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.
1-2 The Components of Power Supply Reliability
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. Ancillary services in Taipower
In keeping with global trends, the R.O.C. government is making every effort to promote renewable energies. The Taiwan government amended the Electricity Act in 2017, setting a target of 20% of electricity from renewable energy, 50% of natural gas, and 27% of coal-fired power plants and other resources.
In order to integrate a large amount of renewable energies and remain the system’s stability and reliability, Taipower has adopted four different types of ancillary services, including Fast Response, Regulation, Spinning Reserve, and Supplemental Reserve to cope with the uncertainty, intermittence and uncontrollability of renewable energies.
The challenges of the new era should be solved with new technologies. Taipower plans to introduce nonconventional resources such as energy storage systems and demand response to increase system flexibility.
2-2 Ancillary services in Taipower
Beginning in April 2020, Taipower has implemented the "non-traditional generators providing spinning reserve ancillary services" mechanism and introduced external resources to help adjust the system frequency. By the end of 2020, a total of 33MW of aggregator, energy storage, and self-use power generation equipment have participated. They can respond quickly to services within 30 minutes and provide power support for the system for 60 minutes.
Taipower has purchased 30MW high-efficiency ancillary services in 2020: "Automatic Frequency Control (AFC) Ancillary Services for Energy Storage Systems". AFC ancillary services can assist the system to adjust the frequency in real time, maintain system stability and prevent the frequency from falling below 59.5Hz (normal state is 60Hz) causing under frequency load shedding (UFLS). Both cases are currently under construction and testing and are expected to be completed in June 2021.
The Ministry of Economic Affairs (electricity industry regulatory authority) is currently piloting a market mechanism to obtain various ancillary services required by the system. Taipower is cooperating with the "Key Points for Setting Up a Trial Platform for Ancillary Services and Reserve Capacity Trading" announced by the Ministry of Economic Affairs on December 24, 2020, to establish a pilot platform for the ancillary service market. This trial trading platform is expected to be launched in 2021.
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
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
When more than two feeders have fault occurred at the same time, we accelerate the accidental feeder trip 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 the digital relay is used on fault location system on transmission line. The fault ranging system platform calculates automatically to revise the fault ranging while the line fault is occurred. The calculated results can be sent directly to the newsletter. (Fig. 1), allowing specific personnel to obtain fault data in real time to facilitate field colleagues to find the actual location of the line fault. Meanwhile, with the combination of geographic data, the coordinate positioning is simultaneously displayed on the e- map, and the information of the fault zone is imaged (Fig. 2). It is convenient for inspectors to quickly find the fault point and improve inspection efficiency on transmission line.
Through the ranging of the digital relay, the distance measured by the two-terminal distance relay must be input at first, then calculate with the total line length obtained from lightning fault information system. The correction method of the fault location 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
Figure 2. The combination of fault information and geographic data
By inputting fault data to the lightning fault information system and combining geographic data with e- maps to indicate fault zone, the maintenance personnel are notified to find the fault location as soon as possible. In this way, it can improve the efficiency of maintenance inspection and troubleshooting and shortens the 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.
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) The recognition rate is as high as 90%, which 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 Power 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
Figure 1. The Planning and Design
8-2-2 Engineering Management
Figure 2. Comparison
In 2020, the number of automated feeders has reached 77.1%, and the number of covered users has reached 71.5%.
In 2020, the number of power recovery accidents in the downstream of the automated feeder within 5 minutes accounted for 25.2%, saving 23,901 hours of manual operation time. And 71,885 times of automatic line switch operations are performed remotely. Reducing the time for repair personnel to operate equipment on site can speed up the time of recurrence of accidents and 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
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.