1. Supply Reliability Index
Taipower company adopts the System Average Interruption Duration Index (SAIDI) and the System Average Interruption Frequency Index (SAIFI), which are commonly used in the international power industry. It is in compliance with IEEE 1366 std and the World Bank for SAIDI and SAIFI measures basic conditions.
SAIDI (min / household•year)
The System Average Interruption Duration Index (SAIDI) indicates the total duration of interruption for the average customer during a predefined period of time. It is commonly measured in minutes or hours of interruption.
SAIFI (times / household•year)
The System Average Interruption Frequency Index (SAIFI) indicates how often the average customer experiences a sustained interruption over a predefined period of time.
1-2 The Components of Power Supply Reliability
In recent years, the actual planned outage time accounts for about 70%~76% of the company's average power outage time.
In recent years, no warning accidents, force outages time accounts for about 24%~30% of the Taipower's average power outage time.
The Statistics for Power Outage Time (which is) more than 1 minute
If the customer interruptions is more than 1 minute, it will be counted in the statistics for SAIDI & SAIFI in Taipower company； however, if the time of customer interruption is more than 5 or 3 minutes, that will be counted in the statistics in most power companies. Thus, the requirements for reliability in Taipower is more stringent for current power companies standard.
2. Taiwan Electricity Trading Development
Taiwan power company (hereinafter referred to as “TPC”) has made it a priority to enhance the flexibility and resilience of the grid in order to achieve net-zero emissions. Firstly, in 2019, TPC launched Non-Conventional Power Resources Participating Ancillary Services on Electricity (NCPRS), a program for end-user to reduce load or use their own electricity generation equipment. This program successfully attracted more than 84MW of resources to participate, and these resources can be used as a conventional generation unit to provide spinning reserve for the Central Dispatch and Control Center (CDCC). Along with the establishment of the market operator of TPC and with the participation of the international power industry, the average executive rate of ancillary service provided by these resources are over 106%. This result can be seemed as the achievement of the LAAR (Load as a resource) goal.
In addition, TPC has also planned how to use energy storage system (ESS). In collaboration with domestic enterprises and ESS manufacturers, TPC has initiated the "Asia's first" AFC project to procure 15MW ESS resources providing frequency regulation services. These AFC ESS resources can automatically follow the frequency variation and can adjust its output/input within 1 second. The functionality of AFC ESS resources has been proved during the blackout incident happened in 2021, which means that they have the capacity to prevent the power grid contingency.
Based on the success of the AFC project mentioned above, Taiwanese government has drafted a formal regulation conce
rning the “Energy Trading Platform” which instructed TPC to establish a " Energy Trading Platform "(ETP) in July 2021. Nowadays, along with the participation of the utility generation enterprise, TPC has successfully recruit dozens of enterprises to participate in the ETP. TPC also created the role of QSE which ask participants of ETP to pass the ETP Proficiency test, and there has been more than thousands of people passed this test. The capacity of resources which has registered to ETP has over than 170MW until the end of January 2022.
TPC expects also to create a new trading product in July 2022 for long-term ESS and expects to implement 1,000MW ESS in 2025. It is expected to provide smoothing and load-shifting services to the grid.
Along with the energy transition goal in 2025, it is expected to obtain more than 3,900MW power resources with various types through ETP. TPC also plans to further open the intraday imbalance energy market. With the participation of these dispatchable power resources, Taiwanese power grid can be one of the most sustainable and robust grids in the world, which can also bring greater confidence in the path to achieve net-zero emission goal.
(Currently, the types of decentralized power resources acquired include ESSs, electric vehicle charging stations, telecommunication equipment rooms, self-generating equipment, cogeneration, demand response from industrial or domestic users, etc.)
3. The Building and Application of IEC 61850
At present, nearly 90% of the substation automation monitoring architecture adopt remote terminal units (RTUs), and most of the power meters, IEDs and RTUs use communication protocol DNP3.0. The monitoring architecture of the other substations adopt Local SCADA and gateway. The communication protocols between the gateways and IEDs are different (Modbus, DNP, LON, Profibus, etc.). The main function of these two substation automation methods is updating the real-time operation information in substation to the control center for dispatching (vertical communication), while the information cannot be exchanged horizontally between substations.
The full name of the IEC 61850 standard is "Communication networks and systems for power utility automation." The latest version, Edition 2, is an internationally accepted power automation standard that conforms to the future development trend of smart grids. Its main purpose is to provide the interoperability between different brands of IEDs.
3-2 The Building and Application of IEC 61850
In addition, the substation automation following the IEC 61850 monitoring architecture (shown as Figures 1) is also beneficial for the improvement of the reliability of power supply. This architecture provides a platform for horizontal communication (GOOSE) of automated equipment in the substation, enabling various equipment that enables to complete the application scenario of protection and operation in power system.
Figure 1. The architecture of IEC 61850
The application of smart grids in the field of power transmission and transformation is mainly on the construction of substation automation based on the internationally accepted IEC 61850 standard. Intelligent electronic devices (IED) are the basic elements of digital automation substations, providing the protection, measurement, control and communication functions required by the system, and the GOOSE function which transmit events fast is used to transmit important instantaneous command signals between multiple IEDs. For this reason, the digital network communication is the substitute for the hard-wired control loop between traditional devices to achieve IEDs interoperability. In order to solve the problem of protection coordination difficulty caused by the simultaneous failure of the common feeders, which caused cross-zone tripping, the GOOSE information can be used to detect the IED trip protection logic to speed up feeder tripping, which strengthen the protection coordination between upstream IEDs and downstream IEDs, speed up the IED tripping on fault feeder to isolate the fault and reduce the scope of power failure.
Taking the 11.95kV BUS devices in Figure 2 as an example, there are MCB, CB1, CB2, CB3, and CB4, five circuit breakers. Among them, the CB1, CB2, CB3, and CB4 are feeder circuit breakers, and their IEDs planning GOOSE command accelerates CB tripping.
Figures 2. Application of GOOSE
MMS is another service and protocol of IEC 61850. It contains two operating modes(shown as Figures 3). In one operating mode, the MMS client (generally the SCADA or the gateway) sends a request for a specific data item to the MMS server of an IED, identified by its IP address. The server returns the requested data in a response message to the IP address of the client. In another mode, the client can instruct the server to send a notification spontaneously upon occurrence of an event.
Figures 3. MMS protocol time/distance chart
For example, the SCADA system can send a control command to the IED. After the IED receives the control command and completes the command action, it will send the message back to the SCADA system. In addition, when an accident occurs, the IED can also send messages to the SCADA system immediately.
3-3 Taipower IEC 61850 Training Center
3-3-1 Build purpose
Cooperate with the company policies regarding the establishment of smart grids, realizing smart substations, promote the introduction of new automated monitoring architecture of the IEC 61850 standard, achieve standardization and unification, and establish the relevant knowledge and core maintenance capabilities of on-site maintenance personnel. Establish a training environment for equivalent protection, monitoring, measurement, and control substation automation equipment.
3-3-1-1 Environment introduction
The IEC 61850 education and training venue was built in the Kaohsiung Training Center, the classroom is constructed with an elevated floor configuration, a teaching demonstration area and six teaching practice areas are built above the elevated floor to simulate the operation of the substation and provide students with a realistic IEC 61850 learning environment. The configuration diagram is as follows:
Figure 4. Schematic diagram of the classroom in the Kaohsiung Training Center
3-3-1-2 System introduction
In the Education and Training System (ETS) architecture, the hardware of the network switch is a multiple-connection architecture. All devices are connected to the Station Bus using a parallel redundancy mechanism PRP (Parallel Redundancy Protocol) architecture. The Communication uses IEC 61850-8-1 for high-speed point-to-point GOOSE messaging exchange and client-server MMS communication. In addition, the control software is based on the Elipse Power edit version, while the SCT is based on the Grid Software SCL Matrix suite.
Taipower refers to the SCL Testing content in the International Interoperability Test (IOP Test) and selects Test Case: Top Down-Interoperability between SCT and ICT of Bay Level IED as the planning method for each IED in this verification. The main purpose is to test the interoperability between planning tools. Therefore, there are 3 sets of IEDs built-in each cabinet that pass the IOP Test, which are provided for ABB-REF620, SIEMENS-7SJ82 and INGETEAM-DAPT1 to provide Taipower employees with practice operations. Refer to Figure 5 for the simple system architecture in the cabinet.
Figure 5. Simple system architecture in the cabinet
3-3-1-3 Multiple applications
Because the hardware and software equipment provided by the classroom are all products that have passed the IOP test. In addition to being used as a teaching venue for IEC 61850 personnel training, the training classroom can also be used as a venue for IEC 61850 integration tests or simulation tests.
At present, major power users in Taiwan have successfully updated their substations to the IEC 61850 system architecture. In addition to providing internal training, the training classrooms can be considered as a venue for technical exchanges and seminars with private companies.
3-3-2 Framework for future expansion
Combine the existing IEC 61850 education and training classrooms with Taipower’s primary substation equipment decoration site. To Establish a practice field for the concept of power grid architecture, simulate the actual substation failure situation, and cooperate with the related software and hardware equipment of the Gateway to achieve the function of simulating the master station, and add more IEDs in the interoperability test qualified list to improve colleagues Adaptability to facilitate future skill competition projects. As shown in Figure 6
Figure 6. Future expansion framework
3-3-2-1 Information security demo
In order to improve the information security protection measures of smart substations, Taipower assesses the information security risks of industrial control systems, and refers to various information security protection measures and certification schemes based on the IEC 62443 industrial control information security standards, and establishes appropriate information security protection measures for this case. The framework adds firewalls and information security analysis tools to filter potential threats and monitor network traffic to help the company improve the robustness of the smart grid and maintain the safe operation of the grid. As shown in Figure 7
Figure 7. Information Security Architecture of Kaohsiung Training Center
With the IEC 61850 MMS and GOOSE protocol, the communication mode of the devices in the substation can be made smarter, and devices from different manufacturers can also communicate with each other. Finally, the goal of substation automation will be achieved.
4. Transformers Condition Monitoring
Base on power supply dispatch’s substation maintenance manual, TPRI’s oil test will be done every year unless fault or abnormal situation of transformer happens. It is impossible to know the internal fault situation of the transformer in advance if we cannot obtain the gas content of the oil in the transformer and the operating status of the equipment timely. Current DGA(Dissolved gas analysis, DGA) shows the total amount of gas, it is hard to know exactly the amount of each gas, and the high number of abnormalities and expensive maintenance makes it not economical.
4-2 Transformers Condition Monitoring
To ensure the operation safety and prevent preventive maintenance, power supply dispatch must install DGA, current combustible gas detection device replaced from total type to component type. It can obtain the content of gas components (H2, CO, water content) in the oil and alarm information, and judge the health of the internal operation of the transformer through each gas trend chart as the basis for CBM. It is expected that the effectiveness of the staff can be increase, equipment failure and blackout time can be decrease and ensure stable power supply.
Besides DGA, planning of existing transformer oil gas monitoring, transformer equipment asset management, and artificial intelligence AI applied to the transformer operation and maintenance strategy expert system for horizontal information integration and database interface to further master the transformer operation situation. If the abnormal situation of transformer is analyzed correctly, power outage maintenance can be arranged in time to avoid unforeseen power outages caused by accident.
Figure. DGA Monitoring System
5. Application of Fault Location System on Transmission Line to Improve Inspection Efficiency
The positioning function of digital relay is used on the Transmission Fault Location System (Fig. 1) to obtain the fault distance when the fault occurs. Then, the distance is automatically calculated and corrected through the length of the transmission line set in the ledger data of the Transmission Facility Maintenance Management System. The distance is estimated to be an interval in which the fault occurred. At the same time, combined with GIS geographic map data, it will be displayed on the electronic map in the form of coordinate positioning (Fig. 2), supplemented by navigation and Google Street View functions, to quickly determine the topography of the line location, which is convenient for maintenance personnel to quickly detect faults with the help of drones to improve the efficiency of fault investigation and repair.
By inputting the distance measured by the two-terminal distance measuring station, and then calculating with the total length of the line set in the Transmission Facility Maintenance Management System, the correction method of the fault point is as follows:
TOTAL：Total fault indication distances at both ends of the line (km)
FA：A-end distance after correction (km)
FB：B-end distance after correction (km)
OA：A-end original fault indication distance (km)
OB：B-end original fault indication distance (km)
DST=The total length of transmission line(km)
Figure 1.Fault Location System
igure 2. The combination of fault information and geographic data
The fault information is input through the Transmission Fault Location System, combined with the geographic map to mark the fault zone on the electronic map, and notify the maintenance personnel to find the fault point as soon as possible. It not only improves the efficiency of maintenance inspection and troubleshooting, but also shortens the power outage time.
6. The Big Data and AI Analysis of Circuit Breaker Operating Time
In 2014, our company developed and built an online query system for circuit breaker operating time. The operating time information of circuit breaker is recorded by the monitoring system of the dispatching center, which is used to establish a database of operating time data, and the status of circuit breaker can be effectively found through webpage. Substation is the main core of power grid, while building smart substation is an important process to make the grid smarter. In order to improve the quality of power supply meanwhile elevate the power system’s reliability and stability, substation automation and information digitalization are main task that we need to rely. By expanding the concept, Circuit Breaker Operating Time Online Query System will make a great improve on smart grid.
6-2 AI Analysis
In response to current smart grid trend, our company also introduces the concept of Artificial Intelligence. By building a big data analysis model and analyzing the characteristics of the circuit breaker operating time, we can predict the normal circuit breaker operating time, and filters out a list of high-risk circuit breakers regularly sent to local colleagues. With the help of this warning, local colleagues can arrange maintenance, reaching preventive maintenance, reducing the possibility of power outages, and make the public feel that power supply is stable.
6-3 Historical Trend Analysis
Not only importing the concept of Artificial Intelligence, but also use its own median as the benchmark for historical trends. From the historical trend curve, we can know whether the operating mechanism of the equipment is abnormal. Plan outage schedules for abnormal equipment and clean and lubricate operating mechanisms.
The system not only can reach preventive maintenance, but also makes the maintenance mode transfer from Time-based Maintenance (TBM) to Condition-based Maintenance (CBM). Related information can provide reference for decision-making in asset management and risk management as well.
7. Smart Inspection-UAV Application
Through the rapid development of communication technology in recent years, the unmanned aerial vehicle (UAV, as called drone) has gradually matured. Power Supply Department of TPC tried to use drone to assist the inspection work, and successfully found the fault location of the tower on the river bed. As the technology became more mature, the works of the tower foundation monitoring, line inspection, finding fault location, and tower corrosion investigation are implemented. Especially the extreme climatic in recent year, there’s more nature disasters. After wind, rainstorms or road landslides, vehicles could not be reached, so the location of faults on transmission line were found with assistance of drones. In addition, the types of occupational disasters for overhead transmission line operations are mainly "falling" and "inductive". With the assistance of the drones, this type of disasters can also be reduced.
7-2 Smart Inspection
Most of Taiwan’s overhead transmission line towers are located on the middle of high mountains or river catchment areas. Traditional inspections mostly rely on manpower. Currently, TPC is actively promoting the transformation of UAV smart inspections and commissioned Microsoft Corporation to develop an AI image recognition system, combined with UAVs to do the work. Smart inspection can improve the visual blind spots of traditional manpower limited by terrain and environment in one fell swoop, and improve inspection efficiency.
After carrying out drone aerial photography through a licensed pilot, the video of the fault location will be sent back to the cloud for data processing. The professionals will perform manual annotation and model training for abnormalities such as obstacle flashover, damage, and iron corrosion, and establish artificial intelligence abnormalities image recognition model. It will be used to assist in the abnormal detection of related transmission equipment. (Fig. 1) It effectively improves the efficiency of transmission line operation and maintenance, and improves the stability and reliability of the power system.
Figure 1. AI Image Recognition System for Equipment of Transmission System
Due to the rapid development of information in recent years, the transmission of messages requires fast and accuracy. Traditional line inspection is often limited by terrain, environment factor etc. By the assistant of drones for line inspection, the efficiency and effectiveness of inspection can be improved, also it can improve the quality of inspections.
"Smart inspection" is the future and ongoing type of transmission line inspection. The complete fleet management and operation manpower training establishes the foundation. New technologies are successively introduced to make the inspections more accurate and reliable, and the weaknesses can be detected efficiently to improve stability of power supply.
8. Accelerating the automation of distribution feeders
To cooperate with the overall project of the smart grid plan, we continue promoting the feeder automation projects of the distribution system, with the goal of gradually including all users into the automated feeder, further improving the automation benefits of distribution feeders and increasing the reliability of power supply. The department of Distribution has continued to strengthen the handling and rolling review of the following aspects.
8-2 Actual Action
8-2-1 The Planning and Design
Installation of automatic circuit breakers on divergent small loops:
In addition to the deployment of automatic circuit switches on distribution feeder trunks, the implementation of the installation of automatic circuit switches on divergent small loops in metropolitan areas such as Taipei, Taichung, and Kaohsiung is included and monitored. Depending on the automation benefits of the divergent small loops implemented in the metropolitan area, the deployment area will be expanded to reduce the power outage range and time for resumption of divergent lines.
Figure 1. Incorporate automation switches into monitoring
8-3 Engineering Management
Accelerated completion of bidding announcements:
We claim the branch office that handles the annual project of feeder automation shall complete the bidding announcement before the end of the previous year and including the time of the project bidding announcement into the operation performance index scoring items of each branch business office.
Regularly fill in the progress of management and control tracking:
The branch office regularly fills in reports such as “Bi-weekly Management Report before Signing the Contract”, “Monthly Report on Construction and Management of Distribution Feeder Automation Engineering” and “Monthly Report on Implementation of Control and Management of Distribution Feeder Automation Project” to facilitate tracking and manage.
Keep tracking and control of cooperative projects:
When coordination projects and pre-operations are hindered or delayed, a coordination meeting or other ways would be held to notify relevant departments to assist the branch office.
Statistics until 2021, the department of Distribution has deployed 7,969 automated feeders, and accounting for 78.6% of the total feeders. The proportion of “Number of accidents with downstream power restoration within 5 minutes ” in 2021 accounted for 45%, it accelerates the accident recovery time significantly.
Figure 2. The Proportion of the number of automated feeder
Figure 3. The proportion of “Number of accidents with downstream power restoration within 5 minutes”
Compared to traditional field operations, 88,061 times of automatic line switch operations at work are performed remotely. And saving 29,353 hours of manual operation time. Reducing the time for personnel to operate equipment on site. Furthermore, it can improve the safety of personnel at work.
9. The Improvements to Reduce Power Blackout Time
With the changes of the times, the living standards of the people are improving, and the customers are increasingly demanding the quality of the services provided by Taipower company. In order to effectively reduce the time of power outages and improve the reliability of power supply, the department of Distribution has reviewed and continued the following aspects:
9-2 Actual Action
9-2-1 The Planning and Design
Planning and designing the power distribution line system as a loop-type method, and adding switches to isolate and change power transmission way that reduce the scope of power outages when the construction or maintenance operations are proceeded in the future
Before designing a case, the designers consider the factors, such as the site environment and the conditions of the power distribution line equipment, to plan the optimal design to reduce the construction projects with power outage (e.g., live line operations or high-voltage parallel transfer operations).
9-2-2 The Construction
Before the construction of the project, we review the methods of the case and prioritize the work without power outages, and send personnel to survey the site in advance to check whether the information about the relevant equipment is correct or not that eliminates all factors that affect the construction, and plan a suitable work schedule to shorten working hours and reduce the area of impacted users.
Before arranging the power outages works, review and address the cases with the same power outage scopes and implement controlling them to reduce the number of power failure. In addition, according to the content of the case, properly plan the operation process and deploy appropriate constructers and equipment to complete within the planned time.
9-2-3 The Technique
Continue referring to the foreign construction technologies and improve various construction methods, and gradually promote non-blackout construction operations to reduce the time and the number of power outages works under the premise of ensuring safety at work.
The construction projects that have been implemented without power outages include "live line operations", "high-voltage parallel transfer operations" and "temporary transformer operations". The construction department can choose the appropriate operation way according to the content of the case and considering the site environment and system to reduce the time and number of power outages.
Figure 1. temporary transformer operations
9-2-4 The Distribution lines
Covering the overhead bare lines:
Since 1999, the overhead bare aluminum wires have been gradually replaced with cross-linked PE covered wires, and the equipment such as terminal cable clamps and wiring rings have been continuously developed to reduce the chance of overhead lines being touched by something and effectively prevent people from touching high-voltage lines.
Figure 2. Covered terminal cable clamps / Figure 3. Covered wiring rings
Covering the line switches:
The single-phase switches are all exposed, which easily lead to feeder tripping caused by something likes birds, beasts, trees, etc. Therefore, the three-phase connected dynamic load on-off switch has been developed to completely cover the charged parts.
Figure 4. single-phase switches (left one) and the three-phase connected dynamic load on-off switch (right one)
Improved exposed weaknesses in overhead equipment:
In order to reduce the damage of overhead lines caused by wind disasters and the contact of birds, animals and trees, etc., we gradually develop the equipment to improve the exposed parts of transformers and power fuses, and pursue the full-covered the power distribution lines in the future.
In summary, the improvement measures implemented by Taipower will effectively reduce power blackout time.