Power Supply Systems and Their Guardians: Ensuring Safe and Reliable Energy

The transmission, distribution, and control equipment covers various aspects of the power system

The power system is a complex system that produces and provides electrical energy to meet societal power demands, consisting of generation, transformation, transmission, distribution, and consumption stages. Power plants convert various forms of energy into electrical energy using generation equipment. This electrical energy is then stepped up to appropriate voltage levels at substations for transmission and subsequently stepped down for distribution through the power grid to the final electricity users, completing the entire process from production to consumption.

The transmission network is the main network in the power system, responsible for delivering electrical energy from power plants to load centers and enabling energy transfer between different grids. The distribution network operates within a supply area to distribute electrical energy directly to users. Substations are involved in voltage level transformation and the redistribution of electrical energy. In long-distance transmission, higher voltage results in lower current and reduced losses, so the primary purpose of voltage transformation is to minimize losses.

The power system can be divided into primary and secondary systems based on the different functions and roles played by various devices that make up the system.

The primary system includes equipment such as generators, transformers, transmission lines, and switches, which are capable of completing tasks like power generation, transmission, and distribution. These devices are referred to as "primary equipment."

The secondary system primarily consists of various relay protection devices, automatic control devices, automation terminal equipment, substation automation systems, distribution automation systems, and communication systems. These devices are generally referred to as "secondary equipment." The secondary equipment mainly performs tasks such as fault protection, operational control, and monitoring of the primary equipment, thereby ensuring the safe and stable operation of the entire power system.

Protection Relay is an important guardian for ensuring the safety of the power system

In the operation of a power system, various electrical devices may experience faults or abnormal operating conditions. If not addressed promptly, these issues can lead to accidents. When an incident occurs in the power system, it not only affects normal power supply but can also cause damage to electrical equipment and pose risks to personal safety. To prevent such accidents, protection relays were developed. Protection relay devices are automatic systems that can detect faults or abnormal operating conditions in electrical components of the power system and respond by tripping circuit breakers or issuing signals.

The role of protection relay

1. Fault Isolation: Automatically, quickly, and selectively isolates faulty components from the power system, preventing further damage to the faulty elements and ensuring the unaffected parts of the system quickly return to normal operation.

2. Response to Abnormal Operating Conditions: Detects abnormal operating conditions of electrical components and, based on operational and maintenance requirements, either triggers an alarm or initiates a delayed trip action to isolate the fault.

Basic Requirements of Protection Relay:

1. Selectivity: Selectivity means that when relay protection operates, only the faulty component or line is isolated from the power system, allowing the fault-free parts of the system to continue operating. Selectivity ensures that the protection operates only in the fault zone, and does not trip outside the fault zone. If the main protection does not operate, the fault is cleared by nearby or remote backup protection, minimizing the area affected by the power outage.

2. Speed: Speed refers to the ability of relay protection to operate as quickly as possible, within allowable limits, to trip the circuit breaker and isolate the faulty component or line. The benefits of rapid fault isolation include:

• Improved system stability.

• Reduced operation time of the system under low voltage conditions.

• Reduced damage to faulty components and prevention of further expansion of the fault.

The typical operation time for fast protection is between 0.06 and 0.12 seconds, with the fastest being 0.01 to 0.04 seconds.

The typical operation time for a circuit breaker is between 0.06 and 0.15 seconds, with the fastest being 0.02 to 0.06 seconds.

The fastest fault isolation time is 0.03 to 0.1 seconds.

3. Sensitivity: Sensitivity refers to the ability of relay protection to respond to faults and abnormal operating conditions within the design protection range. Sensitivity generally means that under the most adverse conditions, the protection device should respond to faults by activating overload protection (e.g., current protection) for rising values and underload protection (e.g., voltage protection) for falling values.

4. Reliability: Reliability is the most fundamental performance requirement for power system relay protection, ensuring that the protection operates when it should and does not operate when it should not. Reliability is influenced by both internal and external factors:

• Internal factors: The quality of the device itself, including the quality of components, the rationality of the structural design, the level of manufacturing processes, and the simplicity of internal and external wiring and contact points.

• External factors: The level of operation and maintenance, and whether the installation and commissioning are correct.

How Protection Relay Testers Keep Electrical Systems in Check

As protection relay plays a crucial role in safeguarding electrical safety, the protection relay tester, as an important power testing device, plays a vital role in fault diagnosis, testing, and debugging of protection devices within power systems.

Working Principle of the Protection Relay Tester

A protection relay tester is a device used to simulate various faults and operating conditions in a power system to test and verify the performance of protection devices. It can simulate fault scenarios such as short circuits, overloads, overvoltage, undervoltage, and more, in order to assess the protection device's operational performance and reliability. This ensures that the protection devices can correctly respond to faults in the power system, isolate the fault, and maintain the safe and stable operation of the power system.

The working principle of a protection relay tester is based on the mathematical model of the power system and fault characteristic analysis. It generates various simulated signals, such as current, voltage, and frequency, and applies them to the protection device under test. At the same time, it collects the action signals and response parameters from the protection device for analysis and evaluation. Based on the protection device's operational logic and setting values, the tester determines whether the protection device operates correctly and meets the power system's protection requirements.

Technical Specifications of Protection Relay Testers

1. Accuracy and Stability of Output Quantities: This includes the accuracy and stability of electrical quantities such as current, voltage, and frequency, which directly affect the accuracy of the test results.

2. Output Range: The tester should cover the operating range of the protection devices being tested, to meet the testing requirements of various types of protection devices.

3. Testing Speed and Response Time: The tester should have fast testing speeds and response times to simulate the transient processes in the power system.

4. Human-Machine Interface and Ease of Operation: The tester should feature a user-friendly interface and simple, easy-to-use operation, allowing operators to conduct tests and process data conveniently.

5. Communication Interfaces and Data Storage: The tester should be equipped with standard communication interfaces and large-capacity data storage functions, facilitating data exchange with other devices and data recording.

Development Trends of Protection Relay Testers

1. Intelligence: With the continuous advancement of artificial intelligence technologies, protection relay testers will become increasingly intelligent, featuring adaptive testing, fault diagnosis, and prediction functions.

2. Multifunctionality: Protection relay testers will gradually evolve towards multifunctionality, offering testing capabilities for various protection functions, such as line protection, transformer protection, and generator protection, to meet the testing needs of different types of power equipment.

3. Networking: As power systems become more networked and information-driven, protection relay testers will increasingly integrate network capabilities, supporting remote monitoring and data transmission, enabling remote testing and fault diagnosis.

4. High Precision: As power systems demand higher precision in protection devices, protection relay testers will continually improve the accuracy and stability of output quantities to meet the high-precision protection requirements of the power system.

With the growth of the global population, increasing incomes, and the rise in electrified end-users, global electricity demand is expected to grow rapidly across all scenarios in the future. Ensuring that electricity demands are met while safeguarding electrical safety is of paramount importance. The development of both primary and secondary equipment presents a wealth of opportunities and challenges. As power systems continue to evolve, the need for advanced technologies that enhance reliability, efficiency, and protection grows ever more critical. This dynamic landscape not only drives innovation in power generation and distribution but also requires continuous improvements in protection mechanisms to secure the stability and safety of global energy networks.