AbstractThis article introduces the configuration and application of arc protection in hydropower stations, providing references for relevant personnel.
Keywords:Hydropower Station; Switchgear; Arc Light
0 Preface
Arc light is formed by air ionization during phase-to-phase or ground faults. Arc fault incidents within switchgear are not uncommon in our country's power system, and once an arc fault occurs, it can cause significant damage to both personnel and equipment.
The export busbar switchgear for hydro-turbine generating sets is a crucial transmission hub for hydropower stations. The ability to quickly isolate internal faults is vital for the power station's production. Since the national standard "Design Code for Relay Protection and Automatic Equipment of Electric Power Installations" (GB50062) and the current regulations in the electric power industry do not specify the protection for 6KV (10KV) busbars, hydropower stations generally do not have dedicated fast busbar protection. Given the current status of busbar protection configuration in hydropower stations, it is highly necessary to add fast protection. Some domestic experts have also consistently emphasized the importance of installing dedicated medium and low-pressure busbar protection, and users hope for a cost-effective, simple-principle busbar protection suitable for 6-35KV that can minimize the damage to equipment from busbar faults and enhance transmission reliability.
The Necessity of Arc Fault Protection Configuration
In power systems, busbars rated at 35kV and below typically do not require busbar protection due to the absence of stability issues. However, due to the numerous outgoing lines on medium and low-voltage busbars and their frequent operations, the distance between the three-phase conductor lines and the ground is relatively close, making them susceptible to damage from small animals. The manufacturing quality of these busbars is also inferior to that of high-voltage equipment, and issues such as insulation aging and mechanical wear, along with harsh operating conditions, system changes, and human errors, significantly increase the likelihood of faults on medium and low-voltage busbars compared to high-voltage and medium-voltage busbars. However, for a long time, insufficient attention has been given to the protection of medium and low-voltage busbars, and no advanced and reasonable solutions have been identified. Consequently, most installations rely on backup protection with significant delays to isolate faults on busbars, often allowing the faults to escalate and cause substantial economic losses. The primary reason for this is the lack of medium and low-voltage busbar protection, which prevents the rapid isolation of faults. Therefore, to ensure the operation of transformers and busbar switchgear, and in accordance with the requirements for relay protection speed, there is an urgent need to configure dedicated medium and low-voltage busbar protection.
In this scenario, arc light protection has emerged as an ideal choice for low and medium voltage busbar protection among a wide range of hydropower plant users. The dedicated busbar arc light protection not only operates swiftly and reliably but also offers a price advantage compared to other dedicated busbar protections.
China began using imported busbar arc protection in 2004, and currently, the power system, particularly the power generation system,
Approximately 70-80% of new power plants have implemented dedicated busbar arc protection.
The Benefits of Using Dedicated Busbar Arc Fault Protection
Due to the photometric arc protection system measuring light and electricity as two completely different physical parameters, the dual criterion action principle using light signals and fault current signals ensures its false operation rate is significantly lower than that of other primary protections in the system (including generators, transformers, and lines). This not only guarantees the safe operation of high-voltage cabinets but also ensures the normal production of the power station.
The use of dedicated busbar arc fault protection offers several advantages:
1) Protect nearby staff from the harm of electric arc to the human body.
2) Protect medium and low-pressure equipment from severe damage and prevent fires from occurring.
3) Protect the main transformer or on-site transformer from severe shock damage.
4) Prevent the spread to the station's DC system to avoid significant economic losses.
5) Minimize user downtime to a few hours (reducing the power restoration time from 2-3 weeks to a few hours).
6) Extend the lifespan of existing switchgear.
Arc Flash Protection System Configuration for Hydropower Stations
3.1 Arc Light Protection System Configuration
Arc Light Protection Systems typically consist of a main unit, an expansion unit, and an arc light sensor. Thanks to the arc light sensor detecting arc light and outputting a circuit breaker trip signal through a high-speed solid-state interface, the system's response time from detecting the arc light to emitting the trip signal is no more than 7 milliseconds.
Arc Light System Protection Mechanism: Upon detecting a bus arc fault, the sensor sends the arc light signal to the expansion unit, which then transmits the signal to the main unit via the bus. Upon receiving the signal, the main unit sends a tripping signal to the circuit breaker, thus interrupting the incoming circuit breaker and halting the arc's progression.
When the sensor detects an arc fault in the cable room, the expansion unit can directly trip the circuit breaker in the cabinet without affecting the incoming line.
3.2 Electrical Principle Scheme
1) Under normal circumstances, the equipment self-check and arc sensor self-check are functioning. If an arc fault is detected, it provides arc fault information. Additionally, if an equipment fault occurs, it will lock the circuit breaker trip output to prevent false operation. This signal can be output from an alarm node to an alarm busbar or signal acquisition device.
2) Due to an issue, busbars produced an arc light. Upon detecting the arc, the arc light sensor in the corresponding busbar room uploaded the signal to the expansion unit.
3) In the case of segmented bus operation, each main unit compares the current signal it collects with the arc signal received. If both the arc and current meet the criteria, an arc has occurred on this section of the bus, triggering a trip signal. The circuit breaker for this section of the incoming line trips, extinguishing the arc, and simultaneously providing a trip signal.
4) In the event of an arc fault in the cable room, the corresponding extension unit will activate, tripping the corresponding circuit breaker in the cabinet.
5) In single-line operation with busbars I and II, the master units of each busbar immediately synchronize and forward the arc signal to another master unit upon receiving it. If the master unit of the working line receives an arc signal (either from this section or forwarded by another master unit) and the current meets the conditions, a trip signal is issued to open the section circuit breaker, extinguishing the arc. Simultaneously, an inter-trip signal is provided, ensuring the normal operation of other busbars.
6) Failure Protection: In the event of a failure in the main busbar circuit breaker, the failure protection is triggered to bypass the low-voltage side incoming line; if the low-voltage side incoming line fails, the failure protection is activated to bypass the high-voltage side circuit breaker.
7) If the main units of any section busbars are taken out of service, the arc protection for that section will be disabled.
AnkoRi ARB5-M Arc Flash Protection Product Selection Guide
ARB5 - Arc Control Unit
*(1) * indicates an optional attachment, which will incur an additional fee of 1500 RMB.
(2) The total number of masterboards and acquisition boards cannot exceed 4.
The length from the arc probe to the collection board cannot exceed 20 meters.
(4) Please specify any special requirements.
Ankorri ARB5-M Arc Flash Protection Product - Features and Technical Specifications
6 Ankorui ARB5-M Arc Protection Product Field Installation
Arc Light Protection Master Control Unit and Probe Installation Diagrams are as follows.
7 Closing Remarks
As research and understanding of arc fault incidents deepen, many hydropower stations have begun to implement arc fault protection systems. Stations such as our company's Shuikaka Hydropower Station and Saduo Hydropower Station's 10kV high-voltage switchgear are equipped with arc fault protection.
We recommend adding an arc light protection system to the 35kV and below busbars as the primary bus protection, to compensate for the current technical defect of only having busbar backup protection. Reduce or avoid personal injuries caused by arc light faults inside the switchgear, and enhance productivity: minimize the losses to key equipment like switches and transformers, allowing for a quick resumption of production; and provide necessary safeguards for the "unmanned operation, minimal staffing" production model of the hydropower station.
Reference:
- Xia Yan, Zheng Xianwu. Configuration Research of Arc Protection System for Hydropower Stations[J].
- Cai Bin, Chen Degui, Li Zhipeng. Simulation and Experiment on Internal Arc Fault in Switchgear (English) [J]. Journal of Electrical Engineering Technology, 2004(03).
Yang Jianhong, Zhang Rencheng, Fang Huaiying. Fault Arc Short-Circuit Monitoring System Based on Duffing Oscillator Signal Detection [J]. Electrician and Electric Power Technology, 2007(01).
Dong Aihua, Gu Bin. Development Trends of Low-Voltage Distribution Switch Arc Fault Detection Technology [A]; Proceedings of the 9th Academic Conference on Full Circular Information Acquisition and Processing [C]. 2011.
[5] AnkoRe Enterprise Microgrid Design and Application Handbook, 2022.5 Edition.
