Capacitive bushing is the key equipment of power transformer, and the dielectric loss and equivalent capacitance parameter is an important index to measure the insulation condition of capacitive equipment. Through real-time on-line monitoring of leakage current, equivalent capacitance and dielectric loss of capacitive equipment, real-time monitoring of insulation condition of high-voltage electrical equipment can be realized. At the same time, potential faults of capacitive bushing can be found in time by analyzing monitoring data, which provides important data basis for condition-based maintenance and provides strong and reliable guarantee for safe, reliable, stable and economical operation of power system, provide reliable equipment insulation information and scientific maintenance basis for operation and maintenance personnel, so as to reduce accidents, extend maintenance intervals, reduce the number and time of power outage maintenance, and improve equipment utilization and overall economic benefits.

system structure

The capacitive bushing online monitoring system consists of four unit devices: capacitive bushing online monitoring device, high and low frequency integrated sensor, bus voltage online monitoring device and monitoring host/IED:

1. Online monitoring host, used for all monitoring unit control, data management, data storage, data communication, etc;

2. The capacitive equipment monitoring device is used to collect the leakage current of the capacitive bushing;

3. Bus voltage monitoring device, used to collect the three-phase voltage of the bus where the capacitive bushing is located;

4. High and low frequency integrated sensor, used for capacitive bushing end screen current sampling and PD signal sampling;

The capacitive bushing on-line monitoring system adopts advanced hierarchical distributed structure, bus control technology and modular design principle, so that the anti-interference performance, measurement accuracy and stability of the system have been greatly improved, to meet the practical requirements of industrial field.

System features

Using high-precision active sensor, according to the size of the current to be measured automatically select the magnification, high-precision measurement;

The dynamic phase compensation algorithm is used to achieve high-precision measurement signal analysis;

A digital filtering algorithm is used to eliminate the "zero drift problem" caused by analog filters ";

It adopts distributed measurement structure, I .e. local measurement and digital transmission;

The use of complex wavelet denoising technology, high-performance amplification filter components; perfect solution to the interference problem in the field electromagnetic environment,

Frequency domain selective filtering technology is used to analyze the accurate filtering of signal components in each frequency band,

It can be installed with electricity, that is, it does not need the main equipment to be installed without power failure, and it is convenient and fast to access the system.

6. device function

The capacitive bushing online monitoring device has the following functions:

1. Collect the leakage current of the capacitive bushing, and calculate the fundamental wave and the 3rd, 5th, 7th and 9th harmonics of the leakage current of the capacitive bushing;

2. Collect PT bus voltage and calculate fundamental wave and 3rd, 5th, 7th and 9th harmonics of bus voltage;

3. Calculate the dielectric loss and capacitance of capacitive equipment (casing);

4. The minimum measured discharge amplitude is 20mV (on site), the frequency range is 200kHz ~ 300MHz, the time resolution of discharge pulse is 10μs, and the phase resolution is 0.18.

5. Provide 50 power frequency periodic discharge diagram, two-dimensional (q-φ,N-φ,N-q) and three-dimensional (N-q-φ) spectrograms, which can be used to analyze the type of discharge.