1. General
Network equipment operating ratings are provided to NEMMCO by asset owners. The ratings may be provided as static data for use under specified conditions, telemetered dynamic real time data for use in dispatch timeframe, or may be hand dressed by NEMMCO in urgent circumstances.
Rating data used by NEMMCO is defined by equipment identifiers, a number of rating application levels, and rating application rules:
- Equipment identifiers are described in section 2.
- Rating application levels are described in section 3.
- Application rules are described in section 4.
Asset owners may provide additional information.
The basic structure employed in NEMMCO network modelling includes provision for multiple points of rating application on any transmission element. The structure allows for the application of a rating at both ends of the element and allows for flow in both directions. In addition to this, a number of levels of rating are accommodated to allow for different operating scenarios.
2. Equipment Identifiers
The equipment identifiers included in the published static ratings information are those used in the NEMMCO ESCA SCADA system. They are as follows.
Site Name - The Substation, Terminal Station, or Power Station name.
Plant Type - Transmission Lines may be Line, Tie, Summ for summated lines, or S_REACT for series reactors. Transformers may be Trans, Tx, or Tf.
Plant ID - The equipment identifier.
Region - The NEM region.
Measurement - All values included in the publication process are MVA quantities.
Level - NORM, EMER, or LDSH as described in section 3 below.
Alternate Value - An identifier which describes when the rating is applicable, such as summer, winter, etc. Alternate Value application rules at the time of publication of this document are described in section 3 below. Note that any rating with an associated Alternate Value suffix of '_DYN' has a real time telemetered rating supplied by the asset owner. This telemetered value would normally be the rating applied in real time processes. If telemetered data is available, any associated static ratings will be used for predispatch, and for dispatch only on telemetered data failure.
Low and High - The low and high provide a directional feature in the application of the rating. When associated with the Site Name, the Low and High are interpreted using the convention of :
A positive value is power flow from the Site into the equipment.
3. Rating Application Levels
The rating application levels applied by NEMMCO are defined below.
3.1 NORM
A continuous rating value. The NORM value is applied under pre-contingent conditions. This applies to security analysis and constraint equation application. This alarm level is used in monitoring and control of actual power flow through equipment without considering contingent events. For transformers the rating applied to this alarm level may be a fixed constant rating or the peak value of a continuous cyclic rating where the cyclic rating is comparable to the equipment loading profile.
Any continuous ratings provided for this purpose will be assumed valid by NEMMCO unless otherwise advised by NSP control room staff.
3.2 EMER
A rating value to be applied for a sustained period in emergency conditions. The EMER value is applied under post-contingent conditions. This applies to security analysis and constraint equation application. This alarm level is used in monitoring and control of actual power flow through equipment following the occurrence of a contingent event. For transformers the rating applied to this alarm level may be a fixed constant rating or the peak value of an 'emergency use' cyclic rating where the cyclic rating is comparable to the equipment loading profile.
The Emergency rating is subject to the NSP's assessment of the impact of the prevailing operating conditions and known ambient weather conditions at the time. When requested, the TNSP will assess the amount of EMER rating that is available for use in emergency conditions.
The same rating value as used for the NORM level of alarm will be used in this place if no value is supplied by a NSP.
3.3 LDSH
A short time rating. The LDSH value is applied under post-contingent conditions. The LDSH limit applies to security analysis and selected constraint equation application. This alarm level is used in monitoring and control of actual power flow through equipment following the occurrence of a contingent event.
Any short time ratings provided for this purpose will be assumed valid by NEMMCO unless otherwise advised by NSP control room staff.
The same rating value as used for the EMER level of alarm will be used in this place if no value is supplied by a NSP.
- Transmission Line or Cable Definition:
A short time transmission line or cable rating. The minimum time applicable is 15 minutes. A time greater than 15 minutes for lines or cables may be provided by an NSP however this nominated time must be consistent within the NSP boundary.
Note that a NSP may supply shorter time based rating values to be applied in specific agreed circumstances such as those included in contingency plans. Time based values of less than 15 minutes will be dealt with independently and will not be entered into the ESCA LDSH data fields for routine application. - Transformer Definition:
A short time transformer rating. Nominal time applicable is 2 hours. For distribution transformers times other than 2 hours may be provided by a NSP however this nominated time should be consistent within the NSP boundary. For main grid tie transformers times other than 2 hours may be provided by a NSP on a case by case basis as required for routine operational purposes.
4. Alternative Value Application Rules
4.1 Queensland Transmission Assets
Asset Owners based in Queensland apply seasonal alternate rating values. The selection of a particular season is advised by the asset owner depending on conditions at that time. This process is managed manually.
- QLD 3 Season
Winter - (QLDWIN) June, July and August
Shoulder - (QLDAUT/SPR) September
Summer - (QLDSUM) October to March
Shoulder - (QLDAUT/SPR) April and May
4.2 New South Wales Transmission Assets
Asset Owners based in New South Wales apply numerous sets of seasonal alternate rating values. The selection of a particular rating is time based as indicated below.
- NSW Summer / Winter
Summer - (NSWSUM) Start of November to End of April
Winter - (NSWWIN) Start of May, End of October - NSW Other Time / Winter Night
Winter Night - (WIN_NIGHT) 1700 to 0700 1 June to 31 August
Other Time - (OTHER_TIME) All times except 1700 to 0700 1 June to 31 August - NSW 3 Season Day Night
Summer Day - (N_SUM_D) 05:00 - 19:00 1 December to 28 February Summer Night - (N_SUM_N) 19:00 - 05:00 1 December to 28 February Spr/Aut Day - (N_AUT/SPR_D) 06:00 - 18:00 1 September to 30 November 06:00 - 18:00 1 March to 31 May Spr/Aut Night - (N_AUT/SPR_N) 19:00 - 05:00 1 September to 30 November 18:00 - 06:00 1 March to 31 May Winter Day - (N_WIN_D) 07:00 - 17:00 1 June to 31 August Winter Night - (N_WIN_N) 17:00 - 07:00 1 June to 31 August - NSW Monthly Day Night
January Day - (JAN_DAY) 05:00 - 19:00 1 January to 31 January
January Night - (JAN_NIGHT) 19:00 - 05:00 1 January to 31 January
February Day - (FEB_DAY) 05:00 - 19:00 1 February to End of February
February Night - (FEB_NIGHT) 19:00 - 05:00 1 February to End of February
March Day - (MAR_DAY) 06:00 - 18:00 1 March to End of March
March Night - (MAR_NIGHT) 18:00 - 06:00 1 March to End of March
April Day - (APR_DAY) 06:00 - 18:00 1 April to End of April
April Night - (APR_NIGHT) 18:00 - 06:00 1 April to End of April
May Day - (MAY_DAY) 06:00 - 18:00 1 May to End of May
May Night - (MAY_NIGHT) 18:00 - 06:00 1 May to End of May
June Day - (JUN_DAY) 07:00 - 17:00 1 June to End of June
June Night - (JUN_NIGHT) 17:00 - 07:00 1 June to End of June
July Day - (JUL_DAY) 07:00 - 17:00 1 July to End of July
July Night - (JUL_NIGHT) 17:00 - 07:00 1 July to End of July
August Day - (AUG_DAY) 07:00 - 17:00 1 August to End of August
August Night - (AUG_NIGHT) 17:00 - 07:00 1 August to End of August
September Day - (SEP_DAY) 06:00 - 18:00 1 September to End of Sept
September Night - (SEP_NIGHT) 18:00 - 06:00 1 September to End of Sept
October Day - (OCT_DAY) 06:00 - 18:00 1 October to End of October
October Night - (OCT_NIGHT) 18:00 - 06:00 1 October to End of October
November Day - (NOV_DAY) 06:00 - 18:00 1 November to End of Nov.
November Night - (NOV_NIGHT) 18:00 - 06:00 1 November to End of Nov.
December Day - (DEC_DAY) 0500 - 19:00 1 December to End of Dec.
December Night - (DEC_NIGHT) 19:00 - 05:00 1 December to End of Dec.
- NSW Snowy Mountains 2 Season
Summer - (SNOSUM) Start of October to End of April
Winter - (SNOWIN) Start of May, End of September
4.3 Victorian Transmission Assets
Asset Owners based in Victoria apply seasonal alternate rating values. The selection of a particular rating is time based as indicated below.
- VIC 2 Season
Summer - VICSUM) Start of November to End of April
Winter - (VICWIN) Start of May, End of October - VIC temperature based
Asset Owners based in Victoria also apply temperature based ratings with selection based on ambient temperatures with 5 degree steps from 5 degrees to 45 degrees. The areas of BENDIGO, DEDERANG, HEYWOOD, HAZ_WOOD, KEILOR, M_RABOOL, REDCLIFF, and ROWVILLE are included. The temperature base is indicated with the suffix '_temperature'. For example, the rating associated with the Alternate Value of HEYWOOD_15 will be applied when the temperature at Heywood is 15 degrees. The temperature is telemetered as a real time quantity to NEMMCO for use in dispatch timeframe. Predefined temperature profiles are applied to predispatch timeframe.
Please refer to the 2006 Sample Temperature profiles. These profiles are applied in NEMMCO applications and the same temperature profiles are repeated each year.
4.4 South Australian Transmission Assets
Asset Owners based in South Australia apply seasonal alternate rating values. The selection of a particular season is managed by a telemetered selection indicator (1, 2, or 3) provided by the asset owner. This indicator equates to:
- SA 3 Season
Winter - (SAWIN) < 20 degrees
Spring/Aut - (SAAUT/SPR) > 20 & < 30
Summer - (SASUM) > 30 degrees
4.5 Tasmanian Transmission Assets
Asset Owners based in Tasmania apply seasonal alternate rating values. The selection of a particular rating is time based as indicated below.
- TAS 2 Season
Summer - (TASSUM) Start of Dec to End of Feb
Winter - (TASWIN) Start of March to End of Nov - TAS temperature based
To accommodate the temperature based ratings in Tasmania, 6 temperature zones are defined. Each end of all lines in Tasmania are allocated a temperature zone. The 6 temperature zones are CENTRAL, NORTH, NORTH WEST, SOUTH, WESTand Far North West. Ratings for transmission lines within each zone are provided on a 5 degree incremental basis from 0 degrees to 40 degrees as static rating data. The temperature base is indicated with the suffix '_temperature'. For example, the rating associated with the Alternate Value of TASNORTH_15 will be applied when the temperature at TASNORTH zone is 15 degrees. The temperature is telemetered as a real time quantity to NEMMCO for use in dispatch timeframe. Predefined temperature profiles are applied to predispatch timeframe.
Please refer to the 2006 Sample Temperature profiles. These profiles are applied in NEMMCO applications and the same temperature profiles are repeated each year.
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