Impulse Voltage Test System

Impulse voltage test system is used in Lightning impulse test (L1), chopped lightning impulse test (C1) of high voltage power equipment with no more than 35kV.

Description

APPLICATION SCOPE

IVG bodyOur impulse voltage test System is designed to generate impulse voltages to simulate lightning strikes. It is used in Lightning impulse test (L1), chopped lightning impulse test (C1) of high voltage power equipment such as power transformer, instrument transformer, insulator and cables etc. with no more than 35kV.

OPERATION CONDITION

  • Height above sea level:≤1000m
  • Ambient temp.:-5℃-40℃
  • Relative humidity:≤90%(non-condensing)
  • Installation site: indoor
  • Seismic capacity:level 8 intensity
  • Ground resistance:≤5Ω
  • Operation ambient: no conductive dust,no corrosive insulation material or gas or liquid on the surface of metal.

STANDARD

  • IEC 60-1:1989 High-voltage test techniques Part 1: General definitions and test requirements
  • IEC 60-2:1994 High-voltage test techniques Part 2: Measuring Systems
  • IEC 60076-3:2000 Power transformers Part 3: Insulation levels, dielectric tests and external clearance in air

MAIN CONFIGURATION

  • Impulse voltage generator (IVG) body
  • Low damping capacitive voltage divider
  • Single sphere gap chopping device
  • DC charging device
  • Computer measuring & controlling (fiber optics) system

CHARACTERISTICS AND ADVANTAGES

  • We dedicated to develop small impulse voltage test system and customized test equipment to meet customer’s special requirement.
  • The generator body adopts aluminum alloy chassis to reduce its weight and improve its mobility, which keeps the system nice after a long time.
  • Inductance capacitor frame is especially designed for object with small inductance, which improves experimental capability and efficiency.
  • Single sphere chopping device can also be used as protection sphere gap in power frequency test, which improves utilization efficiency of test equipment.
  • Computer communicates with PLC via optical fiber, which improves EMC of controlling system.
  • There are three indication resistors, among which one will be provided first, parameter of another two pieces will be determined after field test result (resistance parameter differs according to different power transformer design)
  • Designed continuous test sequence function for insulator producer. For example, you can set charging voltage 70kV, first group test is positive charging, interval between two times impulse 20s, 15 times, second group test is negative charging, interval between two times impulse 15s, 10 times, intervals between two groups is 30s. control system will complete the test automatically, meanwhile link with waveform recording analysis program, when product breakdown to stop the test, the interface will show which group and which test breakdown the sample product.

MAIN CONFIGURATION

The impulse voltage test system consists of the following parts.

Impulse Voltage Generator Body

  • Structure and features
    • High strength aluminum alloy chassis, nice appearance, which reduces weight of body, while improves its mobility. It would be quite nice at the very beginning if install common carbon steel chassis, however it is hard to avoid damaging the paint during operation which will rust, difficult to clear. While aluminum alloy chassis will not rust, easy to clean.
    • The external modulated inductive resistor frame of chassis is basic component of generator body.
    • The generator body is composed of capacitor tower formed by two high strength one-step forming epoxy column, splice each level, easy to disassemble and maintain. The whole structure is stable. Each level can be disassemble separately without influence other level, which greatly saves disassemble and installation time.
    • Main capacitor adopts double casing pulse capacitor with iron shell, oil insulation composite film, features in compact design, light weight. Natural inductance of capacitor is less than 0.2μH, lead-out bushing of capacitor can bear vertical force 10kg.
    • Plate structure wave head, wave tail and charging resistors are epoxy casting, non-inductive winding. Spring compression type joint, easy to change-over. Three wave head resistors can be connected in parallel, two wave tail resistors can be connected in parallel. Short circuit bar which is the same length and joint as head resistors and charging resistors is standard component of generator body. This can easily and correctly change main loop structure (four stage series connection, four stage parallel connection, three stage parallel connection, two stage parallel connection, two stage series two stage parallel connection), which makes experiment fast and convenient.
    • An automatic grounding device for power loss is designed for high voltage outlet terminal of capacitor (another outlet terminal is grounded via head resistor and tail resistor). When the generator is not in use or generator not under charging or when pressing emergency button, the impulse voltage test system will let main capacitor of generator be grounded via discharge resistor.
    • Use single side voltage multiplying charge mode. Charge voltage 100kV. Silicon controlled constant current voltage adjustment. Charge voltage can be adjusted continuously from 10kV to 100kV. Instantaneous charging power automatically cut off before triggering, which protects charging transformer and voltage regulation system. Silicon rectifier stack, charging transformer and protection resistor are placed separately on an aluminum chassis for easy disassemble and movement. It can change relative position of charge device and the body according to specific condition of laboratory, fully utilize limited space of the lab.

Low Damping Capacitive Voltage Divider

  • Structure and feature

Low damping capacitive voltage divider is consist of an MWF400-400 impulse capacitor with built-in multi-grade distributed damping resistor, its low voltage arm is consist of non-inductive multi-layer ceramic capacitors in parallel connection. It is with movable aluminum alloy chassis, and grading shield on the top. Square wave response characteristic is in compliance with GB/T311.1 and GB/T 16927.

Gap Chopping Device

  • Structure and feature

Single sphere gap chopping device is consist of a pair of discharge ball gap and transmission mechanism etc. It is installed on a movable aluminum alloy chassis. The control system changes gap distance according to peak value of lightning impulse and polarity.

LC artificial line fixed delay, chopping time 4.5μs.

Illustration: in present national standard GB7449-87 and its corresponding international standard, there is no definite requirement on chopping time adjustable.  For easy comparison of oscillogram current waveform under 50% to 70% test voltage and 100% test voltage, it only requires chopping time of chopping wave under two voltage best to be the same (fixed value between 2μs to 6μs). Under 100% test voltage, gap distance increases, breakdown delay time of chopping gap will be around 100ns longer, obviously can fully cover standard deviation range of chopping time. Besides, delay time of single sphere gap is less than 20ns which can be neglected.

DC Charging Unit

  • Structure and feature

Charging mode adopts constant current charge by silicon controlled voltage regulating method. According to preset charging voltage, it will generate opto-electronic isolation control signal towards trigger terminal of silicon controlled through analog output unit of PLC, change conduction angle of thyristor, modulate output voltage, finalize charging process towards generator body. Compared with traditional voltage regulating method by voltage regulator, thyristor voltage regulating method features small size, fast response and high control accuracy.

Computer Measuring and Controlling (Optic Fiber) System

PLC, computer, opto-electronic isolation and optical fiber transmission technologies are applied to impulse voltage test system.

Display, industrial computer and oscilloscope is installed on the control panel. PLC is installed on the control box of chassis of DC charging device, computer communicates with PLC via optical fiber.

Button indicator and meter: generator grounding control button; generator sphere gap increase button, reduce button; chopping device sphere gap increase button; reduce button; rapid charging button, slow charging button; trigger button; alarm button; body gap distance indicator; chopping device gap distance indicator; body charging voltage indicator.