Variable Frequency Series Resonance Test System | VS-JLXZ

Products Details

AC withstand voltage testing is a key procedure for verifying the insulation condition of power cables and high-voltage electrical equipment. In field testing, however, long cables and large capacitive test objects can require high reactive power if tested with a conventional power-frequency test transformer. This makes ordinary test equipment heavy, difficult to transport, and less convenient for installation or maintenance teams working at different substations.

The VS-JLXZ Variable Frequency Series Resonance Test System is designed to solve this field testing problem. It uses the capacitance of the test object and the system’s resonant reactor to form a series resonant circuit. When the frequency is adjusted to the resonant point, the system can generate the required high voltage across the test object while the input source mainly supplies the active loss of the circuit. This helps reduce the required power source capacity and makes the complete test set more practical for mobile field use.

The system is mainly composed of a variable frequency power supply, excitation transformer, high-voltage resonant reactors, and capacitive voltage divider. The reactors are designed as separate modular units, allowing series or parallel combinations according to the test object. This configuration can meet high-voltage, small-current test requirements for transformers, switchgear, and busbars, while also supporting lower-voltage, higher-capacitance cable withstand tests.

For 10 kV cable testing, the system can be configured with four 27 kV / 1.25 A reactors in parallel. For 35 kV cable testing, reactors can be connected in series-parallel combinations. For 35 kV switchgear, busbars, and other low-capacitance electrical equipment, the reactors can be connected in series to reach higher voltage output. This flexible reactor arrangement gives the VS-JLXZ a wide application range across cable and substation equipment testing.

The variable frequency power supply provides automatic and manual operation modes. It supports automatic frequency sweeping, resonance point search, voltage boosting, protection monitoring, data storage, and large LCD curve display during frequency scanning. Operators can select the frequency sweep start point and sweep direction according to the site condition, which makes it easier to find the resonance point and complete the test safely.

The system also includes protection functions such as overvoltage, overcurrent, zero-position start, and detuning or flashover protection. When a flashover occurs, the system can act quickly and record the flashover voltage value for test analysis. Because a series resonant circuit loses resonance after breakdown, the high voltage collapses rapidly, helping reduce large short-circuit current at the fault point compared with some conventional withstand test methods.

Specification

Technical Parameters
Item	Specification
Product model	VS-JLXZ
Product type	Variable Frequency Series Resonance Test System
Rated capacity	135 kVA
Rated output voltage	108 kV
Rated voltage combinations	27 kV, 54 kV, 108 kV
Application voltage class	35 kV and below electrical equipment
Frequency adjustment range	20 Hz to 300 Hz
Variable power supply output frequency	30 Hz to 300 Hz
Frequency step	0.1 Hz
Frequency instability	≤0.02%
Output voltage waveform distortion	<1.0%
Continuous working time	60 minutes under rated condition
System quality factor	Q > 50
Cable test quality factor at full load	Q > 30, load related
Transformer test quality factor at full load	Q > 30, load related
GIS / switchgear test quality factor at full load	Q > 50, load related
System measurement accuracy	1.50%
Protection functions	Overvoltage, overcurrent, zero-position start, detuning / flashover protection
System input power	Single-phase 380 V
Variable frequency power supply rated power	7.5 kVA
Variable frequency power supply input	Single-phase 220 V or three-phase 380 V ±10%, 45-65 Hz
Variable frequency power supply output voltage	0-400 V adjustable
Variable frequency power supply output current	0-18 A
High-voltage resonant reactors	4 units, 27 kV / 1.25 A each
Reactor rated voltage	27 kV
Reactor rated current	1.25 A
Reactor rated inductance	100 H
Reactor continuous working time	60 minutes
Reactor temperature rise	<60°C
Reactor working frequency	30 Hz to 300 Hz
Excitation transformer capacity	7.5 kVA
Excitation transformer input voltage	200 V / 400 V
Excitation transformer output voltage	1.2 kV / 3 kV / 5 kV
Capacitive voltage divider	110 kV pure capacitive type
Divider capacitance	1000 pF
Divider working frequency	30 Hz to 300 Hz
Divider uncertainty	1.50%
Divider rated voltage	110 kV / 1000 pF
Standards stated in manual	GB50150-2016, DL/T 849.6-2004, GB10229.88, DL/T596-1996, IEC358(1990)

Product Guide

Before testing, the operator should identify the test object, rated voltage, required test voltage, estimated capacitance, and applicable test standard. Cable testing, transformer testing, GIS testing, switchgear testing, and busbar testing may require different reactor combinations, excitation transformer taps, and resonance frequency ranges.

For a 10 kV cable AC withstand test, the system can use four 27 kV / 1.25 A reactors in parallel, together with the 1.2 kV excitation transformer tap. For a 35 kV cable test, the reactors may be connected as series-parallel groups, and the 3 kV excitation transformer output can be selected. For 35 kV switchgear, busbar, and low-capacitance electrical equipment, the reactors are generally connected in series, and the 5 kV excitation transformer output may be used.

After wiring, grounding must be completed before energizing the system. The variable frequency power supply, excitation transformer, reactor group, capacitive voltage divider, and test object should be connected according to the selected test scheme. The operator should check all terminals, grounding conductors, control cables, and high-voltage clearances before starting.

During operation, the system can sweep the frequency to locate the resonance point. The large LCD displays the scanning curve so the operator can judge whether resonance has been found. After resonance is located, voltage can be raised automatically or manually according to the selected mode. The system monitors voltage, current, and protection conditions throughout the test.

If flashover or breakdown occurs, the system detunes and the high voltage falls rapidly. Protection functions act to reduce risk to the test object and record the flashover voltage value. After testing, the voltage must be fully discharged and the test object grounded before changing connections or touching any high-voltage part.

Features

• Supports AC withstand voltage testing for 35 kV and below power cables and electrical equipment.
• Provides 135 kVA rated system capacity and up to 108 kV rated output voltage.
• Uses variable frequency series resonance technology to reduce required input power capacity.
• Supports 27 kV, 54 kV, and 108 kV rated voltage combinations.
• Provides modular resonant reactor connection for cable, transformer, switchgear, busbar, and GIS testing.
• Supports automatic mode, manual mode, and automatic tuning with manual voltage boosting mode.
• Automatically sweeps frequency and displays the resonance scanning curve on a large LCD.
• Allows frequency sweep start point and sweep direction to be selected within the specified range.
• Provides overvoltage, overcurrent, zero-position start, and detuning or flashover protection.
• Records flashover voltage value for test review and insulation analysis.
• Stores test data with numeric record identification for later search and review.
• Uses DSP platform control for operation interface and function expansion.
• Provides low output voltage waveform distortion for AC withstand testing.
• Includes capacitive voltage divider for high-voltage measurement.

Application Scenarios

The VS-JLXZ is suitable for AC withstand voltage testing of 10 kV and 35 kV XLPE power cables. For cable installation and commissioning teams, it provides a practical way to generate high AC test voltage for long capacitive cable circuits without requiring a large conventional test transformer.

In substations, the system can be used for AC withstand testing of 35 kV and below transformers, busbars, switches, GIS equipment, and other main electrical apparatus. Its modular reactor design allows the same system to be adapted to different test objects with different capacitance levels.

For power installation and repair companies, the VS-JLXZ supports field acceptance testing after cable laying, substation construction, equipment overhaul, or insulation repair. The portable modular configuration helps reduce transport difficulty compared with large single-piece power-frequency withstand test equipment.

For preventive maintenance teams, the system can be used to verify insulation condition during planned outage testing. The protection and flashover recording functions help engineers review test events and support maintenance documentation.

Applications

The VS-JLXZ Variable Frequency Series Resonance Test System is used by power utilities, high-voltage test departments, substation maintenance teams, cable installation contractors, electrical commissioning companies, power engineering companies, industrial power users, and equipment repair service providers.

Typical test objects include 10 kV cables, 35 kV cables, XLPE power cables, transformers, busbars, switchgear, GIS equipment, circuit breakers, and other capacitive or low-capacitance high-voltage equipment.

For overseas SEO and B2B procurement, the product can be described as a variable frequency series resonance test system, AC resonant withstand voltage test set, cable AC hipot test system, resonant AC test set, variable frequency withstand voltage tester, and high-voltage series resonance test equipment.

Customer Case

A power installation contractor was responsible for commissioning several 10 kV and 35 kV cable circuits after a substation expansion project. The site required AC withstand testing for both long 10 kV cable sections and shorter 35 kV cable circuits, but the contractor wanted to avoid transporting a large conventional AC test transformer.

The team used the VS-JLXZ Variable Frequency Series Resonance Test System. For the 10 kV cable sections, the reactors were connected in parallel to match the higher cable capacitance. For the 35 kV cable section, the reactors were connected in a series-parallel arrangement. The operator used the automatic frequency sweep function to locate the resonance point, then raised the voltage according to the required test procedure.

During testing, the system displayed the resonance curve and monitored voltage and current. Test data was stored for project documentation. The contractor completed cable withstand testing with one modular system instead of preparing separate large-capacity test equipment for each cable type.

The customer used the test records as part of the commissioning file and continued using the system for later cable maintenance and substation equipment testing.

FAQ

• What is the VS-JLXZ used for?
  It is used for AC withstand voltage testing of 35 kV and below power cables, transformers, switchgear, busbars, GIS equipment, and other high-voltage electrical apparatus.
• What is the rated capacity and voltage of this system?
  The system is configured as a 135 kVA / 108 kV variable frequency series resonance test system.
• What voltage combinations does it support?
  The manual states rated voltage combinations of 27 kV, 54 kV, and 108 kV, depending on reactor connection.
• What is the frequency adjustment range?
  The system frequency adjustment range is 20 Hz to 300 Hz. The variable frequency power supply output frequency is 30 Hz to 300 Hz with 0.1 Hz step adjustment.
• What equipment is included in the system?
  The system includes a variable frequency power supply, excitation transformer, four high-voltage resonant reactors, capacitive voltage divider, test leads, and related accessories.
• Can it test both cables and substation equipment?
  Yes. Reactor combinations can be adjusted for cable AC withstand testing, transformer testing, switchgear testing, busbar testing, and GIS testing.
• What protection functions are included?
  The system includes overvoltage, overcurrent, zero-position start, and detuning or flashover protection. It can also record flashover voltage for analysis.
• What is the continuous working time?
  The system can work continuously for 60 minutes under rated conditions according to the manual.
• What standards are referenced?
  The manual references GB50150-2016, DL/T 849.6-2004, GB10229.88, DL/T596-1996, and IEC358(1990).
• Who typically uses this test system?
  Typical users include power utilities, high-voltage test departments, cable commissioning teams, substation maintenance companies, power installation contractors, and industrial electrical maintenance teams.

Weshine Advantages

Weshine Electric provides high-voltage test equipment and electrical diagnostic solutions for utilities, substations, industrial users, contractors, and testing service providers. For the VS-JLXZ Variable Frequency Series Resonance Test System, Weshine supports customers with configuration selection, test object matching, technical parameter confirmation, operation guidance, and after-sales service.

Series resonance systems must be matched carefully to cable length, capacitance, test voltage, frequency range, and field working conditions. Weshine helps customers choose suitable reactor combinations and system configuration for cable withstand testing, substation equipment testing, and commissioning projects.

For overseas buyers and distributors, Weshine can provide product information, application support, and documentation for procurement, tender preparation, training, and resale. The VS-JLXZ is suitable for customers looking for a modular AC resonant test system for medium-voltage cable and electrical equipment withstand testing.