Problems Encountered and Analysis in the Commissioning of Microcomputer Protection Systems in 10KV Substations

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This post was last edited by gozidianli on 2015-11-16 12:23. In power systems, substations play a very important role, contributing significantly to the collection and distribution of electrical energy. For this reason, metallurgy, mining, steel mills, and other manufacturing industries all build their own substations to ensure power supply for their facilities and maintain production. Generally speaking, the 10KV voltage level is quite common, and for large factories and mines, there are also many distributed power stations. Microcomputer protection is also essential in power plants, and many problems arise during the commissioning process; let’s briefly discuss them. http://www.weijizongbao.com/d/file/384bc7c3013e0a21e6ff46401d4ca8d9.jpg 1. Inaccurate measurements. Generally, when conducting experiments on microcomputer-based protection systems, the first step is to check whether the measurement displays of the protection device are normal. Generally, for 10KV systems, two-phase currents are used as the measurement currents, namely phase A and phase C. Phase B does not exist, but it can be displayed on the device and is used as a metering phase. Under normal circumstances, if the amount applied by the microcomputer-based protection tester is correct but the device displays abnormally, the possible reason is shunting at the terminals. Or the voltage readings are unbalanced; this issue usually occurs when the three phases do not share a common ground, and the wires need to be checked to resolve it. 2. The protection device of the switchgear does not operate. During testing, the switchgear should be commanded by the microcomputer protection device to carry out a tripping action. But it is common to see switchgear not functioning. In this case, it is necessary to check step by step. First, determine whether the protection device has issued a protection trip command, which can be seen from the event records in the microcomputer-based protection system. If the microcomputer-based protection system has records of past operations, a manual test can be conducted on the device to see whether it is capable of triggering that protection function; a multimeter can be used for this measurement. If the protection device can also set the protection operating point, then all that remains is to check the wiring issues in the switchgear cabinet. 3. The switchgear closes but does not open, or opens but does not close. In this case, it is usually caused by anti-jump conflicts; that is to say, the microcomputer-based protection system has anti-jump functions, and the switchgear itself also has anti-jump relays. When both exist simultaneously, the switchgear will not function properly, and this phenomenon occurs. After the device is powered off and restarted, it can operate normally once again. For the circuit board of 10KV microcomputer protection devices, every effort should be made to maintain its integrity; a common solution in such cases is to short-circuit the anti-jump relays inside the switchgear so that they cease to function. 4. The switchgear closes and then opens, or opens and then trips. Such problems are also quite common on-site. The most likely reason for this phenomenon is that there is about 110V of positive voltage in series in the closing circuit or the opening circuit. This causes the circuitry for closing or opening to remain energized for an extended period, preventing the switchgear from functioning properly. Another possibility is that the power supply connection is reversed. Of course, before making such a judgment, it is necessary to confirm that one’s microcomputer protection device is functioning properly. How to determine it? It’s simple: isolate the point where the device is connected to the control circuit to ensure that the protection device does not affect the control circuit, and then use a short-circuit wire for testing. Restore it promptly after the testing is completed. 5. The most common issue encountered on site is not a problem with the equipment itself, but rather a mismatch between the design and reality, or a discrepancy between the manufacturer’s drawings and the actual blueprints. In such cases, the solution is to communicate with the various designers. It usually takes a long time; on-site, people typically modify the wiring and conduct experiments based on practical principles and experience. This is understandable, but the most common problem is that the wiring is actually modified on site, yet the drawings remain unchanged. This causes significant difficulties in subsequent maintenance and repairs. Normally, the modified areas should be marked clearly before the final as-built drawings are prepared. In fact, various problems can arise during the debugging process; these are unpredictable, so we need to keep summarizing our experiences, keep learning, and accumulate more knowledge.