Capacitive switching control method for inhibiting zero sequence and negative sequence current of distribution transformer

Abstract

The invention relates to a capacitive switching control method for inhibiting zero sequence and negative sequence current of a distribution transformer. An electric power quality acquisition unit acquires a three-phase voltage current and neutral current signals; a central processing unit calculates voltage, current and power factor parameters according to the acquired signals, and determines an actual switching amount; a capacitor is switched by the control of an intelligent combination switch; current load state and capacity regulation conditions are transmitted to an upper computer through a GPRS (General Packet Radio Service) module; and background software realizes the functions of data recording, analysis and the like. According to the method provided by the invention, the influence of overcompensation on a distribution transformer can be considered according to the acquired electric power quality signals, so that the capacitor can be reasonably regulated, thereby effectively inhibiting zero sequence and negative sequence current of the distribution transformer and improving the electric power quality of the distribution transformer.

Description

technical field

[0001] The invention belongs to the field of power systems, and in particular relates to a capacitive switching control method for suppressing zero-sequence and negative-sequence currents of distribution transformers. Background technique

[0002] A large number of three-phase four-wire wiring methods are used in urban and rural distribution networks in my country. There are a large number of single-phase loads. The long-term three-phase unbalanced operation of distribution transformers will reduce the power quality of users, increase the loss of transformers, and increase the temperature of transformer windings. High, or even burn the winding. If there is a large zero and negative sequence current in the line, the temperature of the local metal parts of the transformer will rise, and even cause a transformer accident in severe cases. In addition, the excessive zero and negative sequence current will reduce the power supply quality of the distribution transfor...

Examples

Embodiment 1

[0031] Example 1 as figure 1, a capacitive switching control system for suppressing zero-sequence and negative-sequence currents of distribution transformers, which consists of a voltage transformer 11, a current transformer 12, a front-end processing circuit 13, a central processing unit 14, a capacitor adjustment cabinet 15, and a GPRS communication The module 16 and the upper computer 17 are composed of the voltage transformer 11 and the current transformer 12 of the power quality acquisition unit to collect the voltage, current and neutral current signals of the transformer during operation, and transmit the collected signals to the central processing unit 14, the central processing unit 14 Calculate the voltage, current, and power factor according to the collected signals, and consider the harm of overcompensation to the distribution transformer, calculate the effective capacitance adjustment amount, obtain the control signal of the capacitance adjustment cabinet 15, and c...

Embodiment 2

[0032] Example 2, it is assumed that the three-phase voltage on the low-voltage side of the distribution transformer is = = =220V, the phase difference is 120 degrees, the three-phase current and power factor are respectively =11.9A, =23.2A, =10.3A, =0.92, =0.96, =0.73, the load is inductive, the reference capacity of the capacitor adjustment cabinet is 1kvar, and the adjustment range of phase-to-phase and phase-to-ground reactive power adjustment is 0kvar to 7kvar.

[0033] According to formula (1), the three-phase active power on the load side is obtained as follows:

[0034] =2.4kw, =4.9kw, =1.7kw;

[0035] According to formula (2), the inductive reactive power at the load side is obtained as:

[0036] =-1.0kvar, =-1.4kvar, =-1.5kvar;

[0037] At this time, the negative-sequence current is 5.1A, and the zero-sequence current is 3.7A. According to formula (3), calculate the reactive power adjustments that should be compensated between phases an...

technical field

[0001] The invention belongs to the field of power systems, and in particular relates to a capacitive switching control method for suppressing zero-sequence and negative-sequence currents of distribution transformers. Background technique

[0002] A large number of three-phase four-wire wiring methods are used in urban and rural distribution networks in my country. There are a large number of single-phase loads. The long-term three-phase unbalanced operation of distribution transformers will reduce the power quality of users, increase the loss of transformers, and increase the temperature of transformer windings. High, or even burn the winding. If there is a large zero and negative sequence current in the line, the temperature of the local metal parts of the transformer will rise, and even cause a transformer accident in severe cases. In addition, the excessive zero and negative sequence current will reduce the power supply quality of the distribution transfor...

Examples

Embodiment 1

[0031] Example 1 as figure 1, a capacitive switching control system for suppressing zero-sequence and negative-sequence currents of distribution transformers, which consists of a voltage transformer 11, a current transformer 12, a front-end processing circuit 13, a central processing unit 14, a capacitor adjustment cabinet 15, and a GPRS communication The module 16 and the upper computer 17 are composed of the voltage transformer 11 and the current transformer 12 of the power quality acquisition unit to collect the voltage, current and neutral current signals of the transformer during operation, and transmit the collected signals to the central processing unit 14, the central processing unit 14 Calculate the voltage, current, and power factor according to the collected signals, and consider the harm of overcompensation to the distribution transformer, calculate the effective capacitance adjustment amount, obtain the control signal of the capacitance adjustment cabinet 15, and c...

Embodiment 2

[0032] Example 2, it is assumed that the three-phase voltage on the low-voltage side of the distribution transformer is = = =220V, the phase difference is 120 degrees, the three-phase current and power factor are respectively =11.9A, =23.2A, =10.3A, =0.92, =0.96, =0.73, the load is inductive, the reference capacity of the capacitor adjustment cabinet is 1kvar, and the adjustment range of phase-to-phase and phase-to-ground reactive power adjustment is 0kvar to 7kvar.

[0033] According to formula (1), the three-phase active power on the load side is obtained as follows:

[0034] =2.4kw, =4.9kw, =1.7kw;

[0035] According to formula (2), the inductive reactive power at the load side is obtained as:

[0036] =-1.0kvar, =-1.4kvar, =-1.5kvar;

[0037] At this time, the negative-sequence current is 5.1A, and the zero-sequence current is 3.7A. According to formula (3), calculate the reactive power adjustments that should be compensated between phases an...

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