Retained Network Definition

The network to be reduced is obtained from a solved base case. The retained system is defined by the user in the INPUT file. Five options are available to the user as shown in the figure below.

Fig. 168 Retained Network Input Options

Each of the options 1 through 5 are affected by the unique control cards described in upper case characters in the blocks in the figure above. Their formats are described in the following paragraphs.

Reduction Cards

The reduction cards specify the retained systems. There are several options available. 1. Zone Selection. The zones which normally define geographical areas may be used to define the retained system. All buses within these zones are then retained. The format is essentially “free-field”. Commas separate the different zones and a period terminates the list. Any blanks are ignored unless immediately preceded by a comma or a period. The command >SAVE_ZONES must begin in column 1. If the zone list is too long to be contained on a single card, continuation cards must be used, in which a blank appears in column 1 and the zone list continued. 2. Base kV Selection. The retained system may be selected as the set of all buses with base kV’s matching the specified set. As with the previous card, the format is essentially free-field. However, decimal points may be part of the base kV, necessitating a double period to terminate the list. The command >SAVE_BASES must begin in column 1. Continuation cards are permitted. If they are used, a blank must appear in column 1 as the base kV list continues. 3. Zone Selection Subjected to Base kV’s. This is a combination of steps 1 and 2 described previously. Each of the zones selected is further stipulated to certain base kV’s. Recognition is acknowledged that different zone/base kV combinations may be desirable, and several zone-base KV cards are permitted. The format is similar to steps 1 and 2 above. The difference is that the last zone (there may be only one) is followed by a comma and the words >SAVE_BASES. Continuation cards are permitted. 4. Inclusion and Exclusion of Buses to Retained System. The general criteria of saved zones, saved bases, or both is recognized as too general to adequately define all retained systems. Provisions permit the system thus defined to be enlarged or contracted by specifying individual buses which are to be included into or excluded from the retained system. The retained system is expanded with the control card. >INCLUDE_BUSES beginning in column 1 and followed with separate bus cards. The bus card need only contain the B in column 1, and the bus name and base kV in columns 7-18. All other fields are ignored. The list of included buses is terminated when a card without a B in column1 is encountered. The retained system is contracted with the control card >EXCLUDE_BUSES beginning in column 1 and followed with separate bus cards as described previously. 5. Individual Bus Selection. In lieu of options 1. through 4.described previously, the retained system could be identified by individually specified bus cards. This request is initiated with the control card >SAVE_BUSES beginning in column 1. Each retained bus is then individually specified with a bus card. Only the bus identification fields need be specified, that is, the B in column 1 and the bus name and base kV in columns 7-18. All other fields will be ignored. The list continues until a card without a B in column1 is encountered.

Input listings

Following the program control card and subsequent reduction cards, the retained system is defined and two listings are produced. The first listing defines the retained network. Each bus name will be preceded with one or two of the following characters: Blank Retained bus is internal and unchanged. E Retained bus is an envelope node and will receive distributed injections and equivalent branches. X Retained bus is also an envelope node. However, everyone of the adjacent nodes is eliminated. This is acceptable but may not be intentional and is intended as an informative diagnostic. * Retained bus is selected by the optimal feature. P Retained bus is a generator. The second listing defines all eliminated nodes.