Basic tasks and steps of relay protection setting calculation

The relay protection setting calculation is an important part of the relay protection work. In the event of a system failure, the relay protection device should meet the requirements of quick motion, selectivity, agility and reliability, which in addition to the reliability requirements Should be completed by the relay protection device itself, the other three requirements should be met with relay protection calculations to enable faulty components to be quickly, reliably, and selectively removed when any point in the power system fails. To minimize the scope of the accident, so that the power system can quickly resume normal operation. The basic task of the relay protection setting calculation is to set the setting values ​​for various relay protections, and for all relay protection in the power system, a setting scheme needs to be worked out.

The setting scheme can usually be compiled according to the voltage level of the power system or the equipment, and can also be divided into small schemes according to the functions of the relay protection. For example, a relay protection setting scheme for a 110 kV power grid can be divided into phase-to-phase distance protection schemes, ground zero-sequence current protection schemes, reclosing schemes, and equipment protection schemes. These programs have both relative independence and a certain degree of cooperation.

The steps for setting calculations are as follows:

(1) According to the relay protection function classification, formulate the short-circuit calculation operation mode, select the short-circuit type, and select the calculation conditions of the branch coefficient;

(2) Short-circuit fault calculation;

(3) According to the protection of the same function to conduct setting calculations, such as by distance protection or by zero-sequence current protection, respectively, to conduct setting calculations, select the setting value, and make the value map;

(4) Compare the setting results, repeat the changes, and select the best solution. Finally summarized the existing problems and put forward the operational requirements;

(5) Draw a fixed value sheet and write a tuning plan specification.

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