Reading a constraint name

The grammar

        N        >>        NIL       _39_11
        |         |         |          |
     Region     Cause    Outage    Unique id
     N = NSW  >> thermal NIL=none  lines 39 and 11

Region

N New South Wales, Q Queensland, V Victoria, S South Australia, T Tasmania. I in a set name marks an inter-regional line outage. F_ instead of a region letter marks an FCAS constraint.

Cause

> thermal overload, ^ voltage stability, : transient stability, _ (or -) other: discretionary caps, unit-specific limits, system strength. Doubled (>>, ^^, ::) means fully co-optimised: every term on the LHS is something NEMDE dispatches. Single means the equation has an inter- or intra-regional form where some contributors sit on the RHS as measured values.

Outage

NIL means the grid is in its normal shape. Otherwise a station or line code names the equipment that is assumed out of service: LDTM for Liddell to Tomago, DTSS for Dapto to Sydney South, MNYS, SETX and so on.

Unique id

Whatever disambiguates: the monitored and contingency line numbers (_39_11), a sequence number, or for discretionary caps the cap itself in megawatts.

FCAS names

FCAS ids follow their own template: F_{scope}{+ or ++}{event}_{service}.

scope

I for the whole NEM (global), or a region group: MAIN mainland, T Tasmania, STHN southern regions, NVS NSW, Victoria and SA, TASCAP a Tasmanian capacity cap.

+ or ++

++ means the requirement is co-optimised with interconnector transfer (Basslink flow can substitute for local reserve); + means it is not.

event

MG or TG: loss of the largest mainland or Tasmanian generator (a raise requirement). ML or TL: loss of the largest load (a lower requirement). BL: Basslink trip. No event token means regulation.

service

R1 R6 R60 R5 raise at 1 s, 6 s, 60 s, 5 min; L1 L6 L60 L5 lower; RREG LREG regulation. A trailing number is often the requirement in MW: F_I+RREG_0220 is 220 MW of NEM-wide raise regulation.

Examples: F_MAIN++NIL_MG_R60 is the mainland 60-second raise requirement for loss of the largest generator, co-optimised with transfer, system normal. F_I+NIL_APD_TL_L60 is the NEM-wide 60-second lower requirement covering the loss of the Portland aluminium smelter's potlines. F_T+LREG_0050 is 50 MW of Tasmanian lower regulation.

Try it

The decoder applies the published naming guidelines mechanically. Real ids occasionally bend the rules (older ids, test constraints, negative-residue ids like NRM_SA1_VIC1, interconnector limits like QNI_SOUTH_590_DYN), so treat its reading as a strong hint and the constraint's DESCRIPTION column as the authority.

Names describe conditions, not wires

This is the trap. A constraint id names a condition: a corridor under an assumed outage state. When a line goes out for maintenance, the system-normal id for that corridor goes quiet and an outage-conditional twin carries the same physical limit; when the line returns, the handover reverses. In July 2026, N>NIL_94T (Molong to Orange North overload, system normal) fell silent at 07:20 on the 16th while its twin N>94T_947_72 carried the corridor until 15:00 on the 19th, then handed back. Anything keyed on the id, from bind-rate statistics to alert cooldowns, silently fragments across such handovers. Track corridors, or aggregate in dollars, when the outage book has changed inside your window.

Round numbers are caps

When the tail of an id is a round number and the cause is _, the number is almost always the RHS: V_DUNDWF1_2_3_168 caps Dundonnell's three units at 168 MW; V_MURRAWRWF_FLT_80 caps Murra Warra at 80 MW; F_I+RREG_0220 requires 220 MW. Discretionary caps are set by operators, not physics, and they bind for long unbroken runs on a named unit, so they concentrate dollar exposure on very few DUIDs. Dundonnell's cap topped the shadow-price table in both of the weekly reviews written during the project this course grew from.

Set names

Constraints are invoked in sets (Chapter 7), and set ids follow a looser convention: a region letter, a dash, and the outage or purpose, such as N-DTSS_11 (NSW, Dapto to Sydney South line 11 out) or S-MSTU (SA, a Mount Barker to Tungkillo outage). A set contains one or more equations; the equation ids inside it carry the outage token that matches.