Supply Reliability

*Targets are referred to TNB DN 5 Years Plan

Table 2: Sustaining SAIDI

Figure 1: SAIDI and SAIFI FY2023 from TNB’s Annual Report Page 78

Achieving and maintaining this standard requires a strategic and proactive approach through robust system planning and diligent asset maintenance. To achieve this goal, TNB Distribution concurrently invests in modernizing and upgrading its infrastructure to mitigate the risks of power interruptions. This includes the implementation of cutting-edge technologies, grid automation, and effective load management systems. Regular maintenance and inspection of critical assets, such as transformers and substations, should be prioritized to prevent unexpected failures. Moreover, effective monitoring and predictive maintenance using data analytics helps identify potential issues before its escalated into major disruptions. By aligning our strategies with system planning and asset maintenance best practices, TNB Distribution consistently delivers on the promise of a SAIDI metric, ensuring a reliable and uninterrupted power supply for our customers. 

Strategy For Supply Reliability Through System Planning

TNB's strategy for ensuring supply reliability through systematic planning is grounded in the principles of Life Cycle Asset Management. This approach is aimed at meticulously planning and expanding our network to enhance system performance while maintaining cost efficiency. To ensure that our network has the necessary capacity, we follow an annual review process, illustrated in Figure 1, which encompasses several key activities:

Figure 1: Planning Cycle Activities

Load Forecasts

These forecasts are based on historical sales data, local factors, and economic indicators. We perform 20-year forecasts annually to anticipate future demands accurately.

Load Disaggregation

In this step, we break down projected demand into state and supply zones. The final demands for each state or supply zone include projections for the growth of demand at Transmission Main-Intake Substations (PMUs) over the 20-year planning horizon.

Capacity Planning

Consisting of Sub-Transmission Capacity Planning (STCP) and Distribution Capacity Planning (DCP)

Sub-Transmission Capacity Planning (STCP)

This involves evaluating the capacity versus demand outlook for each supply zone over a 10-year horizon. It identifies the risk of capacity shortfalls and the need for additional capacity development, including new PMUs or increasing the transformer capacity of existing ones.

Distribution Capacity Planning (DCP)

This is a similar analysis but at the 33kV distribution level over a 5-year planning horizon. It aims to pinpoint capacity gaps and the asset development requirements for Distribution Main Intake Substations (PPUs), mainly those operating at 33/11kV in the distribution system.

Distribution Network Master Plans (DNMP)

These plans are essential documents for the development of our distribution network. They involve the analysis of system security performance and related network enhancement needs for 33kV and 11kV systems in each supply zone. The DNMP report is reviewed annually to ensure that major distribution enhancement projects for 33kV and 11kV are identified, planned, and implemented within the 5-year (33kV) and 4-year (11kV) analysis horizon.

In addition to these planning activities, we identify and execute asset replacement programs based on established criteria and policies in line with best asset management practices. Considerations include the asset's health index, age profile, operational safety, and product support.

The list of 33kV and 11kV system development, system improvement, and asset replacement projects are compiled and prioritized based on their criticality for implementation. This prioritization follows methodologies such as Risk-Based Decision Making (RBDM), Financial Evaluation Template (FET), and Cost-Benefit Analysis (CBA). These practices ensure that we make informed decisions regarding the maintenance and expansion of our network to guarantee a reliable and resilient power supply for our customers.

Strategy for Supply Reliability Through Asset Maintenance

In managing TNB supply reliability, seven (7) core strategies of Sustaining SAIDI have been established in the distribution network where most assets are operating which as follows:

Figure 2: 7 Core Strategies of Sustaining SAIDI

Each strategy is supported by Initiatives as shown in Table 1.

Table 1:  Activities for sustaining SAIDI Performance

TNB has initiated a proactive approach to potential failure detection, incorporating Condition Based Maintenance (CBM) for underground cables, which employs the partial discharge (PD) mapping technique and online partial discharge detection. This system is instrumental in early defect identification, thereby mitigating the likelihood of substantial failures. Furthermore, TNB has extended CBM practices to 33kV switchgears, effectively reducing the risk of defects that could lead to flashovers.

In the realm of system safety, TNB has taken measures to avert catastrophic events through the installation and activation of arc flash protection schemes at PMUs/PPUs. These advanced systems have the capability to detect the initial stages of a flashover in AIS switchgear and promptly isolate the faulty section. Simultaneously, TNB's 11 kV project injections aim to enhance the overall reliability of the system.

In the context of the asset replacement program, TNB is focusing on the replacement of aging and high-risk installations that have the potential to trigger a substantial number of breakdowns, impacting a significant customer base. This category encompasses assets such as critical MV cable sections, including oil-filled cables, as well as high-risk PILC and XLPE cables.

To enhance SAIDI performance, TNB has intensified its deployment of the Distribution Automation (DA) Project. This strategic initiative enhances visibility across the distribution network, particularly at the Control Centre. By harnessing SCADA technology both at the Control Centre and within substations, real-time monitoring capabilities for field equipment are now seamlessly integrated. This empowers the Control Centre with the ability to remotely isolate faults and swiftly restore power during unplanned outages. For a comprehensive overview of these advancements, refer to Dimension 1.

Concurrently, TNB remains dedicated to optimizing restoration time. This involves the ongoing implementation of network automation through SCADA/DA systems, coupled with the integration of cutting-edge technologies. Leveraging SCADA/DA enhances the Network Controller's capacity to expedite supply restoration in outage scenarios.

Innovation is also a key focus, with TNB actively pursuing research and development initiatives aimed at enhancing equipment reliability to further mitigate SAIDI. Additionally, exploration into predictive analytics holds promise for proactively identifying potential faults, thereby contributing to sustained SAIDI reduction efforts. Please refer to Dimension 2 for detailed information on the proactive initiatives.