Three Phase AC Hipot Tester

The structure of the three Phase AC hipot tester is a divided structure, which consists of two

parts: a console and a testing transformer.

This three Phase AC hipot tester can realize measuring, monitoring and operating functions through

connecting the HV output terminal of the testing transformer to the testing object.

(Take the three Phase AC hipot tester of 10kVA/50kV specification as an example, other

specifications can be customized)

1.Oil-filled Testing transformer

--Model No.: HM-YDJ-10kVA/50kV

Input voltage：0~400V/Three phase

Input current：0~14.4A

Rated capacity：10kVA

Output voltage：0~50kV/line voltage

Output current：0~0.11A

CT：HL1-20A/5A

Duty time：≤5mins

Cooling method：oil circulation

2.Manual console

--Model No.: HM-XC-10kVA

Input voltage：380V/Three phase

Rated capacity：10kVA

Input current：15 A

Output voltage：0~400V

Output current：14.4A

Current output indicator：14.4A（it equals low voltage side input current）

High voltage voltage output indicator：50kV（It equals the testing transformer high voltage output）

Meter accuracy：1.5 class

Over-current setting：0~20A（To protect low voltage input of three-phase test transformer）

Overcurrent bounce release time：7mS

Timer Range ：0~999S、M、H can be switched to

Cooling method：Natural cooling

Expａnd knowledge

What is the purpose of the insulation withstａnd voltage test?

Withstａnd voltage test refers to the

test of the withstａnd voltage capability of various electrical devices, insulating materials and

insulating structures. Without damaging the performance of the insulating material, the process of

applying a high voltage to the insulating material or insulating structure is called a withstａnd

voltage test. Generally speaking, the primary purpose of the withstａnd voltage test is to check

the insulation's ability to withstａnd working voltage or overvoltage, and then check whether the

insulation performance of the product equipment meets the safety regulations.

The basic principle

of the withstａnd voltage test: apply a higher voltage than the normal working voltage to the

insulator of the device under test, and continue for a regular moment. If the insulation in

between is good enough, the voltage applied to it will only be small Leakage current. If an

insulator of a device under test maintains its leakage current within a regular range at a regular

time, it can be determined that the device under test can operate safely under normal operating

conditions. When the withstａnd voltage test is performed, the test product has different technical

specifications, and the measurement specifications are also different. For general tested

equipment, the withstａnd voltage test is to measure the leakage current value between the live

wire and the case. The basic rule is: double the working voltage of the tested object plus 1000V

as the test standard voltage. The test voltage of some products may be higher than this rule

value. According to the rules of IEC61010, the test voltage must gradually rise to the required

test voltage value (such as 5kV, etc.) within 5s to ensure that the test voltage value is stably

applied to the tested insulator for no less than 5s, and the leakage current of the tested circuit

at this moment Comparing the value with the leakage current threshold of the specification rules,

it can be judged whether the insulation performance of the tested product meets the specification.

After the test is over, the test voltage must gradually drop to zero within a regular time.

Why is it necessary to insulate after withstａnd voltage? The difference between withstａnd voltage

ａnd insulation

focus on

It should be insulated first, and then withstａnd voltage. Because the

withstａnd voltage is a destructive test, you must first ensure that there is no problem with the

equipment insulation, and then hit the withstａnd voltage to prevent unnecessary burning of the

electrical equipment.

The difference between withstａnd voltage and insulation:

1. Different

definitions

Withstａnd voltage: The puncture test is one of the main methods for testing electrical

appliances, electrical equipment, electrical installations, electrical circuits, and electrical

safety appliances, etc., to withstａnd overvoltage.

Insulation: During operation, electrical

equipment is always under the influence of various external factors, and its performance will

continue to change. These external factors mainly include external electric field, environment,

high voltage, corrosion and machinery, etc.

Under the influence of these unfavorable factors, power

equipment is more prone to unpredictable failures, and in serious cases, power operation will be

interrupted. Therefore, the high-voltage electrical equipment in the power system should be

insulated in advance before it is put into operation to ensure the safe and stable operation of

the power system.

2. Different test methods

Pressure resistance: hydraulic test, pneumatic test.

Insulation: According to the voltage level during the test, the insulation test is divided into

insulation characteristic test and insulation withstａnd voltage test. For equipment to perform

diagnosis and testing in the event of a power failure, the above-mentioned non-destructive test

ａnd withstａnd voltage AC test can be used, and the destructive test can only be implemented after

the non-destructive test is completed.

3. Different voltages

Withstａnd voltage: The insulation

resistance is measured with an insulation resistance tester (below 10000V) or an insulation shaker

(below 2500V). Because the test voltage is relatively low, many insulation defects are not easy to

be found.

Insulation: With a high test voltage in the withstａnd voltage test, it is easy to find

insulation defects in high-voltage equipment.

During the withstａnd voltage test, the possible reasons for the unqualified insulation of the

power equipment are:

(1) The insulation performance deteriorates. If the transformer oil enters

moisture, the solid insulation is damp, and the insulation is aging, it will cause the insulation

performance to decline, and it will fail in the withstａnd voltage test.

(2) The test method and

voltage measurement method are incorrect. For example, in the transformer test, the non-tested

winding end is not grounded, and the non-tested winding may discharge to the ground, which is

misjudged as unqualified. In addition, when testing large-capacity samples, the voltage is still

measured on the low-voltage side. Due to the uplift effect, the voltage actually loaded on the

test product exceeds the test voltage, which causes the test product to breakdown and is misjudged

as unqualified.

(3) The atmospheric conditions that affect the insulation characteristics are not

properly considered. Since air pressure, temperature and humidity have a certain influence on

spark discharge voltage and breakdown voltage, if these factors are not considered, it may lead to

the conclusion that the equipment is unqualified.

Article link: Chemical Instrument Network

What is a converter station,

A converter station refers to a site established in a high-voltage direct current transmission system to complete the conversion of alternating current to direct current or to convert direct current to alternating current, and to meet the power system's requirements for safety, stability and power quality.

The main equipment or facilities that should be included in the converter station are: converter valves, converter transformers, smoothing reactors, AC switchgear, AC filters and AC reactive power compensation devices, DC switchgear, DC filters, control and Protective devices, grounding electrodes outside the station, and remote communication systems, etc.

The main function of the inverter is to perform AC-DC conversion. With the development from the initial mercury arc valve to the current electronic and light-controlled thyristor valve, the unit capacity of the inverter is increasing.

The converter transformer is the key equipment for AC/DC conversion in the converter station. Its grid side is connected to the AC field, and the valve side is connected to the converter. Therefore, the valve side windings need to bear the combined stress of AC and DC. Since the operation of a converter transformer is closely related to the non-linearity caused by the commutation of the converter, it has different characteristics from ordinary power transformers in terms of leakage reactance, insulation, harmonics, DC bias, on-load voltage regulation and testing.

The AC and DC filters provide ground return channels for the characteristic harmonics generated during the operation of the converter. During the operation of the converter, a large number of harmonics will be generated, and 40%-60% of the reactive power of the converter capacity will be consumed. Of course, the AC filter also provides reactive power while filtering. When the reactive power provided by the AC filter is not enough, special reactive power compensation equipment is required.

The smoothing reactor is also called a DC reactor. It is generally connected in series between the DC output end of each pole and the DC line to prevent the current from being interrupted during the operation of the converter to assist in commutation; at the same time, it prevents lightning and lightning on the DC side. Steep waves enter the valve hall, so that the converter valve is free from the stress of these overvoltages; it can smooth the ripples in the DC current. In addition, in the case of a DC short circuit, the smoothing reactor can also reduce the probability of commutation failure by limiting the rapid change of the current.

DC field equipment is mainly used to realize the conversion of DC operation mode, fault removal and maintenance isolation. The basic commutation unit is a commutation system that allows independent operation and commutation in a converter station. It mainly includes a converter transformer, a converter, corresponding AC and DC filters, and control and protection devices.