By Bojan Lazarevic

Previously on 23 July 2004, the parliament of Serbia had adopted the Energy Law and immediately after the Energy Agency was established. The Energy Law is fundamental for restructuring Serbia’s energy sector and integrating it into the European community. One of the most important activities arising from this law is Serbia’s full participation in the regional energy market in southeastern Europe, the Energy Community of South East Europe (ECSEE).

Starting from 1 January 2007, the established annual energy level for granting eligible customer status was decreased from the previous 25 GWh to 3 GWh. This decision was in accordance with the obligation from the ECSEE that all non-domestic customers would become eligible starting 1 January 2008, and domestic customers at the latest by 1 January 2015.

As a result more than 350 customers in Serbia, which account for 21 percent of the total consumption in the country, will be able to choose a supplier. Previously, only 38 customers were able to change supplier, although to date they had not exercised this option, due to the low price of electricity in the region, less than 4 euro cents/ kWh, and the fact that an energy market still does not exist in Serbia.

In terms of the Energy Law, metering is managed by the Distribution System Operator (DSO). Local distribution companies are responsible for purchasing, owning, installing, operating and maintaining electricity meters, including smart meters. The authority sets the requirements for accounting separation of the metering costs, which are now separately identified in the tariff system. There is also an obligation for monthly meter reading, for all buyer categories, for all customers in Serbia.

EXPERIENCE IN LOAD AND TARIFF MANAGEMENT IN ELEKTROSRBIJA
Elektrosrbija has been using a ripple control system (RCS) for tariff and load control, light and heat control for almost 25 years. At this moment, the company has four RC transmitters in use. The carrier frequency is 216.67 Hz. The impulse telegram is Semagyr 52, as well as EDF. Both addressed and direct receivers are in use. Load and tariff management has been used at 18 percent of customers, accounting for more than 40 percent of delivered energy.

ELECTRICITY METERING IN ELEKTROSRBIJA
Elektrosrbija has 853,397 electricity meters. Among these are more than 158 different types of electricity meters. Most of them, 140 types, are electromechanical-based. The average meter age is over 25 years, and the validity period of over 68 percent of meters is expired. If all meters in the network were replaced, commercial losses would decrease by 2 percent.

By the end of 2007, 31,000 three-phase electricity meters and 1,900 single phase electricity meters will be replaced, including 1,500 meters for commercial customers. The meters are electronically based and are secured through international public invitation.

AMR1

Figure 1 - Schematic of Elektrosrbija's first AMR project

THE FIRST AMR PILOT
The first AMR project was started in 2003. It was implemented in two 10/0.4 kV substations (Figure 1). The project was focused on low voltage customers, and included all buyer categories. PLC was used for data transmission from the meters to concentrators in substations and from the substations through the 10 kV medium voltage network to the AMR control centre.

The communication protocol is Lonet®. The meters provide four tariffs and the accuracy class if connected over CT for active energy is 1, for reactive energy is 3, and for maximum demand is 1. For direct connection the accuracy class for active energy is 2. A real time clock module (RTC) is located in the substation containing the tariff tables for all buyer categories. This is synchronised from the AMR control centre and enables time setting in the meters.

THE RESULTS
After replacing all the electricity meters in these two substations and putting into operation the AMR system, there was a significant decrease in commercial losses, by 2 and 10 percent respectively.

The results indicate that the accuracy class of the meter has a significant influence on the management of commercial losses. By analysing data obtained during the AMR process it is easy to detect errors in measurement and locate the consumers where the errors have appeared, thus providing a direct influence on the decrease of commercial losses and improvement in the quality of the network.

THE NEXT STEP
In 2006 Elektrosrbija introduced a second project focused on the low voltage customers, this time for a total of 4,000 meters with four AMR centres and including a remote connection and disconnection functionality.

PLC is used for data transmission from the meters to the concentrators in the substations and GPRS is used for communication between the concentrators and the AMR control centre (Figure 2). The communication protocol for both local and external communication is IEC 62056-21 mod C. However, in the future the intention is that all electricity meters will have IEC 62056-46 DLMS as the communication protocol.

AMR2

Figure 2 - Schematic of Elektrosrbija's second AMR project

The meters for the household customers are also equipped with a three phase breaker (60A) for remote connection and disconnection. The company team of specialists designed the system requirements for this second pilot project. The general requirements for the meters were: interchangeability of meters, minimum dependence on manufacturers, and standardisation in functionality and communication, in order to improve operation and maintenance and to decrease the cost of the equipment.

All meters also must have the certificate of approval issued by the National Measurement and Certification Bureau. Three types of meters are being deployed: For household customers (maximum 60 A), meters with accuracy class for active energy of 2, for commercial customers (maximum 60 A), meters with accuracy class for active energy of 1, reactive energy 3 and maximum demand 1, and for commercial customers connected over CT, meters with accuracy class for active energy of 1, reactive energy 3 and maximum demand 1.

The meters must be multitariff with a maximum of four tariff registers, in order to keep all billing elements within a minimum 12 months. The meters also must be programmable remotely from the AMR control centre or locally with a handheld unit.

For the household customers the PLC modem and three-phase load breaker are built in the meters. The system must provide two way communication between the meters, concentrators and AMR control centre for remote meter reading, changes in tariffs, time and date synchronisation, customer connection and disconnection, load profiling of clients, register and report alarms, detection of irregular consumptions and terminal cover removal, onsite energy quality monitoring, energy balancing and loss determination and monitoring, remote supervision of MV/LV substations, monthly and yearly analysis, and reporting and evaluation of energy consumption. The system should be in operation by the end of 2007.

PLANS FOR THE FUTURE
Meanwhile, there has been technical preparation for a small scale pilot project to replace the electricity meters for the 10 kV medium voltage consumers. In the first place, the technical characteristics for the electricity meters must be defined. In this category, the following values are measured: active energy with accuracy class 0.5, reactive energy with accuracy class 3 and maximum demand with accuracy class 0.5. The meters must be able to store all the billing elements in their memory for a minimum 12 months. GPRS will be used for data transmission between the meters and AMR control centre. The system also has to be compatible with the existing billing system.

The estimated price for the GPRS is €200/month, VAT excluded, for 100 operational lines. This price allows 40 MB data flow per line. The company has 767 consumers in this buyer category, which in 2006 accounted for 934 GWh of electricity.

Considering the number of customers and energy sales in this category, the expectations are to improve the metering and service quality, to improve efficiency and to optimise the billing process, thus decreasing the time for bills to be issued and decreasing the labour costs of the meter reading staff and the costs for meter reading. There is also the possibility to significantly improve the network and energy quality monitoring. In addition, there is no need to access the consumer’s property.