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GSO will normally dispatch the lowest-cost generation to meet system demand. A system constraint is applied in the Grid operation’s generation dispatch when the unconstrained dispatch does not allow GSO’s operation to meet the TSRS(Transmission System Reliability Standards)’s Performance Criteria and Limits. For example, system constraint shall be applied to generation dispatch under conditions whereby transmission assets are expected to be operated above their thermal capacity limits under basecase condition or under any defined contingency event. GSO shall conduct appropriate system studies and publish system constraints which may be applied under:

  1. Existing Constraint – when the Grid system are all intact without major impacting system outages but due to inherent Grid system shortcomings, lowest-cost generation dispatch may not be possible and may result in unsecure system operation. Existing Constraint shall be published until Grid system shortcomings are lifted.
  2. Constraints Due to Outage – conditions when the Grid system has to deal with an outage situation when some assets are not available. Constraints Due to Outage shall be published as an information seven days ahead until the outage is normalised.
Existing Constraints
Existing Constraint is described by its type of constraints such as inter-area power transfer limitation; circuits in the Grid being constrained; transmission assets’ voltage and thermal limits impacted by the constraint; quantum of generation limit to be limited from which generation clusters; and some additional operational remarks if any.
TypeConstrained CctVoltageMax Overload(%)Generation LimitGeneration ClusterOther
Basecase275kV and 132kV cables into Penang Island132100GLGR Min = 70GLGRMin 1 GLGR GT on-bus required for thermal loading control and voltage support in Penang Island
Contingency275kV ATWR-PRMS-SGRI-BGJH-TPAH-BTRK (2x683 MVA)275150Limit based on max secured Perak-Central Area transferNorthernLimit to the max secured Perak-Central Area transfer to cater for thermal overload and system stability under n-2 contingency of 500kV BTRK-JMJG & BTRK-ATWR
Basecase and Contingency132kV KSTR-ASTR & 132kV KSTR-MGON (1x77 MVA)132100PLPS Min = 200NorthernMin 1 PLPS GT on-bus required for thermal loading control for 132kV KSTR-ASTR & 132kV KSTR-MGON lines and voltage support under n-2 contingency of 275kV BDNG-KSTR lines
Constraints Due to Outage (for the next 7 days)
Constraints Due to Outage is described in similar manner however additional information is included which is the outage duration period of the transmission assets giving rise to the system constraints.
StartEndTypeConstrained CctVoltageMax Overload(%)Generation LimitGeneration ClusterOther
Regional Generation Availability
Generation Clusters are defined as the composition of major generators with distinctive generation-transmission operation boundaries.
  • Northern Generation Cluster is composed by PLPS, GLGR, SKSP, NPRI, SGRI, JMJG, BSIA, TMGR, KNRG, LPIA, UPIA, CEND, UJLI, SYPS and SIHY generators.
  • Eastern Generation Cluster is composed by PGAU, HTRG, KNYR, YTL PAKA and PAKA generators.
  • Southern Generation Cluster is JMAH, PDPS, TJGS, PGLA, PTEK, MPSS, TBIN, PGPS and PCGP generators.
  • Central Generation Cluster is composed by PKLG, CBPS, SRDG and KLPP generators.
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