NEMS Activities

EMA is engaged in various activities in the National Electricity Markets of Singapore (NEMS). To ensure our systems operate smoothly, EMA as the Power System Operator (PSO) works together with market participants to ensure compliance with operational standards and obligations. These include both market administration and market operation activities as described below:

Market Administration  

Agreements with Market Participants

Market Participants in the National Electricity Market of Singapore (NEMS) are required to enter into regulatory agreements with the PSO.

Facility Registration 

Every market participant is required to provide up-to-date data of its facilities to the PSO, including the physical characteristics, ratings and operational limits of all relevant equipment/facilities connected to the PSO-controlled system. PSO utilises this information to: 

The timely submission of accurate and complete data is critical to participate in the NEMS. This is also necessary for real-time operation of the power system, outage planning, and stability and security assessment applications. Register for a Generation Facility with the Energy Market Company (EMC).

Market Operations

NEMS Data Exchange between PSO & EMC

Details of power system information, such as network status, outage schedules and load forecasts that are sent to the EMC, are described below.  

  • Energy Management System Network Status
  • The NEMS Market Clearing application requires the most recent network status and measurements data from PSO’s Energy Management System (EMS). The network status file is produced once prior to each trading period.  
  • EMS Outage Schedule  
    The Outage Schedule files covers all planned network outage schedules for the day and the following seven days. This is produced at least daily. If a change is made to the planned network outage for the day or the following day, a new Outage Schedule will be produced and sent to the NEMS.  
  • EMS Load Forecasts  
    The EMS system sends short-term load forecast (STLF) and very short-term load forecast (VSTLF) data to the NEMS. The VSTLF forecasts load by trading period for up to three hours ahead, and is generated once per trading period. The STLF forecasts load by trading period of up to 14 days and is generated daily.  
  • Dispatch Schedules from EMC  
    PSO receives the generation dispatch schedules produced by the EMC and assesses the schedules' feasibility before dispatching to the generators.  
  • Market Dispatch Instructions  
    The NEMS produces dispatch schedules prior to each trading period. These are deemed to be dispatch instructions unless overridden by PSO. Dispatch instructions include energy, regulation and reserve schedules for each generation/load facility.  
  • Market Short-Term Pre-Dispatch, Market Pre-Dispatch and Market Outlook Schedules  
    The Market Clearing application produces short-term pre-dispatch, pre-dispatch and market outlook schedules as defined by the Market Rules. These schedules provide PSO with medium and long-term view of operational feasibility of the dispatch schedules.

Electricity Market Compliance Monitoring

The PSO ensures all non-compliance notices issued to market participants are shared with the Market Surveillance and Compliance Panel via the Market Assessment Unit of the EMC. A non-compliance notice can be issued to market participants on either an event of non- compliance with the PSO's directions or dispatch instructions. This could also be due to a breach of market rules, especially with regard to the operation of the PSO-controlled system.

Ancillary Services

Ancillary services deal mainly with balancing the power supply and demand over short time intervals throughout the power system. These services, regulation and reserves are essential to ensure the reliable operation of the power system and the acceptable quality of electricity supplies in Singapore.

In addition, the following contracted ancillary services may be procured:

    • Reactive support and voltage control service  
    • Black-Start capability  
    • Fast-start services  
    • Reliable must-run services  

Currently, only Black-Start services are required. The ancillary services may be called upon by the PSO to ensure security and reliability of the power system.

An “Ancillary Services Contract" can be obtained from the Energy Market Company.

Outage Co-ordination

The PSO is responsible for coordinating the outage schedules of registered generation facilities, generating stations and transmission facilities. This also covers new or retrofitted facilities for construction, testing, commissioning/re-commissioning, and maintenance/repair.

The PSO also coordinates the outages. This ensures sufficient generating units and adequate transmission network capacity to meet forecasted demand, operating reserves and the reliable operation of the transmission system.

Power System Adequacy & Security Assessment

The PSO assesses the adequacy and security of the PSO-controlled system on a daily and monthly basis. It prepares the Adequacy and Security Assessment (ASA) over the following two time frames: 

    • Monthly assessments, covering a 12-month period commencing from the following month; and  
    • Daily assessments covering a 14-day period beginning from the following day.   
These adequacy and security assessments are used to identify possible periods of inadequate generation/transmission capacity to cater for expected load. These could also be used when security-related events on the PSO-controlled system require actions to be taken by market participants or the PSO. 


The PSO is represented in various NEMS committees and panels as described below:

  • Dispute Management 
    This comprehensive but flexible dispute resolution procedure is set out in the Market Rules. This covers all market participants, the Market Support Services Licensee, the EMC and the PSO.
  • Technical Working Group 
    The Technical Working Group reports to the Rules Change Panel. The group is responsible for examining proposed changes to the dispatch and price discovery process. It is also in charge of balancing economic, financial and technical considerations to create a more efficient wholesale electricity market.
  • Rules Change Panel 
    The Rules Change Panel reviews all proposed modifications to the Market Rules. Thereafter, the panel makes recommendations to the EMC Board, which then submits the Rules Change to EMA for approval.
  • Urgent Rules Modification Committee 
    Urgent modifications by this Committee are valid for up to only one year. During this period, EMC has to submit the urgent modification to the Rules Change Panel for consideration via the usual rules change approval processes.
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