CN103954889A - Capacitive type device insulation parameter electrification testing method based on pincerlike current sensors - Google Patents

Abstract

The invention discloses a live test method for insulation parameters of capacitive equipment based on a clamp current sensor. The method is realized through the following steps. Off line; voltage sampling method: Connect a measuring resistor (3) between the secondary 100/√3V (R terminal and L terminal) of the voltage transformer to form a loop, and the clamp current sensor (2) is stuck on the second voltage transformer The connection line between the secondary 100/√3VR terminal and the measuring resistance or the connection line between the secondary 100/√3VL terminal of the voltage transformer and the measuring resistance. The invention proposes a live test method based on the clamp current sensor to realize the insulation parameters of the capacitive equipment. On the premise of ensuring the test accuracy of the clamp current sensor, it realizes "instant use" without power failure, which is very convenient, and It also fundamentally avoids potential safety hazards such as open circuits at the end screen.

Description

Live test method for insulation parameters of capacitive equipment based on clamp current sensor

technical field

The invention relates to a live test of insulation parameters of capacitive equipment in a power system, and belongs to the field of live test of insulation parameters of capacitive equipment.

Background technique

Capacitive equipment in the power system mainly includes current transformers, high-voltage capacitive bushings, coupling capacitors, capacitive voltage transformers, compensation capacitors, etc. If the high-voltage electrical equipment operating in the power grid has insulation defects caused by factors such as poor manufacturing, aging, and external force damage, insulation accidents that affect the normal operation of high-voltage equipment and the power grid will occur. In order to prevent such major safety accidents, the current traditional method is to regularly cut off the power for preventive tests and maintenance after the equipment is put into operation, so as to detect the insulation defects inside the equipment in time. However, the test conditions of the power failure preventive test are quite different from the operating state, so it is not easy to correctly diagnose the insulation condition of the high-voltage equipment under the operating condition, and it is even more difficult to find the defects developed between the two preventive tests, which will directly affect to the experimental effect of preventive trials. At the same time, with the development of the national economy, the whole society has higher and higher requirements for the reliability of power supply and the reduction of power outage time; the scale of the power system gradually grows, and the traditional preventive tests of regular power outages are time-consuming, laborious and experimental. Unsatisfactory and many other disadvantages obviously cannot meet the requirements of safe, reliable and efficient operation of the power grid. Therefore, implementing automatic monitoring of electrical equipment operation and online monitoring of insulation conditions to achieve condition-based maintenance has become an inevitable development direction for future high-voltage equipment tests. The online monitoring method can obtain the characteristic parameters reflecting the abnormality of the equipment insulation at any time, which is convenient for automatic management, but the investment is relatively large, the installation and construction are troublesome, and regular maintenance is required, and its accuracy and reliability cannot be tested after installation.

The live test is between the power failure pre-test and on-line monitoring, which can better overcome the shortcomings of the two methods and has its technical advancement.

Contents of the invention

The technical problem to be solved by the present invention is to provide a live test method for the insulation parameters of capacitive equipment based on clamp current sensors that does not need to be installed and does not need to be powered off, which can overcome the deficiencies of the prior art.

The technical solution of the invention is: the signal sampling structure adopts a clamp current sensor. Current sampling method: the clamp current sensor (1) is directly stuck on the grounding down conductor of the last screen of the capacitive equipment; voltage sampling method: connected between the secondary 100/√3V (R terminal and L terminal) of the voltage transformer A measuring resistor (3) forms a loop, and the clamp current sensor (2) is stuck on the connecting line between the secondary 100/√3VR terminal of the voltage transformer and the measuring resistor or stuck on the secondary 100/√3VL terminal of the voltage transformer and measuring resistor connection line.

Described a kind of live test method based on the insulation parameter of capacitive type equipment of clamp-on current sensor, comprises the following steps:

Step 1: Clip the clamp current sensor (1) to the grounding down-conductor of the last screen of the capacitive device A, and extract the current waveform.

Step 2: Connect a measuring resistor (3) from the secondary 100/√3V of the voltage transformer (R terminal and L terminal) to form a loop, and the clamp current sensor (2) is stuck on the secondary 100/√3VR of the voltage transformer terminal and the measuring resistance or stuck on the connecting line between the secondary 100/√3VL terminal of the voltage transformer and the measuring resistance to extract the voltage waveform.

Step 3: Connect the current waveform of the clamp current sensor (1) and the voltage waveform of the clamp current sensor (2) to the analyzer (4). Thus, the insulation parameters of capacitive equipment can be calculated, and the calculation process is as follows:

According to the formula (1) (2), the effective value I and U of the two signals of the clamp current sensor (1) and the clamp current sensor (2) can be calculated,

C=I/314U (3)

According to the formula (3), the capacitance can be calculated.

In practice, the measured waveforms all contain different degrees of harmonic components. Any periodic function is composed of periodic fundamental waves, 2, 3, 4...k harmonics are superimposed, as shown in formula (4), through Formula (5) and formula (6) can separate the fundamental wave component and each harmonic component.

In the formula, A ₀ is the DC component, which needs to be filtered out.

Among them, A _mk is the amplitude of the fundamental wave or the kth harmonic, a _k is the real component of the fundamental wave or the kth harmonic phasor, and b _k is the imaginary component of the fundamental wave or the kth harmonic phasor.

Only calculate the fundamental wave, when k=1, according to the formula (5) and formula (6), the vector real part of the fundamental wave of the two signals of the clamp current sensor (1) and the clamp current sensor (2) can be calculated respectively and the imaginary part of the vector, the mathematical expressions of the two vectors are a _n + j b _n and a _x + j b _x respectively.

Let θ ₁ be the angle between the a _n + j b _n vector and the positive direction of the X-axis, and θ ₂ be the angle between the a _x + j b _x vector and the positive direction of the X-axis, then the dielectric loss angle δ=90°-(θ ₁ -θ ₂ ), according to the relationship of trigonometric functions:

Compared with the prior art, the present invention regards the insulation structures of current transformers, high-voltage capacitive bushings, coupling capacitors, capacitive voltage transformers, compensation capacitors, etc. as composed of several capacitors connected in series and parallel; In this case, the insulation state can be judged by detecting its current, capacitance, and dielectric loss tangent. Among them, the dielectric loss tangent (tanδ), also known as the dielectric loss factor, referred to as the dielectric loss angle or dielectric loss, is a characteristic parameter that characterizes the loss of the insulation under the action of alternating voltage. It only depends on the characteristics of the material and has nothing to do with the shape of the insulator. It has nothing to do with the size, so tanδ is very effective as a parameter reflecting the overall insulation status of the equipment. On the basis of the above, on the premise of ensuring the test accuracy of the clamp current sensor, the clamp current sensor is used to realize the "instant card and use" ", without power failure, very convenient, and fundamentally avoid safety hazards such as open circuit at the end screen.

the

Description of drawings

Fig. 1 is the schematic diagram that carries out live test to capacitive equipment;

In the figure, 1——clamp current sensor (1), 2——clamp current sensor (2), 3——measuring resistance, 4——analyzer,

5——End screen, 6——Ground, 7——Soft plastic tube, 8——Grounding down conductor, A——Capacitive equipment

Detailed ways

Embodiment: This embodiment is the live test of the insulation parameter of the capacitive device based on the clamp current sensor, as shown in Figure 1, the tested product is a capacitive device A, and the clamp current sensor (1) is stuck in the connection capacitor On the grounding down conductor of terminal 5 and ground terminal 6 of type equipment A, the clamp current sensor (2) is stuck on the loop formed by the secondary voltage terminal of the PT through 3 measuring resistors, the clamp current sensor (1) and The two-way signals of the clamp current sensor (2) are connected to the analyzer 4 at the same time. After the above connection is connected, the live test method of the insulation parameter of the capacitive device based on the clamp current sensor is completed through the following steps:

Step 1: Clip the clamp current sensor (1) to the grounding down-conductor of the last screen of the capacitive device A, and extract the current waveform.

Step 2: Connect a measuring resistor (3) from the secondary 100/√3V of the voltage transformer (R terminal and L terminal) to form a loop, and the clamp current sensor (2) is stuck on the secondary 100/√3VR of the voltage transformer terminal and the measuring resistance or stuck on the connecting line between the secondary 100/√3VL terminal of the voltage transformer and the measuring resistance to extract the voltage waveform.

Step 3: Connect the current waveform of the clamp current sensor (1) and the voltage waveform of the clamp current sensor (2) into the analyzer (4). Thus, the insulation parameters of capacitive equipment can be calculated, and the calculation process is as follows:

(2)

According to the formula (1) (2), the effective value I and U of the two signals of the clamp current sensor (1) and the clamp current sensor (2) can be calculated,

C=I/314U (3)

According to the formula (3), the capacitance can be calculated.

In practice, the measured waveforms all contain different degrees of harmonic components. Any periodic function is composed of periodic fundamental waves, 2, 3, 4...k harmonics are superimposed, as shown in formula (4), through Formula (5) and formula (6) can separate the fundamental wave component and each harmonic component.

In the formula, A ₀ is the DC component, which needs to be filtered out.

Among them, A _mk is the amplitude of the fundamental wave or the kth harmonic, a _k is the real component of the fundamental wave or the kth harmonic phasor, and b _k is the imaginary component of the fundamental wave or the kth harmonic phasor.

Only calculate the fundamental wave, when k=1, according to the formula (5) and formula (6), the vector real part of the fundamental wave of the two signals of the clamp current sensor (1) and the clamp current sensor (2) can be calculated respectively and the imaginary part of the vector, the mathematical expressions of the two vectors are a _n + j b _n and a _x + j b _x respectively.

Let θ ₁ be the angle between the a _n + j b _n vector and the positive direction of the X-axis, and θ ₂ be the angle between the a _x + j b _x vector and the positive direction of the X-axis, then the dielectric loss angle δ=90°-(θ ₁ -θ ₂ ), according to the relationship of trigonometric functions:

Claims (1)

1. a charged test method for the capacitance type equipment insulation parameter based on pincerlike current sensor, base is characterised in that: the method comprises the following steps

Step 1: pincerlike current sensor (1) is stuck in to the end shield down conductor place of capacitance type equipment A, extracts current waveform;

Step 2: form loop from connecing a measuring resistance (3) between the secondary 100/ √ 3V (R end and L end) of voltage transformer (VT), pincerlike current sensor (2) is stuck on the connecting line of voltage transformer secondary 100/ √ 3VR end and measuring resistance or is stuck on the connecting line of voltage transformer secondary 100/ √ 3VL end and measuring resistance, extracts voltage waveform;

Step 3: access the current waveform of pincerlike current sensor (1) and the voltage waveform of pincerlike current sensor (2) in analyser (4), calculate the insulation parameter of capacitance type equipment, its computation process is as follows:

According to formula (1) (2), can calculate effective value I and the U of pincerlike current sensor (1) and pincerlike current sensor (2) two paths of signals,

C=I/314U (3)

According to formulism (3), can calculate electric capacity;

Step 4: because the waveform of surveying in reality all contains harmonic component in various degree, any one periodic function is all by periodic first-harmonic, 2,3,4 ... k subharmonic is formed by stacking, as shown in formula (4), by formula (5) and formula (6), can isolate fundametal compoment and each harmonic component;

A in formula ₀for DC component, need to filter;

A wherein _mkfor first-harmonic or k subharmonic amplitude, a _kfor first-harmonic or k subharmonic phasor real component, b _kfor first-harmonic or k subharmonic phasor imaginary part component;

step 5: only first-harmonic is carried out to computing, when k=1, vectorial real part and the vectorial imaginary part that according to formula (5), formula (6), can calculate respectively pincerlike current sensor (1) and pincerlike current sensor (2) two paths of signals first-harmonic, two vectorial mathematic(al) representations are respectively a _n+ j b _nand a _x+ j b _x;

If θ ₁a _n+ j b _nvector and X-axis positive dirction angle, θ ₂a _x+ j b _xvector and X-axis positive dirction angle, dielectric loss angle δ=90 °-(θ ₁-θ ₂), according to trigonometric function relation, can obtain:

。