Wiener bus differential protection switching operation

1. Whether the scale of bus differential maintenance is determined, and whether the maintenance goal is unchanged

Generally, differential maintenance includes bus differential maintenance, transformer differential maintenance, generator differential maintenance and line differential maintenance. The basic principle of differential maintenance is common, that is, the current transformer of each side or each component is wired according to the differential connection method, and when there is a fault outside the normal operation and maintenance scale, the differential current is equal to zero, and the difference current is equal to the fault current within the maintenance scale, and the action current of the differential relay is calculated and set according to the maximum unbalanced current generated when avoiding external faults.

But it should also be very clear that the bus differential maintenance is very different from the transformer differential maintenance and generator differential maintenance: that is, the main junction mode of the bus will change the operation mode with the reverse operation of the bus, such as the double bus to single bus operation, the double bus parallel operation to the double bus segmented parallel operation, bus components (such as lines, transformers, generators, etc.) can be switched from this section of the bus to another section of the bus and so on. In other words, the scale of bus differential maintenance will change (expand or shrink) with the operation of the bus and the change of the bus operation mode, and the goal of bus differential maintenance can also be changed (increased or reduced) because of the switching operation of the bus components.

Wiener bus differential protection switching operation

Wiener bus differential protection switching operation

2. Whether the bus differential maintenance must be withdrawn during the bus reversal operation

"When carrying out the reversing operation, the bus differential maintenance must be withdrawn" is faulty, and the reason why this fault is known is because some operators have seen and even produced bus differential maintenance malfunction during the bus reversing operation, but the basic reason is the lack of correct knowledge of the bus differential maintenance. If the bus reversal operation is carried out in strict accordance with the regulations, that is, the equipotential operation when merging and decoupling, the potential difference when operating the isolation switch is reduced as much as possible, the secondary side reverse charging of the bus voltage transformer is prohibited, and the pulling, closing and switching of the low-voltage locking bus differential maintenance pressure plate are fully considered for bus differential maintenance, etc., which will not cause bus differential maintenance malfunction. Therefore, in the process of inverting the busbar, the operating principle of the differential maintenance of the bus should generally be put into operation if it is not damaged. According to the statistics of the past years, the probability of bus short circuit incident caused by misoperation is still very high. Although in recent years, in order to prevent misoperation, the primary and secondary equipment of substations and power plants have installed five-proof locking equipment, some operators still use the master key in violation of regulations to go to the wrong distance, misclose, and pull by mistake. This makes it extremely important to insist on the bus differential maintenance investment when the bus is reversed. Investing in the differential maintenance of the bus bar can be used to maintain the equipment to remove the fault in case of a short circuit caused by misoperation, and then avoid the further expansion of the incident, so as to prevent serious damage to the equipment, loss of stability of the system or personal injury or injury.

In fact, it is not so much that the bus reversing operation is easy to cause the bus differential maintenance malfunction, but rather that the bus reversing operation often makes the bus differential maintenance lose selectivity and mistakenly cut the non-faulty bus.

3. After the bus reversal operation, whether the non-selective switch for bus differential maintenance should be incorporated into the practical operation

Some operators one-sidedly believe that the bus reverse operation will make the bus differential maintenance lose selectivity, so after the operation is completed, the non-selective switch of bus differential maintenance is closed. The root cause of this misunderstanding is that they do not understand the purpose of this non-selective switch in the busbar differential maintenance equipment.

There are many types of bus maintenance, and the operating principle of different types of bus maintenance is different. Some types of bus maintenance are defective because of their own operating principles, which will make the equipment lose its selectivity to faulty buses when performing bus reversal operations. Therefore, the key to the problem is that the operator should figure out what type of bus maintenance will lose the selectivity of the faulty bus during the bus reverse operation, and how to merge the non-selective switch of the equipment at the appropriate time, and when should the non-selective switch of the equipment be opened, or whether the switch should be insisted on being closed.

Wiener bus differential protection switching operation

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