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 electric power engineering, petrochemical, metallurgy, railway, aviation, and national defense.
Introduction to the 4 protections of relay protection devices:
1. Current Protection
A protection device composed based on the characteristic that the current of a faulty line significantly increases is called current protection. When the current detected by the fault tester exceeds the protection setting value (starting current), the current protection operates immediately. When the time exceeds the de-excitation 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 a 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 next level line's instantaneous overcurrent protection 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. 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 operate, thereby preventing misoperation during reverse faults.
2. Distance Protection
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 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 total length of the line and section I of the next line.
Distance section III: Protects the total length of the line and serves as backup protection for the next line.
3. Zero-Sequence Protection
A protection device that reflects the zero-sequence component of the current or voltage during a ground fault. It is mainly used for ground fault protection in neutral point directly grounded systems. It can be divided into zero-sequence current protection and zero-sequence voltage protection.
Zero-sequence current protection: Uses the zero-sequence current generated during a ground fault to operate. It is generally composed of a zero-sequence current transformer and a relay.
Zero-sequence voltage protection: Uses the zero-sequence voltage generated during a ground fault to operate. It is generally composed of a voltage transformer and a relay.
4. Differential Protection
A protection device that compares the current at both ends of the protected equipment. Under normal operation or external faults, the currents at both ends are equal, and the differential current is zero. When an internal fault occurs, the differential current is not zero, and the protection operates. It is mainly used for transformers, generators, and busbars.
Transformer differential protection: Compares the currents on the high-voltage and low-voltage sides of the transformer. Under normal operation, the currents are balanced. When an internal fault occurs, the balance is broken, and the protection operates.
Generator differential protection: Compares the currents at the neutral point and the outlet side of the generator. Under normal operation, the currents are equal. When an internal fault occurs, the differential current is not zero, and the protection operates.
Busbar differential protection: Compares the currents of all branches connected to the busbar. Under normal operation, the sum of currents is zero. When an internal fault occurs, the sum is not zero, and the protection operates.
The above is an introduction to the 4 protection devices of the microcomputer relay protection tester. I hope it helps you understand the tester better. If you have any questions, please feel free to contact us.
