The microcomputer relay protection tester is developed using modern electronic information technology, high-precision electronic components, microcomputer system software, new circuits, and new structures. It can independently perform equipment testing in professional technical industries such as microcomputer protection, relay protection devices, excitation regulators, metrological verification, and common fault recording. It is widely used in scientific research, production, and on-site testing of electrical equipment in manufacturing industries such as power engineering, petrochemical, metallurgy, railway, aviation, and national defense.
Introduction to the 4 protections of relay protection devices:
1. Current Protection Device
A protection device composed based on the characteristic that the current of a faulty line significantly increases is called a current protection device. When the current of the line fault detector exceeds the protection setting value (starting current), the current protection device operates immediately. When the time exceeds the de-excitation value, it trips the line circuit breaker. Current protection is generally divided into: instantaneous current protection, overcurrent protection, and directional current protection.
1. Instantaneous current protection: Its advantages are simple equipment, reliability, and fast action, but it can only protect a part of the line.
2. Time-delayed instantaneous current protection: Refers to a protection device with a short operating time limit, which can not only protect the entire length of the line but also extend to the instantaneous protection of the next-level line as a backup.
3. Overcurrent protection: Refers to a protection device whose starting current is set to avoid the maximum load current for de-excitation. It can protect not only the entire length of the line but also the entire length of the next-level line, and can serve as backup protection for the line.
4. Directional current protection: That is, on the basis of overcurrent protection, a power direction discrimination component is added. When the short-circuit power direction flows from the busbar into the line, the component operates; otherwise, it does not operate, thereby preventing misoperation during reverse faults.
2. Distance Protection Device
A protection device that can reflect the distance (impedance) between the fault point and the installation location of the protection. It has good selectivity and is widely used in ring network lines with higher voltage levels. Currently, three-stage distance protection is commonly used, namely distance sections I, II, and III.
Distance section I: Instantaneous action. Protects 80%-85% of the total length of the line.
Distance section II: Protects the entire length of the line and section I of the next line.
Distance section III: Protects the entire length of the line and the next line, serving as backup protection.
3. Zero-sequence protection: In a three-phase AC power system, when a ground fault occurs, a zero-sequence current and zero-sequence voltage appear. These electrical quantities are used to form protection devices, which are called zero-sequence protection. It is mainly used for ground fault protection in neutral point directly grounded systems.
4. Differential protection
Differential protection is a protection device that compares the current at the beginning and end of the protected component. When the difference between the two currents exceeds the setting value, it operates. It is mainly used for short-circuit protection of transformers, generators, motors, and busbars.
The above is an introduction to the 4 protection devices of the microcomputer relay protection tester. I hope it helps you understand the product better.
