SU1394324A1 - Device for protecting shunt capacitor banks arranged in a triangle against internal damages - Google Patents

Abstract

The invention relates to electrical engineering and can be used for protection against internal damage to shunt capacitor banks assembled in a triangle. The aim of the invention is to increase reliability. The goal is achieved by the fact that the organ of comparison 5 is made as an intermediate three-winding current transformer, and its first winding 4 is connected to the output of the zero sequence current filter. 2 yl. (Ls

Description

The invention relates to electrical engineering, in particular, to the technique of protecting capacitor installations, and can be used to protect internal damages of capacitor banks assembled in a triangle with any number of series-connected parallel-connected capacitors against internal damage.

The purpose of the invention is to increase reliability by eliminating the influence on the operation of the device of higher harmonics of the supply network,

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FIG. 1 is a schematic diagram of the proposed device for protecting a shunt capacitor bank assembled in a triangle of single-phase capacitors; in FIG. 2, the compensation block of the initial unbalance.

The shunt capacitor battery 1 is assembled into a triangle of single-phase capacitors 2. Current measuring transducers (current transformers) are included in the phase circuits of battery I, and their secondary windings 3 are assembled into a star according to the zero-sequence current filter circuit. The output winding of the circuit includes the first winding 4 of an intermediate three-winding transformer 5 of the current. The second winding 6 of the transformer 5 is connected to the actuator 7 acting on the switches 7.1-7.3, and its winding 8 is connected to the initial unbalance compensation unit 9 associated with the source 10 reference stress.

Block 9 contains a chain of two adjustable resistors II and 12 and two capacitors 13 and 14 connected between the winding 8 of the intermediate current transformer 5 and the source 10 of the reference voltage,

The compensation unit 9 is designed to eliminate the initial unbalance caused by the difference in capacitances of the battery phases and the analysis of the transformation ratios of current transducers,

 The device works as follows.

If the capacitances of the phases of the battery are equal and the trans coefficients are identical

Formations of current transducers, the geometric sum of the phase currents in the secondary windings 3 is zero, i.e. current in the winding 4 transformer.

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 five

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Matora 5 is equal to zero and, accordingly, in winding 6, connected to the executive body 7, is also zero.

A change in the conductivity of any of the battery phases, due to damage to the capacitors, causes a change in the magnitude of the current of the corresponding phase, and consequently, the appearance in the winding 4 of the unbalance current. When the last set point is reached, the executive unit 7 is activated, which performs a protective shutdown of the battery.

With an uneven distribution of the capacitance in the battery phases, which usually takes place, the current at the output of the zero sequence filter is not zero and causes the appearance of a signal of constant magnitude at the input of the actuator 7.

In order to increase the sensitivity of the protection, a compensating signal, equal in magnitude but opposite in sign to the vector of the initial unbalance current, is introduced into the secondary protection circuits through the CTBOivi unit 9. Obtaining the required value of the compensating signal is accomplished by adjusting the resistors 11 and 2. Moreover, a change in the resistance of resistor 12 causes a change in the magnitude and phase of the compensating signal, and the resistance of a resistor 11 only changes its value.

The presence of an isolating capacitor 13 makes it possible to connect the winding 8 of the current transformer 5 to the voltage source 10.

The inclusion of current transducers into phase circuits of the battery and the connection of their secondary windings into a star according to the zero-sequence current filter circuit allows protection against internal damage to the battery, assembled in a triangle of single-phase capacitors with a nominal voltage corresponding to the supply voltage.

Claims (1)

Invention Formula A device for protection against internal damage to a shunt capacitor battery, assembled in a triangle, containing current sensors, the inputs of which contain terminals for connecting -. than the corresponding phases of the shunt capacitor battery, the organ compared, the output of which is connected to the inlet 3139432 The house of the executive body, characterized in that, in order to increase reliability by eliminating the operation of the device of higher harmonics of the power supply network, the secondary windings of current sensors are connected in a star according to the zero-sequence current filter circuit, the comparison element is made as an intermediate three winding a current transformer, the first winding of which is connected to the output of the zero current filter, the terminals of the second winding are the output of the reference element, and the outputs of the third winding are connected to the output of ov inputted initial unbalance compensation unit having an input coupled to an output of the newly introduced reference voltage source. 0Na feedstuff ъ f (motorneV) -j-i Fie.2