Photo Electric Cell Unit Arrays

Design

A photo-electric cell unit (PECU) Array is a box about 1 x 0.6 x 0.3m fitted with 30 photocell NEMA sockets, within the box are terminal blocks, a data logger and a cellular modem. Options include a fixed line modem, a light meter and blanking plates to install non-NEMA cells.

Location

The following should be considered in determining the location of the PECU Array:

  • Typical location is the flat roof of a local authority building within the lighting authority area, near the centre of the street light load
  • Location should be accessible for safe / easy replacement of photocells
  • Location should not be subject to excessive shadows from trees, buildings, lift shafts, air conditioning units, etc
  • Artificial lighting (e.g. floodlights) should not interfere with the Array
  • The location on the roof should be sufficiently elevated to ensure that Array is not flooded if the roof ‘puddles’ due to blocked gutters, drainage, etc
  • Elevation should be consistent with normal photocell locations - the top of a two storey office building is ideal, a 20 storey tower block is not appropriate!
  • Array requires a small electricity supply (13amp socket)
  • Communication is normlly provided using a cellular modem, but where communications is via a fixed phone line, then a ‘direct dial in’ phone number and analogue line (like a fax machine) is required
  • If communications are via a cellular modem then a good signal strength is required for the chosen service provider
  • The Meter Administrator will need to formally agree the chosen location with the local distribution company (UMSO).

Operation

  • The Array is populated with 30 photocells which represent the whole lighting inventory
  • If more than one type of photocell is in use, then the Array is populated with a representative proportion of each
  • This proportion is reviewed at least annually to reflect changes to your inventory
  • The photocells should be representative of the physical construction: NEMA, one-part miniature and two-part miniature, etc
  • The photocells should be representative of the age of the photocell population, a brand new Array should be populated with photocells recovered from a representative sample of lighting columns
  • Power Data Associates interrogate each PECU Array and download the events recorded by the data logger each night
  • Power Data Associates then validate and check the event data for each array to check for faulty photocells and other anomalies

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