To ensure a secure and reliable power system, system planning is critical. EMA, as the Power System Operator (PSO), takes measures to ensure that the current and future electricity and natural gas systems are adequate. This includes the:
Review of Plans for the Development of the Transmission Network
PSO ensures the long-term electricity and natural gas transmission system development plan by the Transmission Licensee and Gas Transporter meets the planning criteria required by the Transmission Code and Gas supply Code, respectively.
Design and Impact Assessment of Proposed Generating Plants
PSO also reviews the design of generating plants that plan to connect to the power system. It assesses the plants' impact on the stability and security of the power system. This includes reviewing test plans and witnessing site tests to ensure the generating plants' compliance with requirements stipulated in the Transmission Code.
The factors that PSO takes into account in its assessment include:
Renewable energy sources like wind and solar are considered Intermittent Distributed Generators. These pose a major challenge when assessing their impact on the power system operation. As more of these generators are expected to be installed in the near future, this will provide a better gauge of how intermittency can be better managed and mitigated.
The need for electricity, steam and cooling from industries such as petrochemicals and pharmaceuticals drives the requirements for combined-heat power plants. The capacity of these plants varies from 1MW to 110MW. They are connected to the power system at both the transmission and distribution network and are typically operating at a constant power output level.
Inter-dependency of Gas and Electricity System
Natural gas currently accounts for about 95 percent of electricity generated in Singapore. A reliable gas supply is thus critical to keeping the lights on. PSO conducts studies on the inter-dependency of the electricity and gas systems to assess the impact of gas and electricity supply disruption and possible mitigation measures.
Interruptible Load Facility
The Interruptible Load (IL) scheme for the National Electricity Market of Singapore was introduced on 1 January 2004. It is an important development in the liberalisation of the country's electricity industry.
This scheme enables consumers to voluntarily choose to have their electricity supply interrupted in exchange for reserve payment. This thus competes with the generating plants directly in the reserve market.
Depending on the types of reserves the consumers participate in, these ILs should either be disconnected automatically once the system frequency reaches a pre-set threshold setting, or manually disconnected by the IL provider when instructed. To ensure that the inadvertent non-performance of ILs does not compromise power system security, PSO estimates the safe quantum of ILs that can be scheduled as reserve. This quantum is reviewed annually
Operating Reserve Policy
A Spinning Reserve (SR) is necessary to prevent an outage in the event any generating unit fails. It is defined as the amount by which the total generation capacity exceeds the annual electricity peak demand. In Singapore, the minimum reserve margin to maintain system security is currently 30 percent. This is based on a loss of load probability of three days per year. The 30 percent required reserve margin is to cater to scheduled maintenance as well as forced outages of generating units in the power system.
The power system must match aggregate generation and load instantaneously and continuously. The Regulation Reserve (RR) is employed to achieve this generation/load balance to maintain the system frequency close to 50Hz. A deviation of ±0.2Hz is allowed. The RR requirement can vary from one dispatch period to another. This is reviewed annually based on historical records of actual RR used.
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