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 fields 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 electrical equipment testing in industries such as electric 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 formed by utilizing the characteristic that the current of a faulty line increases significantly is called a current protection device. When the current of the line fault detector exceeds the maintenance setting value (starting current), the current protection device operates immediately. When the time exceeds the demagnetization value, it trips the line circuit breaker. Current protection is generally divided into: instantaneous overcurrent protection, overcurrent protection, and directional overcurrent protection.
1. Instantaneous overcurrent protection: Its advantages are simple equipment, reliability, and fast action, but it can only protect part of the line.
2. Time-delayed overcurrent protection: Refers to a protection device with a short action 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 supplement.
3. Overcurrent protection: Refers to a protection device whose starting current is set to avoid the maximum load current for demagnetization. It can protect not only the entire length of the line but also the entire length of the next-level line. It can serve as backup protection for the line.
4. Directional overcurrent 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, 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 on high-voltage ring network lines. 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 entire length of the next line, serving as backup protection for sections I and II.
3. Zero-Sequence Protection Device
A protection device that reflects the characteristics of zero-sequence current, zero-sequence voltage, and zero-sequence power when a ground fault occurs in a grounded neutral system. It is mainly used for ground fault protection in power systems.
4. Differential Protection Device
A protection device that compares the current at both ends of the protected component (or the current at each branch) to determine internal or external faults. It has high sensitivity and selectivity and is widely used for the protection of transformers, generators, busbars, and other important equipment.
