QLDCJ-400 Lightning impulse equipment

Scope of Application

This generator is suitable for standard lightning impulse voltage full-wave tests on test objects such as air gaps, reactor switches, insulator strings, bushings, power transformers, and instrument transformers of 35KV and below.

General Operating Conditions

• Altitude: 1000m
• Ambient Temperature: -5℃～＋40℃
• Relative Humidity: 90%
• Maximum Daily Temperature Difference: 25℃
• Operating Environment: Indoor
• Free from conductive dust
• No fire or explosion hazards
• No gases are corroding metals or insulation
• Power supply voltage waveform is an actual sine wave with waveform distortion <5%

 Standards to be Complied With

• GB/T 311.1 Insulation and Coordination of High Voltage Transmission and Transformation Equipment
• GB/T 16927.1 High Voltage Testing Techniques – Part 1: General Test Requirements
• GB/T 16927.2 High Voltage Testing Techniques – Part 2: Measurement Systems
• GB/T 16896.1 Digital Recorders for High Voltage Impulse Testing
• JB/T 7616 Steep Wave Impulse Withstand Test for High Voltage Line Insulators
• DL/T 557 Steep Wave Impulse Test, Definition, Test Method and Criteria for High Voltage Line Insulators
• ZBF 24001 Detailed Rules for the Implementation of Impulse Voltage Test

Rated Parameter Values

•  Nominal Voltage: 400kV
•  Rated Class Voltage: 100kV
• Nominal Energy: 20kJ
•  Total Impulse Capacitance: 0.25µF (2.0µF/50kV per pulse capacitor, 8 units in total).
•  Total Number of Classes: 4 Classes
• Standard Waveform Parameters: Standard lightning impulse voltage full wave, 1.2/50s voltage utilization factor >85% (greater than 90% at 300pF no load); Impulse voltage waveform parameters and their deviations all comply with the requirements of relevant national standards GB311 and GB16927.
•  Minimum Output Voltage >10% of Nominal Voltage
• Operating Duration: Above 70% of rated voltage, continuous operation is possible with a charge-discharge cycle every 120 seconds; below 70% of rated voltage, continuous operation is possible with a charge-discharge cycle every 60 seconds.

Main Components

1. Charging Section

•  A constant current charging device is used.
•  Oil-immersed charging transformer is used, secondary voltage 85kV, rated capacity 5kVA;
• 2DL-200kV/200mA high-voltage rectifier silicon stack is used, reverse withstand voltage 200kV, average current 0.2A. The high-voltage rectifier silicon stack is installed next to the charging transformer, and the charging voltage polarity can be automatically reversed by the transmission mechanism. There is a polarity switch button on the control panel.
•  The high-voltage rectifier silicon stack protection resistor is made of enameled resistance wire inductively wound on an insulating tube.
• A bilateral symmetrical constant current charging method is used.
•  During automatic control, the constant current charging device operates within a 10%–100% rated charging voltage range. The actual charging voltage deviation from the set voltage is no greater than ±1%, the charging voltage instability is no greater than ±1%, and the adjustable accuracy of the charging voltage is 1%.
•  Two DC resistance voltage dividers are used, employing 50kV, 300M, oil-immersed metal film resistors. The low-voltage arm resistor is installed inside the bottom flange of the voltage divider, and the voltage signal on the low-voltage arm is introduced into the control console via a shielded cable.
•  The automatic grounding switch uses an electromagnet-based grounding mechanism. When the test stops, it can automatically short-circuit the main capacitor and ground it through the protective resistor.
•  The inductors, capacitors, charging transformers (including high-voltage rectifier silicon stack and polarity conversion device), their protective resistors, automatic grounding switches, and insulating supports of the constant current charging device are installed on a single chassis.

Main Body

• The main structure adopts a four-column structure, with two capacitors suspended in parallel on a steel support consisting of four flanges, forming a stable structure at level 1. The main equipment is at level 4, forming a combined tower structure. Each level is stacked sequentially, making disassembly and testing convenient and ensuring overall structural stability.
•  The main body adopts an asymmetrical constant current charging method with constant current voltage regulation. The voltage is continuously adjustable from zero to the set voltage. The charging power supply is automatically shut off at the moment of ignition discharge. The rated voltage of each level is 100kV.
•  The main body has a 4-level tower structure with insulating supports. Each level includes two MWF50-2.0 iron-cased oil-immersed pulse capacitors, charging resistors, wavefront resistors, wavetail resistors, and ignition ball gaps, etc. All synchronous discharge balls are installed in a closed insulation enclosure. The ball gaps can be manually or automatically adjusted via the control console. (4) The single pulse capacitor is 2.0-0.05F, with a DC operating voltage of 50kV, an inductance of 0.2H, and composite film oil-immersed insulation. Under normal operating conditions, the capacitor outlet bushing can withstand a vertical tensile force of 15kg without damage or oil leakage.
•  Both the wavefront (front) resistor and the wavetail resistor adopt a plate structure and are non-inductively wound. Their self-inductance is 2.5H (the purpose of reducing inductance is to increase the load capacity. For extra-large loads (such as those greater than 5000pF), this can be achieved by adding an appropriate combination of external tuning capacitors and tuning resistors to increase the load). The connectors are all spring-loaded.
• The wavefront (front) and wavetail resistor brackets can be made of four resistors connected in parallel. The lengths of the wavefront (front) and wavetail resistors are equal and interchangeable. Each stage has a location for storing excess tuning resistors and a short-circuit rod. The short-circuit rod can be used to easily connect the generator in series.
• The complete set is equipped with 7.1 7.2 Lightning wavefront resistors: 3 sets; 7.3 Wavefront resistors: 2 sets; 7.4 Charging resistors: 1 set (1 spare);
• The first-stage ball gap uses double-sided opposite polarity triggering, and the second to fourth-stage ball gaps all use three-gap ball gap ignition, with a synchronization error rate or failure rate not exceeding 2%; synchronization range ≥20%.
• The distance between each ball gap is linearly adjusted by a motor drive, and the control system indicates the charging voltage corresponding to the ball gap. The transmission structure has upper and lower limit switches;
• The ball gap distance can be manually or automatically adjusted on the control system.
• The main body can be used in parallel for every two or three stages. The parallel connecting rods use a unified connector for easy replacement. Excess tuning resistors can be placed on the equipment without affecting electrical performance;
• Each stage has a bracket for storing tuning resistors and connecting rods.
• Each stage uses a two-end sealed insulating cylinder with good sealing performance;
• Anti-corona measures are taken between each stage, and no obvious corona occurs during the entire charging process.
• The inter-stage insulation and mechanical support are capable of withstanding 100kV DC voltage without discharge.
• The generator is equipped with an equalizing shield on top.

400kV Weakly Damped Capacitive Voltage Divider

• The high-voltage arm capacitor consists of one section, rated at 400kV/300 picofarads, with a rated lightning impulse withstand voltage of 400kV.
• This voltage divider is equipped with a low-voltage arm capacitor, resulting in a voltage division ratio of 1500 with an accuracy of less than ±1%. The square wave response characteristics of the weakly damped capacitive voltage divider meet the requirements of the GB311 standard.

400kV Multi-Stage Cutoff Gap Device

Includes three 900 picofarad/150kV equalizing capacitors, six pairs of cutoff ignition spheres, and a 2-5s delay triggering device. The cutoff time is 2-6s, with a standard deviation of cutoff time dispersion not exceeding 0.1s. The distance between the multi-sphere cutoff spheres is adjusted by the control console via an electric drive mechanism.

IMCS1012 Impulse Voltage Generator Control and Computer Waveform Analysis System

Main functions of the control system

•  Synchronous ball gap setting, charging voltage; manually adjust the ball gap distance and display the actual distance value. Ball gap limit switch activation.
•  Charging speed selection: users can select the charging speed in two levels according to experimental needs.
•  Standardized waveform editing system: waveform measurement can be completed by dragging with the mouse, and waveforms can be easily zoomed in and out.
•  Overvoltage and overcurrent protection, automatic grounding.
•  Automatic ignition: Manual control.
•  Emergency tripping: Unlike manual tripping, emergency tripping directly cuts off the main circuit power supply via a button, used in abnormal situations such as control room power outages.

System architecture diagram

The power supply and the cutoff device are connected. All low-level operations, such as relay opening and closing, are controlled by the lower-level computer. The upper-level computer is connected to the lower-level computer through optical fiber. The upper-level computer drives the main body, power supply, and cutoff device by sending commands to the lower-level computer. The lower-level computer continuously collects data to obtain the current status, and at the same time, continuously sends the collected data to the upper-level computer. The voltage and current signals of the voltage divider are connected to the upper-level computer through the acquisition module.

Technical parameters