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What do Wattwatchers devices measure and report?

by Darius Salgo
posted on Sunday, May 6th, 2018

All Wattwatchers devices supply energy data in two forms:

  • ‘Short energy’ or ‘SE’: This is ‘PUSHED’ frequently by the device. SE does not have guaranteed delivery. It is used for control and observation, and also to inform hosting servers that the device is online.
  • ‘Long energy’ or ‘LE’: This is logged every 5 minutes and “PULLED” by hosting servers. Hosting servers are responsible for reading logged data, usually asking for it soon after the end of each 5-minute period.

Traditional meter data transport has a lot of gaps, mostly due to the prevailing ‘PUSH’ model where systems cannot ask for missing data. This has resulted in a mass of regulatory intervention that specifies different types of missing data and how each case should be handled. This in turn spawns systems and companies that implement these rules, at very substantial cost.

The advantages of frequently streaming data are many. During installation, the data provides an immediate sanity check, and immediately reflects any installation corrections that are required. Gaps in the data flow provide diagnostic data on the connecting networks. Systems can always interrogate meters if data is missing.

The PULL model has consequences for system design. Systems can keep data in memory and checkpoint infrequently because the data is effectively cached in the meters themselves.

The 3G products send UDP packets over the network, and are secured by the the mobile network. This level of security can be enhanced as required. Each device has a private key that is generated and captured at manufacture time that can be used for encryption. OTA firmware updates use TCP.

The WiFi product uses http(s) for all data transfers.

LoRaWAN products are secured by an Application Key, Application Session Key, and Network Session Key. See  https://labs.mwrinfosecurity.com/assets/BlogFiles/mwri-LoRa-security-guide-1.2-2016-03-22.pdf for more information.

 

As outlined above, Wattwatchers devices support two data protocols, with both active all the time.

All data is time stamped at the meter.

  • SE (short energy) packets, with 5 to 30 seconds interval data, sent at 5-30 second intervals (configurable), not logged in the meter
  • LE (long energy) packets, with 5 minute interval data (not configurable), logged in the meter

 

The SE packets include:

  • Real and reactive energy in the interval (resolution 1J)
  • Vrms (0.1V)
  • Irms (1mA)
  • Frequency (0.01Hz)

 

The LE packets include:

  • Imported real and reactive energy in the 5 minute interval
  • Exported real and reactive energy
  • Net real and reactive energy
  • Vrms (min), Vrms (max)
  • Irms (min), Irms (max)
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