RF METERS DEPLOYMENT IN INDIA

A GUIDE LINE REPORT Rev 2.1, Date 15 July 2012

BY

NARENDER RAO SAINENI, M.Tech(IIT)

VIJETHA TECHNOLOGIES PVT LTD.

CONSULTANTS AND DESIGN HOUSE

FOR ELECTRIC METERS AND OTHER EMBEDDED SYSTEMS

HYDERABAD,

INDIA-500062

narender@vijethatechnologies.com

Date: 17 Nov 2011

Please send your feedback to the given mail-id

Or discuss on the google site https://sites.google.com/site/energymetersindia/home

INTRODUCTION In India there are several states/provinces, each state has its own electric utility company (mostly

govt owned) and some states have more region wise. India has electric meter specification from two

standardisation bodies BIS and CPRI. Both these are national level bodies; duplication of standards

for the same product from two different bodies is creating some confusion to the utility companies

and suppliers. Regarding communication port and protocol there is no national standard so far,

every company is following its own protocol, so on the whole there are several hundreds of

variants of these meters.

Now India has started implementing the LPRF/ZIGBEE based electricity energy meters on trial basis.

Some states are going in a big way even without proper field trial.

This new technology allows the utility companies to read the meters staying outside the customer

premises, and going forward they can get the readings directly to their server on the internet.

Considering these advantages this technology is being adopted now. However compared to the

earlier method of manual reading /auto reading through optical port, zigbee is more complex.

To help the utility companies in preparing the specification of LPRF meters communication aspects,

this document is prepared.

In this document my effort is to clearly show a road map of implementation to the utility companies.

As we are not into manufacturing, we are not biased towards one or the other spec, our interest is

to create good standards for every body’s sake.

PROTECTING THE INVESTMENT AND CHOOSING THE ROAD

MAP:

It is possible to evolve the implementation in stages, protecting the investment of the utility

companies and insuring against costly mistakes of wrong decisions.

To evolve without loss to anyone, the required features in the system should be like these.

Meter should have the provision for doing the FOTA (FIRMWARE UPDATE OVER THE AIR).

Once the meter has this facility its firmware can be upgraded to enhance the features to meet the

evolving standards and requirements of the end customer. However the metrology engine should

run on a dedicated processor without FOTA facility, only the LPRF communication unit should have

its dedicated processor with FOTA facility, this way we will have both the flexibility and security of

the basic metering functionality against tampers.

FOTA is now part of the zigbee standard.

When the meter is specified and designed as per the above architecture , the meter can not be

tampered in the field, however utility company investment is protected allowing the evolvement of

future communication needs by upgrading the firmware of the communication module over the air

without opening the cover.

Meter module though having its own firmware and non volatile memory, nothing should be

writable in it so that the metrology engine , the cumKWH reading on the display will be as reliable as

the present meters.

The communication module should have the full flexibility to evolve as per the new evolving

standards by having upgradability of its firmware over the air i.e qualified FOTA facility

as per zibgee standard .

The communication module reads some registers from the meter module and sends them to the

outside world i.e meter reader or another network node. Today the utility company may need to

read only 2 or 3 parameters like cuKWH , MD, Tampers. Tomorrow they may need to implement

different tariff rates in different time slots and inform the dynamic tariff rate to the customer

premises display. So by having firmware upgradability of the communication module they can

easily evolve towards the same without changing anything in the meter module.

The meter module allows the reading of certain registers ( like in modbus registers) , the

communication module may read those registers at any frequency as per its needs.

Important Note

The communication module should have over the air firmware

upgrade facility as per Zigbee cluster. This has to be tested to

qualify the vendor technically. Again this is a must whether you use

Zigbee standard or some other LPRF standard.

If you are starting with Zigbee then you need to allocate 64 bit

extended PAN Ids area wise. First obtain the most significant 24 bit

organizational part of the extended PAN ID from IEEE. Allocating

the least significant bits are in your control. Divide the available

addresses into geographical circles take the help of google maps.

The possible scenarios the utility companies are considering now, are shown as phases of evolution

below.

But my personal preference is to go for the phase-4 directly which is possible with the available

technology today and your investment will be fully protected.

Today in India there is major confusion to choose the right frequency band apart from technologies

to be used. Whatever the frequency band is chosen it is important to remember that , the module

should accept the over the air firmware update to implement newer technology software in the

same module. For example today the RF module may only support a star topology or point to point

connection , but in future it should take new software to implement proven mesh algorithm. or

today security may not be strong , nut tomorrow as security requirements grow the same module

should accept new firmware over the air to implement stronger technology.

PHASE-1: ( READING METERS FROM THE GATE)

LPRF (ZIGBEE MESH) BASED ELECTRICITY METER NETWORK

REPEATER

HOME-MTR

APARTMENT-COMPLEX

FLATMTR

FLATMTR

FLATMTR

HOME-MTRREADER

Install the LPRF meters without dedicated head end/concentrator node.

Take a reader as is being done now, but now take a notebook/laptop/tablet-pc based CMRI/reader

to the site (in place of a proprietary hardware) to take the readings. On manual invocation the

reader becomes the co-ordinator node and forms the network and reads all the meters which are in

its radio range(limit to 2/3 hops), to get the meters out of range move the reader towards them , so

that until all meters are read.

The reader having big LCD display shows which are read and which are not read from the existing list

in easily understandable format (may be with a different colour).

Some utility companies can consider having the LPRF communication module as an upgradable unit

without affecting the basic metrology functionality (this will allow upgrade of hardware too)

PHASE-2: ( READING METERS FROM TRANSFORMER)

LPRF (ZIGBEE MESH) BASED ELECTRICITY METER NETWORKGPRS

Head End/ESP/NET-COORDINATOR

ZIGBEE

REPEATER

HOME-MTR DISPLAYINHOUSE

APARTMENT-COMPLEX

FLATMTR

FLATMTR

FLATMTR

HOME-MTR DISPLAYINHOUSE

HOME-MTRREADER TABLET PC

Install a dedicated head end/concentrator node. And take the readings of all the meters in the

region from this node only, even during power failure.

To go from PHASE-1 to PHASE-2 , only the dedicated node with enough memory is to be added

which can collect and store data from all meters.

PHASE-3:( AUTOMATIC READINGS TO CENTRAL SERVER)

Upgrade the concentrator node such that it has uplink to the server on the internet through GPRS or

any other available back haul network. The concentrator reads the meters and send the data

collected to a central server database. The GPRS application protocol in concentrator should reside

in GPRS-FOTA capable block. The meter FOTA should be possible from the central server.

Implement one gateway/concentrator per transformer and all the meters under this transformer

under the corresponding concentrator, this helps in easy audit of the power which is becoming

more and more scarce.

PHASE-4 ( FULL AUTOMATION INCLUDING CONTROL)

Implement the protocol in the meters and concentrator node such that any end device will be visible

to the utility company/consumer to take reading or even control like disconnect/reconnect of

prepaid meters. And the visibility and control is through a web server.

Some important specifications to ensure quality and avoid

confusion:

Frequency band

The frequency band to be considered to begin with, is 2.4 GHZ, which is as per the zigbee PRO

standard without any deviation. If this frequency is has any problem in PHASE-1, they can try sub

GHZ band( india has 865-867 MHZ free , earlier reserved for RFID purpose).

Application profile: The meters should implement smart energy 1.1 profiles upgradable to smart energy 2.0 soon. All the

parameters already defined in the smart energy profile should be available in the standard fashion,

in addition if the utility company wants more parameters which are not defined in the smart energy

profile, they can be provided from another end point with utility company specific profile.

Range of RF communication This should be specified in terms of allowed power output, and the antenna direction/gain.

Once these are fixed, it will have the range as specified in the standard in free air line of sight

conditions. But since zigbee gives us more range with mesh network, there is no point in

unnecessary pumping out more power from each and every node.

Range extenders These have to be procured in some numbers ( may be one in 20 ). They are power operated totally

enclosed units to improve the reach ability of the meters.

Enclosure: Enclosure size and plastic weight should be mentioned in the tender to be more than a certain

minimum limit to ensure quality. And less than a certain maximum size to ensure easy installation.

TERMINALS: The terminals for power wiring should be big ( at least 6 mm hole dia), standard across all suppliers

to improve reliability of the joints.

Display CBIP has to specify the size & segments of LCD to be uniform all across. The parameter list and

display sequence too. The no of LEDS and their purpose.

Super Cap/StdBy battery: They are better avoided, to lower the meter cost and increase the reliability.

RTC: RTC may be retained in the metrology block in PHASE-1, after successful PHASE-4, the RTC per

meter will not be required.

The Surge Voltage Limit:

The surge voltage limit should be limited to 4KV as per 61000-4-5.

Magnetic tamper limits:

If either the ac/dc magnetic field is less than 10mTesla the meter should be immune.

Beyond 10milliTesla until it records the tamper it should be accurate to within 4% ( for 1 % meter).

While it records the tamper it should run at ( Imax*240V +/- 10%) . This will meet the field

requirement and ensure easy testing.

Power consumption The single phase meter with LPRF communication port , consumption during idle time (Tx off, Rx ON,

router mode) should be less than 2.5 Watts. VA rating less than 10VA.

Tamper records: Record of latest 6 tampers with time stamp are enough, there is no need to ask for big no of

tampers, the six are sufficient to analyse/penalise the customer as needed.

The storage location of the parameters:

The basic single record of cukwh, tamper, MD should be stored in the metrology block ( in which fota

will not be present).

The communication module should read from the metrology block and store records in its own

memory so that in future its firmware can be updated and more versatile form of data may be

collected and used.

Note: The other specifications may be followed now as per CBIP-304.

Introduction to ZIGBEE technology

Glossary LPRF – Low Power Radio Frequency

ZigBee – the name of the wireless communication standard , which is based on zigzag dance of bees

to communicate among themselves.

Version History

ZigBee 2004, Original ZigBee version.

ZigBee 2006, Backward compatibility with ZigBee 2004 not required.

ZigBee 2007/PRO, Backward compatibility with ZigBee 2006 required.

Zigbee certified product

Frequency Bands and Channels

Frequency Bands available in India

Frequency Band: 865-867 MHz

Low power RFID equipments or any other low power wireless devices or equipments

Power: Maximum transmitter output power of 1 Watt ( 4 Watts Effective Radiated Power)Carrier

Bandwidth: 200 KHz

Reference: GSR 564 ( E) dated 30 July 2008

Frequency Band: 2.4-2.4835 GHz

Use : Low power equipments

Power: Maximum transmitter output power of 1 Watt ( 4 Watts Effective Radiated Power)

Carrier Bandwidth: spectrum spread of 10 MHz or higher

Reference: GSR 45E dated 28.1.2005

The ZigBee Network Description

Device Types ZigBee networks include the following device types:

• Coordinators

• Routers

• End devices

Coordinator This device starts and controls the network. The coordinator stores information about the network,

which includes acting as the Trust Center and being the repository for security keys.

Router These devices extend network area coverage, dynamically route around obstacles, and provide

backup routes in case of network congestion or device failure. They can connect to the coordinator

and other routers, and also support child devices.

End Devices These devices can transmit or receive a message, but cannot perform any routing operations. They

must be connected to either the coordinator or a router, and do not support child devices.

Mesh Network Topology Mesh topology, also called peer-to-peer, consists of a mesh of interconnected routers and end

devices. Each router is typically connected through at least two pathways, and can relay messages

for its neighbors.

As shown in the image above, a mesh network contains a single coordinator, and multiple routers

and end devices.

Mesh topology supports “multi-hop” communications, through which data is passed by hopping

from device to device using the most reliable communication links and most cost-effective path until

its destination is reached.

The multi-hop ability also helps to provide fault tolerance, in that if one device fails or experiences

interference, the network can reroute itself using the remaining devices.

Benefits

• This topology is highly reliable and robust. Should any individual router become inaccessible,

alternative routes can be discovered and used.

• The use of intermediary devices in relaying data means that the range of the network can be

significantly increased, making mesh networks highly scalable.

• Weak signals and dead zones can be eliminated by simply adding more routers to the network.

Addresses

Addressing within ZigBee includes all the following components

PAN ID ( MAC)

NwkAdr(NWK)

Endpoint(APS)

Profile ID(APS)

Cluster(APS)

Command and/or attribute(ZCL)

The application can configure and access the parameters of the network layer through the ZDO.

PAN ID ( Personal Area Network ID):

ZigBee Personnel Area Network identifiers (or PAN IDs) are used to logically separate a collection of ZigBee nodes from other ZigBee nodes in the same vicinity or on the same physical channel. This allows nework A and network B to exist in close proximity without interfering with each other, other than consuming over the air bandwidth that they both share. ZigBee PAN IDs are 16-bit numbers that range from 0x0000 to 0x3fff.

PanID - the same for all devices in a network, assigned by the network coordinator

This is the network ID ( 16 bit 0x0000 – 0x3fff) which uniquely identifies a set of nodes forming the

network. There can be multiple networks operating on the same channel. But there is should be

only one PAN ID across all the zigbee channels ( as per 2007 spec to ensure frequency agility of the

network). This ID is randomly chosen by the coordinator ensuring that this ID is not being already

used. Some times this 16 bit alone is not sufficient to ensure conflict or fast selection of the suitable

network running required application. Hence 64 bit extended PAN ID is used, this is used during

initial joining, but once the network is formed the selected 16 bit PAN ID is used. The 64 bit PAN ID

will have organisational part in it.

Extended PAN IDs Extended PAN IDs are 64-bit numbers that uniquely identify a PAN. ZigBee communicates using the shorter 16-bit PAN ID for all communication except one. The beacon response issued as the result of a beacon request contains an Extended PAN ID to allow a node that wishes to join a network to pick exactly the right one. Every time a ZigBee node wishes to join a network, it sends out a beacon request. It then pays attention to all of the beacon responses, and picks the “best” network out of these responses.

Sometimes a PAN ID is just not enough. A particular application may want to only join a network that has a particular (probably private profile) application on it. One way is to use a special PAN ID and hope, but that's not a very sure way to join the right network. Another way is to join the network and see if the application is on it, but this takes time to join the other network, and may require special code to be implemented. ZigBee thought of this and provided a mechanism to join only those PANs which are released by your corporation, which leads us to extended PAN IDs.

Network Address ( Short Address) Short Address (NWK) - unique for each device in a network, assigned when it joins the network

The network address, also called NwkAddr, short address, or node address, is

a 16-bit number used to uniquely identify a particular node on a ZigBee

network. The ZigBee Coordinator is always NwkAddr 0x0000.

Two ZigBee coordinators can exist on the same channel with NwkAddr 0x0000,

because they are on different PAN IDs. The 16 bit Network address uniquely

identifies a node in the network.

The network address to a joining node is assigned based on distributed assignment strategy. The

coordinator gives a block of addresses to a joining router, the router in turn assigns one from its pool

to a joining end device.

MAC Address ( Long Address ) Long Address (IEEE) - unique for each device, usually assigned by a manufacturer at the factory,

never changes

The MAC address, also called IEEE address, long address, or extended address, is a

64 bit number that uniquely identifies ZigBee device from all other ZigBee devices in

the world. The top 24 bits of this address consist of the Organizational Unique

Identifier (OUI). The lower 40 bits are managed by the OEM producing the boards.

The 64-bit MAC address has no direct relationship to the 16-bit Network address. If a

node leaves one ZigBee network and joins another, its MAC address will remain the

same, but Network address will likely change.

Forming a new Network

The Co-ordinator is responsible for starting a ZigBee network. Network initialisation involves the following steps:

1. Search for a Radio Channel

The Co-ordinator first searches for a suitable radio channel (usually the one which has least activity). This search can be limited to those channels that are known to be usable - for example, by avoiding frequencies in which it is known that a wireless LAN is operating.

2. Assign PAN ID

The Co-ordinator starts the network, assigning a PAN ID (Personal Area Network identifier) to the network. The PAN ID can be pre-determined, or can be obtained dynamically by detecting other networks operating in the same frequency channel and choosing a PAN ID that does not conflict with theirs.

At this stage, the Co-ordinator also assigns a network (short) address to itself. Usually, this is the address 0x0000.

3. Start the Network

The Co-ordinator then finishes configuring itself and starts itself in Co-ordinator mode. It is then ready to respond to queries from other devices that wish to join the network.

Joining a ZigBee Network

Once the network has been created by the Co-ordinator, other devices (Routers and End Devices) can join the network. Both Routers and the Co-ordinator have the capability to allow other nodes to join the network. The join process is as follows:

1. Search for Network

The new node first scans the available channels to find operating networks and identifies which one it should join. Multiple networks may operate in the same channel and are differentiated by their PAN IDs.

2. Select Parent

The node may be able to ‘see’ multiple Routers and a Co-ordinator from the same network, in which case it selects which one it should connect to. Usually, this is the one with the best signal.

3. Send Join Request

The node then sends a message to the relevant Router or Co-ordinator asking to join the network.

4. Accept of Reject Join Request

The Router or Co-ordinator decides whether the node is a permitted device, whether the Router/Co-ordinator is currently allowing devices to join and whether it has address space available. If all these criteria are satisfied, the Router/Co-ordinator will then allow the device to join and allocate it an address.

Typically, a Router or Co-ordinator can be configured to have a time-period during which joins are allowed. The join period may be initiated by a user action, such as pressing a button. An infinite join period can be set, so that child nodes can join the parent node at any time.

Device Discovery Device discovery is the process whereby a ZigBee device can discover other ZigBee devices. There are two forms of device discovery requests: IEEE address requests and NWK address requests. The IEEE address request is unicast to a particular device and assumes the NWK address is known. The NWK address

request is broadcast and carries the known IEEE address as data payload.

Service Discovery Service discovery is the process whereby the capabilities of a given device are discovered by other devices. Service discovery can be accomplished by issuing a query for each endpoint on a given device or by using a match service feature (either broadcast or unicast). The service discovery facility defines and utilizes various descriptors to outline the capabilities of a device. Service discovery information may also be cached in the network in the case where the device proffering a particular service may be inaccessible at the time

the discovery operation takes place.

Endpoints and clusters

Devices are defined by profiles and implemented as application objects. Each application

object is connected to the rest of the ZigBee stack by an endpoint, which is an addressable

component within a device.

For example, a remote control might allocate endpoint 6 for the control of lights in the master

bedroom, endpoint 8 to manage the heating and air-conditioning system, and endpoint 12 for

controlling the security system. This allows the remote control to independently communicate

with these devices and identify which packets are intended for each application and device.

Communication is made from endpoint to endpoint through data structures called clusters.

Clusters contain a set of attributes that represent device state together with commands that

enable communication between application objects. Each cluster is identified with a unique

ID.

Clusters used in a specific application are defined within its profile. For example, the Home

Automation profile contains a cluster dedicated to the control of lighting subsystems.

Each cluster has two ends:

The client/output requests and manipulates the data.

The server/input has the source data.

The ZigBee Cluster Library (ZCL)

All ZigBee application profiles are defined using clusters from the ZigBee Cluster Library.

This library allows common clusters to be reused across a number of different functional

domains, for example, the same lighting clusters can be used for any application that requires

lighting control, such as home automation and commercial building automation.

Clusters within the ZCL are organized into a number of different functional domains,

including Lighting, HVAC (Heating, Ventilation, Air Conditioning), Measurement and

Sensing, Security and Safety, and General.

Each cluster specification within the ZigBee Cluster Library defines

mandatory and optional attributes

cluster-specific commands

functional description

Each device specification within an application profile defines

mandatory and optional cluster usage

values of free parameters in the ZCL

any additional functional description

Bindings

At a high level, binding is the process of establishing a relationship between two devices that

can communicate in a meaningful way, for example, which switch controls which lights.

Each binding supports a specific application profile, and each message type is represented by

a cluster within that profile.

Bindings can be created between either individual or groups of endpoints, such as lights and

switches, that have matching input and output clusters (with the same cluster ID). ZigBee

devices can have up to 240 endpoints, so each physical device can support multiple bindings.

Conclusion

By providing the ZigBee Cluster Library and application profiles, the ZigBee Alliance has

already done a lot of the hard work for you.

If you need your device to perform a specific function or behave a specific way, there is no

need to create things from scratch. You can simply implement the ZigBee cluster that already

exists for that purpose.

Adherence to the application profiles and the ZCL also helps to achieve ZigBee certification

to ensure interoperability with other ZigBee devices.

- Node A and B are given unique addresses when they join a Zigbee network

- Switch 1 and 2 would have unique endpoint numbers - Lamps 1, 2, 3 and 4 would have unique endpoint numbers

as well - Setup allows Switch 1 to uniquely address and control

Lamps 1, 2 and 3 using clusterIds

Hope this helps the stake holders in india implementing this technology in the smart grid

infrastructure.