The influence of capacitive current on the operation of the substation

The capacitance current in the substation and power plant generally refers to the power distribution network, the ground capacitance (including generators, transformers, cables, lines, etc.), and the ground current generated at a certain voltage level, which is generally generated in the event of a single-phase fault. The magnitude of the capacitance current has an impact on determining the neutral grounding method of the distribution system.

The capacitance current is small, and when the system is single-phase grounded, the equipment damage is small, and the non-grounding system can be operated with faults. Plenty of time to look for the point of failure.

The capacitance current is large to a certain extent, and when a single-phase grounding occurs, the capacitance current is large, which is easy to produce continuous arcing, damage the equipment, and expand the fault. It is necessary to use the neutral point to be grounded by resistance or grounded by arc suppression coil to suppress the overvoltage caused by arc and capacitance. And the action is tripping, and the fault part is cut off in time.

Capacitive currents are generated in the grid by capacitive or capacitive loads.

Substations have inductive loads such as transformers, which generate reactive inductive currents. The capacitive current and inductive current are neutralized by the capacitor invested in the power grid to achieve the purpose of compensation.

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Reward points: 20 - 14 days and 23 hours before the end of the problem is an ineffective back-and-forth flow, and the amount of capacitive current has a negative impact on the operation of the substation.

How is the capacitive current in the substation generated, is the capacitive load and the "compensation current" that replaces the capacitive current

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The simplest capacitors consist of plates at both ends and an insulating dielectric (including air) in the middle. When energized, the plates become electrified, forming a voltage (potential difference), but the entire capacitor is not conductive due to the insulating material in the middle.

1. Coupling: The capacitance used in the coupling circuit is called the coupling capacitor, and the capacitance circuit is widely used in the resistor-capacitance coupling amplifier and other capacitive coupling circuits to play the role of blocking the DC flow and AC.

2. Filtering: The capacitor used in the filter circuit is called the filter capacitor, which is used in the power supply filter and various filter circuits, and the filter capacitor removes the signal in a certain frequency band from the total signal.

3. Decoupling: The capacitor used in the decoupling circuit is called the decoupling capacitor, which is used in the DC voltage supply circuit of the multi-stage amplifier, and the decoupling capacitor eliminates the harmful low-frequency cross-connection between each stage of the amplifier.

4. High-frequency vibration cancellation: The capacitor used in the high-frequency vibration cancellation circuit is called the high-frequency vibration cancellation capacitor, in the audio negative feedback amplifier, in order to eliminate the high-frequency self-excitation that may occur in the vibration cancellation, this capacitive circuit is used to eliminate the high-frequency acoustic noise that may occur in the amplifier.

5. Resonance: The capacitor used in the LC resonant circuit is called the resonant capacitor, and the capacitor circuit is required in the LC parallel and series resonant circuit.

There is no problem with the visual inspection of the power capacitor in operation, and the temperature of the capacitor basically does not change, the temperature of the series reactor with the capacitor rises very high, and the current is at least one current larger than that of normal operation.

Cause analysis: If the capacitor check is normal (check the capacitance and leakage of the capacitor in a power failure, etc.), the main reason for the sudden increase in the current of the power capacitor in operation is that the load in the running power system has added equipment with higher harmonic generation (such as electric arc furnace, electroplating rectifier, frequency conversion speed regulation or DC speed regulation equipment, etc.), and the other situation is that other users in the same 10kV power distribution system have added equipment with higher harmonic generation and caused by system interference.

Article. The steady state that the capacitor withstands.

Overvoltage. It should not exceed a multiple of the rated voltage of the capacitor.

When the rated voltage of the capacitor does not meet the actual operating voltage requirements, two or more capacitors can be connected in series.

Use. Article.

The choice of capacitor should allow for steady state.

Overcurrent. Dayin hungry sail to the capacitor stove hail.

Rated current limb transport.

times. For capacitors with the maximum positive deviation of capacitance, the allowable value of the overcurrent should reach the rated current of the capacitor. Fold.