Dielectric Loss Tester
The dielectric loss tester is a core instrument used in power preventive testing to detect the insulation performance of transformers, instrument transformers, bushings, cables, and other equipment. The key to model selection lies in "matching the test object" and "on-site anti-interference capability." Based on your procurement needs, the following are the core selection points for dielectric loss testers and references to local and surrounding manufacturers:
Core Selection Parameters
During selection, the following parameters must be carefully matched to ensure measurement accuracy and adaptability to on-site working conditions:
Instrument Type and Test Object: Dielectric loss testers are mainly divided into two categories, and the choice should be made according to the actual test object:
High-Voltage Equipment Dielectric Loss Tester: Used to measure the dielectric loss factor (tanδ) and capacitance (Cx) of solid/liquid insulation such as transformer windings, bushings, instrument transformers, and power cables. It must support multiple wiring modes such as forward connection, reverse connection, and CVT self-excitation method. The internal high voltage is usually adjustable in multiple ranges from 0.5kV to 10kV, and the capacitance measurement range must cover 3pF to 60000pF (10kV range).
Insulating Oil Dielectric Loss Tester: Specially used to test the dielectric loss angle and volume resistivity of liquid insulating media such as transformer oil and capacitor oil. It adopts an integrated design with a built-in dielectric loss oil cup, temperature controller, and high-frequency induction heating system (temperature control up to 90°C). The test voltage is usually continuously adjustable from 0 to 2000V, compliant with the GB/T 5654 standard.
Measurement Accuracy and Resolution: Accuracy directly determines the ability to detect insulation defects and is a core indicator in selection:
tanδ measurement: A wide range (0–100%) is preferred. The accuracy of conventional models should be ≤±(reading × 1% + 0.0005). For testing transformers of 110kV and above, high-precision models with accuracy ≤±(reading × 0.5% + 0.0003) should be selected, with resolution ≥0.001%.
Cx measurement: Range 0–60000pF, accuracy ≤±(reading × 0.5% + 1pF), resolution ≥0.1pF.
Anti-Interference Capability: Strong electromagnetic interference exists at substation sites, so models with variable-frequency anti-interference technology must be selected. By outputting different-frequency test signals such as 45Hz/55Hz, it avoids 50Hz power-frequency interference and ensures accurate measurement even in strong electric field environments. Some high-end models can maintain nominal accuracy even under 200% interference.
Safety Protection Configuration: It must have multiple protection mechanisms such as grounding detection (voltage boost locked if not grounded), high-voltage short-circuit/overcurrent protection, prevention of the "capacitance rise" effect, zero-crossing switching, and lightning strike protection to ensure the safety of test personnel and equipment.
References to Local and Surrounding Manufacturers
Jiangsu is an important industrial belt for power testing instruments in China. Yangzhou and its surrounding areas have many professional manufacturers of dielectric loss testers, making on-site inspections and after-sales support convenient:
Local in Yangzhou: Yangzhou Guoshi Electric Co., Ltd. is located in Yangzhou and integrates R&D, production, and sales of power testing equipment such as dielectric loss testers, DC high-voltage generators, and insulating oil dielectric strength testers. Its product line covers conventional high-voltage dielectric loss testing and insulating oil testing needs, and it supports localized services. Yangzhou Baoce Electric Co., Ltd. is located in the northern part of Yangzhou and specializes in producing "Baoc" brand intelligent dielectric loss testers and other high-voltage test equipment. Local enterprises such as Yangzhou Haotai Electric Power Technology Co., Ltd., Yangzhou Jinli Electric Co., Ltd., Yangzhou Yongmao Electric Power Equipment Factory, Yangzhou Enyuan Electric Co., Ltd., Yangzhou Ketuo Electric Technology Co., Ltd., and Yangzhou Pinsheng Electric Technology Co., Ltd. also have dielectric loss tester product lines and can be inspected nearby.
Surrounding areas: Wuhan is the most concentrated industrial belt for power testing instruments in China, with many professional manufacturers such as Wuhan Moen Intelligent Electric (MOEORW/Fankester brand, producing the MEJS-801 series fully automatic anti-interference dielectric loss tester), Wuhan Zhizhuo Measurement and Control, Wuhan Dingsheng Electric Power, Nanao Electric, Wugao Xigao Electric, Zhuoya Electric Power, and Wuhan Musen Electric. Their products cover the full series of variable-frequency anti-interference dielectric loss testers and insulating oil dielectric loss testers, with high technical maturity and the ability to provide complete testing solutions. In addition, Beijing Kanggaote (Taiyi series), Beijing Beiguang Jingyi, and Shanghai Precision Instruments are also well-known brands in the industry.
Selection Precautions
First confirm whether the on-site test object is high-voltage equipment (transformer/instrument transformer/bushing) or insulating oil, or both, to avoid choosing the wrong instrument type.
If it is used in strong-interference sites such as 500kV substations, high-precision models with variable-frequency anti-interference technology must be selected, and the metrological calibration certificate provided by the manufacturer (according to JJF 1618-2017) must be verified to ensure data traceability.
During procurement, attention should be paid to the instrument's calibration cycle (recommended not to exceed 6 months), and it should be confirmed whether the manufacturer provides after-sales services such as regular calibration and maintenance, so as to avoid compliance risks such as "still issuing reports after the calibration has expired."
