UHV(L) Variable Frequency Series Resonant Test System

This system is designed and manufactured for the communication withstand voltage test of 11kV/30MW hydro-generator

With over voltage, over current, zero start, system detuning (flash down) and other protection functions
Series resonance device adopts DSP platform technology
Multiple work modes, high test speed/li>

Note: Regarding product purchase, technical maintenance and other services, welcome to send email: send email

Product Parameters

AC withstand voltage test voltage and time for rubber cable lines

Rated voltage U0/U(kV)	Test voltage time	Time(min)
18/30 and below	2U0	15(or 60)
21/35-64/110	2U0	60
127/220	1.7U0(or 1.4U0)	60
190/330	1.7U0(or 1.3U0)	60
290/500	1.7U0(or 1.1U0)	60

Cross linked polyethylene cable line AC withstand voltage test voltage and time

Rated voltage U0/U(kV)	Test voltage		Time(min)
	New operational lines or non new operational lines not exceeding 3 years old	Non new operational routes
48/66	2u	1.6U	60
64/110
127/220	1.7U	1.36U
190/330
290/550

Reference Table for AC Test Voltage of Power Transformers

System nominal voltagekV	The highest voltage of the equipment is kV	AC withstand voltage kV
System nominal voltagekV	The highest voltage of the equipment is kV	Oil immersed power transformer	Dry-type power transformers
<1	≤1.1	——	2
3	3.6	14	8
6	7.2	20	16
10	12	28	28
15	17.5	36	30
20	24	44	40
35	40.5	68	56
66	72.5	112	——
110	126	160	——

Neutral point AC withstand voltage test voltage value (kV) for power transformers with rated voltage of 110 (66) kV and above

System nominal voltage	Maximum voltage of equipment	Neutral point grounding method	Factory AC withstand voltage	Handover communication withstand voltage
66	--	--	--	--
110	126	not directly grounded	95	76
220	252	directly grounded	85	68
220	252	not directly grounded	200	160
330	363	directly grounded	85	68
330	363	not directly grounded	230	184
500	550	directly grounded	85	68
500	550	Grounding through a small resistor	140	112
750	800	directly grounded	150	120

AC test voltage value of power transformer

Rated voltagekV	Maximum working voltage kV	Terminal AC test voltage value kV		Neutral point AC test voltage value kV
Rated voltagekV	Maximum working voltage kV	Replace all windings	Partial replacement of windings or handover	Replace all windings	Partial replacement of windings or handover
<1	≤1	3	2.5	3	2.5
3	3.5	18	15	18	15
6	6.9	25	21	25	21
10	11.5	35	30	35	30
15	17.5	45	38	45	38
20	23.0	55	47	55	47
35	40.5	85	72	85	72
66	72.5	140	120	140	120
110	126.0	200	170（195）	95	80
220	252.0	360	306	85	72
220	252.0	395	336	（200）	（170）
330	363.0	460	391	85	72
330	363.0	510	434	230	195
500	550.0	630	536	85	72
500	550.0	680	578	140	120

AC withstand voltage test voltage for stator winding

Capacity(kW)	Rated voltage(V)	Test voltage(V)
Below 10000	36 or above	(1000+2Un)*0.8,The minimum is 1200
10000 and above	Below 24000	(1000+2Un)*0.8
10000 and above	24000 and above	Negotiate with the manufacturer

AC voltage withstand test of stator winding

AC voltage withstand test of stator winding	1) Before major overhaul 2)After replacing the winding	1)The test voltage after replacing all stator windings and repairing them is as follows:			1)It should be carried out in a hot state before cleaning the dirt after shutdown. When in standby mode, it can be carried out in a cold state. The test conditions for hydrogen cooled generators are the same as those specified in Table No. 3 2)Water cooled motors should generally be tested with water flowing. Imported units should be tested according to the manufacturer's regulations, and the water quality requirements are the same as those specified in Table 3 (Note 5) 3)When conditions permit, ultra-low frequency (0.1Hz) withstand voltage can be used, with a peak test voltage of 1.2 times the peak power frequency test voltage 4)Please refer to relevant materials for the test voltage during the process of replacing all or part of the stator winding
		capacity kW or kVA	rated voltage Un V	test voltage V
		Less than 10000	36 or above	2 Un+1000, but the minimum is 1500
		10000 and above	Below 6000	2.5Un
			Below 6000	2 Un +3000
			Above 18000	According to a specific agreement
		2)The test voltage before or after partial replacement of the stator winding and repair is:
		Operating for 20 years or less		1.5Un
		Those who have been operating for more than 20 years and are directly connected to overhead power lines		1.5Un
		Those who have been operating for more than 20 years without direct connection to overhead lines		(1.3~1.5) Un

Note:

1.The appearance of the product shall be subject to the actual product，Technical parameters with model if there are any changes，without notice.In case of misappropriation or copying, legal liability will be investigated.

2. For more information about Wuhan UHV, please enter product center . Service email：info@hvtest.cc

UHV(L) Power Frequency Series Resonant Test System vs. UHV(L) Variable Frequency Series Resonant Test System

Feature	UHV(L) Power Frequency Series Resonant Test System	UHV(L) Variable Frequency Series Resonant Test System
Primary Application	Specifically designed for AC withstand voltage testing of single hydro-generators with a capacity of 250MW or less and similar high-voltage electrical apparatus.	Designed for a broad range of applications, including AC withstand testing of power cables (e.g., XLPE), GIS, main transformers, and busbars.
Operating Principle	Achieves resonance by physically adjusting the inductance of its reactors to match the capacitance of the test object at a fixed 50Hz power frequency.	Achieves resonance by adjusting the output frequency (typically 30-300Hz) of its power supply to match the resonant frequency of the circuit. The reactor inductance remains fixed.
Output Frequency	Fixed at 50Hz.	Variable (e.g., 30-300Hz). This is the defining feature.
Test Object Capacitance	Optimized for the specific capacitance range of large generators (e.g., 0.4μF to 3.3μF).	Highly versatile and can be adapted to a wide range of test object capacitances by tuning the frequency, making it suitable for long cables and other equipment.
Configuration & Tuning	System configured with a combination of fixed and adjustable reactors to match the generator's capacitance. Requires selecting the correct physical tap setting.	The system uses an electronic control unit that automatically sweeps through frequencies to find the exact resonant point. No physical reactor adjustments needed.
Key Advantage	Provides a pure 50Hz test waveform which perfectly matches the operational frequency of generators. This is a requirement for some international standards for generator testing.	Provides high flexibility and portability with a single set of reactors suitable for testing cables, GIS, and transformers in the field.
Core Components	AC power source, voltage regulator, excitation transformer, inductance-adjustable reactors, and a high-voltage divider.	Variable frequency control power supply, excitation transformer, reactors (usually fixed inductance), and a capacitive voltage divider.

Product Characteristics

1、The required power capacity is greatly reduced. Series resonant power supply generates high voltage and high current through resonance between resonant reactor and the tested capacitor. In the entire system, the power supply only needs to provide the active consumption part of the system. Therefore, the required power supply for the experiment is only 1/Q of the test capacity.
2、The weight and volume of the equipment have been greatly reduced. In a series resonant power supply, not only is the bulky high-power voltage regulating device and ordinary high-power power frequency test transformer eliminated, but the resonant excitation power supply only requires 1/Q of the test capacity, greatly reducing the system weight and volume, usually 1/10-1/30 of ordinary test devices.
3、Improve the waveform of the output voltage. The resonant power supply is a resonant filtering circuit that can improve the waveform distortion of the output voltage, obtain a good sine waveform, and effectively prevent the accidental breakdown of the test sample by harmonic peaks.
4、Prevent large short-circuit currents from burning the fault point. In the series resonance state, when the weak point of the insulation of the test sample is broken down, the circuit immediately disengages and the loop current rapidly drops to 1/Q of the normal test current. However, when conducting voltage withstand tests in parallel resonance or test transformer mode, the breakdown current immediately increases by several tens of times. Compared with the two, the short-circuit current is hundreds of times different from the breakdown current. So, series resonance can effectively identify insulation weaknesses without the risk of large short-circuit currents burning the fault point.
5、There will be no overvoltage recovery. When the test sample breaks down, due to the loss of resonance conditions, the high voltage immediately disappears, the arc immediately extinguishes, and the process of re establishing the recovery voltage is long. It is easy to disconnect the power supply before reaching the flashover voltage again. This voltage recovery process is an intermittent oscillation process of energy accumulation, which is long and does not result in any recovery overvoltage.

Product Advantages

1、Wide Range of Use
The system is designed for a broad spectrum of high-voltage AC withstand tests. It is suitable for testing various equipment including cross-linked power cables (XLPE), GIS and switchgear, power transformers (oil-immersed and dry-type), and large generators and motors. This versatility makes it an indispensable tool for utility companies, industrial plants, and field testing organizations.
2、High Cost Performance
By utilizing series resonance technology, the system significantly reduces the required power supply capacity to only a fraction of the test capacity. This, combined with its lightweight design (1/10–1/30 of conventional equipment) and multi-functionality, offers an excellent balance between capital investment and operational capability. It eliminates the need for multiple specialized test sets, making it a highly economical solution.
3、One-to-One Solution
The system is not a one-size-fits-all product. It provides tailored, one-to-one solutions based on the customer's specific test objects and requirements. Whether testing a 11kV generator or a 500kV power cable, the system's configuration (reactor combination, control console, excitation transformer) can be customized to achieve optimal performance and meet unique technical parameters.
4、DSP Platform Technology
At the core of the system is an advanced Digital Signal Processing (DSP) platform. This technology enables precise and rapid control of the frequency conversion process, ensuring accurate resonance tracking, stable voltage regulation, and reliable system operation. The DSP platform also supports complex control algorithms that enhance system responsiveness and measurement accuracy.
5、Flexible On-Site Selection
The system offers flexible configuration options for on-site use. Depending on the test object's capacitance and required voltage, users can select from various reactor and excitation transformer combinations. This modularity allows the system to be quickly adapted to different on-site conditions and test requirements, from short cable sections to large generators.
6、Quickly Find the Resonance Point
Equipped with intelligent frequency-sweeping and automatic resonance search functions, the system can rapidly locate the exact resonant frequency of the test circuit. This automatic tuning feature significantly reduces setup time and eliminates the need for manual adjustments, allowing testing to commence quickly and efficiently.
7、Easy to Use On-Site
The system is designed with field operation in mind. It features an intuitive control interface, clear displays, and automated testing sequences that guide the user through the process. The significantly reduced weight and compact size of the equipment also simplify transport and setup in often challenging on-site environments.
8、Store Data at Any Time
Advanced models include data storage capabilities, allowing operators to save test parameters, results, and waveforms in real-time. This feature facilitates comprehensive test documentation, simplifies report generation, and enables easy traceability and future trend analysis for preventive maintenance programs.

Application Scenarios

1、AC Withstand Testing of Power Cables: It is particularly suitable for testing high-voltage cross-linked polyethylene (XLPE) cables. The page provides reference tables for test voltages and durations for various cable ratings (e.g., 18/30kV up to 290/500kV), with test voltages up to 2U0 and durations of 60 minutes.
2、AC Withstand Testing of Power Transformers: The system can be used for testing both oil-immersed and dry-type transformers. Detailed reference tables are included for test voltages at various system nominal voltages (e.g., 3kV to 500kV) and for testing the neutral point of transformers.
3、AC Withstand Testing of Generators and Motors: It is also applicable for stator winding tests. The product page mentions its design for a 11kV/30MW hydro-generator and includes reference tables for test voltages based on the equipment's capacity and rated voltage.
4、Testing of GIS and Switchgear: Its flexible frequency and resonant principle make it suitable for testing Gas Insulated Switchgear (GIS) and other high-voltage apparatus.
5、On-Site Field Testing: The system's portability and low power requirements make it ideal for field testing in substations, power plants, and other remote locations where large power supplies are unavailable.

FAQ

1、What is the primary advantage of using a Variable Frequency Series Resonant Test System?
The main advantage is its ability to perform high-voltage tests using a much smaller, lighter, and more portable power source. By resonating at a specific frequency, it overcomes the limitations of traditional heavy test transformers.
2、How do I determine the correct test voltage for my equipment?
The system is designed to meet international standards. The product page provides comprehensive reference tables for AC withstand test voltages for various equipment, including rubber cables, XLPE cables, power transformers (oil-immersed and dry-type), and generator stators, based on their rated voltage and type.
3、What safety features protect the test object and the operator?
The system has multiple safety features, including overvoltage, overcurrent, and zero-start protection. Critically, if the test object breaks down, the system immediately detunes (flashover protection). This causes the high voltage and short-circuit current to drop rapidly to a very low level, preventing damage to the fault point and ensuring safety.
4、Is this system suitable for testing long power cables?
Yes, it is particularly well-suited for this. By tuning the frequency to resonate with the cable's capacitance, the system can effectively test long high-voltage cables (XLPE) with reduced power requirements, as detailed in the application reference tables.
5、How does this system compare to a traditional test transformer?
Compared to a traditional transformer, the variable frequency resonant system is far lighter and smaller (1/10 to 1/30 of the weight) and requires much less input power. It also provides a superior, low-distortion waveform and significantly enhanced safety by limiting fault current and eliminating recovery overvoltages.

Product Video

Product Picture

Product attachment drawing

Host

Host and sensor

Adjustable reactor

Manual adjustable reactor

Incentive Transformer

Compensation capacitor

Product detail picture

Induction resonance complete set

Inductive reactor

Excitation transformer tap

Voltage divider

Gear

Electric gear

Electric motor

Manual sensitivity adjustment

Product Certificate

Enterprise products in strict accordance with international and national standards and rules of industry production, through the national, provincial and municipal electric power research institute and electric power authorities detection, measuring center, fully passed the ISO9001 international quality management system certification, the licence for manufacturing measuring instruments of the People's Republic of China, GB/T19001-2016 quality management system requirements, GB/T24001-2016 environmental management system requirements, GB/T45001-2020 occupational health and safety management system requirements.