to IEC 60924 (about 85% of maximum rated voltage)
• Product identification and labels according to IEC 60924 and 60925
  

Documentation must include:

• Technical data
• Operating instructions
• Installation instructions
• Personal safety instructions
• Environmentally safe recycling and disposal instructions
• Warranty conditions
• Accessories
  

The visual inspection will evaluate the quality performance of the light fixture, the electronic ballast and the accessories.

Electrical parameters and performance tests:

• Starting performance test according to IEC 60925, paragraph 5 at ambient temperature of 20 to 25°C, start within 5 seconds, 1 firing failure permitted.
• Preheating condition test (if preheating is applied) according to IEC60925, section 7, electrode voltage range: 6.5 V < V_el < 11 V for high-resistance electrodes, 3.05 V < V_el < 6.5 V for low-resistance electrodes. Preheating is recommended, but is not imperative.
• Open circuit voltage at lamp terminals as of IEC 60925, section 6.
• Lamp current shall not be 25% higher than in operation with the reference ballast in the voltage range 8.5 V < V_bau < 13.6 V for a 12 V system (17 V < V_bau < 27.2 V for a 24 V system).
  
• Input current of the electronic ballast during operation with reference lamps shall only deviate from the data given by the manufacturer by less than 15%. No alternating effective current components may exceed 10% of the direct current.
• Maximum electrode current given in IEC 60081 or IEC 60901 data sheets may not be exceeded.
• Waveform of the lamp operating current shall not exceed the tolerance limits given in IEC 60925, crest factor of the lamp current may not exceed 3, direct current components may not exceed 2% of the RMS value.
• Stability of operation: uninterrupted, flicker-free and stable operation within the rated voltage range.
• Power consumption of the lamp should range between 90 to 110% of the nominal power consumption of the lamp within the rated voltage range.
• Efficiency test is still under consideration.
• Switching durability of the ballast/lamp combination shall be a minimum of 10,000 operating cycles with 60 s ON and 120 s OFF time.
  

Mechanical parameters and environmental conditions:

• Mechanical stability of all components shall be tested by vibrations test (acc. IEC 60068-2-6, stringency, see proposed standard) and
• shock test (acc. to IEC 60068-2-27, stringency, see proposed standard), while specimens are not packed and not live.
• Temperature and humidity resistance shall be defined and tested in accordance with the climatic conditions of the project (application) region (see IEC 60068-1).
• For application in tropical climates, a “cyclical damp heat test” (acc. to IEC 60068-2-30) will be performed with temperatures up to 55°C (specimen not live, resp. 40°C (specimen run with design voltage).
• Corrosion resistance and long-term stability will be evaluated after this damp-heat test.
• Operation at different temperatures will be tested according to IEC 60925, with five cycles between lowest and highest ambient temperature given by the manufacturer and 200 hours at maximum surface temperature (surface temperature may not exceed 80°C).
• Suitability of construction and sturdiness of casing as of IEC 60068-2-63 or IEC 60335-1, section 21 with a 250 g dead stroke hammer from different directions, operational test of changing fuse and lamp without danger of injury.
• IP protection code according to IEC 60529, IP 20 for solidly built indoor applications, otherwise IP 54.
  

Safety tests according to IEC 60598 and IEC 60924:

• Insulation resistance as of IEC 60598, section 10 and IEC 60924, sections 12 and 13
• Dielectric strength as of IEC 60598, section 10 and IEC 60924, sections 12 and 13
• Voltage impulses at electronic ballast as of IEC 60924, section 18
• Terminals as of IEC 60598, sections 14 and 15
• Safety earth terminal as of IEC 60924, section 9
• Creepage and clearance distances as of IEC 60924, section 10 for electronic ballast and section 11 for lighting system
• Fault conditions at electronic ballast as of IEC 60924, section 14
• Abnormal operating conditions will be tested as of IEC 60924, section 19:
  • Removal of lamps
  • Non-igniting lamps
  • Reverse polarity of input voltage
  • Surge voltage of 26 V for 12 V system (52 V for 24 V system) as maximum open circuit voltage from PV generator
  
• Screws, conductive components and connections as of IEC 60598, section 4
• Heat and fire resistance as of IEC 60695-2-1 (glow wire ) and –2 (needle flame)
• Protection against accidental contact with live parts as of IEC 60598, section 8, and IEC 60924, section 11
  

Electromagnetic compatibility (EMC) tests:

• Line-conducted interference emission shall be tested at least on the output (load) line in the radio-frequency range from 10 kHz to 30 MHz (acc. to EN 55015).
• Irradiated interference emission at a distance of 3 meters will be tested in accordance with EN 55015, limit values acc. to EN 55015.
• Resistance to interference from fast, low-energy pulses (pulse group) will be tested according to IEC 61000-4-4 (0.5 kV).
• Resistance to interference from single high-energy impulses like atmospheric discharges (lightning) according to IEC 61000-4-5 with 0.5 kV.
• Optional: Resistance to interference due to electromagnetic fields shall be tested in reference to IEC 61000-4-3 (required field strength 3 V/m), only if broadcasting transmitters or portable or non-portable transmitters are expected to influence the operation of the charge regulator.
• Optional: Resistance to interference from electrostatic discharge measurements are only required if touching the equipment by operators or other persons is expected to influence the operation of the charge regulator (IEC 61000-4-2, stringency: 8 kV air discharge).
  

All test results must be documented and summarised in a test report, which can be requested from the supplier or manufacturer by the tendering institution.

Comment: As the specifications described in the above proposal version of the standard are not yet final and binding for suppliers, the following specifications were selected from various other sources. Additionally or alternatively to the standard formulated above, the following specifications can be selected individually in consideration of the local requirements in a tender for SHS and RHS:

A minimum of ....(Fill in according to requirements; typically 3 - 4) pieces of 12 V_DC fluorescent tube or compact lamp light fixtures, each with its own electronic ballast shall be supplied.

Every fluorescent light must have a minimum light output of 200 lm (400, 600, 900 lm) when operated at an ambient temperature of 25° C.

The luminous efficiency of a new light, with any lenses, covers or grids in place, shall be greater than 35 lm/W (50 lm/W), inclusive of power requirements of the ballast when operated at an ambient temperature of 25° C and an input voltage of 12.5 V_DC.

Lights should be “daylight white” with a colour temperature >4000 K (“warm-tone” with a colour temperature of approx. 2700 K, similar to incandescent bulbs)

Expected lifetime of the tube in the light fixtures shall exceed 5,000 (8,000) operating hours. The lifetime test procedure should be in accordance with IEC 60081.

Expected lifetime of the electronic ballast should exceed 10,000 (15,000) operating hours.

Ballasts must ensure soft and regulated ignition and operation in the voltage range from -15% to +25% of the nominal voltage (10.3 V to 15 V for a 12 V battery).

The ambient temperature range for operation of the lamp and the ballast is ....°C to ....°C (normal: -10°C to +40°C, in tropical climates: +5°C to 50°C, in extremely hot desert climates (e.g. Tunisia): -10°C to 70°C).

The maximum relative humidity can be ... % (95% in tropical climates).

Ballasts must be protected against destruction when:

• the lamp is removed during operation or the ballast is operated without the lamp.
• the lamp does not ignite.
• the polarity of the supply voltage is reversed.
• the output terminals of the electronic ballast are short-circuited.

The minimum operating frequency should be 20 kHz.

The ballast must not produce any radio frequency interference. The wiring length from the ballast to the fluorescent lamp must be kept short to avoid radio interference.

Measures to preheat the electrodes are recommended. The filaments on the fluorescent tube shall not be heated during normal operation.

The minimum electrical efficiency of the ballast must be 70% in the entire range of operating voltage (-15% to +25% of the nominal voltage).

The waveform of the current through the fluorescent lamp must be symmetrical in time to within 10% (i.e., 60%/40% waveform maximum difference in symmetry) over the voltage range of 11 to 12.5 V at an ambient temperature of 25°C.

The maximum crest-factor (ratio of maximum peak to RMS voltage of the waveform applied to the fluorescent tube) should be less than 2 over the voltage range from 11 to 12.5 V at an ambient temperature of 25°C.

The light fixture should be covered by a diffuser or other enclosure (or can be open, i.e. the tube can be bare). If the tube is covered, the cover should be resistant to insect ingress. Lenses, covers, grids, etc. (if used) shall be easily removable without special tools and without the fixture being taken from its mounting by the user for bulb replacement or for cleaning. Reflectors are recommended to maximise lighting effectiveness.

A fuse or similar device should be used to prevent more than double the rated current from being drawn for longer than 100 seconds.

Each light shall be individually switched and the switch shall be rated for DC operation (and shall be of the toggle or rocker variety). The switch should be clearly marked with the international I/0 to indicate the position.

The light fixtures should be installed approximately 2.4 m (8 ft) above the floor, but not lower than 2.0 m (7 ft) and not higher than 2.8 m (9 ft).

Fixing material (screws and wall plugs) for ceiling or wall-mounting shall be included. The light fixture shall have a strain relief for the supply cable. If no strain relief is provided in the casing, an external strain relief must be delivered with the light fixture.

The input terminals must be able to accommodate a cross-section of 2.5 mm² of each conductor.

No part of the fixture should be flammable and any plastic parts should be of self extinguishing material.

Light fittings must be labelled with the manufacturer’s name, model number, rated operating voltage range, rated current and date of manufacture or batch number.

The warranty period is at least 1 year. Longer warranty periods granted by the manufacturer shall be passed on to the user.

Further Information

• Battery Charging Systems

References

This overview on standards for loads connected to solar home systems is an extract of the publication: Gtz quality standards for solar home systems and rural health power supply.pdf