Rules on balancing, users imbalance and imbalance charge

In order to provide necessary conditions for safe, reliable and quality transmission of gas to all transmission system users it is necessary to keep the transmission system continuously at the regular operation conditions and within the allowed imbalance limits.

Transmission system balancing and the calculation of the imbalance expenses have been carried out in compliance with the provisions of the Rules on the Gas Market Organization (Class: 011-03/14-01/03, File No.: 251-544-12/2-14-3 dtd 30 December 2014) issued by the Croatian Energy Market Operator and the Methodology for determining the price of the gas system balancing energy (OG 155/14) issued by the Croatian Energy Regulatory Agency.

The primary responsibility for the daily balancing of its balance group portfolio lies on each balance group leader. The balance group leader is obliged to balance gas volumes delivered into the transmission system by its balance group with the volumes taken from the transmission system by its balance group on a daily basis. In order to balance the portfolio of its balance group the leader may use contracted transmission system capacities and its right to renominate transmission and use a gas storage system as well as trading at the virtual trading point on a day before and within the relevant gas day.

By using available information from the transmission nominations, operative information on actual status of the system, collected by SCADA system, and own estimates of gas consumption the transmission system operator continuously monitors and forecasts movements of the transmission system balance status.

In case the balance group leaders fail to perform balancing activities or if the activities they perform are not sufficient to balance the transmission system, the transmission system operator shall use the balancing energy from a daily and annual balancing energy offer in order to balance the system.

Balance group leaders deliver balancing energy offers to the Croatian Energy Market Operator (CEMO). The CEMO prepares a balancing energy offer list on a daily basis and delivers it to the transmission system operator. The transmission system operator uses offered balancing energy when necessary, respecting the order specified in the delivered list.
 
When the relevant month is over and the information on the final allocation of the gas quantities per user are collected, the transmission system operator calculates daily imbalance of each balance group. In a monthly balancing energy calculation the CEMO performs distribution of the total activated balancing energy to the balance groups in the following way:

The total activated positive balancing energy for the observed month is distributed to the balance groups proportionally to their share in the sum of all calculated negative daily imbalances. The total activated negative balancing energy for the observed month is distributed to the balance groups proportionally to their share in the sum of all calculated positive daily imbalances. In this way, the entire activated balancing energy is allocated to the balance groups which have caused its utilisation.
The balancing energy calculation is delivered to the balance group leaders by 15^th day in the month for the previous month.

If after in this way distributed balancing energy the balancing groups still have the remaining accumulated imbalance they can reduce it by mutual trade at the CEMO´s information platform, within the period of 5 days upon the delivery of the balancing energy calculation. The trading is bilateral between the balance group leaders. The participants in the trading announce their transactions to the CEMO which confirms them and records them.  

If the trading in the remaining imbalances fails to take place or the balance group leaders do not reduce their remaining imbalances entirely by mutual trading, the CEMO shall calculate all remaining imbalances at the valid prices of the positive and the negative balancing energy. The imbalance that remains after such calculation shall be transferred to the following month.

By 15^th day in the month the CEMO makes a calculation of the balancing energy. Those bidders whose negative balancing energy offer was used, are issued an invoice, whereas those bidders whose positive balancing energy offer was used, are paid an amount in compliance with the relevant calculation.



Calculation of the nomination imbalance

Nomination imbalance (ΔN_bs) is determined in an absolute amount for each balance group and each gas day according to the following formula:

ΔN_bs = |N_iz,bs - V_iz,bs| [kWh]

where:

N_iz,bs – is a gas quantity nominated at the transmission system exit points in a gas day, determined for each balance group, excluding the balancing energy of a bidder on a yearly and daily basis used in a gas day, based on the information on determined gas quantities from a monthly report of the transmission system operator in compliance with the Network Code of the transmission system and rounded up to a multiple of number 10 [kWh].

V_iz,bs  – is a gas quantity taken from the transmission system in a gas day, determined for each balance group based on the information on the determined gas quantities from a monthly report of the transmission system operator in compliance with the Network Code of the transmission system, excluding the balancing energy of a balancing energy bidder on a yearly and daily basis used in a gas day and rounded up to a multiple of number 10 [kWh].

The allowed deviation from nomination (ΔNdoz,bs) has been determined for each balance group and each gas day in compliance with the following formula:

ΔN_{doz, bs} = 0,10* V_iz,bs [kWh]

If, at the end of a particular gas day a deviation from nomination (ΔNbs) for a particular balance group is bigger than the allowed deviation from nomination (ΔNdoz,bs), the gas market operator shall deliver an invoice for the deviation from nomination to that balance group and the means collected under that invoice shall be paid to the transmission system operator.

The amount calculated for the deviation from nomination equals the result we get by multiplying 3% of the positive balancing energy price by the number we get when we subtract the allowed deviation from nomination from a deviation from nomination.

The gas market operator makes and issues the calculation and the invoice to the balance group leader by 15^th day in a month, for all gas days in a previous month.