Manufacturer of Low and Medium Voltage Switchgear

High Voltage Insulation Online Monitoring Device

Ungrounded Neutral System (KCJD-XGK)

The device is suitable for 0. 4-3 5KV neutral point grounding power system
The device is suitable for neutral grounding system and generator grounding system

 Fault alarm function: When the sensor fails, the corresponding A, B, C phase indicator lights are on, and the fan starts at the same time, and the alarm contact is connected, and the display shows the fault phase.
Fan start and close function: When the temperature of one phase in the three-phase winding wire package reaches the set fan start temperature, the fan automatically starts, and the fan automatically shuts down when the temperature value drops to the set point.
 Over-temperature alarm function: When the temperature of one phase in the three-phase winding wire package reaches the set over-temperature, the thermostat will send out sound and light alarm, and turn on the alarm output to send sound and light alarm to the remote control cabinet.
 Automatic tripping function: When one phase in the three-phase winding wire package reaches the set tripping temperature value, the controller sends a tripping signal to start the tripping circuit.
 Intelligent controller “black box” function: It can record the temperature of the three-phase coil winding at the time of power failure of the thermostat, monitor the unbalanced current of the neutral point and the grounding current in real time, and when the grounding current is detected to exceed the set value, the device will issue an alarm signal, and record the ground current data.
 The resistor is made of stainless steel or alloy material, which is resistant to high temperature, the maximum operating temperature can reach 1670℃, the temperature coefficient is small, the resistance value is stable, corrosion resistance, flameproof and explosion-proof, and high reliability. According to different customer requirements, our company can use imported resistance materials from American AVR PGR company or Canadian Gard company to manufacture products. When the transformer winding is a delta connection surface and the Z-type winding grounding transformer needs to be installed independently, the K CJD power grid grounding monitoring and management system can be used together with it.

Since the selection of the neutral point grounding method of the transformer is a comprehensive problem involving factors such as the insulation level of the line and equipment, communication interference, relay protection, and the safety and reliability of the power supply network, the power supply system practice of my country’s distribution network and large industrial and mining enterprises Different, in the past, most of them used the operation mode of ungrounded neutral point and grounded arc suppression coil. In recent years, due to the development of the power system and the increase of electricity consumption by users, some provincial and municipal power grids have vigorously promoted the operation mode of resistance grounding. When the neutral grounding resistance cabinet is installed, when non-metallic grounding occurs, the current flowing through the grounding point and the neutral point is significantly reduced compared with the metallic grounding due to the influence of the grounding point resistance. At the same time, the sound phase voltage rises. It is also significantly reduced, and the zero-sequence voltage value is about half of that of single-phase metallic grounding. It can be seen from this that the neutral point is grounded through a resistor, which can limit the current and reduce the voltage when there is a ground fault. Experiments have shown that because the neutral point resistance can absorb a large amount of resonance energy, in the grounding method with a resistor, the system resonance overvoltage is fundamentally suppressed.
When the transformer is connected to star, the resistance grounding system can be used directly. When the transformer is connected to the corner, an independent grounding transformer can be installed, and the neutral point resistance can be connected to it. When the single-phase metallic grounding occurs in the system using the resistance grounding method, the sound phase voltage rises to the system voltage, and after the grounding trips, the three-phase voltage quickly returns to the normal value. It is possible to keep the system from being grounded for a short time and stop power transmission.
During the operation of the generator, the occurrence of single-phase grounding is the most common fault. The danger is that the arc grounding at the fault point will further expand the scope of the stator winding insulation damage, and even burn the iron core. If the fault is not detected and quickly removed, Will develop into phase-to-phase or turn-to-turn short circuit. Based on the above reasons, high-resistance grounding of the neutral point of generators is widely used internationally to limit the grounding current and prevent various overvoltage hazards.
Grounding the neutral point through the resistor can limit the fault current to an appropriate value. On the one hand, the relay protection has sufficient sensitivity and selectivity, and at the same time, the fault point may only be slightly damaged locally, and the transient overvoltage is limited to normal. The line voltage is 2.6 times of the neutral point voltage, which limits the re-ignition of the arc, prevents the arc gap overvoltage from damaging the main equipment, and also plays a significant role in preventing the ferromagnetic resonance overvoltage.
3. Scope of application
The device is suitable for 0. 4-3 5KV neutral point grounding power system
The device is suitable for neutral grounding system and generator grounding system

Ungrounded Neutral System (KCJD-XGK)

This device is suitable for 6 ~ 35 KV neutral point ungrounded power system, neutral point grounded by arc suppression coil

1. The accuracy rate of the grounding line selection device can reach 99%;
2. The entire network voltage suppressor can absorb overvoltage capacity of 4000KJ;
3. The 2ms square wave impulse current of the high-energy-capacity explosion-proof composite overvoltage protector can reach a maximum of 1000 A;
4. The controller adopts an industrial-grade computer platform, and the operation is stable and reliable;
5. Adopt large-screen touch LCD display in Chinese, parameter display, setting and query are convenient and intuitive;
6. The adjustment is accurate, the speed is fast, and the adjustment range is wide, which can be adjusted in the full range of 0 ~ 100% of the rated current;
7. Built-in high-voltage grounding line selection module, using residual current incremental method and active power method, etc., to make line selection fast and accurate;
8. Equipped with RS 232 and RS 485 communication interfaces, IEC 6185 0 communication protocol can realize communication with the upper computer and realize long-distance transmission of signals;
9. It can realize the sound and light control alarm function of single-phase ground fault;

    In the neutral point non-effectively grounded system, a neutral point is drawn through the grounding transformer, and the neutral point is grounded with the nonlinear resistor. The system operates normally, and the neutral point is not grounded. When an intermittent arc or permanent arc ground fault occurs in a circuit of the system, the neutral point voltage of the grounding transformer rises, the non-linear resistance is turned on, and the zero-sequence loop will flow through a zero-sequence current amplified to the ground. It is sent to the main controller through the fault loop acquisition unit. At the same time, the dynamic capture monitor is used to monitor the real-time dynamic monitoring of the three-phase voltages of A, B, and C in the whole network system, and the variation of the monitoring voltage and the phase angle of the system are judged and analyzed to select the fault of the system. Mutually.
When intermittent arc overvoltage occurs in the system, the voltage of the non-faulty phase can increase to 1.5-3.5 times, which seriously affects the normal operation of the system, causing the system to generate instantaneous intermittent overvoltage and develop into arc. The control system detects the voltage of the whole network After the change, let the whole network overvoltage suppressor be put into use to absorb various overvoltages and intermittent arc overvoltages generated by the system to protect the system and maintain the safe operation of the system.
When the intermittent arc overvoltage capacity is large, and it is converted into a single-phase fault grounding or a permanent single-phase grounding fault, the control system monitors the system changes and exits the voltage suppressor of the whole network, and switches the arc suppression input to eliminate the system arc. When the arc of the system is eliminated, the voltage suppressor of the whole network is rewashed and put into operation to eliminate the peak overvoltage of the system, maintain the parallelism of the system voltage, and stably ensure the safety of equipment power supply.
When the system has overvoltage fluctuations, high-resistance grounding or metallic grounding, instantaneous or permanent grounding faults, the system will generate low-frequency, intermediate-frequency or high-frequency oscillations to cause primary and secondary resonance, which seriously affects the stability of measurement and protection signals. In severe cases, the voltage transformer will be burnt, and the voltage transformer will be tripped. When the system has a primary or secondary resonance, the control system will eliminate the secondary resonance, and at the same time, send an instruction to put the instantaneous switch on to eliminate the primary resonance and ensure the safe operation of the system.

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