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The input data are divided into three parts: general data, component data and common cause data.

 

General data

The data input procedure is as follows:

•Choose Application menu | Options.

•Select the Calculation tab and the Reliability tab.

•Signal fault: time needed to signal the fault. Short: time to signal when remote signalling is present; Long: time in any other case.

•Activate trouble shooting team: time needed for the repair crew to be in the fault locating starting position.

•Locate fault: mean time to locate the fault. Short: time when all nodes are equipped with short circuit indicator; Long: time in any other case.

•Sequential search: mean time to locate the fault when the repair crew follows the cable path.

•Binary search: mean time to locate the fault when the repair crew follows the binary search method (starting half way).

•Isolate fault: mean time to isolate the fault, when found. Short: time when alle switches are remote controlled; Long: in any other case.

•Switch in/over: mean time to switch on the outaged components or to change net openings. Short: time when alle switches are remote controlled; Long: in any other case.

•Emergency power supply: mean time to install an emergency generator. The maximum power is specified.

•Default failure frequencies for cables: General failure frequency, applied when the failure frequency of a cable is not filled in.

•Choose OK.

 

When locating the fault it is also possible to indicate a search strategy. Each strategy has its own long times. The times are based on a number of stations. The times for the strategy chosen must be filled in.

 

When sequentially searching the stations are gone over one by one to search for the fault, for this an average time must be indicated and the number of stations for which this average applies. If an average time of 60 minutes is indicated for five stations (from own experience) then in a group of ten stations the time will vary between 12 minutes (fault at first station) and 120 minutes (fault at last station).

 

In a binary search first the middle station of the string is looked at, then in the middle of half of the string, and so on. In this way the search process is reduced until the fault is found. The time required to find the fault is then logarithmically dependent here on the number of stations. Here too it is necessary to indicate the average time for a number of stations (from own experience).

 

Object-specific input data.

Reliability and switch data must be provided for each object in the grid. This data is on the Reliability tab of the input forms. The Reliability tab contains the failure, repair and maintenance data. Additional data can also be specified for some objects. The specific data include:

•node: presence of remote signalling.

•cable: failure frequency of one joint; the number of joint is the number of cable sections minus 1.

•switch: presence of remote control and/or indication.

•short-circuit indicator: presence of remote indication.

 

 

Tip

A new or existing network file often has no reliability data entered yet. These data are statistical and are the same for many objects. Therefore, these data do not have to be entered for each object individually. The reliability data can be entered for several objects at once using Start | Edit | Collective.

 

Common cause failures

For two or more of components, the failure data for common cause failures must be specified separately. The procedure is as follows:

•Select the two or more components for which the common cause failure rate will be entered.

•Choose Insert | Selection.

•Enter the name for this selection as:

 common <failure frequency> <repair duration> [<name>]

where the name is optional. So, for example for a selection of components with a common cause failure frequency of 0.0001 and a repair duraition of 480 minutes, the name for this selection becomes:

 common 0.0001 480

•Select OK to save the data.

 

See also:

•General

•Concept

•Specifications

•Modeling

•Calculation

•Result