Open Breakers Overview

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There are several places in Simulator where functionality is available to open breakers in order to isolate a particular device or devices. This functionality is generally available when breakers, or other branch devices that are allowed to be automatically switched, are defined in the case. For some functionality, the Integrated Topology Processing add-on is required in addition to having breakers defined.

This overview is intended to provide information on which branch device types can be automatically switched, how breakers are selected, and the tools in Simulator that make use of open with breakers functionality. Additional information about how this functionality might work differently with specific tools will be described with those particular topics.

 

Branch Device Types that will Automatically Operate

The Branch Device Type field for a branch must be set to one of the following options in order for a branch to be considered a device that can automatically operate when using open breaker functionality:

Not all of the types listed above can be used for automatic switching with all tools that allow this. The different tools will indicate which types are allowed. For brevity, the term breaker will be used throughout this discussion to indicate branch devices that can be automatically switched.

Added in version 20

For a branch to be considered for automatic switching it must also have its Allow Open or Close Breakers field set to YES. This field can be changed by the user, and there are several options that will update this field based on the present case. For more information on how this field can be updated by Simulator, see the Update Allow Open or Close Breakers topic. When Allow Open or Close Breakers = NO and a branch is closed, it will be traversed when looking for breakers to open regardless of its Branch Device Type instead of being included in the devices to switch.

 

Algorithm Description for Open with Breakers

This algorithm is applied to each terminal bus of the device specified. For generators, loads, shunt, and buses this is done on a single bus only. For an Injection Group, each generator, load, and switched shunt in the injection group will be processed in turn. For an interface, each line in the interface is processed in turn. For substations, each ac line or dc line in the substation connected to another substation are processed in turn. Starting at each terminal bus of the device and marching outwards, the algorithm traverses closed branches (except for breakers), dc lines, and multi-terminal DC lines and will flag any closed breakers at buses that are visited. The buses that are visited are also flagged. (Note: the algorithm will NOT traverse across the breakers unless for an exception noted below). When buses are visited that have online generators, a list of generators is maintained that must be opened as well. In order to prevent the degenerate case where breakers do not fully isolate any portion of the network, only 10 buses with online generation are permitted for visitation. If more than 10 buses are encountered with online generation, the algorithm will immediately abort and a log message is written saying that the device "cannot be isolated from online generation".

If this part of the algorithm completes it will have obtained a list of flagged breakers and a list of visited buses (as well as a list of generators to open). The list of flagged breakers is then examined to ensure that each breaker actually isolates the original device. Each flagged breaker will be examined and if a flagged breaker has a terminal bus that is NOT in the list of visited buses, then this breaker disconnects the device from another part of the system and will be maintained. Breakers for which both terminal buses have been visited will be discarded because these breakers do not actually isolate anything. If at least one flagged breaker is maintained then the process is deemed successful and the contingency will outage the list of maintained flagged breakers. If all the flagged breakers are discarded, then the breakers do not isolate anything, and therefore a log message is written saying that "no part of the system can be isolated," and nothing is done.

 

Open Normally Open Disconnects Added in version 20

Some tools allow normally open disconnects that are currently closed to be open during the process of identifying breakers. The tools that allow this will have an option for using this feature. Disconnects are considered to be only branches where Branch Device Type is Disconnect.

This option will modify the open with breakers algorithm slightly. Without this option, the open with breakers algorithm searches across closed branches until a closed breaker is found along a traversal path. That breaker is then included in switching devices to open and the search terminates along that path. When using this option, any disconnects along a traversal path that are encountered that are presently closed but normally open will be included in the switching devices to open, and the search for breakers and disconnects will terminate along that path.

The normal status of a branch is determined by the Normal Status field.

 

Breakers in Series with Shunt Devices (Switched Shunts, Generators, and Loads) Added in version 20

When attempting to isolate any device except for a switched shunt during the process of searching for breakers and disconnects to open, any breaker or disconnect that is strictly in series with only switched shunts and disconnects will be excluded from the switching devices that can close. This check effectively looks for switched shunts that are connected radially by a breaker or disconnect. This will prevent switched shunt breakers from operating inappropriately when opening a line that has a tap point with switched shunts.

Modified in version 20, build on May 18, 2018

In addition to switched shunts, generators and loads are included in the series check for breakers and disconnects when identifying which switching devices can open. If a particular switched shunt, generator, or load should be disconnected, only that particular device will be disconnected if other radially connected shunt devices are found.

 

Tools that Use Open Breakers Functionality

Contingency Analysis

Local menu option for display objects and case information displays

Several objects (buses, branches, dc lines, generators, loads, and switched shunts) have a special local menu option, Open Breakers to Isolate, that allows them to be open using breakers. This option is present on both the local menu for display objects and the local menu of case information displays for the specified types. This option does not require having the Integrated Topology Processing add-on to work. When using this option, a dialog will open indicating which breakers have been identified and are being opened.

There are three sub-options available:

Only Breakers

Only Branch Device Type of Breaker will be included as valid switching devices.

Breakers and Load Break Disconnects

Only Branch Device Types of Breaker and Load Break Disconnect will be included as valid switching devices.

With Options

A dialog will open that allows for user input on the Branch Device Types that are included for valid switching devices. There is also an option Open Normally Open Disconnects. If this option is selected, Disconnects will be included in the search algorithm as described in the Open Normally Open Disconnects section above.

OpenWithBreakers script command

Scheduled Actions