Has QAS changed the weighted average calorific value?

On 15th February 2011 FGSZ published the natural gas quality accounting system (QAS) for the natural gas transmission system delivery points for the 2011-2012 gas year. Apropos of this, we have examined the changes in the weighted average calorific value of some selected delivery point.

QAS is the method of quality accounting system of delivered natural gas through the delivery points of the gas transmission system network, valid for a calendar year.

QAS is defined as follows: "The rules of procedure which determine the assigning of the chromatographs’ samples belonging to certain network points to the delivery points, and which also regulates the substitution of the sample flow of chromatographs depending on gas traffic order, and also determines the annual weighted average calorific value and the gas group for each network point. (Source: Operational and Commercial Regulation of the Hungarian Natural Gas System, here to fore: OCR)

In the case that no measurement data are available to toggle between the volume (m3) and the amount of energy (MJ) (e.g. in capacity booking periods), the calorific values ​​(MJ/m3) determined in the QAS will be applied. In Hungary the number of the chromatographs (167 units) rated to the supplied area, is rather high, so we can get an accurate picture of the quality and ingredients of the gas.

Interesting: whom and why?

It is interesting to natural gas trading licensees, to consumers on transport system, to system operators. QAS is mainly used during transmission system capacity bookings.

Capacity booking and gas restriction data

The weighted average calorific value of gas appears as input data primarily when booking capacity for the following gas year or gas years. Capacity booking takes place on energy basis, the measuring infrastructure and hydraulic sizing of the transport systems, however, it is of volume based. Therefore, there is a need for a consensual converting system.

The system operators need QAS data to provide the restriction information (limitation rating). The system operators have to classify the consumers’ booked gas rates into restriction categories determined on volume (m3) basis. Capacity bookings however, take place, on energy basis. Therefore, the operators apply the calorific values determined in MJ/m3 by the QAS for converting the units.

The restriction categories are regulated by the 265/2009. (XII.1.) Governmental Decree on The necessary measures in case of natural gas supply crisis. The resolution of the Hungarian Energy Agency on the use of the calorific values ​​in relation with restriction data provision is published in its letter numbered GEFO-197/2/2010.

While the original measurement data are generally given for separately measured points (physically existing gas delivery stations), the QAS provides calorific values also for unified delivery points.

The following table shows some selected points of the major transport system, where we have examined the weighted average calorific values in the years 2009 and 2010.

Unified withdrawal: from the figures we can see that a withdrawal of better gas quality can be calculated, compared both to the previous and to this year. I.e. in case of unchanged volume based capacity booking, withdrawal represents higher energy based capacity.

Budapest: The calorific value has increased. That is, an energy based capacity of higher rate will have to be booked compared to the usual volume (m3) based one. In fact, if someone has set a volume based standard at Főgáz, in case of annual reading he will have to pay more, due to the higher GCV.

Unified injection: the heating value has decreased significantly - by more than 0,3 MJ/m3. This means that to inject the same amount of energy, a significantly greater hydraulic rate is required for storing. It is also important because of the much smaller injection capacity due to technological reasons (32 Mm3/d) than the withdrawal (54 Mm3/d).
Ukraine / Hungarian border entry point Beregovo: The calorific values are the same in the two examined cases.

Austrian / Hungarian border entry point from Baumgarten: the calorific value has changed to a slightly lower. This means that if someone has a MWh quantity based contracts on the Austrian side, he has to book higher capacity in MJ on the Hungarian side. (Assuming that they calculate with the GCV of the last year during conversion.)

The sources used in writing the article:

• Operational and Commercial Regulation of the Hungarian Natural Gas System
• Quality of accounting system for the gas year 2010/2011
• Quality of accounting system for the gas year 2011/2012
• Guide to the 2010/2011 gas year to prepare for the classification of natural gas restrictions

The accurate definition of the QAS in the OCR

Operational and Commercial Regulation of the Hungarian natural gas system (2010th September 15) - 6.8.1.7. Quality Accounting System (QAS)

(a) QAS regulates which chromatograph sample rates be assigned to certain points of the network, furthermore regulates the substitution order of the sample flow of chromatographs depending on gas traffic order.

(b) QAS includes the following:

i. The supply directions of chromatographs, the codes of the sample flows;

ii.The gas traffic dependant classification of certain points, their natural gas groups and connecting system operators.

iii. The annual weighted average calorific value, which is the weighted annual average of the daily average heating values weighted by the daily volumes and is determined for each network point. The annual weighted average calorific value is calculated by the natural gas supplier on the basis of the previous year for the period January 1 until December 31.

(c) The gas supplier is responsible for the preparation and annual review of the QAS. It is valid for a whole gas year. Its publication takes place not later than Feb. 15 - on the website of the natural gas supplier. It enters into force on the first day of the gas year.

(d) The natural gas supplier updates and publishes the QAS on its website before commissioning a new entry or exit point or installing a new chromatograph - notifying the connecting system operators at the same time.

(e) The natural gas supplier, with regard to the previous day’s gas traffic, assigns the relevant chromatograph code to the entry and exit points, after each gas day. If the chromatograph measurement data are not available, then a substitute chromatograph determined by the QAS must be assigned to the entry or exit points. If there is no substitute chromatograph available, then the data measured by the laboratory should be used.