CN106546859A - A kind of on-line monitoring system for cable arrester - Google Patents

Abstract

An online monitoring system for cable arresters, which is mainly composed of two parts: a data acquisition system and a data receiving system. The data acquisition system uses an embedded microcomputer system to automatically collect the arrester leakage current output from the arrester monitor, counter action signal, and perform data processing and storage, and transmit the collected data processing to the background monitoring data receiving system through the GPRS network; the data receiving system uses the server as the hardware platform, and the server is arranged in the substation, power plant or system operation monitoring center And constitute a monitoring terminal, at the same time, the client terminal can be easily connected to the monitoring terminal through the network through the PC; the data receiving system is mainly responsible for receiving the arrester monitoring data sent by all data acquisition systems, and completing the comprehensive calculation , Display storage, trend analysis, database and alarm management and other tasks; it has the characteristics of reasonable system composition, convenient and reliable use, etc.

Description

An On-Line Monitoring System for Cable Lightning Arrester

technical field

The invention relates to an on-line monitoring system for cable arresters, belonging to the technical field of on-line monitoring of cable arresters.

Background technique

The surge arresters used for cables are all zinc oxide arresters (MOA). During the long-term operation of the MOA arrester, on the one hand, it withstands power frequency voltage and impulse voltage for a long time, and there will be leakage current flowing. The long-term action will cause the zinc oxide valve to age, or even Thermal breakdown occurs; on the other hand, due to the influence of the environment, the interior of the arrester will be damp and deteriorated. When the MOA arrester is affected by the above reasons and the insulation performance is reduced, the power equipment connected in parallel with it will lose protection. The traditional monitoring method for MOA surge arresters is to conduct regular off-line preventive tests on MOA surge arresters that are put into operation. The test must stop the main equipment. The arrester cannot be tested on time, so it is necessary to use real-time online monitoring to monitor the operating status of the MOA arrester.

However, in order to realize the online monitoring of lightning arresters for cables, the following difficulties need to be overcome:

1) It is difficult to obtain the power supply of the monitoring device;

2) Since the lightning arrester for cables is usually installed on the tower, away from the substation, the voltage signal cannot be obtained from the voltage transformer, so the resistive current cannot be calculated by the phase angle difference between the leakage current and the voltage;

3) The field interference signal is strong.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, and provide an on-line monitoring system for cable arresters with reasonable system composition, convenient and reliable use, which can effectively avoid the occurrence of arrester accidents and ensure the safe and reliable operation of the arrester.

The purpose of the present invention is accomplished through the following technical solutions, a kind of on-line monitoring system for cable lightning arrester according to the present invention, it is mainly made up of two parts of data acquisition system and data receiving system, described data acquisition system The embedded microcomputer system is adopted to automatically collect the arrester leakage current and counter action signal output from the arrester monitor, and perform data processing and storage, and transmit the collected data processing to the background monitoring data receiving system through the GPRS network; the data receiving The system uses the server as the hardware platform, and the server is arranged in the substation, power plant or system operation monitoring center and constitutes the monitoring terminal. At the same time, the client terminal can be easily connected to the monitoring terminal through the network through the PC; the data receiving The system is mainly responsible for receiving the arrester monitoring data sent by all data acquisition systems, and completing tasks such as comprehensive calculation, display storage, trend analysis, database and alarm management.

As a preference: the data acquisition system collects the leakage current of the cable arrester through the passive resistive current test module, and transmits the leakage current signal to the embedded microcomputer system through the signal converter and the optical brazing isolation/signal output device Signal input/signal converter; the counter action signal records the discharge times of the arrester through the action current, that is, the data of 5A-50kA peak value, and uses the passive monitor configured in the data acquisition system to collect and return in real time.

As a preference: the leakage current is obtained by detecting the full current and resistive current of the arrester; the data acquisition system uses a high-voltage CT sensor to obtain electricity from the cable, and passes through the rectifier bridge, voltage stabilizing capacitor, and energy discharge circuit , filter circuit and voltage stabilizing block are converted into a constant low-voltage power supply.

The present invention utilizes modern power electronic technology, computer technology and GPRS communication technology to develop the on-line monitoring system of lightning arrester for cables, which can monitor the full current and resistive current of lightning arrester in real time, and can draw trend waveform diagrams of various parameters, record data tables, etc. The method provides analysis, and uses the method of trend analysis to judge whether the health status of the arrester is good. If a certain operating parameter fails, the fault information can be sent to the operation and maintenance personnel in the form of GSM SMS, which fundamentally avoids the occurrence of arrester accidents and ensures The lightning arrester operates safely and reliably; after comparing with the data obtained by the traditional method test, it is found that the data tested by the monitoring system is accurate and reliable.

Description of drawings

Fig. 1 is a schematic diagram of the system composition of the present invention.

Fig. 2 is a schematic diagram of resistive current monitoring of the present invention.

Fig. 3 is a working principle diagram of the power supply of the present invention.

Fig. 4 is the equivalent circuit diagram of the MOA valve plate.

Figure 5 is a graph of the volt-ampere characteristic of the MOA valve.

Fig. 6 is a graph showing the variation of the volt-ampere characteristic of the MOA valve.

Fig. 7 is a schematic diagram of optical fiber isolation transmission according to the present invention.

detailed description

The present invention will be described in detail below in conjunction with accompanying drawing: As shown in Fig. 1, a kind of on-line monitoring system for cable arrester of the present invention, it mainly is made up of two parts of data acquisition system and data receiving system, described The data acquisition system adopts an embedded microcomputer system, which automatically collects the arrester leakage current output from the arrester monitor and the counter action signal, and performs data processing and storage, and transmits the collected data processing to the background monitoring data receiving system through the GPRS network; The data receiving system uses a server as a hardware platform, and the server is arranged in a substation, a power plant, or a system operation monitoring center to form a monitoring terminal. At the same time, a client terminal can be easily connected to the monitoring terminal through a network through a PC; The data receiving system described above is mainly responsible for receiving the arrester monitoring data sent by all data acquisition systems, and completing tasks such as comprehensive calculation, display storage, trend analysis, database and alarm management.

As shown in Figure 2, the data acquisition system of the present invention collects the leakage current of the cable arrester through the passive resistive current test module, and transmits the leakage current signal to the embedded The signal input/signal converter in the microcomputer system; the counter action signal records the discharge times of the arrester through the action current, that is, the data of the 5A-50kA peak value, and uses the passive monitor configured in the data acquisition system to collect and collect in real time. Feedback; the leakage current mentioned above is obtained by detecting the full current and resistive current of the arrester.

As shown in Figure 3, the data acquisition system uses a high-voltage CT sensor to take power from the cable, and converts it into a constant low-voltage power supply through a rectifier bridge, a voltage stabilizing capacitor, an energy discharge circuit, a filter circuit, and a voltage stabilizing block.

Example:

Theoretical basis for online monitoring parameters:

1) Leakage current of the valve plate, Figure 4 is the equivalent circuit diagram of a common MOA valve plate, ix is the total leakage current flowing through the arrester; _ir is the resistive leakage current; _{ic is} the capacitive leakage current; U is the grid voltage ; C is the equivalent capacitance between MOA valves; R is the non-linear resistance of MOA valves.

The volt-ampere characteristic curve of the MOA valve is shown in Figure 5.

Area a is a linear area, and the volt-ampere characteristic is close to a linear relationship; area b is a pre-breakdown area, and the volt-ampere characteristic is a weak nonlinear relationship. Under normal operating voltage, the MOA valves in areas a and b show high resistance, and the current flowing through the MOA valve is very small; area c is the breakdown area, and the volt-ampere characteristics present a strong nonlinear relationship; the volt-ampere characteristics of area d Compared with the weakening of area c, the volt-ampere characteristic curve begins to rise. The MOA valve slices in c and d areas show low resistance, and the current flowing through the MOA valve slices becomes larger.

Under the action of continuous voltage, the volt-ampere characteristics of the MOA valve will change, and its curve will shift to the right, as shown in Figure 6.

It can be seen that, under the same voltage, the current flowing through the aged MOA valve is larger, and the increase of current will aggravate the aging of the MOA valve ^[6] , the MOA valve The volt-ampere characteristic curve continues to move to the right, which is a positive feedback process, resulting in: the aging of the MOA valve is getting faster and faster.

According to DL 474.5-2006 "Guidelines for the Implementation of Field Insulation Test Part 5: Arrester Test" and related tests, it can be known that resistive current is the main criterion for the aging degree of metal oxide valves. This is because the capacitive current is determined by the internal structure of the arrester, and it will not change after the arrester is produced and finalized; after the arrester is put into operation, with the gradual change of the external environment such as lightning strikes, its own structure will also change accordingly. The resistive current will gradually increase, so the resistive current is an important parameter that can really reflect the working condition of the arrester.

2) Leakage current, leakage current can be divided into volume leakage current and waste surface leakage current, and the leakage current of the above valve is volume leakage current. The size of the surface leakage current is related to the surface condition of the selenium type product, such as the surface is dirty and damp, and does not directly reflect the condition inside the insulation, and will not reduce the electric strength. Under harsh conditions, the surface leakage current is much larger than the volume leakage current; the three-phase installation position of the arrester is close to the surface; the pollution conditions and environmental parameters are basically the same, so the initial values of the monitoring data are basically the same. Based on the three-phase leakage current and resistive current trend lines, if the three-phase change trends are consistent, it can be determined that the arrester is normal. On the contrary, if there is one phase whose change trend is different from the other two phases, especially if it increases significantly, further analysis should be carried out. After eliminating interference factors, it should be determined that the arrester is abnormal.

The goal of the on-line monitoring system for lightning arresters for cables in the present invention is to monitor the leakage current, resistive current and discharge times of the arresters in real time, transmit the data to the monitoring center through GPRS communication in a safe manner, and connect to Fujian Electric Power Co., Ltd. Substation On-Line Monitoring System Platform (OMDS), through the server software, displays the monitoring results in the form of lists and images, and sends out alarm signals in time when abnormalities occur.

3) system composition, the present invention is made up of two parts of data acquisition system (front-end system) and data receiving system (background system). The front-end system adopts an embedded microcomputer system, which automatically collects the arrester leakage current output from the arrester monitor, counter action and other signals, and performs data processing and storage, and transmits the collected data processing to the background monitoring system through the GPRS network. The background system uses the server as the hardware platform, and the server is arranged in the substation (power plant) or the system operation monitoring center, and at the same time, it can be conveniently connected to the network through a PC. The background system is mainly responsible for receiving all the lightning arrester monitoring data sent by the front end, and completing tasks such as comprehensive calculation, display storage, trend analysis, database and alarm management. The composition of the monitoring system is shown in Figure 1.

4) Development of passive monitor: The passive monitor adopted in the present invention adopts low power consumption chip internally, can work without external power supply (i.e. passive), and does not need other auxiliary signals at the same time, and is directly connected in series In the grounding loop of the arrester, the leakage current and the number of lightning strikes of the arrester are monitored online.

5) Resistive current collection and calculation method: The monitoring system uses a current detection method with no residual voltage and full isolation, uses a current transmitter to collect full current signals, and uses a single-turn core-through current sensor, advanced microtechnology and unique The transient parameter test technology performs linearization processing and calculation, and the structure is shown in Figure 2.

Under normal circumstances, the resistive component current accounts for about 10% to 20% of the full current, and its order of magnitude is microampere, so it is difficult to directly measure the resistive current. From the quantitative relationship between the resistive current and the full current, measuring the phase difference between the resistive component and the full current is the main link in calculating the resistive current of the arrester. The algorithm adopted only needs the full current signal, without the full voltage signal and other external conditions, and can obtain the resistive current, which reduces the cost, can effectively suppress the interference of harmonics and noise, and improves the accuracy. Include the following steps:

1) First, define I _C , I _R , I, and U to denote capacitive current vector value, resistive current vector value, full current vector value and voltage phasor value respectively, so that In the formula: I represents the effective value of the full power supply, f ₀ is the power frequency of 50Hz, is the initial phase;

2) If there is no harmonic component, the algorithm is as follows:

3) If there is a harmonic component, or there is a deviation in the power frequency, make the following corrections to ① and ② in step 2: ① After completing the discrete sampling of the full current, filter out 3 times and higher when performing orthogonal transformation Sub-harmonic components; ②There is a deviation in the power frequency, which is regarded as an unknown frequency signal, using the frequency estimation method, and then using the frequency estimation value to construct a reference signal.

6) Monitoring terminal power supply design: Cable arresters are usually located in the field or in unattended areas, and it is often difficult to obtain the low-voltage power supply required for the system to collect terminal work. Now outdoors mainly use CT to obtain electric energy from cables, solar power, storage batteries For power supply, etc., considering the advantages and disadvantages of several commonly used energy supply methods, the on-line monitoring system of cable surge arresters decided to use CT to obtain power from cables based on the idea of obtaining materials nearby.

Aiming at the two design difficulties of this method, the design task is mainly focused on converting a large-scale variable current into a constant voltage source. The design idea is to use the saturation characteristics of the power supply CT to convert the operating current of tens of amperes to thousands of amperes on the line into a constant low voltage. The working principle of the power supply is shown in Figure 3.

The power supply CT directly induces the AC voltage from the operating current of the line, and after conversion through full-wave rectification, a relatively stable DC voltage is obtained on the voltage stabilizing capacitor C, and then transformed into a stable power supply through the filter circuit and the voltage stabilizing block for system data Electronic circuit boards used in sampling terminals.

The CT iron core of the power supply uses magnetic materials with high magnetic permeability and low saturation magnetic induction intensity, which is conducive to improving the power output in the starting current state and avoiding excessive temperature rise when the CT is in a deeply saturated state. The high-voltage protection circuit is used to prevent the instantaneous sudden change of the primary side current of the energy harvesting power supply CT from damaging the power harvesting module. The bleeder circuit is used to bleed off excess energy on the energy storage stabilizing capacitor to avoid damage to the stabilizing block due to excessive induced voltage. The measured data of the designed energy harvesting module are shown in Table 1

Table 1 Measured data of energy harvesting module

Tablel Measured data of energy taking module

From the test data, the power module designed by this system, which uses CT to obtain energy from the running high-voltage cable, meets the design purpose and achieves the effect of practical application.

7) Monitoring of the number of discharges: record the discharge times of the arrester through the data of the operating current (peak value) (5A-50kA), use the passive monitor for real-time collection, and send the data back once a day.

8) High and low voltage isolation method based on plastic optical fiber isolation transmission: At present, the data transmission of the traditional lightning arrester online monitoring device is transmitted with 485 or 232 signals. The entire power transmission and transformation integrated automation system causes huge hidden dangers. Aiming at the problems and deficiencies of the existing technology, the present invention provides an online monitoring device for lightning arresters based on plastic optical fiber isolation transmission that can completely isolate high and low voltages and greatly guarantee system security, as shown in Figure 7. The device includes a high-voltage module and a data processing module connected with it, and the high-voltage module is connected with the data processing module through a plastic optical fiber. The plastic optical fiber is connected with the photoelectric conversion module to effectively isolate the high voltage (10-1000kV). Its dielectric strength is 1kV/cm. Usually, the length of the optical fiber used is 10m, and its dielectric strength can reach 1000kV. The optical fiber can only transmit optical signals. , only light intensity and frequency changes are transmitted, and electrical signals such as voltage and current are not transmitted, and the attenuation is 180dB/km, and the impact on data transmission is within the effective range.

Claims (3)

1. a kind of on-line monitoring system for cable arrester, it is mainly by data collecting system and data receiving system two Part constitutes, it is characterised in that described data collecting system adopts embedded pc system, automatic data collection to monitor from arrester The leakage current of an arrester of instrument output, counter action signal, and data processing and storage are carried out, the data processing of collection is led to Cross the data receiving system that GPRS network is transferred to backstage monitoring；The data receiving system is taken with server as hardware platform Business device is arranged in transformer station, power plant or system operation Surveillance center and constitutes monitor terminal, meanwhile, client terminal passes through PC Machine then can be connected with the monitor terminal conveniently by network；Described data receiving system is mainly responsible for receiving all data The arrester Monitoring Data that acquisition system sends, and complete COMPREHENSIVE CALCULATING, show storage, trend analysis, database and warning The tasks such as management.

2. the on-line monitoring system for cable arrester according to claim 1, it is characterised in that described data are adopted Collecting system gathers the leakage current of cable arrester by passive resistive testing current module, and passes through signal adapter, light pricker Isolation/signal output device, will leak out signal input/signal adapter of the current signal transfer in embedded pc system；Institute The counter action signal stated records the discharge time of arrester by the data of action current, i.e. 5A-50kA peak values, utilizes The passive monitor configured in data collecting system carries out Real-time Collection and returns.

3. the on-line monitoring system for cable arrester according to claim 1 and 2, it is characterised in that described leakage Electric current is by detecting that arrester total current and current in resistance property are obtained；Described data collecting system using high pressure CT inductors from Power taking on cable, and be converted to by rectifier bridge, electric capacity of voltage regulation, energy leadage circuit, filter circuit and regulator block constant Low-tension supply.