Since entering the 21st century, China has vigorously promoted the construction of smart grids. To accelerate the intelligent transformation, electronic instrument transformers have been widely adopted in smart substations due to their advantages of simple structure, wide dynamic range, small size, light weight, and convenient output signal interfaces. However, due to issues such as insufficient design capabilities of some manufacturers, lack of production process control, inadequate testing equipment, and incomplete type test items, electronic instrument transformers—one of the key components in smart substation projects—have experienced breakdowns and even explosions after commissioning. Such incidents have occurred in smart grid substations in Hunan, Yunnan, Fujian and other regions.

The main fault types of electronic instrument transformers include:

Collector faults caused by electromagnetic compatibility issues

Error faults induced by ambient temperature fluctuations in substations

Optical fiber link faults triggered by external vibrations

Equipment failures arising from laser power supply systems

In the Notice on Effectively Strengthening the Operation Management of Electronic Instrument Transformers issued by State Grid Corporation of China, it is clearly stipulated that existing transformers should not be replaced with electronic ones unless the relay protection devices undergo overall or major modifications. Given the current maturity and cost-effectiveness of electronic instrument transformers, it is not advisable to carry out digital transformation on transformers of 35kV and below for the time being.

Despite these challenges, industry experts have pointed out that under stable conditions, electronic instrument transformers have irreplaceable advantages over traditional ones. It is an inevitable trend for electronic instrument transformers to replace traditional ones in the construction of smart grids. However, the current standard system for electronic instrument transformers is still incomplete, and their on-site reliability needs further improvement. As a pioneer, State Grid Shanghai Electric Power Company has mainly commissioned electronic instrument transformers in 35kV and below systems, with a few 110kV substations serving as pilot projects.

△ DCM-330 Electronic Instrument Transformer Calibrator

To improve the practical application of electronic instrument transformers, the State Grid Shanghai Electric Power Research Institute (SPEPRI) places great importance on performance testing. Recently, technical personnel from Wuhan Haomai Electric Power collaborated with SPEPRI and Shanghai Electric Power Maintenance Company to conduct calibration tests on 35kV grounding transformer electronic current transformers.

The test used the DCM-330 Electronic Instrument Transformer Calibrator in conjunction with standard current transformers and electronic current transformers (wiring diagram as follows).

A standard current output by the standard current transformer was fed into the primary bus, and a monitoring current signal was derived from the secondary side of the standard transformer. The bus current then flowed into the electronic current transformer, which converted and transmitted it to the merging unit. A converted current signal was taken from the merging unit for comparison. The DCM-330 monitored the outputs of both the standard current transformer and the electronic current transformer, along with harmonic content, error curves, ratio errors, phase errors, message jitter, composite errors, and other relevant test data. After the test, a test report was automatically generated.

"Originally scheduled to be completed in one day, the work ticket task for one and a half days was finished in less than three hours," stated a relevant staff member from SPEPRI. The DCM-330 Electronic Instrument Transformer Calibrator offers more comprehensive test items, more intuitive data, simpler operation, and higher efficiency. Based on the test results, manufacturers can make timely adjustments and optimizations, leading to a significant reduction in the failure rate of electronic instrument transformers. This also provides a feasibility guarantee for their full-scale promotion in smart grids in the future.