Residential Smart Gas Meters

Laurentiu Gavra SC AEM SA, RESEARCH DEPARTMENT

TIMIŞOARA, ROMANIA sales@aem.ro

Monica Sabina Crainic SC AEM SA, RESEARCH DEPARTMENT

TIMIŞOARA, ROMANIA sales@aem.ro or monicacrainic@yahoo.com

Petru Pupsa SC AEM SA, RESEARCH DEPARTMENT

TIMISOARA, ROMANIA sales@aem.ro

Gheorghe Popa SC AEM SA, RESEARCH DEPARTMENT

TIMISOARA, ROMANIA sales@aem.ro

Abstract—Natural gas is a non-regenerable energy source. For this motive she must be managed properly to protect it for future generation. Proper management of natural gas reserves requires submetering. Submetering of natural gas consumption and revenue collection is traditionally accomplished using residential gas meter. To resolve some problem of revenue collection residential smart gas meters is implemented. In this context we at SC AEM SA from Timisoara, Romania produce smart gas meters such as diaphragm gas meters with an electronic index and ultrasonic gas meters.

Keywords - diafragm gas meters, ultrasonic gas meters, smart gas meters,

I. INTRODUCTION

Revenue collection is one of the core activities of any utility inclusive natural gas distribution company. This has traditionally been accomplished using conventional credit meters like diaphragm gas meter, with regular meter reading, extension of credit to customers and normal credit collection mechanisms.

This process is costly, with numerous inherent problems for both utility and customers. To solve some of these problems new residential smart 1 gas meters are implemented which offer benefits to both parties.

Available technology for smart gas meters deployment are [1]: 1) Conventional Meter + retrofit kit: provides the Remote index reading functionality with possible bidirectional communication [2]. 2) New Smart Meter: requires the additional costs associated with new equipment, new installation and additional operations to be carried out after the meter replacement. These are the following technical alternatives for installing a new smart meter: 2.1. New meter fitted with integrated communication module; 2.2. New meter fitted with communication module + valve (both integrated);

1 A smart meter, according to regulatory authorities , is an advanced meter that records consumption in intervals of an hour or less and communicates that information at least daily via some communications network back to the utility for monitoring and billing.

2.3. New meter fitted with communication module + temperature conversion + valve (integrated). 2.4. New meter fitted with communication module + temperature conversion (integrated)

In this situation we presented in this paper the smart gas meters manufactured in Romania by SC AEM SA from TIMISOARA.

II. MECHANICAL GAS METERS WITH AN ELECTRONIC INDEX

These are volumetric dry, diaphragms gas meters type

G1.6; G2.5; G4; G6 [3-4] (with measuring chambers with deformable walls) meant for measuring domestic natural gases consumption. Mechanical movement is transmitted through a coupling (magnetic or mechanical) the housing to drive the decoder. Instantaneous flow rate is typically not measured. The meters are in accordance to EN 1359 and The Directive 2004/22/EC for measuring instruments (MID).

A. Construction of Gas Meters

The meters are built in boxes made of moulded steel sheet which give them strength, external protection, resistance to external or internal corrosion and resistance to high temperatures. The transmission of the movement from inside the box to the outside can be magnetic or mechanical

The electronic index that is a part of the gas meters is powered by a battery. The box of the electronic index has two compartments. In the upper compartment there is the metrological module. This compartment allows the metrological sealing.

The lower compartment contains the battery and the M-bus communication interface. This compartment can be sealed.

B. Main Features of the Electronic Index

The volume can be displayed with 3 or 4 decimal digits expressed in m3. Furthermore, the consumption values can be displayed by pushing the button, as follows: • daily consumptions of the last 24 hours,

978-1-4673-1176-2/12/$31.00 ©2012 IEEE

• monthly consumptions of the last 7x24 hours, • annual consumptions of the last 30x24 hours.

Some other technical characteristics of the electronic index are presented in Table 1

Table 1 Some technical characteristics of an electronic index for mechanical gas meters [5]

Display LCD with nine digits Power lithium battery Communication interfaces

M-bus through wires or radio Optical port.

Degree of protection IP54 Storage temperature - 25…+60 °C

The display of the historical data is signaled by the movement of a marker next to the markings on the scale label, i.e. 1T for 24 hours, 7T for 7x24 hours or 30T for 30x24 hours. Each sum is displayed for approximately 5 seconds. After 15 seconds it goes back to displaying the volume.

Through configuration/programming other dimensions can also be displayed by the LCD, as follows: the measured gas volume, the measured temperature, the cyclic volume of the gas meter, the instantaneous flow, corresponding to the measured gas volume, the time, the date, the display test, the events/errors.

The electronic index is equipped with a non-volatile memory. This memory archives: autosaves of the daily meter value of the last 120 days, autosaves of the monthly meter value of the last 36 months, autosaves of the annual meter value of the last 16 years, a log of the last 200 events, with the date of occurrence and end date, values of the hourly consumptions of the last 365 days and configuration data.

The gas meters with an electronic index has an auto diagnostic system, which monitors the following meter conditions: interruption/ lack of communication with the temperature sensor, opening of upper lid, opening of lower lid, exceeding of the maximum flow value, battery voltage under 3.05V, measured temperature under -25°C, measured temperature over 55°C, Gray code error.

Gray-code detection [6-7] ensures absolute calculation of gas volume. The movement of the gas measuring unit (see fig. 1) is detected by a unique, high frequency optical detection system. The optical encoder wheel has transparent and opaque areas, and is placed between a light source and a photo detector. When a transparent section of the wheel is between the light source and the photo detector, there is a several milivolt signal output — when it is an opaque section of the wheel, there is no signal. Usually a light source and a photo detector array are used with an encoder wheel to detect rotation direction and flow volume.

Depending on the interface at the communication unit various interfaces (interface converter) are available to integrate the coder gas meters in the remote meter reading

and to read out the meters with addresses according to IEC standards.

The system offers high resolution, tamper proofness and failsafe detection fit for instant flow calculation and error curve detection

Fig. 1 Coder with Gray code for gas meters

The electronic index includes a serial interface via an optical port. The optical port has physical and optical dimensions in accordance with EN 62056-21. The protocol used by the application complies with EN 13757-3.

The communication speed is of 4800 bauds, 8bits of data, even parity. The optical port is designed for the configuration and the metrological verification or data reading.

The electronic index can be built with a second serial interface designed for the transmission of data. The interface can be connected in association with an M-bus module with wires, in accordance with EN 13757-2; EN 13757-3 or M-bus radio EN13757-3 EN 13757-4 (Mode T2) and with the OMS 2.0 specifications.

III. ULTRASONIC GAS METERS

The ultrasonic gas meters which complies with EN14236:2007, UNI TS 11291_1~UNI TS11291_8, are designed and manufactured to measure the volume of natural gas and GPL, having maximum working pressure of 0.5 bar within a measurement range of 0.04-6 m3.

A. Measurement Principle

When ultrasound is transmitted between two transducers, the speed at which the sound travels through the fluid (natural gas or GPL) is accelerated slightly by the velocity of the fluid in the pipe. When ultrasound is transmitted in the opposite direction the flow of the liquid causes the transmitted sound to decelerate. The subsequent since the velocity v of the fluid is likely to be much less than the velocity C of sound in the fluid time difference

2CcosLv2T θ=Δ (1)

where L is path length through the fluid and θ - the relative angle between the transmitted ultrasonic beam and the fluid flow is directly proportional to the flow velocity in the pipe. Having measured the flow velocity v and knowing the pipe cross-sectional area S, the volumetric flow

SkvQ ××= (2) where k is a flow coefficient can easily be calculated [8]

B. Construction of ultrasonic gas meters

The structure of ultrasonic meters is greatly simplified by having no moving mechanical parts for measuring, as shown in Fig. 2.

The structure of ultrasonic meters is greatly simplified by having no moving mechanical parts for measuring, as shown in Fig. 2 (a). The meters with a Panasonic ultrasonic measurement unit (see fig, 2 b) are made from pressed steel ensuring robustness, external tightness, resistance against external and internal corrosion and resistance to high environment temperatures. Ultrasonic measurement unit is mounted inside the meter case on the run way of the gas flow. The meter is populated with a shut off valve on the inlet path. The shutoff valve automatically interrupts the gas flow when it detects an abnormal gas flow rate. This type of valve can be controlled local or remotely.

The electronic circuit, including the ultrasonic sensor module, is powered from a local battery with life time of min. 10 years. The electronic parts are distributed in two compartments: one having metrological functionalities - completely sealed, and the second having: communication modem, valve driver, and battery monitor functionalities. In the second compartment is placed the battery and it can be open without breaking the metrological seal.

C. Basic Specifications

The gas meter developed by us is a domestic model with maximum flow rates of 7.2 m3/h. Table 2 shows some technical specifications of the ultrasonic gas meters.

(a)

(b)

Fig. 2 (a) Structure and (b) ultrasonic unit of a gas meter [9]

Table 2 Some technical specifications of ultrasonic gas meters [10]

Operating temperature -25…+ 55°C Power supply Lithium battery Battery life minimum 10 years Measurement performance

40 to 600L/ within ±3%, with EN 14236:2007 600 to 6000L/h within ±1.5% acc with EN 14236:2007

Accuracy class 1,5 Pressure loss less than 200 Pa acc with EN

14236:2007 Class of protection IP54 Display LCD custom design, 14 digits Humidity 95%,at atmosphere

temperature 0~35 °C, for Ta>35 °C max amount of water vapor is 37.6 g/m

The volume is displayed in cubic meters with 3 or 4 decimals and the LCD display sequence can be changed through the display mode button.

The ultrasonic gas meter has a non volatile memory in which are stored events and diagnostics such as the followings: all data related to the last 70 gas-days for normal and error working mode; all data for current and previous period useful for billing purpose.

The events register has max. 180 events capability with the following parameters for each event: hour and date for each event; type of event; number of events started from the last reset; ID number of operator who has generated the event; previous and current value for the parameter used for volume calculus (in case); total value of the volume in reference conditions at the moment of event.

The ultrasonic gas meter has two serial communication interfaces: one optical interface for local communication purpose and another one with radio modem for remote communication purpose - both of them are using DLMS/COSEM protocol.

The optical interface complies with EN 62056-21 and the protocol used at application level is DLMS/COSEM. The optical port is designed for configuration, metrological checking or data reading, having a communication speed of 9600bps, 8 bits of data and even parity.

The remote communication interface can be populated with M-Bus radio modem having 169MHz/868MHz carrier frequency acc. with EN13757-3 and EN13757-4 or GSM/GPRS modem using DLMS/COSEM protocol.

Displayed values are: data and hour in format: day_months_year; hour_minute, current billing, redelivering station ID, diagnostic; total volumes in base conditions, total volumes in alarm mode, ID of current billing period, total volume per each phase of current billing period, end of previous billing period, total volumes in base conditions for previous billing period, total alarm volumes recorded at the end of previous billing period, tariff ID used for previous billing period, total volume per each phase of previous billing period, maximum conventional gas flow for previous billing period, status of the meter such as unconfigured; normal; service and status of shut-off valve.

On LCD can also be displayed some diagnostics of ultrasonic gas meters such as: battery missing, 10% of battery life, 90% of events register, events register full, opening the metrological compartment, opening the battery compartment, measured temperature over the working temperature range, tampering attempts.

IV. CONCLUSIONS

Gas utilities worldwide are placing increased emphasis on upgrading their operations with smart gas meters that utilize advanced metering infrastructure (AMI) technologies to enable two-way communications between meters and utility systems.

In this situation in this paper we have presented two new residential smart gas meters:

• a mechanical gas meter with an electronic index fitted with communication module + temperature conversion (integrated) and • an ultrasonic gas meter fitted with communication module + temperature conversion + valve (integrated).

The major benefits associated with introducing smart gas meters to the natural gas system are [1]: • lower meter reading costs and fewer special meter visits and readings • optimization of the gas network (transportation and distribution) • saving gas from reduced and shifting demand • remote disablement/enablement • lower call centre costs • alternative offers and prepayment • better switching procedures • better knowledge of unaccounted for gas volumes ➢ fraud detection ➢ better knowledge of meter readings • saving carbon emissions

REFERENCES [1] *** “Eurogas Distribution Committee - Report on Smart Gas

Metering” The European Union the Natural Gas Industry Brussels 2010

[2] M S Crainic "AMR gas meters system by radio - a new trends in natural gas metering technology in Romania" in SYMPOSIUM OF ELECTRONICS AND TELECOMMUNICATIONS "ETC 2006" - SEVENTH EDITION -"Politehnica" University of Timisoara, Faculty of Electronics and Telecommunications &IEEE Romania Section September 21-23, 2006, TIMISOARA, ROMANIA, Scientific Bulletin of the "Politehnica" University of Timişoara, Romania, Transactions on Electronics and Communications Tom 51 (65),, 2006, p.448

[3] *** Omega Transactions: Technical Reference Series vol. 4 Flow & Level Measurement 2001

[4] Dane Enrich “A guide to metering technologies” ASHRAE Journal October 2001 p.33

[5] *** “ Gas Meters with an Electronic Index GN G2,5…G6 E GNM G 2,5…. G6 E” prospect SC AEM SA Timisoara, ROMANIA 2012

[6] Nick Wang, “Gas and Water Metering application with MC9S08GW64” Freescale Semiconductor Inc Application Note AN 4262 February 2011

[7] Larry Sears “Water Meter Technology: Understanding the Meter to AMR Interface” Distributech 2005

[8] S. Kono, N. Nagai, K. Yuasa et al “Development of Intelligent Domestic Ultrasonic Gas Meters” 23 rd World Gas Conference, Amsterdam 2006

[9] *** “Prototype Specifications Ultrasonic Measurement Unit” Panasonic Corporation April 2011

[10] *** “Ultrasonic Gas Meters” Prospect SC AEM SA Timisoara, ROMANIA 2011