Balancing the portfolio 24 hours per day

25-04-2019

What is involved in balancing a large gas portfolio? Fourteen dispatchers work day and night to carry out this responsible task.

Balancing an extensive gas portfolio is difficult. At GasTerra, we have 14 dispatchers who work in shifts. 24 hours per day, they are responsible for the fulfilment of GasTerra's gas procurement and sales obligations and for balancing the company's gas portfolio.

How does it work? We talk to Steven Neijenhuis, commercial dispatcher. Steven has been working as a dispatcher at GasTerra for nearly eight years and has seen many developments in the field of gas portfolio balancing.

Where does the gas come from?

“GasTerra sources gas from the small fields, Groningen, TTF (trade hub) and imports. Usually I start with the example of an offshore scenario. Gas sourced from the North Sea is transported to shore via pipelines and then enters the Gasunie network. Gasunie, known as the TSO, the Transmission System Operator, in technical jargon, is responsible for the domestic transport of gas to our customers. Gas destined for foreign customers is transferred to the TSO of the relevant country at the border.”

How do we know how much gas is being transported at any moment?

“GasTerra, also known as the ‘shipper' in transport terms, has concluded an agreement with the TSO stipulating that there must be a balance between the gas volumes entering and exiting the network. The system has to be at the right pressure for all the users.

To specify how much gas has to be transported, there is a lot of communication between the various shippers in a country and the relevant TSO. This communication takes place via Edigas messages; standardised messages that indicate, per hour:

  • how much gas enters or exits the network in KWh/h;
  • who supplied the gas;
  • who the gas is intended for;
  • the location where the gas enters or exits the network.

This allows the TSO to determine exactly how much gas GasTerra wants transported from its portfolio. The personal balance of a shipper is called the POS, the Portfolio Imbalance Signal. In addition to GasTerra, there are of course a lot more shippers who want their gas transported in the Netherlands. These shippers are also all required to balance their portfolio: gas in equals gas out.”

And the TSO supervises the system?

“Yes, the TSO receives all the Edigas messages, compiles them and has an overview. The TSO monitors the system, to check that the same gas volume enters and exits the system every hour. When all Portfolio Imbalance Signals are added together this is called the SBS (System Balance Signal). 

If all shippers achieve a good portfolio balance, there is no ‘imbalance’. If, on balance, too much gas is fed into the system by all the shippers, the SBS is ‘long’; if there is a shortage of gas, the SBS is ‘short’. The shippers are therefore jointly responsible for the balance of the network (SBS). There is sufficient bandwidth to keep the balance right.”

So a POS can be positive or negative, but doesn't your own portfolio have to be exactly balanced?

“During the gas day, you are allowed to use the flexibility/buffer of the gas network, also called the Linepack Flexibility Service. However, at 6.00 am, when the gas day starts, you are assessed on your imbalance. The system is largely automated these days and we can monitor the balance position with the TSO directly and in real time. This enables us to determine whether we run the risk of going long or short.”

“The following two diagrams show the POS (top) and SBS (bottom) from 1.00 am until 1.00 am the next day. You can clearly see we are faced with an imbalance and that it has to be adjusted 24/7.”

Portfolio Imbalance Signals (POS)

Portfolio Imbalance Signals (POS)

System Balance Signal (SBS)

System Balance Signal (SBS)

What happens where there is an imbalance in the system?

“Sometimes shippers create so much imbalance that the TSO has to take measures to maintain the pressure in the system and to guarantee the security of supply. The TSO then has the authority to implement a WDBA, a Within Day Balancing Action. In the event of a WDBA, the TSO can buy or sell gas at the expense of the parties who caused the imbalance, who are then allotted that gas (pro rata). This gas is bought or sold on a virtual hub, in this case Ice Endex.  The price of gas is determined by the providers on the market.”

So it is better to make sure your own portfolio is balanced?

“Yes, it's important to keep your own portfolio in balance so you're not causing an imbalance and then liable for the costs involved. At GasTerra, we do this through the CDC, the Commercial Dispatching Centre. We make use of various tools, such as gas storages, the Groningen field and trade hubs, the so-called virtual trading platforms.

Every hour, we take stock and make adjustments where necessary. The tools we use have been set out in advance in a plan. This dynamic plan gives a prioritisation of which tools we can use and at what price.  The speed of deployment of the tool is also decisive. The prioritisation is done by our Optimisation & Planning department.”

So you have a close working relationship with your colleagues?

“Definitely. Not just the dispatchers among themselves, but broad collaboration and communication with the Planning & Optimisation department is also important. Every morning during the morning call, we discuss the important issues and current events, the plans for the day, how warm or cold it's going to be, as well as developments in the various networks and prices. Dispatchers, traders and Planning & Optimisation all work together to make sure the system is kept in balance.”