High-voltage PT cabinet alarm fault
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Recently, the high-voltage PT cabinet has given resonance alarm and PT disconnection alarm, but it continues to operate normally. Could the experts please explain what the cause of this is and how to resolve such an issue? Thank you
Check the secondary side of the voltage transformer, especially the open delta circuit.
Your protection device must be broken; it’s normal for the ground fault light to turn on during resonance, but it’s not normal for it to turn on when the PT is disconnected. Resonance occurs in power supply systems when the inductance and capacitance reach their resonant values. Reasons for PT disconnection: burnout of one phase in the PT, breakage of secondary wires, blown fuse, and false alarms from the protection device.
Thank you! The PT disconnection issue was resolved because a high-voltage fuse in one phase blew. How can the resonance problem be solved? Can a harmonic suppressor be used?
Upload an article on resonance for you to study*.
Could you please explain how resonance is generated? I’m not quite sure about this statement: Resonance occurs in power supply systems when the inductance and capacitance reach their resonant values! Thank you!
Ferromagnetic resonance is induced when the inductive components of the core, such as generators, transformers, voltage transformers, reactors, and arc suppression coils, together with the capacitive components of the system, such as transmission lines and capacitor compensators, create resonant conditions, thereby triggering sustained ferromagnetic resonance and resulting in resonant overvoltages in the system. II. Phenomena of ferroresonance
1. Forms and manifestations of ferroresonance
1) Fundamental wave resonance: The voltage of one phase decreases, while the voltages of the other two phases increase above the line voltage; or the voltages of two phases decrease while the voltage of one phase increases above the line voltage, with a ground fault signal being generated.
2) Harmonic resonance: The voltages of all three phases increase simultaneously, with low-frequency fluctuations.
3) Higher-order harmonic resonance: The voltages of all three phases increase simultaneously above the line voltage.
2. Phenomena of series resonance: The line voltage increases, meters fluctuate, and the voltage across the open delta connection of the voltage transformer exceeds 100V.
III. Causes of ferroresonance and their analysis
1. Causes of ferroresonance:
1) System disturbances caused by line grounding, breaks in the lines, or asynchronous closing of circuit breakers.
2) Resonance is triggered by switching between busbars or by system disturbances.
3) Under certain special operating conditions, the parameters of the system match, resulting in resonance conditions being met.
2. Causes of series resonance: When switch operations are carried out, the circuit breaker’s disconnecting switch becomes connected to the busbar, allowing the capacitance at the circuit breaker’s terminals to couple with the transformers on the busbar, thus meeting the conditions for resonance.
3. Analysis of the causes of ferroresonance in power systems
A power system is a complex electrical network that contains many inductive and capacitive components. In particular, in ungrounded systems, ferroresonance often occurs, posing risks to the safe operation of equipment. Below, we will analyze the causes of ferroresonance starting with simple ferroresonance circuits.
1. Forms and manifestations of ferroresonance
1) Fundamental wave resonance: The voltage of one phase decreases, while the voltages of the other two phases increase above the line voltage; or the voltages of two phases decrease while the voltage of one phase increases above the line voltage, with a ground fault signal being generated.
2) Harmonic resonance: The voltages of all three phases increase simultaneously, with low-frequency fluctuations.
3) Higher-order harmonic resonance: The voltages of all three phases increase simultaneously above the line voltage.
2. Phenomena of series resonance: The line voltage increases, meters fluctuate, and the voltage across the open delta connection of the voltage transformer exceeds 100V.
III. Causes of ferroresonance and their analysis
1. Causes of ferroresonance:
1) System disturbances caused by line grounding, breaks in the lines, or asynchronous closing of circuit breakers.
2) Resonance is triggered by switching between busbars or by system disturbances.
3) Under certain special operating conditions, the parameters of the system match, resulting in resonance conditions being met.
2. Causes of series resonance: When switch operations are carried out, the circuit breaker’s disconnecting switch becomes connected to the busbar, allowing the capacitance at the circuit breaker’s terminals to couple with the transformers on the busbar, thus meeting the conditions for resonance.
3. Analysis of the causes of ferroresonance in power systems
A power system is a complex electrical network that contains many inductive and capacitive components. In particular, in ungrounded systems, ferroresonance often occurs, posing risks to the safe operation of equipment. Below, we will analyze the causes of ferroresonance starting with simple ferroresonance circuits.
Can connecting light bulbs or resistors across the open triangle suppress the occurrence of resonance?
Sure, this belongs to the secondary resonance elimination method, which is used to address the problem of first-order resonance