The synchronous coupling of the two transmission systems leads to reduced frequency deviations after a large, sudden loss of power. This is a result of the mutual cooperation, which is automatically activated by primary control within the whole synchronous area. The amount and distance of the related power flows increase in proportion to the capacity of the synchronous area and its geographical extension, respectively.
The installed power and the control reserve in both systems are in the same range. Figure 7 illustrates the distribution of the control power flow after a loss of 3000MW generation capacity in Germany. In the case of a 3000 MW outage (the dimensioning amount of reserve power in the UCTE system), a ~1500 MW regulating power flow will cross the interface area. This flow has to be managed in a secure manner. Hence, free transfer capacity has to be maintained at any time in order to allow this regulating power to flow through the interface in both directions.
Therefore, a synchronous coupling of the UCTE and the IPS/UPS would require the consideration of an additional Control Power Flow Margin (CPFM) for determining the Available Transfer Capacities (ATC). The CPFM is not incorporated in the Transmission Reliability Margin (TRM) according to definitions applied in the UCTE at the present time.
Thus, in order to respect system security, the required amount of CPFM has to be determined and the ATC has to be reduced correspondingly for the market across the IPS/UPS-UCTE interface.
