Check Power Transformer Protection Method Of Direction - Transformers, Power Of - Hc Net Electrical

Abstract: The phase transformers, grounding power directional protection of a calibration method

. In this method phase transformer on the power system, ground fault analysis, combined with PT, CT wiring polarity, the fault simulation system test the entire group can be simple and reliable manner on the direction of protection to check the power transformer.

Keywords: power direction of phase ground fault protection fault polarity

1 Introduction Transformer power directional protection (including the white-power directional protection and zero-sequence power protection) is an important backup protection of transformers. As the adjacent components and transformer internal fault backup protection, the scope of the expansion in the prevention of failure to ensure safe operation of the system plays an important role. The correctness of its direction, and the current transformer primary and secondary wiring, voltage transformer secondary wiring and protection devices have a secondary connection between them in actual operation, it is easy to mistake as wiring polarity misoperation caused or Refuse. This paper attempts to explore the power directional protection, summed up a simple and reliable calibration methods. The results show that the power system by simulating the actual failure, combined with CT, PT wiring polarity analysis, can be simple and reliable protection against power direction to test the correctness of the direction, the equipment inspection and routine scheduled inspection work, which greatly simplifies the work volume.

2 of the problem The direction of the correctness of directional power protection can be protected by checking the voltage, current wiring polarity to check, but for the actual installation site, the second line of many, access method complex and difficult to straighten out the trend line, easily error. Furthermore, the increasing application of computer for transformer protection, power point to the direction of the direction of protecting the general setting by software control words, the direction is in the protection of software modules to determine the default system wiring polarity voltage and current conditions, calculated by the software protection control set. For example, for WBZ 2 500 microprocessor transformer protection, the configuration with the direction of the function, determine the direction of polarity wiring must be in the following manner: CT polarity is when the primary current into the transformer, the device of the induced current is a positive polarity current into the device; PT polarity access device is positive polarity. In this way, and discrete components can not be equally protected by checking the relay connected in the polarity of the voltage and current power of direction to check the direction of protection. Simple and reliable method is to combine the protection of the entire group of tests, based on the protection of the setting and the CT, PT wiring polarity, simulate the system forward and reverse direction of failure, the failure to protect the added analog voltage and current, checking their movements point of view and sensitivity.

3 phase power direction of the calibration

To simulate system failures, for the entire group of tests, we should first analyze a failure of the system. I Bureau of 220kV transformer

phase power direction is the direction of the protection setting points to the bus bar. First, consider the failure of the positive direction. Shown in Figure 1, white bus outside the circuit failure occurs, the protection of the transformer CT, with bus flow positive direction for current transformers. Set line impedance angle is 70 , can make a voltage and current vector diagram in Figure 2. Visible fault current I K lag phase voltage U K160 .

Figure 1 system is the direction of phase failure

Vector for the secondary voltage and current relationship will depend on the PT, CT polarity of the access law vary. Generally used by polarity PT Law, the secondary winding of the polar Access Protection (PT wiring diagram, see later in Figure 9). The CT, is also a method used by polarity (CT connection diagram see Figure 10 later), when a winding L1 to point bus, the second side of the current outflow from the K1, you can view the current secondary currents and in phase one, this time can be to secondary voltage and current vector diagram shown in Figure 3; the other hand, when the secondary current flow from K2, the second current and a current of opposite phase, secondary voltage and current vector relations shown in Figure 4.

by: gaga

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