IEC 61334
Encyclopedia
IEC 61334 is a standard for low-speed reliable power line communication
s by electricity meter
s, water meter
s and SCADA
.
It is also known as S-FSK, for "spread frequency shift keying" and was formerly known as IEC 1334 before IEC's most recent renumbering. It is actually a series of standards describing the researched physical environment of power lines, a well-adapted physical layer, a workable low-power media access layer, and a management interface. Related standards use the robust physical layer (e.g. IP
over S-FSK), but not the higher layers.
The physical layer synchronizes a small packet of tones to the zero-crossing of the power line's voltage. The tones are chosen by utilities, not specified in the standard. Tones are usually between 20KHz and 100 kHz, and should be separated by at least 10 kHz to prevent cross talk. One tone is chosen for mark (i.e. a binary
1), and the other for space (i.e. 0). The standard permits each zero-crossing to convey 1, 2, 4 or 8 bits, with decreased sensitivity to timing as the number of bits increases. In multiphase power lines, a separate signal might be sent on each phase to speed up the transmission.
The standard's low speed is caused by the limited number of bits per power line cycle. The high reliability comes from its reliable timing system (i.e. zero crossing), high signal to noise ratio (frequencies are chosen to avoid common power line noise), lack of intermodulation distortion, and adaptive signal detection.
The most significant bits are sent first, unlike a conventional serial port
. The data from zero crossings should be collected into 8-bit bytes. Each byte is collected into 42-byte packets. The first four bytes of each packet are a preamble to measure the channel's current condition. This is followed by 38 bytes of data, and 3 byte-times of silence.
The physical layer is adaptive. The silence and the preamble allow the receiver's signal processing to measure the channel's noise ratios. Depending on the signal to noise ratios, the bits can be recovered from the difference between the power of the mark and space tones, the power of the mark tones only, or the space tones only. The system should be able to adjust the receiving method on each 42-byte packet.
The bytes from the low-layer packets are reformed into bytes for the higher layers. The higher link-layer strongly resembles HDLC, except with a novel feature that allows selected stations to retransmit messages. The management interface layer provides remote control of a station's protocol layers, including diagnostics and configuration. For example, it lets a central controller read a unit's signal to noise ratios, and set the bit that enables a station to retransmit weak stations.
The protocol layers are designed to integrate with any application layer, but the presence of a management interface suggests a design targeted to DLMS/COSEM
, a widely-used EU standard for the application layer of meters and SCADA. DLMS/COSEM requires a management interface.
Power line communication
Power line communication or power line carrier , also known as power line digital subscriber line , mains communication, power line telecom , power line networking , or broadband over power lines are systems for carrying data on a conductor also used for electric power transmission.A wide range...
s by electricity meter
Electricity meter
An electricity meter or energy meter is a device that measures the amount of electric energy consumed by a residence, business, or an electrically powered device....
s, water meter
Water meter
A water meter is a device used to measure the volume of water usage. This article provides an overview of technical aspects of water meters. The worldwide prevalence of metering as well as its economic benefits and costs are covered in the separate article on water metering.In many developed...
s and SCADA
SCADA
SCADA generally refers to industrial control systems : computer systems that monitor and control industrial, infrastructure, or facility-based processes, as described below:...
.
It is also known as S-FSK, for "spread frequency shift keying" and was formerly known as IEC 1334 before IEC's most recent renumbering. It is actually a series of standards describing the researched physical environment of power lines, a well-adapted physical layer, a workable low-power media access layer, and a management interface. Related standards use the robust physical layer (e.g. IP
Internet Protocol
The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
over S-FSK), but not the higher layers.
The physical layer synchronizes a small packet of tones to the zero-crossing of the power line's voltage. The tones are chosen by utilities, not specified in the standard. Tones are usually between 20KHz and 100 kHz, and should be separated by at least 10 kHz to prevent cross talk. One tone is chosen for mark (i.e. a binary
Binary numeral system
The binary numeral system, or base-2 number system, represents numeric values using two symbols, 0 and 1. More specifically, the usual base-2 system is a positional notation with a radix of 2...
1), and the other for space (i.e. 0). The standard permits each zero-crossing to convey 1, 2, 4 or 8 bits, with decreased sensitivity to timing as the number of bits increases. In multiphase power lines, a separate signal might be sent on each phase to speed up the transmission.
The standard's low speed is caused by the limited number of bits per power line cycle. The high reliability comes from its reliable timing system (i.e. zero crossing), high signal to noise ratio (frequencies are chosen to avoid common power line noise), lack of intermodulation distortion, and adaptive signal detection.
The most significant bits are sent first, unlike a conventional serial port
RS-232
In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE and a DCE . It is commonly used in computer serial ports...
. The data from zero crossings should be collected into 8-bit bytes. Each byte is collected into 42-byte packets. The first four bytes of each packet are a preamble to measure the channel's current condition. This is followed by 38 bytes of data, and 3 byte-times of silence.
The physical layer is adaptive. The silence and the preamble allow the receiver's signal processing to measure the channel's noise ratios. Depending on the signal to noise ratios, the bits can be recovered from the difference between the power of the mark and space tones, the power of the mark tones only, or the space tones only. The system should be able to adjust the receiving method on each 42-byte packet.
The bytes from the low-layer packets are reformed into bytes for the higher layers. The higher link-layer strongly resembles HDLC, except with a novel feature that allows selected stations to retransmit messages. The management interface layer provides remote control of a station's protocol layers, including diagnostics and configuration. For example, it lets a central controller read a unit's signal to noise ratios, and set the bit that enables a station to retransmit weak stations.
The protocol layers are designed to integrate with any application layer, but the presence of a management interface suggests a design targeted to DLMS/COSEM
IEC 62056
DLMS or Device Language Message Specification , is the suite of standards developed and maintained by the DLMS User Association and has been co-opted by the IEC TC13 WG14 into the IEC 62056 series of standards.COSEM or Companion Specification for Energy Metering, includes a set of specifications...
, a widely-used EU standard for the application layer of meters and SCADA. DLMS/COSEM requires a management interface.
See also
- Power line communicationPower line communicationPower line communication or power line carrier , also known as power line digital subscriber line , mains communication, power line telecom , power line networking , or broadband over power lines are systems for carrying data on a conductor also used for electric power transmission.A wide range...
for a survey of the topic. - Universal powerline busUniversal powerline busUniversal powerline bus is a protocol for communication among devices used for home automation. It uses power line wiring for signaling and control....
is the more common shorter-ranged competitor.