1. Scope

The technical specifications for the online monitoring system of partial discharge in high-voltage cables stipulate the structural composition, working conditions, technical requirements, experimental items, etc. of the online monitoring system for partial discharge in high-voltage cables. It is suitable for online monitoring of partial discharge in cross-linked polyethylene insulated power cable lines with rated voltage of 110kV (66kV) and above.

2. System architecture composition

The online monitoring system for partial discharge of high-voltage cables adopts a layered and distributed structure, consisting ofHigh current sensor HFCT (maximum output corresponding frequency: 1MHz~30MHz)It consists of a reference phase sensor, a signal acquisition unit, a transmission channel, and a monitoring host. Partial discharge sensors, reference phase sensors, and signal acquisition units are installed on site to sense and collect partial discharge state variables and power frequency current phase signals. The monitoring host is a computer device installed in the monitoring room, used to process and analyze state parameter data and control signal acquisition units, and communicate with the comprehensive monitoring and analysis system.

3. Basic functional requirements

3.1Monitoring function:

a) The online monitoring system can continuously or periodically automatically monitor the partial discharge state of high-voltage cable lines during operation:

b) The signal acquisition unit has the function of phase acquisition of power frequency current, and can use a reference phase sensor to collect the phase of power frequency current from the high-voltage cable body or the grounding lead out line;

c) The information upload frequency of the signal acquisition unit can be set, and when using on-site industrial control bus or fiber optic transmission, the upload frequency should not be less than once every 10 minutes;

3.2Data recording function

3.3Data analysis function:

a) The online monitoring system is capable of detecting partial dischargeAmplitude, phase, frequencyProcessing and displaying basic characteristic parameters can provide local informationTrend chart of discharge signal amplitude and frequency changes;

b) The online monitoring system can providePartial Discharge Phase Distribution Diagram (PRPD)、Pulse sequence phase distribution map (PRPS)orAmplitude (Q), Phase (), Discharge Frequency (N)Two dimensional spectra (Q -, N1, etc.), three-dimensional spectra (Q Φ - N, O -, etc.), and equivalent time-frequency spectra are used to describe discharge characteristics;

c) The phase resolution of the partial discharge spectrum provided by the online monitoring system should not be lower than 120 points or integer multiples of 120 points within each power frequency cycle. The spectrum should be uploaded to the comprehensive monitoring and analysis system in the form of data description;

d) The online monitoring system has the ability to analyze the time-domain and frequency-domain characteristics of partial discharge pulse waveforms;

e) The online monitoring system has a discharge type recognition function, which can determine the typical partial discharge types of high-voltage cable lines;

3.4alarm function

The online monitoring system can set alarm conditions, realize abnormal alarm of partial discharge state quantity, and upload the alarm information to the comprehensive monitoring and analysis system; When the system malfunctions during operation, it can automatically prompt fault information and establish event logs.

3.5Communication function