Buying and installing a smart meter
I'd like to install a smart meter so I can collect whole-house readings of real and reactive power and voltage once every five seconds for my PhD work on disaggregation. For several months I've been prodding my utility company to replace my "spinning-disk" meter with a smart meter but this isn't going to happen any time soon, even if I offer to pay for the hardware and installation. The existing spinning-disk meter is owned by the utility company so I can't touch it. So my plan is to hire an electrician to install a smart meter downstream of my spinning-disk meter. This blog post is just my notes about smart meters (which to buy? how to communicate with it? etc.)
Smart meter shops
- Universal Meter Services (only sells the ISKRA ME372 as of Nov 2012)
Open Energy Monitor
Energy Meter (extended range plus communications board)
- Not sure if I need the "extended range" model or not for 230V single phase? Most likely I just need the basic model.
- Update interval???
- 1,2 or 3 CTs (which open to allow easy installation)
- +-1% accuracy from 2% to 100% of CT rating (on a 100A CT this means accuracy drops off below 500W!)
- Comms board provides RS485 modbus RTU
- Meter is in the CT
- Enhanced model gives real, reactive and apparent and voltage
- +-1% from 10-100% of CT rating (not great for my application).
- Accuracy? "1% of reading. Additional error of 0.05 of full scale for meter input current below 100mA". CTs deliver 0-5Amps. Lowest CT is 40A. 0.1/5 = 2% (same as Energy Meter). 2% of 40A = 0.8A. 0.8A*230V = 184W.
- "Entry range power meter"
- updates readings once per second
- active power (class 1 accuracy), reactive power (class 2 accuracy), voltage, current, frequency, power factor
ION6200 with EP#2
- Measures current using a CT clamp
- 4-quadrant metering, class 0.5 accuracy (IEC, ANSI) 0.5%
- Voltage, current, power, frequency, power factor, demand, energy
- RS-485 communications port Modbus RTU slave
- 64 samples per cycle (3.2kHz sample rate at 50Hz mains)
- The ION6200 EP#2 "M6200 A0 A 0 B 0 A0 A 0 R" costs £327.14
For details of PowerLogic, contact:
- Peter Meredith 01249 456 020. email@example.com
- CT clamps (I think I need the 40A clamp for cables routed through the clamp, cat number 16500). These clamps do not appear to open so will need cables to be disconnected to be re-routed through the clamp.
Nipun Batra uses a Schneider Electric EM6400 (with RS485) with a 60:5 turn ratio class 5 CT with accuracy 0.1%.
EM21-72D DIN Rail or Panel Mount Electricity meter
- CT-connected and has a pulse output and RS485 Modbus communications.
- A full set of instrumentation values (Voltage, Current etc.) is available on the multi-line LCD display. Class 1 accuracy.
- £102 inc VAT
Single-phase direct-connect smart meters
- IrDA (this blog describes reading the IrDA from an A100C to get real power, apparently once a second).
- Dr (Prof?) Gregory has used a laptop's IrDA adapter to talk to a A100C and he describes some of the packet structure. No mention of reactive power.
- The A102C gives gives kwh and kvarh measurements. I need the "Import kWh and kvarh, one rate" version with IrDA. Register 2 = Total kWh. Register 3 = Total kvarh (ADD kvarh Q1 lagging/inductive reactive import). "Most reactive loads are inductive, so at most sites the PF is lagging"
- The A103C gives voltage and current (as well as kvarh?) but isn't readily available in the UK
- Low cost and relatively compact
- A100C Operating and Maintenance Instructions
- Purchase from Energy ICT on 01920 871094
- could get 2: one for aggregate, one for lighting circuit (but buy just one to start with to make sure it works as I want)
- Current favourite
- Optional RS485
- Measuring instantaneous values
- active, reactive and apparent
- emailed Elster on 5/12/12 for more details
- emailed Tony Townley (UK sales for Elster UK) on 3/1/2013
- emailed JWInstruments and smartprocess.co.uk to ask if they can get hold of an A220.
- Specifically mentions WAN (wide area network) and HAN (home area network) in the specs
- optical bidirectional IEC 62056-21 comms port. "The modular and optical port can be used to read data from any meter connected to the HAN... HAN interface will be available to match market requirements... M-Bus allows any remote meter to be read directly by the Utility or to be viewed on the Home Display."
- "If you do want a live stream there is something called a live link that will show readings every few seconds for as long as the optical (62056-21) port is open"
- CURRENT FAVOURITE (as of9th Jan 2013)
- PC software is available.
- kWh import/export, kvarh and kVA
- serial comms option "Communications are provided via the optical port and are supported by data stream mode, allowing fast reading of meter data. The A1140 permits up to 90 days of load profile data to be collected in less than 30 seconds. The RJ11 socket provides optional serial communications allowing remote access to the same data as the optical port."
- buy Iskra ME372
- OFGEM approved
- Need to specify options:
- RS485 instead of GSM/GPRS. Protocol: IEC 62056-46 (DLMS) on a GSM modem and optionally on RS485
- Reactive energy measurement (as well as active)
- RTC sync by comm
- instantaneous readings for active power, reactive power and voltage are not available over the RS-485 interface (deal breaker for me)
- Accuracy class: 1 or 2 (active energy), 2 or 3 (reactive energy)
- I emailed Iskraemeco on 16/11/12 to ask for more details; they replied on 20/11/12 and I have updated the above to reflect the new info.
- Pre-payment meter
- No RS-485. Just optical serial.
- Not clear if it can measure reactive power, or how frequently it measures.
It looks like the only meters Landi+Gyr sell in the UK are prepayment meters.
- Measures active, reactive, volts, current, power
- No mention of ANY comms other than GSM.
Hardware used by Kolter and Johnson's REDD system
Enmetric PowerPort and Wireless Bridge for plug-level data
- Bridge talks to up to 50 PowerPorts and connects to Ethernet port
- 802.15.4 wireless comms
- 1Hz sample rate
Powerhouse Dynamics eMonitor for circuit-level monitoring
- About USD 500 - 1000 depending on spec
- up to 24 CTs
- 1 sample every 3 seconds over API
Two 200A TED CTs and Pico TA041 'scope probe to measure voltage (100:1 step down), connected to a National Instruments NI-9239 ADC (24-bit 15kHz)
Hardware used by Kim et al 2011
- Zigbee wireless sensor network using Digi kit.
- Power data collected every 3 seconds.
Other plug-level metering solutions
- Plugwise Pro 50. 50 IAMs for £2055 (£41 per IAM.) ZigBee. Each IAM is called a "Circle"
Getting data from the meter
Most meters appear to support MODBUS over RS-485. My plan would be to install the meter in the fuse box and run an RS-485 cable to the cupboard under the stairs, where a laptop would log data from the smart meter and from my individual appliance monitors.
- Only specified the electrical characteristics, not the protocol.
- RS-485 to USB converters cost about £35
- From Nipun: "Beyond 10 metres, RS485 communication requires very expensive cabling... For cabling, if length is less than 10m, you can use metal shielded cable having 2 wires and plastic encapsulation. For more length, you need to put double shielded cable (which is much more costlier)"
- Serial comms protocol.
- Open and royalty-free.
- Several different versions (RTU, ASCII, Modbus over TCP/IP etc)
- minimalmodbus Python library. Recommended by Nipun Batra.
- libmodbus, written in C. Currently maintained. Can send/receive data using serial port or Ethernet. Official Ubuntu package (available for 12.04 Precise, 12.10 Quantal and 13.04 Raring).