How to Invoke Constraints

WEM Constraint Equation Checker · Set, type, and contingency filters

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What "invoking" means

A constraint equation is enforced only when its Constraint Set is invoked. In the control room one or more sets are placed in force for the current network condition, and every equation in those sets is then checked against the dispatch. This tool reproduces that: pick the sets in force, then narrow the active equations by constraint type and contingency.

The three filters combine with AND. An equation is checked only when its set is invoked and its constraint type is selected and its contingency is selected.

Steps

1

Load the data

Constraint equations and generator limits load automatically. Upload a dispatch .xlsx (drag and drop works anywhere) and set the demand forecast in MW.

2

Invoke constraint sets

In the Constraint Set column, tick every set in force. Multiple sets can be invoked at once.

  • NIL is the base set and is always active. It cannot be unticked.
  • Use the search box to find a set by ID, and All / None to bulk select. None leaves NIL on.
  • Invoking a set automatically selects its contingencies in the Contingency column.
3

Filter by constraint type (optional)

Narrow the active equations by the kind of limit they protect. All types are selected by default.

  • Thermal: conductor and plant current ratings.
  • Transient Stability: post fault rotor angle stability.
  • Voltage Stability: voltage collapse margins.
  • Other: remaining limit types.
4

Filter by contingency (optional)

A contingency is the credible outage an equation defends against. The list shows only the contingencies that belong to the invoked sets, and all are selected by default.

  • NIL here means the intact, pre contingency network.
  • Deselect any contingency to drop its equations from the check.
  • Search, All, and None act on the visible contingencies.
5

Check and read the result

The summary next to the heading shows how many equations the current filters invoke. Press Check to evaluate them, then review the violated and passed tables. Export the full result to CSV from the header.

Worked examples

Match your situation to one of these, then set the three filters as shown. The set IDs and contingency names below are illustrative, use the ones in force for your case.

● Routine check, intact network

Nothing is out of service, you just want to test a dispatch against the base limits.

Constraint Set
Leave defaults: NIL only.
Constraint Type
All selected.
Contingency
All selected.
● A set has been invoked for a planned outage

The control room has placed one set in force, for example for a planned line outage, and you want to check the dispatch against it plus the base set.

Constraint Set
Search the invoked ID, for example AMT-CTE 81, and tick it. NIL stays on.
Constraint Type
All selected.
Contingency
All selected, its contingencies are added automatically.
● Several sets in force at once

More than one set is invoked, for example a line outage set and a transformer outage set together.

Constraint Set
Tick each set in force, for example AMT-CTE 81 and ALB522. NIL stays on.
Constraint Type
All selected.
Contingency
All selected.
● Only thermal ratings of interest

You are screening for conductor and plant rating breaches only and want to ignore stability limits.

Constraint Set
The set(s) in force, NIL stays on.
Constraint Type
Click None, then tick only Thermal.
Contingency
All selected.
● Pre contingency (steady state) limits only

You want only the equations that apply to the intact network, with no outage defended against.

Constraint Set
The set(s) in force, NIL stays on.
Constraint Type
All selected.
Contingency
Click None, then tick only NIL.

Defaults at a glance

Equations with no Constraint Set ID belong to no set and are never invoked.